Detailed DNA methylation characterisation of phyllodes tumours identifies a signature of malignancy and distinguishes phyllodes from metaplastic breast carcinoma

Phyllodes tumours (PTs) are rare fibroepithelial lesions of the breast that are classified as benign, borderline, or malignant. As little is known about the molecular underpinnings of PTs, current diagnosis relies on histological examination. However, accurate classification is often difficult, particularly for distinguishing borderline from malignant PTs. Furthermore, PTs can be misdiagnosed as other tumour types with shared histological features, such as fibroadenoma and metaplastic breast cancers. As DNA methylation is a recognised hallmark of many cancers, we hypothesised that DNA methylation could provide novel biomarkers for diagnosis and tumour stratification in PTs, whilst also allowing insight into the molecular aetiology of this otherwise understudied tumour. We generated whole-genome methylation data using the Illumina EPIC microarray in a novel PT cohort (n = 33) and curated methylation microarray data from published datasets including PTs and other potentially histopathologically similar tumours (total n = 817 samples). Analyses revealed that PTs have a unique methylome compared to normal breast tissue and to potentially histopathologically similar tumours (metaplastic breast cancer, fibroadenoma and sarcomas), with PT-specific methylation changes enriched in gene sets involved in KRAS signalling and epithelial-mesenchymal transition. Next, we identified 53 differentially methylated regions (DMRs) (false discovery rate < 0.05) that specifically delineated malignant from non-malignant PTs. The top DMR in both discovery and validation cohorts was hypermethylation at the HSD17B8 CpG island promoter. Matched PT single-cell expression data showed that HSD17B8 had minimal expression in fibroblast (putative tumour) cells. Finally, we created a methylation classifier to distinguish PTs from metaplastic breast cancer samples, where we revealed a likely misdiagnosis for two TCGA metaplastic breast cancer samples. In conclusion, DNA methylation alterations are associated with PT histopathology and hold the potential to improve our understanding of PT molecular aetiology, diagnostics, and risk stratification. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Integrating single-cell and spatial transcriptomes reveals COL4A1/2 facilitates the spatial organisation of stromal cells differentiation in breast phyllodes tumours

BACKGROUND

Breast phyllodes tumours (PTs) are a unique type of fibroepithelial neoplasms with metastatic potential and recurrence tendency. However, the precise nature of heterogeneity in breast PTs remains poorly understood. This study aimed to elucidate the cell subpopulations composition and spatial structure and investigate diagnostic markers in the pathogenesis of PTs.

METHODS

We applied single-cell RNA sequencing and spatial transcriptomes on tumours and adjacent normal tissues for integration analysis. Immunofluorescence experiments were conducted to verify the tissue distribution of cells. Tumour cells from patients with PTs were cultured to validate the function of genes. To validate the heterogeneity, the epithelial and stromal components of tumour tissues were separated using laser capture microdissection, and microproteomics data were obtained using data-independent acquisition mass spectrometry. The diagnostic value of genes was assessed using immunohistochemistry staining.

RESULTS

Tumour stromal cells harboured seven subpopulations. Among them, a population of widely distributed cancer-associated fibroblast-like stroma cells exhibited strong communications with epithelial progenitors which underwent a mesenchymal transition. We identified two stromal subpopulations sharing epithelial progenitors and mesenchymal markers. They were inferred to further differentiate into transcriptionally active stromal subpopulations continuously expressing COL4A1/2. The binding of COL4A1/2 with ITGA1/B1 facilitated a growth pattern from the stroma towards the surrounding glands. Furthermore, we found consistent transcriptional changes between intratumoural heterogeneity and inter-patient heterogeneity by performing microproteomics studies on 30 samples from 11 PTs. The immunohistochemical assessment of 97 independent cohorts identified that COL4A1/2 and CSRP1 could aid in accurate diagnosis and grading.

CONCLUSIONS

Our study demonstrates that COL4A1/2 shapes the spatial structure of stromal cell differentiation and has important clinical implications for accurate diagnosis of breast PTs.

Malignant phyllodes tumor and invasive lobular breast carcinoma: Morpho-molecular characterization of an uncommon collision tumor and review of the literature

Phyllodes tumor (PT) of the breast is a biphasic neoplasia composed of mesenchymal and epithelial cells. PTs are graded as benign, borderline or malignant according to histological criteria. Invasive lobular carcinoma (ILC) is a special breast cancer subtype defined by non-cohesive growth and loss of E-cadherin. PT is treated by resection. ILC is treated by resection and adjuvant endocrine therapy with or without chemotherapy. Collision tumors composed of PT and concurrent ILC are rare. Due to their dissociated growth, ILC cells may escape histologic detection when admixed with PTs. Here we report the case of a 71-years-old female diagnosed with a PT/ILC collision tumor. The patient presented with a tumor in the right breast. A core needle biopsy showed mesenchymal spindle cell proliferates suspicious for a PT. The resection specimen confirmed a malignant PT with stromal overgrowth. Unexpectedly, the resection specimen also revealed sparse infiltrates of ILC admixed with the PT. Immunohistochemistry of mesenchymal PT cells and ILC cells was consistent with the histomorphological diagnosis. Molecular analyses demonstrated a IDH1 variant of unknown significance and GNAS gene mutation in microdissected PT tissue. ILC tissue showed wild-type IDH1 and GNAS, but harbored CDH1/E-cadherin and TP53 gene mutations, arguing against clonal relatedness of the two lesions. Review of the literature identified six reported PT/ILC collision tumors, involving three benign, two borderline and one malignant PT. In summary, this is the second report on a malignant PT/ILC collision tumor. Correct histologic diagnosis of PT/ILC collision tumors is clinically relevant, because adjuvant endocrine therapy is mandatory for ILC.

Malignant phyllodes tumour with lymph node metastasis: a diagnostic conundrum resolved by next generation DNA sequencing

A malignant neoplasm with spindle cell and chondroid differentiation in the breast, metastatic to lymph node. In this context, a metaplastic carcinoma is typically favored given the exceptional nature of lymph node metastases in malignant phyllodes tumors (MPT). However, we demonstrate pathognomonic hotspot mutations in MED12 and the promoter of the TERT gene by targeted next-generation DNA sequencing, supporting a diagnosis of MPT.

Periductal Stromal Tumor of the Breast with a TERT Promoter Mutation: First Case Report with Comprehensive Molecular Analysis

The molecular pathogenesis of breast fibroepithelial tumors continues to be elucidated. Recently, highly recurrent MED12 mutations arising in exon 2 at codon 44 were discovered in fibroadenomas and phyllodes tumors. In addition, a high prevalence of TERT promoter mutations in two hotspots (124 and 126 bp upstream from the translation start site) was discovered in up to 65% of phyllodes tumors. Breast periductal stromal tumors are a potentially distinct category of fibroepithelial lesions that are exceptionally rare with controversial classification and pathogenesis. Herein, we report the first comprehensive molecular genetic workup of a breast periductal stromal tumor that harbored a TERT promoter -124C > T mutation, supporting a relation to phyllodes tumors.

CD146 promotes malignant progression of breast phyllodes tumor through suppressing DCBLD2 degradation and activating the AKT pathway

BACKGROUND

As a rapid-progressing tumor, breast malignant phyllodes tumors (PTs) are challenged by the lack of effective therapeutic strategies and suitable prognostic markers. This study aimed to clarify the role and mechanism of CD146 on promoting PTs malignant progression, and to identify a novel prognosis marker and treatment target of breast malignant PTs.

METHODS

The expression and prognostic significance of CD146 in PTs was detected through single-cell RNA-sequencing (scRNA-seq), immunostaining, real-time PCR and other methodologies. Functional experiments including proliferation assay, colony formation assay, transwell assay, and collagen contraction assay were conducted to validate the role of CD146 in malignant progression of PTs. The efficacy of anti-CD146 monoclonal antibody AA98 against malignant PTs was corroborated by a malignant PT organoid model and a PT patient-derived xenograft (PDX) model. Transcriptome sequencing, proteomic analysis, co-immunoprecipitation, and pull-down assay was employed to identify the modulating pathway and additional molecular mechanism.

RESULTS

In this study, the scRNA-seq analysis of PTs disclosed a CD146-positive characteristic in the α-SMA+ fibroblast subset. Furthermore, a progressive elevation in the level of CD146 was observed with the malignant progression of PTs. More importantly, CD146 was found to serve as an independent predictor for recurrence in PT patients. Furthermore, CD146 was found to augment the viability and invasion of PTs. Mechanistically, CD146 acted as a protective "shield" to prevent the degradation of Discoidin, CUB, and LCCL domain-containing protein 2 (DCBLD2), thereby activating the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway and enhancing malignant behaviors of PT cells. In the malignant PT organoid and PDX model, a significant suppression of malignant PT growth was observed after the application of AA98.

CONCLUSIONS

These findings suggested that CD146 served as an efficacious marker for predicting PT malignant progression and showed promise as a prognosis marker and treatment target of breast malignant PTs. The study further unveiled the essential role of the CD146-DCBLD2/PI3K/AKT axis in the malignant progression of PTs.

High-Grade Spindle Cell Lesions of the Breast: Key Pathologic and Clinical Updates

Most of the high-grade spindle cell lesions of the breast are malignant phyllodes tumors (MPTs), spindle cell carcinomas (SpCCs), and matrix-producing metaplastic breast carcinomas (MP-MBCs). MPTs have neoplastic spindle stromal cells and a classic leaf-like architecture with subepithelial stromal condensation. MPTs are often positive for CD34, CD117, and bcl-2 and are associated with MED12, TERT, and RARA mutations. SpCCs and MP-MBCs are high-grade metaplastic carcinomas, whereas neoplastic epithelial cells become spindled or show heterologous mesenchymal differentiation, respectively. The expression of epithelial markers must be evaluated to make a diagnosis. SAS, or rare metastatic spindle cell tumors, are seen in the breast, and clinical history is the best supporting evidence. Surgical resection is the standard of care.

Malignant phyllodes tumor in Lynch syndrome: a case report

BACKGROUND

Lynch syndrome, or hereditary nonpolyposis colorectal cancer, is an autosomal dominant genetic syndrome that predisposes individuals to multiple cancer types. The known cancers associated with Lynch syndrome include colorectal and endometrial cancers as well as cancers of the stomach, ovary, urinary tract, hepatobiliary tract, pancreas, small bowel, and brain. There are no searchable cases of malignant phyllodes of the breast associated with Lynch syndrome.

CASE PRESENTATION

Our patient was a 43-year-old Caucasian woman who felt a lump in her left breast and was found to have a spindle cell neoplasm. Definitive surgery revealed a malignant phyllodes tumor. On the basis of her cancer diagnosis and family history of multiple cancers, a Myriad myRisk Hereditary Cancer® test panel of 25 genes was performed. This testing revealed that she had a heterozygous MSH6 mutation as part of the Lynch syndrome panel. Due to positive margins, the patient received adjuvant chemotherapy with doxorubicin and ifosfamide. She also had a subsequent total abdominal hysterectomy and a bilateral salpingo-oophorectomy for risk reduction. She remains in a high-risk surveillance program. Her family members have been tested, which revealed that her two brothers and daughter also carry the genetic mutation.

CONCLUSIONS

This case highlights the importance of genetic testing with rare malignancies because the full scope of phenotypic sequelae for known hereditary syndromes has not been mapped.

MED12, TERT promoter and RBM15 mutations in primary and recurrent phyllodes tumours

BACKGROUND

MED12 and TERT promoter mutations have been shown to be the most common somatic mutations in phyllodes tumours (PTs). The aims of this study were to determine the frequency of these mutations in recurrent PTs, assess whether TERT promoter mutations could be helpful in distinguishing fibroadenomas (FAs) from PTs and identify novel mutations that may be driving malignant progression.

METHODS

MED12 and the TERT promoter were Sanger sequenced in 75 primary PTs, 21 recurrences, 19 single FAs and 2 cases of multiple FAs with benign PTs. Whole-exome sequencing was performed on one borderline PT.

RESULTS

Recurrent PTs and multiple FAs showed temporal discordance in MED12 but not TERT. Recurrent samples did acquire TERT mutations, with recurrent benign PTs more likely to have mutations in both genes. TERT mutations were not helpful in differentiating between benign PTs and FAs in cases of multiple FAs/PTs. Exome sequencing revealed a nonsense mutation in RBM15 and Sanger sequencing revealed another three RBM15 mutations in malignant/borderline PTs.

CONCLUSIONS

This study has shown that MED12 mutations can be heterogeneous in both synchronous and recurrent PTs unlike TERT mutations. We have also shown that RBM15 mutations may be important in the pathogenesis of borderline/malignant PTs.

Phyllodes tumors of the breast in 2 sisters: Case report and review of literature

RATIONALE

Phyllodes tumors (PT) of the breast are rare neoplasm originating from fibroepithelial component. To our knowledge, our report is the first reported case of PT in 2 sisters.

PATIENT CONCERNS

We presented 2 cases of PT of the breast involving in 2 sisters. On physical examination of the younger sister, a firm mass measuring approximately 3 cm in diameter was identified in upper inner quadrant of the right breast. Physical examination of the elder sister revealed a 3 cm lump in upper outer quadrant of the left breast.

DIAGNOSES

Histopathology of the younger sister revealed a malignant PT. The elder sister was diagnosed with borderline PT.

INTERVENTIONS

The younger sister with malignant PT underwent right mastectomy. The elder sister with borderline PT was scheduled for wide resection of the mass in the left breast.

OUTCOMES

After a follow-up of 23 months, no local or distant recurrence was observed.

LESSONS

Our cases indicate that genetic factor may contribute to the risk of PT of the breast. Markers such as p53 and Ki-67 may have some correlation with PT malignancy.

Breast cancer in women in their thirties (2007-2013): a retrospective review

Due to an increasing number of breast cancer diagnoses in younger women anecdotally noted at our institution, we conceived of this study %was to retrospectively review the records of women diagnosed with breast cancer under the age of 40 for potentially alterable versus unalterable risk factors in their history. Between 2007 and 2013, there were 52 patients less than 40 years of age with breast cancer at our institution: 79% (41/52) presented with a clinical abnormality (palpable mass, nipple discharge or inversion) and 21% (11/52) were asymptomatic but diagnosed on early screening mammograms. Seventy-five percent (39/52) of the cancers had an invasive component and 87% (45/52) were intermediate to high grade. Sixty percent (31/52) of subjects had stage 0 or I disease, but 40% (21/52) had later stage disease (stage II or greater). The vast majority of the cancers were ER+ (82%) and PR+ (78%). Fifty-six percent (28/50; 2 unknown) of the subjects had a documented history of hormonal contraception. Fifty-three percent (27/51; 1 unknown) of had no family history of breast cancer whatsoever, and 80% (41/51) had no family history of breast cancer in a first degree relative. Six were positive for BRCA 1, 2, or a variant (6/52 = 12%).

[Clinicopathologic features and prognostic factors of malignant phyllodes tumors]

OBJECTIVE

To study the clinicopathologic features of malignant phyllodes tumors (PT) by histopathologic analyses, immunohistochemical profiling and DNA content assay, and evaluation of the clinical outcome.

METHODS

Ten patients with malignant PT from 1999 to 2013 who were treated by surgery were enrolled in this study. The morphologic characteristics were studied under light microscope, standard two-step EnVision method of immunohistochemical staining was used to assess the expression of CK5/6, CKpan, 34β E12, desmin, p63, ER-α, PR, Ki-67, CD34, SMA, p53, p16, bcl-2 and CD117 in the tumors. The corresponding paraffin blocks were also used for flow cytometric DNA content assay. These data were correlated with the follow-up results.

RESULTS

The median age of onset was 46.5 years old. The mean tumor size was 7.4 cm (2.0-25.0 cm). At the end of the follow-up period (22 to 125 months), there were tumor recurrences in 3/8 patients and the median time of recurrence was 24 months. Metastasis occurred in 3/8 patients who all died of the tumors. PT had heterogeneous histology, with stromal overgrowth with leaf-like projections, periductal stromal overgrowth, and most commonly, diffuse stromal overgrowth with sarcomatous differentiation. The mean positive index of Ki-67 was 11.4%. The stromal tumor cells were positive for CD34, SMA, p53, p16, and bcl-2 in 3/10, 9/10, 6/10, 8/10, and 4/10 cases, respectively. CD117,ER-α and PR were negative. Interpretable DNA histograms were obtained in nine cases with triploidy in two cases.

CONCLUSIONS

The diagnosis of malignant PT should be considered based on the diversity of growth patterns and heterogeneous histology.Ki-67 and CD34 are valuable diagnostic and prognostic factors in patients with malignant PT. Tumors with diffuse stromal overgrowth, heterologous elements, Ki-67 ≥ 20% or aneuploidy are more likely to metastasize.

c-Kit expression and mutations in phyllodes tumors of the breast

BACKGROUND

Phyllodes tumors (PTs) represent uncommon fibroepithelial lesions of the breast that express c-Kit and platelet-derived growth factor receptor-alpha, similar to gastrointestinal stromal tumors (GISTs). 'Activating' mutations in these genes underlie responsiveness of GISTs to imatinib. Standard treatment for breast PTs is wide local excision, with no role for targeted therapies.

PATIENTS AND METHODS

c-Kit (CD117) expression was investigated by immunohistochemistry in 17 cases of breast PTs. Fourteen of these cases were also subjected to KIT mutation analysis by dideoxynucleotide sequencing.

RESULTS

Five out of 17 (29%) tumors showed weak stromal staining for CD117. No previously described 'activating' mutations were found in exons 9, 11, 13, or 17 of the KIT gene. A silent germline point mutation was found in exon 17 of one case.

CONCLUSION

These data do not suggest a pathogenetic role for KIT in breast PTs. Inhibition of c-Kit signaling is unlikely to be helpful in this condition.

DNA methylation profiling of phyllodes and fibroadenoma tumours of the breast

Phyllodes tumours and cellular fibroadenomas are both fibroepithelial tumours of the breast. Phyllodes tumours, unlike fibroadenomas, have the ability to recur and metastasise. Although these lesions can be distinguished by their stromal cellularity, mitotic index, presence or absence of stromal overgrowth and cellular atypia, there is overlap and not infrequently a definitive diagnosis cannot be made, particularly on biopsy. We sought to evaluate whether DNA promoter methylation profiling using selected genes known to be methylated in cancer would allow us to learn more about the biology of these tumours, and whether it could identify methylation markers that could differentiate phyllodes tumours from fibroadenomas and/or distinguish phyllodes tumours of different grades. Methylation-sensitive high resolution melting (MS-HRM) was used to screen promoter DNA methylation changes in 86 phyllodes tumours (15 benign, 28 borderline, 43 malignant) and 26 fibroadenomas. A panel of 11 genes (RASSF1A, TWIST1, APC, WIF1, MGMT, MAL, RARβ, CDKN2A, CDH1, TP73 and MLH1) was tested. Methylation status was correlated with histology and with clinicopathological parameters. Five of the gene promoters showed some methylation in a proportion of phyllodes tumours; RASSF1A, 45.3%; TWIST1, 10.7%; APC, 4.1%; WIF1, 2.9% and MGMT, 1.3%. Only two genes showed any methylation in fibroadenomas usually at background levels; RASSF1A, 53.8% and MGMT, 8.3%. No CDKN2A methylation was observed in either tumour type, contrary to previous reports. Overall, the methylation patterns differed little from that which might be seen in normal cells. However, significant levels of methylation of RASSF1A (24.4%) and TWIST1 (7.1%) was observed in some phyllodes tumours. Elevated RASSF1A and/or TWIST1 methylation was significantly associated with phyllodes tumours compared with fibroadenomas (P = 0.02), TWIST1 methylation correlated with increasing malignancy in phyllodes tumours (P < 0.001). In conclusion, assessment of methylation of RASSF1A and TWIST1 may aid in the diagnosis of phyllodes tumours. The absence of frequent methylation in fibroadenomas supports a non-neoplastic origin.

Association of the BRCA1 missense variant R1699W with a malignant phyllodes tumor of the breast

Familial breast carcinomas that are attributable to BRCA1 or BRCA2 mutations have characteristic morphologic and immunhistochemical features. BRCA1-associated carcinomas are poorly differentiated infiltrating ductal carcinomas frequently exhibiting morphologic features of typical or atypical medullary carcinomas such as prominent lymphocytic infiltrate and pushing margins. We report on a patient carrying the deleterious BRCA1 germline mutation R1699W, who presented with a malignant phyllodes tumor of the breast. The re-investigation of archival material by a reference pathologist of the German Consortium for Hereditary Breast and Ovarian Cancer (GCHBOC) revealed BRCA-associated pronounced pushing margins. In a total of 618 unrelated index patients who are registered in the GCHBOC database, no other phyllodes tumor has been described, while 10 carriers of the R1699W mutant have been identified. We conclude that the histopathologic appearance of the phyllodes tumor indicates an association with the BRCA1 mutation R1699W although it is a rare event in BRCA-positive families.

Phyllodes tumors of the breast segregate in two groups according to genetic criteria

Phyllodes tumors are rare fibroepithelial tumors of the breast. The pathologic grading of phyllodes tumors based on the aspect of the stromal component, is divided into 2 or 3 grades according to the system used. To determine whether genetic markers could be of use for improving the classification of phyllodes tumors and to provide a better knowledge of the genetic alterations in these tumors, we analyzed chromosomal changes detected by comparative genomic hybridization (CGH) in comparison with histological data, in a series of 30 cases. Recurrent chromosome imbalances were observed in 55, 91 and 100% of benign, borderline and malignant phyllodes tumors, respectively. The mean number of chromosome changes was one in benign, six in borderline, and six in malignant phyllodes tumors. Most frequent genetic imbalances were +1q (12/30), -13q (7/30), -6q (9/30), +5 (9/30) and -10p (8/30). Gains of 1q, present in only one of nine benign tumors, were found in 11/21 (51%) borderline or malignant tumors. Losses of 13q have 13q14.2 as smallest region of overlap, suggesting that the RB1 gene could be the target of deletions. Amplifications of 12q14, involving the MDM2 locus, and of 8p24, involving the MYC gene, were observed in one case each. Borderline and malignant phyllodes tumors could not be differentiated on the basis of their genomic imbalances (presence and number of chromosomal changes, presence of 1q gain and/or 13q loss). Conversely, benign tumors could be significantly differentiated from the group composed of borderline and malignant tumors (P<0.01). This study reveals two distinct patterns of genomic imbalance in phyllodes tumors: benign, with none or a few chromosome changes and malignant, with numerous recurrent chromosomal changes, in particular 1q gain and 13q loss. Helpful additional pathological criteria for differentiating the two genetic groups of phyllodes tumors are the nuclear size and the mitotic rate.

Amplifications of EGFR gene and protein expression of EGFR, Her-2/neu, c-kit, and androgen receptor in phyllodes tumor of the prostate

Phyllodes tumor of the prostate is a rare neoplasm with an unpredictable clinical behavior. It may undergo early recurrence with sarcomatous transformation or may even metastasize. Because targeted therapies have shown great success against several malignancies, there is hope that these same therapies may show similar promise in the treatment of other neoplasms. This study was undertaken to investigate both amplification of the epidermal growth factor receptor (EGFR) gene by fluorescence in situ hybridization and the overexpression of EGFR, Her-2/neu, CD117 (c-kit), and androgen receptor by immunohistochemical staining in a series of 11 phyllodes tumors of the prostate. In the stromal elements, EGFR gene amplification was present in four of 11 tumors and polysomy chromosome 7 was present in two of 11 tumors. No amplification was present in the epithelial components. Only one of 11 tumors had polysomy of chromosome 7 in the epithelial components. Immunohistochemically, in the stromal components, EGFR expression was demonstrable in four of 11 tumors and androgen receptor was demonstrated in six of 10 tumors. Neither Her-2/neu nor c-kit expression was seen in the stromal components of any of the 11 tumors. In the epithelial components, EGFR expression was present in all 11 tumors with strong staining in the basal cell layers and weak or no staining in luminal epithelium; androgen receptor expression was seen in seven of 10 tumors; Her-2/neu was weakly positive in four of 11 tumors; and c-kit expression was present focally and weakly in two of 11 cases with only 2-5% of cells staining. The highest staining intensity and the highest percentage of positively staining cells were seen with EGFR immunostaining in both the stromal and epithelial (mainly basal cells) components. Androgen receptor staining showed the next highest staining intensity and percentage of positive cells in both components. Her-2/neu and c-kit were only weakly or infrequently expressed in the epithelial components of prostatic phyllodes tumors. Our data indicate that EGFR and androgen receptor are frequently and strongly expressed in both epithelial and stromal components of prostatic phyllodes tumors. EGFR gene amplification is frequently present in prostatic phyllodes tumors and may account for one of the mechanisms leading to protein overexpression in some but not all cases. Anti-EGFR and/or antiandrogen agents may be potentially useful for management of patients with tumors expressing EGFR and/or androgen receptor.

Genome-wide analysis for loss of heterozygosity in primary and recurrent phyllodes tumor and fibroadenoma of breast using single nucleotide polymorphism arrays

Phyllodes tumors of the breast are biphasic stromal and epithelial tumors histologically similar to benign fibroadenomas, but with a neoplastic stromal component. In contrast to fibroadenoma, phyllodes tumors can recur and be locally aggressive or be malignant. This study uses SNP array analysis to present a genome-wide map of loss of heterozygosity (LOH) in a cohort of phyllodes tumors and fibroadenomas. LOH is frequent and sometimes extensive in phyllodes tumors, but is rarely seen in fibroadenomas. There is heterogeneity between phyllodes tumors of different patients and no one LOH marker identifies a majority of these lesions. However, a subset of LOH loci occur in multiple cases of phyllodes tumors and are not found in fibroadenomas. Primary phyllodes tumors and paired recurrences from the same patient share common regions of LOH. In contrast, metachronous fibroadenomas from the same patient have different LOH patterns with no indication of a shared origin. Specific LOH loci may be associated with pathologic progression in recurrent phyllodes tumors. In a single case of phyllodes tumor containing a malignant epithelial component the malignant epithelium and stroma partially share an LOH genotype, suggesting a common precursor cell for the biphasic malignant components.

Estrogen receptor-beta is expressed in stromal cells of fibroadenoma and phyllodes tumors of the breast

An estrogen dependency has been suggested for the growth of fibroadenomas: however, thus far, none of the steroid hormone receptors acting on breast tissues has been demonstrated in the stroma of breast fibroepithelial lesions. In this study, the expression of estrogen receptor (ER)-alpha and -beta was investigated by immunohistochemistry in 33 fibroadenomas and in 30 benign, three borderline and seven malignant phyllodes tumors, all with spindle cell growth and in one distant metastasis. In addition, the presence of ER-beta mRNA and its variants was evaluated by RT-PCR in microdissected stroma. The possible correlation between hormone receptor expression and differentiation processes of stromal cells was investigated by smooth muscle actin and calponin immunostaining. ER-beta was the only hormone receptor expressed by stroma of fibroadenomas and phyllodes tumors, both at protein and mRNA level. The highest percentage of ER-beta was observed in fibroadenomas with cellular stroma and in phyllodes tumors. In both lesions, ER-beta-positive stromal cells showed expression of smooth muscle actin and/or calponin, as demonstrated by double immunostaining. In addition, the mean age at diagnosis was significantly lower in patients with ER-beta-positive vs ER-beta-negative fibroadenomas. In contrast, in phyllodes tumors, ER-beta expression was higher in older patients. In conclusion, (i) only ER-beta is detected in the stroma of fibroadenomas and phyllodes tumors; (ii) its expression correlates with the expression of smooth muscle markers and suggests a role of ER-beta in myofibroblastic differentiation of stromal cells. These two results, together with the young age of patients carrying fibroadenomas with highly ER-beta-positive stroma cells, may further indicate a hormone-receptor mechanism involved in regulating the growth of fibroadenomas. Conversely, the older age of patients with ER-beta-rich phyllodes tumors suggests that mechanisms, probably independent from estrogen stimulation, act on the growth of these tumors.

Differential expression of glucocorticoid receptor in human breast tissues and related neoplasms

Glucocorticoid receptor (GR) is a steroid hormone receptor that has been shown to play important roles in mammary development and differentiation, and has been implicated in breast tumourigenesis, but its precise biological significance in mammary pathophysiology remains unclear. In order to generate a comprehensive expression profile for GR in normal versus neoplastic breast tissues, GR expression was investigated in situ in 400 human breast tissue samples, comprising normal tissue and a range of benign, pre-invasive, and invasive lesions, using immunohistochemical assays. The novel expression of GR in myoepithelium, not observed in luminal epithelium, not only demonstrates expression patterns exclusive to the alpha form of oestrogen receptor and progesterone receptor and suggests distinctive functions between GR and these two important steroid hormone receptors in the breast, but may also indicate unique physiological and perhaps pathological roles for the myoepithelium in mediating the effects of glucocorticoid hormones in the breast. The strong expression of GR in metaplastic carcinomas (94.4%) and malignant phyllodes tumours (92.3%) suggests a pathogenetic role for GR, and implies that targeting GR in these tumours may have potential therapeutic application. However, studies on the roles of GR in mammary carcinogenesis should be interpreted with great caution, based on the lack of GR expression in cancer cells in the great majority (98.2%) of non-metaplastic carcinomas, which has gone unnoticed in previous studies. This marked discrepancy warrants a re-examination of the biological roles of GR in the pathophysiology of breast malignancy. The lack of methylation in the promoter region of the GR gene in all 118 non-metaplastic carcinomas, as demonstrated by methylation-specific PCR and bisulphite DNA sequencing analysis, indicates that methylation is less likely to play a role in the reduction of GR expression in non-metaplastic carcinoma of the breast.

Amplifications of the epidermal growth factor receptor gene (egfr) are common in phyllodes tumors of the breast and are associated with tumor progression

Phyllodes tumors of the breast are rare biphasic tumors with the potential for invasion and metastatic spread. An important role of the epidermal growth factor receptor (EGFR) in phyllodes tumors has been proposed. However, detailed pathogenetic mechanisms remained unclear. We investigated 58 phyllodes tumors of the breast (40 benign, 10 borderline and eight malignant) by means of egfr fluorescence in situ hybridization (FISH) and gene dosage PCR for a regulatory sequence within intron 1 of egfr. Immunohistochemical staining was performed for EGFR, p16, p21, p27, p53, c-myc, Cyclin A, Cyclin D1, Cyclin E, c-kit and Ki67. Immunopositivity for EGFR was detected in 19% of phyllodes tumors (75% of all malignant tumors) in stromal tumor cells but not in the epithelial component. Whole-gene amplifications were seen by FISH in 15.8% (in stromal cells only) and intron 1 amplifications by gene dosage PCR in as much as 41.8% of all phyllodes tumors. Significant correlations were seen between tumor grade on the one hand and EGFR overexpression (P=0.001) and intron 1 amplifications (P<0.05) on the other. EGFR overexpression further correlated positively with immunohistochemical staining for p53, p16, Cyclin A, Cyclin E, Ki67 and c-kit. Presence of intron 1 amplifications correlated with p16 (P<0.01), p21 (P=0.009) and p53 immunoreactivity (P<0.001). Neither EGFR overexpression nor whole-gene amplification was observed in a control series of 167 fibroadenomas and only one of 43 (2.3%) exhibited intron 1 amplification in gene dosage PCR. In conclusion, our results show for the first time that activating mutations in and overexpression of egfr are associated with the progression in grade of phyllodes tumors of the breast. The observed association between intron 1 amplification and overexpression of EGFR provides further insight into regulation mechanisms of EGFR overexpression.

Molecular genetic evidence for different clonal origins of epithelial and stromal components of phyllodes tumor of the prostate

Phyllodes tumor of the prostate is a rare neoplasm, composed of epithelium-lined cysts and channels embedded in a variably cellular stroma. The pathogenetic relationship of the epithelium and stroma is unknown and whether each is a clonal neoplastic element is uncertain. We studied the clonality of phyllodes tumors from six patients who underwent either enucleation or transurethral resection as their initial treatment. This was followed by total prostatectomy in three of the patients. Laser-assisted microdissection was performed to extract epithelial and stromal components of phyllodes tumor from formalin-fixed, paraffin-embedded tissue. Polymerase chain reaction was used to amplify genomic DNA at specific loci on chromosome 7q31 (D7S522), 8p21.3-q11.1 (D8S133, D8S137), 8p22 (D8S261), 10q23 (D10S168, D10S571), 17p13 (TP53), 16q23.2 (D16S507), 12q11-12 (D12S264), 17q (D17S855), 18p11.22-p11 (D18S53), and 22q11.2 (D22S264). In each tumor, stroma and epithelium were analyzed separately. Gel electrophoresis with autoradiography was used to detect loss of heterozygosity. All tumors showed allelic loss in one or more loci of both the epithelial and stromal components. The frequency of allelic loss in the epithelial component was 2 of 5 (40%) at D7S522, 2 of 6 (33%) at D8S133, 1 of 5 (20%) at D8S137, 3 of 6 (50%) at D8S261, 4 of 4 (100%) at D10S168, 4 of 6 (67%) at TP53, 2 of 6 (33%) at D10S571, 6 of 6 (100%) at D16S507, 1 of 5 (20%) at D12S264, 1 of 6 (17%) at D17S855, 2 of 6 (33%) at D18S53, and 2 of 5 (40%) at D22S264. The frequency of allelic loss in the stromal component was 2 of 5 (40%) at D7S522, 1 of 6 (17%) at D8S133, 2 of 5 (40%) at D8S137, 3 of 6 (50%) at D8S261, 1 of 4 (25%) at D10S168, 3 of 6 (50%) at TP53, 2 of 6 (33%) at D10S571, 3 of 6 (50%) at D16S507, 1 of 5 (20%) at D12S264, 0 of 6 (0%) at D17S855, 1 of 6 (17%) at D18S53, and 0 of 5 (0%) at D22S264. The pattern of allelic loss is significantly different in both stroma and epithelium statistically; completely concordant allelic loss patterns were not seen in any tumor examined. Our data demonstrate that both epithelial and stromal components of phyllodes tumor of the prostate are clonal, supporting the hypothesis that both elements are neoplastic. While both epithelium and stroma are clonal proliferations, they appear to have different clonal origins.

p63 Expression in Breast Cancer

p63, a member of the p53 gene family, is involved in cellular differentiation and is expressed in the nuclei of myoepithelial cells of normal breast ducts and lobules. Although p63 has been reported in metaplastic carcinomas of the breast, its expression pattern in breast carcinomas and sarcomas has not been fully characterized, and its potential diagnostic utility has not been defined. In this study, we determined p63 expression in a large number of breast carcinomas, including metaplastic carcinomas, and in Phyllodes tumors and sarcomas. We examined 189 invasive breast carcinomas, including 15 metaplastic carcinomas, as well as 10 Phyllodes tumors, and 5 pure sarcomas of the breast for pattern and intensity of p63 staining using an anti-p63 antibody (clone 4A4, Neomarkers). p63 was strongly expressed in 13 of 15 metaplastic carcinomas (86.7%). p63 was positive in all the metaplastic carcinomas with spindle cell and/or squamous differentiation (12 of 12), and in 1 of 3 metaplastic carcinomas with cartilage foci. In stark contrast, only 1 of 174 (0.6%) nonmetaplastic invasive carcinomas was positive for p63. All Phyllodes tumors and sarcomas were consistently negative for p63 expression. The sensitivity and specificity of p63 as a diagnostic marker for metaplastic carcinoma was 86.7% and 99.4%, respectively. We propose the inclusion of p63 as part of the diagnostic workup of challenging spindle cell tumors of the breast as a highly specific marker for metaplastic carcinomas.

Cytogenetic findings in phyllodes tumor and fibroadenomas of the breast

The cytogenetic data on fibroadenomas and cystosarcoma phyllodes tumor of the breast, which are both biphasic breast tumors composed of epithelial and stromal components, are quite limited. In this study, we report on clonal chromosomal alterations in three fibroadenomas and one cystosarcoma phyllodes analyzed by GTG banding. The fibroadenomas presented mostly numerical abnormalities involving chromosomes 16, 18, and 21. One case presented a deletion on 17p. The cystosarcoma phyllodes presented numerous numerical abnormalities, mostly chromosome gains, and several marker chromosomes.

Malignant phyllodes tumours show stromal overexpression of c-myc and c-kit

Phyllodes tumours are fibroepithelial neoplasms of the breast, the stroma of which can undergo malignant progression to sarcoma. The frequency of malignant lesions varies in different series from 5% to 30%. The aim of this study was to elucidate potential molecular mechanisms in the progression to malignancy in phyllodes tumours. c-myc and c-kit were studied at the protein, RNA(c-myc only) and DNA level. We chose to study c-myc as we have previously shown that Wnt signalling is important in benign, but not malignant, phyllodes tumours. If c-myc is constitutively activated in malignant tumours, this may provide an explanation for why the Wnt pathway is no longer important in these tumours. c-kit is a membrane-bound tyrosine kinase receptor and overexpression is characteristic of gastrointestinal stromal tumours. A previous report suggested that this may also be the case in malignant phyllodes tumours, and we wished to confirm this. We assessed expression of c-myc and c-kit in 30 phyllodes tumours (10 malignant) using in situ hybridization (c-myc) and immunohistochemistry (c-myc and c-kit). 9/10 malignant tumours showed c-myc expression in the stroma, compared to 7/20 benign tumours (p = 0.006, Fisher's exact test). Stromal c-kit expression was found in 5/10 malignant tumours, compared to 1/20 benign tumours (p = 0.008, Fisher's exact test). One tumour had high-level amplification of c-myc, but we found no evidence of mutations of c-kit. We hypothesize that the overexpression of c-myc may drive stromal proliferation in malignant phyllodes tumours, and that c-kit overexpression contributes to the growth of these lesions. c-kit may also be a new therapeutic target in these tumours.

Gain in 1q is a common abnormality in phyllodes tumours of the breast

We studied DNA copy number changes by CGH and allelic imbalance (AI) on 3p by LOH analysis on 22 phyllodes tumours (PT) of the breast in order to gain insight into the genetic basis of tumour progression in PT. Copy number changes were observed in 14 cases (63%). Gain in 1q with 1q21-23 as the minimal overlapping area was seen in 12 cases (55%). The gain was observed both in benign and malignant tumours. Our study did not reveal any DNA copy number changes or allelic loss on 3p. The results suggest that DNA copy number changes are not associated with the histological grade or clinical behaviour of PT and the chromosomal changes on 3p appear to be rare. Colour figure can be viewed on http://www.esacp.org/acp/2003/25-2/jee.htm

Complex karyotype in a low grade phyllodes tumor of the breast

Cytogenetic analysis of a phyllodes tumor of low grade malignancy disclosed the karyotype 52-55,XX, -1,+5,+7,+9,+10,+11,-15,+18,-19,+20,der(21)t(1;21)(p13;q22),+mar1x 2-4,+mar2[cp18]/46,XX. This study shows that a complex chromosome karyotype can be found in low-grade phyllodes tumors and is not necessarily a sign of extreme malignancy of these neoplasms.

Morphological types of breast cancer in family members and multiple primary tumours: is morphology genetically determined?

BACKGROUND

We conducted the present study to determine whether breast cancer morphology is genetically determined.

METHODS

Using the nationwide Swedish Family Cancer Database, which includes data on 10.2 million individuals and over 25,000 morphology-specific breast cancers, we followed morphological types in familial cancers between mothers and daughters and between sisters. Additionally, we recorded morphological data in women who presented with two primary breast cancers and in those who presented with an invasive and in situ breast cancer. We used kappa statistics to examine the association between genetics and morphology. A kappa value of 0 indicates that the process is random and a value of 1 indicates that it is completely determined (i.e. genetic); values between 0.40 and 0.60 are considered to indicate a moderately determined process.

RESULTS

The study sample included a total of 25,730 first and 3394 second invasive breast cancers, and 2990 in situ breast cancers. Ductal, lobular, tubuloductal and comedo were the most common invasive types. We identified 164 mother-daughter pairs with breast cancer of a defined morphology, yielding a low kappa value of 0.08. Among 100 sister pairs the kappa value was 0.002. In individuals with two primary breast cancers the kappa values were 0.22 and 0.01 for two invasive and in situ-invasive pairs, respectively. However, for a tumour with a subsequent tumour detected in the contralateral breast less than 1 year later the kappa value was 0.47.

CONCLUSION

The data suggest that breast cancer morphology is not genetically determined. However, because of mixed morphologies and the overwhelming prevalence of ductal morphology, the results for rare morphologies should be interpreted with caution.

Phyllodes tumors of the breast: correlation of nucleolar organizer regions with histopathological malignancy grading, flow cytometric DNA analysis and clinical outcome

To examine whether nucleolar organizer regions detected by argyrophilia (Ag-NOR counts) can be used as a prognostic indicator in phyllodes tumors of the breast, and to compare its usefulness with that of DNA flow cytometric analysis, 28 cases of breast phyllodes tumors (including 15 benign, two borderline and 11 malignant tumors) were subjected to Ag-NOR staining and counting as well as DNA flow cytometric analysis. S-phase fraction and DNA ploidy analysis showed useful trends for improving outcome predictions in malignant phyllodes tumors. However, high Ag-NOR counts were significant in predicting survival status (P = 0.013) and reached near statistical significance in predicting survival times (P = 0.07). In predicting survival status, results for Ag-NOR counts were significantly better than those for ploidy analysis (P = 0.02) and S-phase fraction (P < 0.01). Only S-phase fraction was significantly predictive of survival times (P = 0.025). It is concluded that Ag-NOR counts and DNA flow cytometric analysis, easily performed using paraffin sections, give information that can improve predictions made by histopathological classification. Ag-NOR counts are significant in predicting survival in the presence of histopathological features of malignancy.

p53 protein expression and gene mutation in phyllodes tumors of the breast

The malignant potential of mammary phyllodes tumors is difficult to assess on initial pathologic examination. Studies on the p53 tumor suppressor gene have shown that it has an important role in the development of a variety of malignancies, yet the specific contribution to the pathogenesis and development of the malignant potential of phyllodes tumor is largely unknown. We studied p53 protein expression in 25 cases of phyllodes tumors histologically classified as either malignant (12 cases) or benign (13 cases). Using microdissection approach, we also analyzed the p53 gene sequence in a case that demonstrated progression from benign to malignant phenotype. Nuclear p53 staining was detected in various proportions (1-90%) of neoplastic stromal cells of malignant tumors. No staining was found in benign tumors. Progression from benign to malignant phenotype was associated with a significant increase in the accumulation of p53 (more than 20 times). This was caused by an underlying missense mutation in exon 7, resulting in a change from Arg248 to Trp248 in the malignant component of the tumor. Stromal p53 over-expression was observed only in neoplasms histologically classified as malignant and was associated with an increased proliferation index (MIB-1 staining). These two markers may be used as useful adjuncts in the diagnosis of malignancy in difficult cases or when only a limited sample size is available. Somatic mutation in exon 7 of p53 gene in malignant phyllodes tumor points toward the importance of p53 in the malignant transformation of phyllodes tumors.

Pathologic, immunohistochemical, and molecular features of benign and malignant phyllodes tumors of the breast

The histologic distinction between benign and malignant Phyllodes tumors (PT) is often difficult and arbitrary. We analyzed a group of benign and malignant PT to determine whether specific histologic features and expression of Ki-67 and p53 could be useful in distinguishing benign PT from malignant tumors. We also determined whether deletions in Chromosome 3p at the FHIT and hMLH1 loci are common abnormalities in PT. Twenty PT were histologically classified as benign (7) or malignant (13). Seven of the malignant PT were low grade, and six were high grade. Ki-67 and p53 immunohistochemistry was performed on all tumors and analyzed for the stromal and for the epithelial component. PCR-based loss of heterozygosity analyses were performed with the following markers on Chromosome 3p: D3S1478 (3p21.2--21.3), D3S1289 (3p21.1--21.2), and D3S1295 (3p14.3--21.1). The distribution of immunoreactivity for Ki-67 was analyzed by quantifying the percentage of positive nuclei and expressed as the labeling index (LI). Patients' ages ranged from 13 to 71 years (median: 51 y). After a mean follow-up period of 8 years, none of the PT metastasized, whereas three recurred locally. Although malignant PT were larger than benign PT (means, 7.1 versus 4.3 cm), this difference was not statistically significant. Five tumors had infiltrating margins, and 14 were circumscribed. The Ki-67 LI in low-grade malignant PT (16 +/- 25.5) was significantly higher than that in benign PT (3.6 +/- 4.8), whereas the LI in the high-grade malignant PT group (50 +/- 21.9) was significantly higher than that in low-grade malignant tumors (P =.012). The Ki-67 LI in the three tumors that recurred was less than 10%. Two of seven (29%) benign PT were focally positive for p53, whereas four of seven (57%) low-grade malignant and three of six (50%) high-grade malignant PT were diffusely positive for p53. The three tumors that recurred initially were histologically benign, as were two of the recurrences. One recurrent tumor evolved to a high-grade malignant PT. Margins were greater than 1 cm in all tumors except four, three of which recurred locally. No allelic loss of 3p was found. In summary, Ki-67 expression may assist in distinguishing benign from malignant PT in diagnostically difficult cases. 3p deletions do not play a significant role in the development of these tumors. Neither Ki-67 nor p53 can reliably predict recurrence. Histologically high-grade malignant PT have a favorable prognosis if widely excised. We emphasize the importance of adequate margins in the treatment of benign and malignant PT.

Prognostic evaluation of proliferative activity and DNA content in the phyllodes tumor of the breast: immunohistochemical and flow cytometric study of 118 cases

The goal of this study was the prognostic evaluation of histology, mitotic rate, S-phase fraction (SPF) and expression of proliferative antigen Ki67 and p53 protein in phyllodes tumor of the breast. The study was performed in the group of 118 patients with phyllodes tumor treated by surgery from 1952 to 1998. Mitotic rate was assessed on the representative histological specimens. Expressions of Ki67 and p53 were evaluated by immunohistochemistry on a section from the corresponding paraffin blocks which were also used for flow cytometric DNA evaluation. Histologically, 52 tumors were benign (LGM), 24 borderline malignancies (BM) while among 42 malignant tumors, 20 were monomorphous (HGM) and the remaining 22 revealed heterologic elements (HGH). Tumor recurrencies occurred in 17 patients, predominantly during the first three years after surgery, and 13 patients died of the tumor (1 BM, 12 both malignant variants). Multivariate analysis demonstrated mitotic rate, SPF and p53 expression as independent prognostic parameters for the disease-free survival. Histological tumor type and expression of Ki67 influenced independently the overall survival. In conclusion, the histological type of tumor phyllodes forms the basis for the prognosis of clinical outcome, but the indicators of the proliferative activity, especially Ki67 index, are valuable prognostic factors among patients with malignant variant of phyllodes tumor of the breast. Expression of the p53 protein in tumor cells could be also useful when the percentage of cells and intensity of expression are considered.

CD34, CD117, and actin expression in phyllodes tumor of the breast

BACKGROUND

This study investigated the immunophenotypic patterns of CD34, CD117 (a product of the c-kit proto-oncogene), and actin (HHF35) in benign and malignant phyllodes tumors (PTs). We correlated the expression of CD34, CD117, and actin with histopathological grade.

MATERIALS AND RESULTS

We analyzed 19 cases (7 benign and 12 malignant cases) of PTs using immunohistochemical analysis. Six of 7 benign PT stromal lesions stained positively for CD34, while only 3 of 12 cases of malignant PT were focally CD34 positive (P = 0.0106). Only 1 of the 7 benign PTs stromal lesions expressed CD117. Nine of the malignant PTs were composed CD117-positive fibroblasts. This result demonstrated that CD117 expression is associated with the malignant potential of PTs (P = 0. 0106). Actin (HHF-35) expression was found in 8 of 12 cases of malignant PTs (P = 0.027), but in only 1 of 7 cases of benign PTs. Actin expression was significantly (P = 0.04) correlated to frequent mitotic activity (>5 mitoses per 10 high-power fields). The immunophenotypic markers were not related to tumor size. Additionally, we sequenced part of the juxtamembrane region of the c-kit proto-oncogene and found point mutations in two malignant PTs.

CONCLUSION

Our results demonstrated that expression of CD34 was associated with benign PTs, while CD117 and actin were preferentially expressed in malignant PTs. Our results implied that these immunohistological markers might be used for the histopathological grading of PTs.

Phyllodes tumor of the breast: EGFR family expression and relation to clinicopathological features

The expression of EGFR family members was examined by immunohistochemistry in 22 phyllodes tumors, and the results were evaluated together with immunohistochemical findings for proliferation markers Ki67 and BM28, and the tumor suppressor gene product p53. Light and electron microscopy were performed in all cases. Clinical information was obtained from the medial records. We did find that expression of EG FR, c-erbB-3 and c-erbB-4 proteins could be detected in the neoplastic mesenchymal cells, and that the expression increased with increasing malignancy. Increased expressions of Ki67, BM28, p53 and EGFR family members in neoplastic cells were associated with malignancy and unfavorable clinical course. Furthermore, the expression of ER-alpha and PR in the epithelial cells of phyllodes tumors was increased compared to that in normal breast epithelium. Finally, the application of electron microscopy helped to identify a group of malignant tumors, revealing neoplastic cells with characteristic nuclear indentations, as well as an increasing number of myofibroblasts.

Cytogenetics, immunostaining for fibroblast growth factors, p53 sequencing, and clinical features of two cases of cystosarcoma phyllodes

BACKGROUND

We present cytogenetics and fibroblast growth factor immunohistochemistry in one case of cystosarcoma phyllodes with localized disease and one with metastatic spread. The p53 gene was sequenced in the malignant case.

METHODS AND RESULTS

Karyotype analysis used trypsin-Giemsa banding. Immunohistochemistry of FGF1, FGF2, FGFR1 and p53 used avidin-biotin detection of the primary antibody. One case had a mosaic female karyotype and three clones: one normal, one with trisomy 7, and one with both trisomy 5 and a rearranged chromosome 1. In the second case, a resected pulmonary metastasis had the karyotype 43-47,XX,+mar1,+mar2[6]/43-46,XX, +del(7)(p10)[3],+mar2[1][cp3]/46,XX[10]. These tumors expressed FGF1, FGF2, and FGFR1. The malignant case showed immunostaining for p53 protein, but a wild-type gene sequence.

CONCLUSION

The karyotype of cystosarcoma phyllodes is complex, with wide case-to-case variation. These tumors express members of the FGF family. Metastatic behavior can occur in the presence of a wild-type p53 gene.

Detection of alterations in chromosomes 16 and 1 by fluorescence in situ hybridization in breast tumors cytologically or histologically equivocal for malignancy

Structural and numerical alterations, and fusion of chromosomes 16 and 1 have been shown to occur frequently in low-grade breast carcinoma, but not in benign papilloma by fluorescence in situ hybridization (FISH). We carried out FISH analysis of 11 benign tumors and 3 breast tumors for which the preoperative diagnosis was equivocal for cancer. In 11 benign lesions and 1 benign phyllode tumor which was cytologically equivocal for malignancy, alteration of the chromosome 16 or 1 signal was not detected as a predominant cell clone. On the other hand, in 1 grade 1 invasive ductal carcinoma which was judged as equivocal for malignancy and 1 marked adenosis with atypia which was judged as malignant by fine-needle aspiration cytology, the majority of constituent tumor cells showed fusion of chromosomes 16 and 1. Detection of alterations in chromosomes 16 and 1 as a predominant clone was suggested to be an indicator of lesion malignancy even though the grade of malignancy may not be high. As a supportive diagnostic procedure, FISH analysis may give information about the nature of lesions, when the lesions are clinically or pathologically equivocal for cancer.

Cytofluorometric nuclear DNA content analysis of breast tissues after frozen section diagnosis

OBJECTIVE

To establish a suitable method for measurement of nuclear DNA content in breast tissues from frozen storage after frozen section diagnosis.

STUDY DESIGN

For fundamental research, rat liver samples preserved in a deep freezer were used. Four protocols were used (1. fixation with 70% ethanol followed by naked nuclei preparation; 2. fixation with 10% neutral buffered formalin followed by naked nuclei preparation; 3. preparation for naked nuclei prior to fixation with 70% ethanol; and 4. preparation for naked nuclei prior to fixation with 70% neutral buffered formalin). For clinical research, 13 separate fresh frozen breast tissue samples were analyzed after frozen section diagnosis. One contained a malignant phyllodes tumor (MPT) consisting of 2 components, benign epithelial cells and malignant stromal cells; 3 were benign tumors containing fibroadenoma; and 9 cases were carcinomas, consisting of 5 scirrhous, 3 papillotubular and 1 mucinous.

RESULTS

Protocols 1, 2 and 3 were not suitable methods for our purpose because remaining cytoplasm or cohesive nuclei were observed. In protocol 4 the cytoplasm was completely undetectable, and nuclei were suitably separated for nuclear DNA content measurement. Benign epithelial cell component nuclei presented a diploid pattern, and the malignant stromal cell component nuclei indicated a euploid pattern in MPT. All 3 cases of benign constituents in fibroadenoma showed a diploid pattern, as did the 3 carcinoma cases (1 mucinous, 1 scirrhous and 1 papillary). Four scirrhous and 2 papillary carcinomas showed an aneuploid pattern.

CONCLUSION

Our findings show that it is possible to measure nuclear DNA content of human frozen storage tissues after frozen section diagnosis.

Molecular assessment of clonality leads to the identification of a new germ line TP53 mutation associated with malignant cystosarcoma phyllodes and soft tissue sarcoma

Cystosarcoma phyllodes (CSP) is a rare breast neoplasm composed of stromal and epithelial elements. It usually runs a benign course but it may metastasize. In a 31-year-old patient with recurring CSP, a mesenchymal tumor in the leg developed. The question arose whether the latter tumor could be a metastasis from the CSP, which would have major treatment consequences. The problem was addressed using molecular methods, i.e., comparison of the pattern of polymorphic repeat markers on chromosome 17p as well as single strand conformation polymorphism analysis and sequencing of exons 5 to 8 of the TP53 gene in both tumor and normal tissue. An identical pattern of loss of heterozygosity in both breast tumors was demonstrated, but a different pattern was shown in the tumor in the leg. This led to the conclusion that the latter tumor had to be a new primary tumor. A mutation in codon 162 of the TP53 gene was found in the tumor tissue as well as in the normal tissue of this patient. This germ line mutation leads to the replacement of isoleucine by asparagine and most likely has functional consequences. In all four examined tumors of this patient, the normal TP53 allele was lost. This is strong evidence that this germ line TP53 mutation causes the genesis of these two rare primary mesenchymal tumors in this young patient. The current study exemplifies the power of molecular diagnostic methods in investigating the specific clinical problem of clonal relation between two separate tumors. The germ line mutation found in codon 162 of the TP53 gene and the association with cystosarcoma phyllodes have not been described previously.

An important subgroup of phyllodes tumors of the breast is characterized by rearrangements of chromosomes 1q and 10q

From a study of 10 cases of our own and 13 cases of the literature, anomalies of chromosome 1q and 10q emerge as consistently occurring changes in an important subgroup of phyllodes tumors of the breast. Anomalies of chromosome 1 were the most frequent ones, with a gain of 1q material, and histologically the tumors in which these anomalies were found were low grade malignancies. Structural changes of 10q emerged as the second most frequent chromosome change.

Monoclonality in fibroadenomas with complex histology and phyllodal features

Fibroadenoma is a common cause of benign breast masses in young women. These women have a slightly increased risk of subsequent breast cancer, particularly if their tumors have complex histologic patterns. We assessed monoclonality in fibroadenomas and correlated the results with histologic analysis. We performed a clonal analysis of 52 fibroadenomas from 43 patients using X-chromosome inactivation studies. The cases included fibroadenomas with complex and simple histology. Areas examined were predominantly stroma but epithelium was also present. DNA was isolated from paraffin-embedded tissue and was subjected to polymerase chain reaction amplification of the human androgen receptor gene with and without predigestion of the DNA with Hha 1. If a monoclonal process was identified, the epithelial and stromal components were subsequently microdissected and reanalyzed. 36/43 (83.7%) women were heterozygous. We studied 45 tumors in these 36 informative women. 1/20 (5% complex fibroadenomas and 1/25 (4%) simple fibroadenomas were monoclonal. The epithelial component of both monoclonal fibroadenomas was polyclonal. The one monoclonal simple fibroadenoma was also the only one with mixed features to contain a phyllodes component. In this case, monoclonality was found in the stroma of both the fibroadenoma and phyllodes regions. Monoclonality has been previously associated with phyllodes phenotype, but not with fibroadenomas, except for 3 fibroadenomas that recurred as phyllodes tumor. We report that monoclonality may also be seen occasionally in complex fibroadenomas, and was found in a tumors with mixed fibroadenoma/phyllodes features without clinical recurrence for 4 years.

Cytogenetic findings in phyllodes tumors of the breast: karyotypic complexity differentiates between malignant and benign tumors

Clonal karyotypic abnormalities were detected in short-term cell cultures from six phyllodes tumors of the breast. Whereas all five benign tumors had simple chromosomal changes, the highly malignant one had a near-triploid stemline, indicating that karyotypic complexity is a marker of malignancy in phyllodes tumors. Interstitial deletions of the short arm of chromosome 3, del(3)(p12p14) and del(3)(p21p23),were the only aberrations in two benign tumors. Cytogenetic polyclonality was detected in three benign tumors: two had cytogenetically unrelated clones, whereas the third had three different, karyotypically related cell populations as evidence of clonal evolution. The finding of clonal chromosome abnormalities in both the epithelial and connective tissue components of the phyllodes tumors indicates that they are genuinely biphasic, that is, that both components are part of the neoplastic parenchyma.

Phyllodes tumors of the breast analyzed by comparative genomic hybridization and association of increased 1q copy number with stromal overgrowth and recurrence

Phyllodes tumors are rare neoplasms of the breast. Although they contain both epithelial and stromal components they are considered to be stromally derived lesions. The chromosomal copy number changes were determined in 19 well characterized samples from 18 patients using comparative genomic hybridization. Most chromosomes were involved and generally the gains and losses were similar to those found in breast cancer with the exception that the phyllodes tumors showed no evidence of genomic amplification. The one recurrent sample analyzed had the same imbalances as the original tumor. Frequent changes were gain of 1q (7/18) and loss of 3p (6/18), followed by gain of 7q (4/18) and loss of 6q (4/18) and 3q (3/18). Gain of 1q material was significantly associated with histologically defined stromal overgrowth (P = 0.011). In addition, all the cases with gain of 1q material, without 1p gain, had a clinical history of recurrence. Only one case without 1q gain had a recurrence and this had loss of the X chromosome as the sole abnormality. Increased copy number of 1q material in the phyllodes tumors studied, in one case restricted to 1q24-32, was associated with recurrence (P = 0.00365) and might therefore be considered as an indicator of local aggressiveness requiring more radical treatment.

Bilateral breast tumors, malignant phyllodes tumor and invasive lobular carcinoma in a 46,XX/46,XY mosaic female with family history of breast cancer

Bilateral breast tumors, a malignant phyllodes tumor in the right breast and an invasive lobular carcinoma in the left breast, occurred in a 47-year-old woman with 46XX/46XY mosaic karyotype in her peripheral blood lymphocytes and intersex external genitalia. Postmortem examination revealed bilateral ovotestis. Three of the patient's sisters also had breast cancer. In situ hybridization with a Y-specific probe revealed Y-chromosome-specific signal in both tumors, suggesting that the clonal origin of tumors in this patient was Y-containing cells. Androgen-receptor polymorphism also revealed a monoallelic X chromosome pattern in the recurrent phyllodes tumor tissue taken at autopsy, in addition to loss of heterozygosity demonstrated at locus TP53. The slippage of the CA repeats in the tumor was also shown at the loci of D5S82 and D11S527. The mechanistic basis for the occurrence of bilateral malignant tumors of the breast, XX/XY mosaicism, and familial clustering of breast cancer is still unknown. The present study, however, suggests that the sex chromosome abnormality may have modified the cancer phenotype in a manner similar to breast cancer in Klinefelter's syndrome (though phenotypically male) and the Y chromosome may have promoted cell growth.

Evaluation of MYC and chromosome 8 copy number in breast carcinoma by interphase cytogenetics

We used fluorescence in situ hybridization (FISH) to determine MYC and chromosome 8 copy number on whole nuclear imprint preparations of 24 breast carcinomas, seven benign breast samples, and two phyllodes tumors. None of the benign tissues and neither of the phyllodes tumors demonstrated an increased copy number for MYC or chromosome 8, which was defined as greater than two signals in > 10% of nuclei. In contrast, 22 of 24 carcinomas demonstrated an increased MYC copy number. The modal numbers of MYC copies/nucleus were 0-2 in seven cases (29%), 3-5 in seven cases (29%), 6-9 in five cases (21%), and > 9 in five cases (21%). An increased chromosome 8 copy number was observed in 21 of 22 carcinomas with MYC gain, and the modal number of signals/nucleus was either identical to (n = 14; 64%) or less than (n = 8; 36%) the number of MYC copies. The number of MYC copies correlated with cellular DNA content, as determined by using flow cytometry. In peridiploid tumors (DNA index 0.9-1.2; n = 7), the MYC copy numbers/nucleus were 0-2 in five cases and 3-5 in two cases. In contrast, the modal MYC copy numbers/nucleus among the 11 hyperdiploid tumors (DNA index 1.3-1.9) were 0-2 in one case, 3-5 in four cases, 6-9 in five cases, and > 9 in one case. All three tetraploid/hypertetraploid carcinomas exhibited > 9 MYC copies/nucleus. We conclude that an increased MYC copy number, as detected by using interphase cytogenetics, is extremely frequent in human breast carcinomas. However, in most cases, MYC gene duplication is probably secondary to polysomy of chromosome 8 and/or genomic endoreduplication (i.e., DNA aneuploidy).