Diagnostic utility of mammaglobin and GCDFP-15 in the identification of metastatic breast carcinoma in fluid specimens

Utility of TRPS-1 immunohistochemistry in diagnosis of metastatic breast carcinoma in cytology specimens

INTRODUCTION

At present, GATA binding protein 3 (GATA-3) is the most frequently used diagnostic immunohistochemical (IHC) marker for breast carcinoma (BC). However, it is not specific and has very low sensitivity for triple-negative BC (TNBC). SRY-box transcription factor 10 (SOX-10) and trichorhinophalangeal syndrome type 1 (TRPS-1) have been suggested for inclusion in the diagnostic workup of TNBC. TRPS-1 has not been established in cytology specimens as a diagnostic IHC marker for metastatic BC (MBC). Hence, in the present study we evaluated the utility of TRPS-1 in diagnosing MBC in cytology specimens.

MATERIALS AND METHODS

MBC cases diagnosed on cytology specimens from January to October 2020 were included in the present study. Only cases with hormonal status available and ≥20 tumor cells on cell blocks were included in the study. The cell blocks were assessed for TRPS-1, GATA-3, and SOX-10 IHC marker positivity (intensity and percentage of tumor cells). The results were correlated with the specimen type (fine needle aspiration [FNA] versus body fluid) and various BC prognostic subgroups.

RESULTS

We analyzed 61 cases, including 33 body fluid and 28 FNA (13 lymph node, 10 bone, 2 liver, 2 soft tissue, and 1 lung) specimens. TRPS-1 had 97.2% positivity in ER/PR+ (estrogen receptor/progesterone receptor-positive) MBC compared with GATA-3, which had 100% positivity in the same group. TRPS-1 showed high positivity in 35 of 37 cases (94.6%) and intermediate positivity in 1 (2.6%) and was negative/low positive in 1 case (2.7%). In contrast, GATA-3 showed high positivity for all 37 cases (100%). SOX-10 showed positivity in only 1 of 37 cases (2.7%), with intermediate positivity. In the HER2+ (human epidermal growth factor receptor 2-positive) group, TRPS-1 showed high positivity in 5 of 7 cases (71.4%), intermediate positivity in 1 case (14.3%), and negativity in 1 case (14.3%). However, GATA-3 showed high positivity in 6 of 7 cases (85.7%) and negative/low positivity in 1 case (14.3%). SOX-10 was negative in all 7 cases. In TNBC, TRPS-1 showed high positivity in 16 of 17 cases (94%) and intermediate positivity in 1 (5.9%), and GATA-3 showed high positivity in 9 (53%), intermediate positivity in 2 (11.8%), and low positive/negative in 6 of the 17 cases (35.3%). TRPS-1 expression was significantly higher than GATA-3 expression for the number of positive cases (P = 0.07), mean percentage of positive tumor cells (P = 0.005), and intensity of reactivity (P = 0.005). SOX-10 expression was present in only 5 of 17 cases (29%), with a mean percentage of positivity in the tumor cells of 26.5% and intensity of 0.8. No differences were found in the IHC results between the different specimen types (FNA versus fluid) in any group.

CONCLUSIONS

TRPS-1 is a highly sensitive new diagnostic IHC marker for breast carcinoma, with a similar positivity rate in ER/PR+ and HER2+ BC compared with GATA-3 and a higher positivity rate than GATA-3 and SOX-10 in TNBC in cytology specimens. In particular, when only a few clusters of tumor cells are present on the cell block, TRPS-1 can be highly useful, because its mean percentage of positive tumor cells and intensity are higher than those of other IHC markers.

Generation of prolactin-inducible protein (Pip) knockout mice by CRISPR/Cas9-mediated gene engineering

Prolactin-inducible protein (PIP) is a multifunctional glycoprotein that is highly expressed and found in the secretions of apocrine glands such as salivary, lacrimal, and sweat glands including the mammary glands. PIP has been implicated in various diseases, including breast cancer, gross cystic disease of the breast, keratoconus of the eye, and the autoimmune Sjögren's syndrome. Here we have generated a Pip knockout (KO) mouse using the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRSPR-associated (Cas)9 system. The Cas9 protein and two single guide RNAs targeting specific regions for both exons 1 and 2 of the Pip gene were microinjected into mouse embryos. The deletions and insertions promoted by CRISPR/Cas9 system on the Pip gene successfully disrupted Pip protein coding, as confirmed by PCR genotyping, sequencing, and ultimately Western blot analysis. This mouse model was generated in the inbred C57Bl/6J mouse, which exhibits lower genetic variation. This novel CRISPR Pip KO mouse model will not only be useful for future studies to interrogate the multifunctional role of PIP in physiological processes but will facilitate a broader understanding of the function of PIP in vivo while providing unprecedented insight into its role in a spectrum of diseases attributed to the deregulation of the PIP gene.

Metastasis: A Bane of Breast Cancer Therapy

The underlying mechanisms of metastasis in patients with breast cancer is still poorly understood. Approximately 6% of patients with breast cancer present with metastasis at the time of diagnosis. Metastatic breast cancer is difficult to treat and patients with breast cancer with distant metastasis have a significantly lower 5-year survival rate compared to patients with localised breast cancer (27% and 99%, respectively). During breast cancer progression, tumour cells first metastasise to nearby draining lymph nodes and then to distant organs, primarily bone, lungs, liver, and brain. In this brief review, the authors discuss breast cancer metastasis, the role of epithelial–mesenchymal transition and the contributions of the immune system to the metastatic process. The authors also briefly discuss whether there is any relationship between tumour size and metastatic potential, and recent advances in treatment for metastatic breast cancer. The studies highlighted suggest that immunotherapy may play a more significant role in future patient care for metastatic breast cancer.

Ancillary Tests in Breast Cytology: A Practical Guide

Utilization of fine-needle aspiration biopsy (FNAB) cytology for the diagnosis of diseases of the breast has been met with both excitement and uncertainty during the last couple of decades. Presently, FNAB for the diagnosis of primary and metastatic breast lesions is on the rise again. This is probably due to its fast turnaround time, cost efficiency, and minimal invasiveness, characteristics of this sampling modality which are particularly crucial for patients requiring frequent repeat biopsy in the setting of metastatic lesions. In this article, we will briefly review the main modern applications of FNAB of the breast when coupled with contemporary ancillary techniques. Such contemporary ancillary techniques range from classic immunocytochemistry (ICC) to the most modern molecular techniques, particularly next-generation sequencing. Coupled with contemporary ICC and molecular methods, FNAB of the breast can be used for several applications. The applications reviewed in this article include the primary diagnosis of a breast lesion, the identification of the breast as a primary source of a metastatic lesion, the evaluation of breast prognostic/predictive markers, and the tracking of tumor evolution. In our opinion, FNAB of the breast is an ideal sampling method, sharing many of the advantages of truly liquid and of tissue biopsies. Ultimately, we aim at demystifying the complexity of many of the challenges traditionally associated with the application of ancillary techniques to FNAB of the breast and provide insights into some of the most cutting-edge and clinically useful application scenarios.

The human breast cancer-associated protein, the prolactin-inducible protein (PIP), regulates intracellular signaling events and cytokine production by macrophages

The prolactin-inducible protein (PIP) is considered a valuable biomarker that is associated with both benign and malignant pathological conditions of the mammary gland. The function of PIP in breast tumorigenesis remains unknown; however, evidence from our laboratory and others suggest that it regulates host immunity. Studies with PIP-deficient (PIP^-/-) mice demonstrated significantly lower numbers of CD4⁺ T cells in their secondary lymphoid organs, impaired Th1 response, and impaired nitric oxide (NO) production. To further delineate the immunoregulatory role of PIP, we compared the expression of IFN-γR and TLR4, pro-inflammatory cytokine production, and intracellular signaling events by IFN-γ and lipopolysaccharide (LPS)-stimulated macrophages from wild-type (WT) and PIP^-/- mice. We showed that although the expressions of IFN-γR and TLR4 were comparable, productions of pro-inflammatory cytokines were decreased in PIP^-/- macrophages. This was associated with decreased phosphorylation of mitogen-activated protein kinase (MAPK) and signal transducer of activation of transcription (STAT) proteins in macrophages from PIP^-/- mice. Interestingly, the expression of suppressors of cytokine signaling (SOCS) 1 and 3 proteins, known to suppress IFN-γ and LPS signaling, was higher in PIP^-/- macrophages compared to those from WT mice. Collectively, our studies show that deficiency of PIP significantly affects intracellular signaling events leading to decreased pro-inflammatory cytokine production, and further confirms a role for PIP as an important immunoregulatory protein. This direct link between PIP and cell-mediated immunity, a key component of the immune system that is critical for cancer control, may have significant therapeutic implications.

Updates in Effusion Cytology

Effusion cytology plays multiple roles in the management of benign and malignant disease, from primary diagnosis to tissue allocation for ancillary diagnostic studies and biomarker testing of therapeutic targets. This article summarizes recent advances in pleural effusion cytology, with a focus on the practical application of immunohistochemical markers, cytogenetic techniques, flow cytometry, and molecular techniques for the diagnosis and management of primary and secondary neoplasms of the pleura.

Metastatic colonic and gastric polyps from breast cancer resembling hyperplastic polyps

Breast cancer metastasis to the gastrointestinal tract is relatively rare and is generally found when patients complain of symptoms such as gastrointestinal obstruction. Herein, we report a case with metastatic colonic and gastric lesions from breast cancer, with the formation of mucosal polyps which resembled typical hyperplastic polyps.

A 47-year-old woman underwent curable surgery for breast cancer and received standard systemic treatments. Her primary tumor was composed of a mix of invasive lobular and ductal carcinomas. During adjuvant endocrine therapy, she developed multiple colonic metastases, identified by colonoscopy performed as part of a general health check-up. She had no symptoms. Small elevated sessile polyps in the transverse colon and rectum showed histological features of signet-ring cell type adenocarcinoma, similar to the invasive lobular component of the primary breast cancer. During treatments for recurrent disease, she also developed multiple gastric metastases, with the same endoscopic and pathological features as the colonic lesions. Her treatment regimen was switched to oral chemotherapy, and she has since maintained stable disease for nearly 3 years. Multiple bone metastases eventually developed, and she was again switched to another systemic treatment but, to date, has remained free of symptoms.

We emphasize that the endoscopic findings of the metastatic lesions in the colon and stomach in this case highly resembled hyperplastic polyps. Since biopsy is not always performed for hyperplastic polyps in the gastrointestinal tract, we believe that this case report may encourage endoscopists to offer biopsies to the patient who has a history of breast cancer.

Application of Immunohistochemistry in the Diagnosis of Pulmonary and Pleural Neoplasms

CONTEXT

- A vast majority of neoplasms arising from lung or pleura are initially diagnosed based on the histologic evaluation of small transbronchial, endobronchial, or needle core biopsies. Although most diagnoses can be determined by morphology alone, immunohistochemistry can be a valuable diagnostic tool in the workup of problematic cases.

OBJECTIVE

- To provide a practical approach in the interpretation and immunohistochemical selection of lung/pleura-based neoplasms obtained from small biopsy samples.

DATA SOURCES

- A literature review of previously published articles and the personal experience of the authors were used in this review article.

CONCLUSION

- Immunohistochemistry is a useful diagnostic tool in the workup of small biopsies from the lung and pleura sampled by small biopsy techniques.

Cross-reactivity of EGFR mutation-specific immunohistochemistry assay in HER2-positive tumors

The coexpression of HER2 and EGFR L858R in a solitary nodule removed from the lung, whose mutation was not confirmed by molecular techniques, made us think about the possible existence of a cross-reaction between HER2 and the EGFR L858R-specific antibody. Our study was designed to further analyze the existence of this cross-reaction and stress the need to exclude a metastatic breast cancer when dealing with EGFR L858R-positive cases. The series consists of 42 primary breast carcinomas, 22 HER2 positive for overexpression and amplification, and 20 negative for both. EGFR mutations were studied by immunohistochemistry and confirmed using real-time PCR when positive. Immunohistochemistry assay with EGFR L858R was positive in 19 (86%) of the HER2-positive breast carcinomas and negative in all HER2-negative carcinomas. The EGFR L858R antibody gives false-positive results in most of the breast carcinomas with HER2 overexpression/amplification. As a consequence, it is essential to confirm any EGFR L858R-positive cases by molecular methods or at least discard the presence of HER2 overexpression/amplification before rendering a diagnosis. It is also important to consider that HER2 has been described in other carcinomas such as urothelial, gastric or ovarian, as well as lung, although infrequently.

Folate Receptor Alpha Immunohistochemistry in Cytology Specimens of Metastatic Breast Carcinoma

BACKGROUND

Folate receptor alpha (FRA) is involved in folate accumulation and utilization, and is expressed in varying proportions in breast, ovary and parotid epithelial cells, among others. FRA overexpression by immunohistochemistry (IHC) has been shown in estrogen/progesterone receptor (ER/PR)-negative carcinoma (40-74%) and in triple-negative breast carcinoma (TNBC; 50-86%) in histological specimens of primary breast cancers. We assessed the feasibility of IHC in detecting FRA expression and its patterns and clinical significance in metastatic TNBC in fine-needle aspiration (FNA) cell blocks (CBs).

MATERIALS AND METHODS

Metastatic breast ductal carcinoma cases were retrospectively immunostained with FRA IHC on FNA CBs. FRA staining was scored qualitatively (+/-), by intensity (0-3) and by staining area (0-100%). Of these metastatic cases, a subset of primary breast carcinoma cases was also immunostained with FRA. The results were correlated with ER, PR and human epidermal growth factor receptor 2 (Her2/Neu) performed by routine IHC.

RESULTS

A total of 40 FNA CBs with metastatic disease were studied, including hormone (ER/PR) positive (n = 5), triple positive (n = 5), Her2/Neu-only positive (n = 5) and TNBC (n = 25). FRA IHC showed immunoreactivity with moderate positivity in only 1 (4%) TNBC. All the remaining 39 cases were negative for FRA expression. Five cases of primary TNBC were stained with FRA IHC and were negative for FRA expression.

CONCLUSIONS

Our data suggest that FRA expression by IHC was rarely associated with ER/PR-negative tumors relative to ER/PR-positive tumors and, more importantly, with TNBC in FNA CBs. This finding may have a clinical significance and prognostic implications in metastatic breast carcinoma. Furthermore, 5 primary TNBC cases did not overexpress FRA by IHC. Hence, antifolate receptor therapies do not appear to be clinically relevant in TNBC based on immunostaining of FNA CBs of metastatic breast cancers.

Evaluating the utility of trefoil factor 1 as a mammary-specific immunostain compared and in conjunction with GATA-3 and mammaglobin in the distinction between carcinoma of breast and lung

OBJECTIVES

The distinction between metastatic breast carcinomas (BCs) and primary lung carcinomas (PLCs) can be difficult. This study tested the utility of trefoil factor 1 (TFF1) for this purpose and compared it with mammaglobin and GATA protein binding 3 (GATA-3).

METHODS

Tissue microarrays containing 365 BCs and 338 PLCs were stained with TFF1, mammaglobin, and GATA-3, and an H-score was calculated. Sensitivity, specificity, and accuracy were calculated, and logistical regression analysis was performed.

RESULTS

Accuracy of correctly classifying the tumor type was 81.9%, 71.3%, and 64.0% for GATA-3, mammaglobin, and TFF1, respectively. Odds ratios for selecting BCs were 25.69, 93.15, and 4.17, respectively, with P values less than .001. With a single exception, the best immunopanel included GATA-3 and mammaglobin in all comparisons.

CONCLUSIONS

TFF1 demonstrated breast specificity but was inferior to mammaglobin and GATA-3. Therefore, its routine clinical use may not be justified. TFF1 showed little benefit when added to an immunopanel.

Utility of GATA3 immunohistochemistry for diagnosis of metastatic breast carcinoma in cytology specimens

BACKGROUND

GATA3 as a diagnostic marker of metastatic breast carcinoma in cytology specimens has not been fully established.

METHODS

Metastatic breast carcinoma was assessed for GATA3, mammaglobin, and GCDFP-15 immunohistochemistry on cell blocks. GATA3 was scored by intensity (0, negative; 1, weakly positive; 2, moderately positive; 3, strongly positive), and area (0-100%). Mammaglobin (MMG) and GCDFP-15 staining was scored qualitatively (positive vs. negative). Results were correlated with specimen type (fine-needle aspiration vs. body fluid), breast prognostic markers estrogen receptor (ER), progesterone receptor (PR), Her-2/Neu (Her2), and Ki67, and with each other. Statistical significance was determined by chi-squared test and ANOVA for numerical variables. Alpha was set as 0.05. A total of 40 CB specimens containing metastatic breast carcinoma were studied.

RESULTS

GATA3 was positive in 32 (80%) cases. All ER-positive cases (n = 25) were positive for GATA3. Conversely, all GATA3-negative cases (n = 8) were triple-negative breast cancers. On qualitative univariate analysis, GATA3 was statistically associated with ER (P = 0.0001), and PR (P = 0.0468). GATA3 intensity was statistically associated with ER (P ≤ 0.0001), PR (P = 0.0157), Her2 (P = 0.0256), and cancer category (P = 0.0127). GATA3 staining was statistically associated with ER (P ≤ 0.0001), PR (P = 0.0160), Her2 (P = 0.0451), and cancer category (P = 0.0002). MMG and GCDFP-15 were directly compared to GATA3 in 35 samples. The sensitivity was 86% for GATA3, 26% for MMG, and 14% for GCDFP-15.

CONCLUSION

GATA3 is a more sensitive diagnostic marker of metastatic breast carcinoma in CB samples than MMG and GCDFP-15.

A panel of protein markers for the early detection of lung cancer with bronchial brushing specimens

BACKGROUND

To date, no robust biomarkers have been available in clinical practice that can provide an early diagnostic evaluation of lung cancer. The objective of this study was to identify potential biomarkers for the early detection of lung cancer using bronchial brushing specimens.

METHODS

Immunocytochemistry was used to investigate the expression of 35 proteins in 880 bronchial brushing specimens from both outpatients and inpatients who had either lung cancer or benign lung lesions. An optimal panel was identified that had high sensitivity and considerable specificity for detecting lung cancer. Associations between protein expression and clinicopathologic parameters were assessed.

RESULTS

Tumor protein 53 (TP53), TP63, Ki67, epidermal growth factor receptor (EGFR), minichromosome maintenance complex component 6 (MCM6), MCM7, uncharacterized proteins KIAA1522 and KIAA0317, and ubiquitin-protein ligase UHR1 (ICBP90) frequently presented high expression in bronchial brushing specimens from patients who had lung cancer compared with patients who had benign lung lesions. A 6-protein panel consisting of TP53, Ki67, MCM6, MCM7, KIAA1522, and KIAA0317 was identified as the best combination, with sensitivity of 81.1% (309 of 381 specimens) for detecting nonsmall cell lung cancer (NSCLC) and 86.8% (145 of 167 specimens) for detecting small cell lung cancer (SCLC) (specificity, 83.3%; 65 of 78 specimens). The combination of cytology and the protein panel significantly improved the sensitivity of bronchial brushing examination for detecting lung cancer (P<.00001), which increased from 49.1% to 81% in early stage NSCLC (stage I and II). In combined analyses, the protein panel was positively associated with patient sex (P=.00033), tumor type (P<.00001), tumor location (P<.00001), and lymph node metastasis (P=.028).

CONCLUSIONS

The 6-protein panel is a potential biomarker for the early detection of lung cancer in bronchial brushings.

Diagnostic utility of immunohistochemistry in distinguishing between epithelioid pleural mesotheliomas and breast carcinomas: a comparative study

Epithelioid mesotheliomas and breast carcinomas can present a variety of morphologic patterns. Because of this, breast carcinomas that metastasize to the pleura and lung may be confused with mesotheliomas. The aim of the present study is to compare the immunohistochemical markers currently available for the diagnosis of these 2 malignancies and to determine the best panel of markers that can be used to assist in discriminating between them. Sixty epithelioid mesotheliomas and 80 breast carcinomas (40 triple negative and 40 estrogen receptor positive) were investigated for expression of the positive mesothelioma markers calretinin, keratin 5/6, mesothelin, podoplanin, thrombomodulin, and WT1; the positive carcinoma marker claudin 4; and the breast-associated markers gross cystic disease fluid protein 15 (GCDFP-15), mammaglobin, and GATA3. All of the epithelioid mesotheliomas reacted for calretinin and keratin 5/6, 93% for WT1; 88% for podoplanin; 77% for thrombomodulin; 23% for GATA3; and 0% for claudin 4, GCDFP-15, and mammaglobin, respectively. Of the triple-negative breast carcinomas, 100% expressed claudin 4; 5%, keratin 5/6; 30%, GATA3; 18%, mammaglobin; 15%, GCDFP-15; 56%, mesothelin; 38%, calretinin; 18%, thrombomodulin; 5%, WT1; and 3%, podoplanin. Among the estrogen receptor-positive breast carcinomas, 100% were claudin 4 and GATA3 positive; 70% expressed GCDFP-15; 63%, mammaglobin; 13%, calretinin; 13%, thrombomodulin; 8%, WT1; 5%, keratin 5/6; 3%, mesothelin; and 0%, podoplanin. It is concluded that podoplanin and WT1 are the best positive mesothelioma markers for differentiating epithelioid mesotheliomas from breast carcinomas. An accurate differential diagnosis can be reached with the use of these two markers in combination with the breast-associated markers GCDFP-15, mammaglobin, and GATA3.

GATA3: a promising marker for metastatic breast carcinoma in serous effusion specimens

BACKGROUND

The usefulness of GATA3 (GATA-binding protein 3 to DNA sequence [A/T]GATA[A/G]) as a marker for metastatic breast carcinoma in serous effusion specimens was investigated.

METHODS

Cell block sections from 74 serous effusion specimens (32 ascitic, 2 pericardial, and 40 pleural fluids) were stained with an anti-GATA3 murine monoclonal antibody. The specimens included 62 confirmed metastatic carcinomas from the breast (30 specimens), female genital tract (13 specimens), gastrointestinal tract (7 specimens), lung adenocarcinoma (9 specimens), pancreas (1 specimen), kidney (1 specimen), and bladder (1 specimen). The breast carcinoma cases included 15 ductal carcinomas and 8 lobular carcinomas; the histology subtype was not available for 7 specimens. Twelve cases containing florid reactive mesothelial cells were also stained. The breast carcinoma cases were also stained for mammaglobin and gross cystic disease fluid protein of 15 kilodaltons (GCDFP-15) to compare their sensitivity with GATA3.

RESULTS

Positive nuclear staining for GATA3 was found to be present in 90% of metastatic breast carcinoma specimens (27 of 30 specimens). All nonbreast metastatic carcinomas tested were negative with the exception of the single case of metastatic urothelial carcinoma. No staining was observed in any of the benign reactive cases or in benign mesothelial cells present in the malignant cell block preparations. Two cases demonstrated weak positivity of benign lymphoid cells. Staining results were unambiguous because all positive cases demonstrated intense nuclear staining in > 50% of tumor cells. Mammaglobin (57% staining; 17 of 30 cases) and GCDFP-15 (33% staining; 10 of 30 cases) were found to be less sensitive markers of breast carcinoma. If used in a panel, mammaglobin and GCFP-15 staining would have identified only 1 additional case compared with those stained with GATA3.

CONCLUSIONS

GATA3 may be a useful addition to immunostaining panels for serous effusion specimens when metastatic breast carcinoma is a consideration.

Utility of mammaglobin immunohistochemistry as a proxy marker for the ETV6-NTRK3 translocation in the diagnosis of salivary mammary analogue secretory carcinoma

Mammary analogue secretory carcinoma is a recently described salivary gland neoplasm defined by ETV6-NTRK3 gene fusion. Mammary analogue secretory carcinoma's morphology is not entirely specific and overlaps with other salivary gland tumors. Documenting ETV6 rearrangement is confirmatory, but most laboratories are not equipped to perform this test. As mammary analogue secretory carcinomas are positive for mammaglobin, immunohistochemistry could potentially replace molecular testing as a confirmatory test, but the specificity of mammaglobin has not been evaluated across a large and diverse group of salivary gland tumors. One hundred thirty-one salivary gland neoplasms were evaluated by routine microscopy, mammaglobin immunohistochemistry, and ETV6 break-apart fluorescent in situ hybridization. The cases included 15 mammary analogue secretory carcinomas, 44 adenoid cystic carcinomas, 33 pleomorphic adenomas, 18 mucoepidermoid carcinomas, 10 acinic cell carcinomas, 4 adenocarcinomas not otherwise specified, 3 polymorphous low-grade adenocarcinomas, 3 salivary duct carcinomas, and 1 low-grade cribriform cystadenocarcinoma. All 15 mammary analogue secretory carcinomas harbored the ETV6 translocation and were strongly mammaglobin positive. None of the 116 other tumors carried the ETV6 translocation; however, mammaglobin staining was present in 1 (100%) of 1 low-grade cribriform cystadenocarcinoma, 2 (67%) of 3 polymorphous low-grade adenocarcinomas, 2 (67%) of 3 salivary duct carcinomas, 2 (11%) of 18 mucoepidermoid carcinomas, and 2 (6%) of 33 pleomorphic adenomas. Mammaglobin is highly sensitive for mammary analogue secretory carcinoma, but immunostaining can occur in a variety of tumors that do not harbor the ETV6 translocation. Strategic use of mammaglobin immunostaining has a role in the differential diagnosis of salivary gland neoplasms, but it should not be indiscriminately used as a confirmatory test for mammary analogue secretory carcinoma.

Expression of mammaglobin and gross cystic disease fluid protein-15 in breast carcinomas

Immunohistochemical analysis of gross cystic disease fluid protein-15 (GCDFP-15) and mammaglobin (MGB) is frequently used in routine practice for assessment of metastases or regional recurrences of breast origin. Breast cancer is highly heterogeneous. Expression of these 2 markers in various breast cancer subtypes has not been well studied. In addition, the usefulness of these two markers in combination in detecting breast origin has not been explored. In this study, a large cohort of breast cancers was evaluated for GCDFP-15 and MGB expression, both individually and combined. Their expression was correlated with cancer subtypes, other biomarkers and clinicopathologic parameters. A higher sensitivity for MGB (42.3%) than GCDFP-15 (31.6%) in detecting cancers of breast origin was observed. Combining both increased the sensitivity further, both for primary tumor (53.0%) and for nodal metastases (69.0%). GCDFP-15 was associated significantly with a breast cancer profile of good prognosis tumors, including lower grade (P < .001), pN (P = .029) and Ki-67 (P < .001) as well as negative basal markers expression (P = .043, .009, and .049 for c-Kit, CK5/6 and epidermal growth factor receptor, respectively) and, thus, may not be sensitive for detection of poor prognosis tumors. MGB has the highest expression in HER2-overexpressing cancers (56.6%), and may be a potentially useful marker for this subtype. Nonetheless, both markers showed low expression in the basal like (BLBC) subtype (11.9% and 21.4% for GCDFP-15 and MGB respectively), therefore, the detection of BLBC remains problematic. Negative results need to be interpreted with caution, and correlation with other clinical findings may be required to exclude the possibility of metastatic BLBC.

Metastases to and from the Breast

Breast cancer is a common source of systemic metastatic disease. Distinguishing metastatic breast cancer from other types of malignancies can be diagnostically challenging but is important for correct treatment and prognosis. Nonmammary tumors can also metastasize to the breast, although this is a rare phenomenon. Differentiating a metastasis to the breast from a primary breast cancer can likewise be difficult. Knowledge of the clinical history and careful morphologic evaluation are the cornerstones of diagnosis. A panel of immunohistochemical stains tailored to the differential diagnosis at hand can provide helpful information in ambiguous cases.

Intratumoral expression level of epidermal growth factor receptor and cytokeratin 5/6 is significantly associated with nodal and distant metastases in patients with basal-like triple-negative breast carcinoma

Triple-negative (TN) breast carcinoma, characterized by estrogen receptor, progesterone receptor, and HER2 negativity, is a group of aggressive tumors that can be further classified into 2 subtypes: basal-like, defined as CK5/6 and/or epidermal growth factor receptor (EGFR) positive by immunohistochemistry; and non-basal-like. Clinical characteristics and tumor profiles were analyzed in 105 cases of TN tumors. Among these cases, 35 had distant metastasis, 34 had axillary nodal metastasis only, and 36 were nodal negative. Our results indicate basal-like TN breast tumors with nodal and distant metastases are significantly associated with a higher intratumoral expression of EGFR and CK5/6 compared to those in the nodal negative group. High level of intratumoral EGFR and CK5/6 expression may play a role in development of nodal or distant metastases in patients with basal-like TN tumors and may be predictive of metastatic disease. Furthermore, EGFR targeted therapy may be potentially useful in the treatment of basal-like TN breast cancer.