Skin-type hidradenoma of the breast parenchyma with t(11;19) translocation: hidradenoma of the breast

Invasive Carcinoma With Skin Adnexal Trichilemmal Hair Follicular Differentiation Occurring in the Breast: A Case Report With Detailed Immunohistochemical and Molecular Analysis

Cutaneous-type adnexal tumors involving the breast are rare and create a diagnostic dilemma as they are often indistinguishable from primary mammary neoplasms. Tumors showing hair follicular differentiation are particularly challenging due to their rarity and the subtle appreciation of the intricate microanatomy of the hair follicle. We report a triple negative cutaneous-type adnexal carcinoma with follicular differentiation involving the breast to bring attention to the existence of these specialized group of tumors which should be managed differently from conventional triple negative carcinomas of the breast.

Clear cell hidradenoma of the breast with MAML2 gene rearrangement

Clear cell hidradenoma is a rare benign tumor of the breast, its origin and pathogenesis are controversial. We have experienced a case of breast clear cell hidradenoma with mastermind like transcriptional coactivator 2 (MAML2) gene rearrangement. The patient found a painless mass with a hard texture in the left breast areola without nipple discharge. Microscopically, the tumor was cystic and solid, locally arranged in a glandular structure, covered by single cuboidal cells; it was composed of clear cells, epidermoid cells, and basaloid cells; there were no necrosis or mitotic figures. Immunohistochemical staining showed that the tumor cells positively expressed low-molecular cytokeratin 7, low-molecular cytokeratins (Cam5.2), high-molecular cytokeratin 5/6, cytokeratin 14, CD117, and p63; and did not express calponin, and smooth muscle myosin heavy chain. The cuboidal cells were positive for SOX10 but negative for p63. Additionally, periodic acid-Schiff reaction showed purple-red granules in the tumor cytoplasm, but Alcian blue staining showed no blue mucus in the cytoplasm. The split signals of MAML2 gene were detected by fluorescence in situ hybridization. Subtle histological and immunophenotypical differences may help to distinguish breast clear cell hidradenoma from common breast tumors. Furthermore, the MAML2 gene rearrangement may be a molecular genetic characteristic of breast clear cell hidradenoma.

Genetic and Immunohistochemical Profiling of Mammary Hidradenoma and Comparison to Mucoepidermoid Carcinoma

Mucoepidermoid carcinoma (MEC) is exceedingly rare in the breast, with <45 cases reported in the literature. Although estrogen receptor/progesterone receptor/human epidermal growth factor 2 triple-negative, MEC is characterized as a special subtype of breast carcinoma with significantly better prognosis than conventional basal-type tumors. Cutaneous hidradenoma (HA) is considered a benign adnexal neoplasm showing histomorphologic overlap with MEC. Rare cases of HA have also been reported in the breast, but these are relatively uncharacterized. In this study, we examined the clinicopathologic, immunohistochemical (IHC), and genetic features of 8 breast HAs, in comparison to 3 mammary MECs. All cases were positive for MAML2 break-apart fluorescence in situ hybridization. Eight cases demonstrated a CRTC1::MAML2 fusion, and one MEC harbored a CRTC3::MAML2 fusion; the latter is a novel finding in the breast. Mutational burden was very low, with only one HA exhibiting a MAP3K1 pathogenic alteration. By IHC, both MEC and HA demonstrated cell type-dependent expression of high- and low-molecular-weight keratins and p63, as well as negative to low-positive estrogen receptor and androgen receptor. Smooth muscle myosin and calponin highlighted an in situ component in the 3 cases of MEC; expression of these myoepithelial markers was negative in HAs. Additional distinguishing characteristics included the growth pattern and tumor architecture, the presence of glandular/luminal cells in HA, and overall higher IHC expression of SOX10, S100 protein, MUC4, and mammaglobin in MEC. Morphologic findings were also compared to a series of 27 cutaneous nonmammary HAs. Mucinous and glandular/luminal cells were identified in significantly more mammary HAs than nonmammary lesions. The findings provide insight into the pathogenesis of MAML2-rearranged neoplasms of the breast, underscore the overlapping genetic features of MEC and HA, and highlight similarities to their extramammary counterparts.

The Peritumoral CD8 + /FOXP3 + Cell Ratio Has Prognostic Value in Triple-negative Breast Cancer

Compelling data has demonstrated the prognostic significance of tumor-infiltrating lymphocytes (TILs) in triple-negative breast cancer (TNBC), a subtype generally associated with a poor clinical outcome but highly heterogeneous in nature. There have been limited studies investigating the importance of subsets of T cells in TILs. Further, the significance of intratumoral versus peritumoral TILs remains controversial. We examined the prognostic value of tumor-associated CD8 + cytotoxic T cells and FOXP3 + regulatory T cells in 35 chemotherapy-naive TNBC cases with a tumor-host interface in the tissue sections. The CD8 + and FOXP3 + cell count was expressed by immunoreactive cells per high-power field in an average of 10 high-power fields. There was a wide range of CD8 + and FOXP3 + T cells within the peritumoral and intratumoral stroma. Both CD8 + and FOXP3 + TILs were significantly higher at the former location as compared with the latter ( P <0.0001 and 0.003, respectively). The numbers of CD8 + and FOXP3 + T cells, either within peritumoral or intratumoral stroma, were not significantly associated with distant relapse-free or disease-specific survival. However, the peritumoral CD8 + /FOXP3 + ratio of TILs was significantly associated with prolonged relapse-free survival ( P =0.04) and disease-specific survival ( P =0.02). This association was not observed with the CD8 + /FOXP3 + ratio of intratumoral TILs. These observations suggest that the immunologic balance in the tumor microenvironment might determine antitumor immunity. Further, the peritumoral TILs appear to play a more important role in the progression of TNBC when compared with the intratumoral TILs, thus reaffirming the necessity of revisiting the method for the assessment of TILs.

Atypical Nodular Hidradenoma Versus Low-Grade Hidradenocarcinoma in a Young Female Patient: A Case Report and Review of Literature

The objective of this study was to discuss an unusual postauricular mass in a pediatric patient. This mass had a broad differential including congenital anomaly, neoplasm, infection, and lymphovascular malformation. Atypical nodular hidradenoma is a rare adnexal tumor that is difficult to differentiate from hidradenocarcinoma. It is a rare entity, but especially rare in the pediatric population. This study aims to provide guidance on diagnosing hidradenoma and distinguishing it from hidradenocarcinoma through case presentation with a review of the literature. The patient in this report underwent wide location resection with close surveillance and has been disease-free during follow-up.

Clear Cell Hidradenoma of the Breast Diagnosed on a Core Needle Biopsy: A case report and review of the literature

Clear cell hidradenoma (CCH) is a tumour originating from the eccrine sweat glands. It usually presents in the limbs, axilla or trunk. CCH of the breast is rare and can present as a cystic lesion in the breast that can be easily misdiagnosed as malignancy. We report a 36-year-old female patient who presented at the Sultan Qaboos University Hospital Breast Clinic, Muscat, Oman, in 2018 with a lump in her left breast. Ultrasound examination reported a complex cystic lesion with a solid, vascular component. An ultrasound-guided core needle biopsy was suggestive of clear cell hidradenoma. Surgical excision was performed and histopathology confirmed the diagnosis of CCH of the breast. This is the first ever case of a diagnosis of CCH made using core needle biopsy. CCH can be challenging to diagnose; therefore, awareness of its histopathological and ultrasonographic features are essential to avoid misdiagnosis and over treatment.

Clear cell papillary neoplasm of the breast with MAML2 gene rearrangement: Clear cell hidradenoma or low-grade mucoepidermoid carcinoma?

Clear cell hidradenoma (CCH) is an uncommon adnexal tumor usually arising from eccrine glands and commonly seen on the face and the upper extremities. CCH occurring in the breast is extremely rare. Herein we report a case of MAML2-rearranged CCH of breast with a papillary architecture closely mimicking intraductal papilloma, adenomyoepithelioma and low-grade mucoepidermoid carcinoma, thus representing a source of diagnostic confusion. An overview of salient histologic features and immunophenotypes to distinguish CCH and low-grade mucoepidermoid carcinoma is also integrated into the report.

Current concepts in breast cancer genomics: An evidence based review by the CGC breast cancer working group

BACKGROUND

Genomic abnormalities in breast cancer have been described according to diverse conceptual frameworks, including histologic subtypes, clinical molecular subtypes, intrinsic DNA, RNA, and epigenetic profiles, and activated molecular pathways.

METHODS

The Cancer Genomics Consortium (CGC) Breast Cancer Workgroup performed an evidence based literature review to summarize current knowledge of clinically significant genomic alterations in breast cancer using CGC levels of evidence. Targetable or disease-defining alterations were prioritized.

RESULTS

We summarized genomic alterations in breast cancer within a framework of existing clinical tools for diagnosis, risk stratification, and therapeutic management. Using CGC levels of evidence, we catalog copy number profiles, gene expression profiles, and mutations in clinically significant genes. We also describe emerging molecular markers such as methylation profiling and immunotherapy biomarkers.

CONCLUSION

A summary of currently available information on breast cancer genomics will enhance precision medicine by serving as an interpretive resource for clinical laboratory geneticists, providing a foundation for future practice guidelines, and identifying knowledge gaps to address in future research.

Molecular mechanisms and pathobiology of oncogenic fusion transcripts in epithelial tumors

Recurrent fusion transcripts, which are one of the characteristic hallmarks of cancer, arise either from chromosomal rearrangements or from transcriptional errors in splicing. DNA rearrangements include intrachromosomal or interchromosomal translocation, tandem duplication, deletion, inversion, or result from chromothripsis, which causes complex rearrangements. In addition, fusion proteins can be created through transcriptional read-through. Fusion genes can be transcribed to fusion transcripts and translated to chimeric proteins, with many having demonstrated transforming activities through multiple mechanisms in cells. Fusion proteins represent novel therapeutic targets and diagnostic biomarkers of diagnosis, disease status, or progression. This review focuses on the mechanisms underlying the formation of oncogenic fusion genes and transcripts and their impact on the pathobiology of epithelial tumors.

Landscape of gene fusions in epithelial cancers: seq and ye shall find

Enabled by high-throughput sequencing approaches, epithelial cancers across a range of tissue types are seen to harbor gene fusions as integral to their landscape of somatic aberrations. Although many gene fusions are found at high frequency in several rare solid cancers, apart from fusions involving the ETS family of transcription factors which have been seen in approximately 50% of prostate cancers, several other common solid cancers have been shown to harbor recurrent gene fusions at low frequencies. On the other hand, many gene fusions involving oncogenes, such as those encoding ALK, RAF or FGFR kinase families, have been detected across multiple different epithelial carcinomas. Tumor-specific gene fusions can serve as diagnostic biomarkers or help define molecular subtypes of tumors; for example, gene fusions involving oncogenes such as ERG, ETV1, TFE3, NUT, POU5F1, NFIB, PLAG1, and PAX8 are diagnostically useful. Tumors with fusions involving therapeutically targetable genes such as ALK, RET, BRAF, RAF1, FGFR1-4, and NOTCH1-3 have immediate implications for precision medicine across tissue types. Thus, ongoing cancer genomic and transcriptomic analyses for clinical sequencing need to delineate the landscape of gene fusions. Prioritization of potential oncogenic "drivers" from "passenger" fusions, and functional characterization of potentially actionable gene fusions across diverse tissue types, will help translate these findings into clinical applications. Here, we review recent advances in gene fusion discovery and the prospects for medicine.

Thymic Mucoepidermoid Carcinoma

Thymic mucoepidermoid carcinoma (TMEC) is a vanishingly rare entity that usually presents as low to intermediate grade MEC and carries a better prognosis when compared with other poorly differentiated thymic carcinomas. The recently described fusions, t(11;19)(q21;p13) CREB (cAMP response element-binding protein)-regulated transcription coactivator 1 and MAML2, mastermind-like gene 2 (CRTC1-MAML2) and t(11:15)(q21;q26) CRTC3-MAML2 characterize a considerable proportion of MEC examples arising from a variety of anatomical sites. Recent data point out that the aberrant proteins produced by this fusion drive oncogenesis by disrupting the cAMP/CREB and NOTCH1 pathways. To date, only 2 TMEC cases have been reported to have MAML2 rearrangements, a feature that was found to be absent in TMEC mimics. These findings led the authors to recommend this test as a diagnostic tool in the differential diagnosis for thymic carcinoma. Herein, we present a case of TMEC arising in a 58-year-old woman, which was predominantly cystic with intracystic papillary formations composed of a mixture of mucinous cells and intermediate/epidermoid eosinophilic cells. This case was negative for CTCR1-MAML2 and CTCR3-MAML2 fusion transcripts by reverse transcriptase polymerase chain reaction and lacked a MAML2 rearrangement by fluorescence in situ hybridization. We report a CTCR1/3-MAML2 fusion and MAML2 rearrangement–negative TMEC, indicating that a different molecular pathway must be involved in the generation of these tumors. The possibility of fusion-negative TMEC should be taken into consideration in the differential diagnosis of a thymic carcinoma.

CRTC1/MAML2 gain-of-function interactions with MYC create a gene signature predictive of cancers with CREB-MYC involvement

Chimeric oncoproteins created by chromosomal translocations are among the most common genetic mutations associated with tumorigenesis. Malignant mucoepidermoid salivary gland tumors, as well as a growing number of solid epithelial-derived tumors, can arise from a recurrent t (11, 19)(q21;p13.1) translocation that generates an unusual chimeric cAMP response element binding protein (CREB)-regulated transcriptional coactivator 1 (CRTC1)/mastermind-like 2 (MAML2) (C1/M2) oncoprotein comprised of two transcriptional coactivators, the CRTC1 and the NOTCH/RBPJ coactivator MAML2. Accordingly, the C1/M2 oncoprotein induces aberrant expression of CREB and NOTCH target genes. Surprisingly, here we report a gain-of-function activity of the C1/M2 oncoprotein that directs its interactions with myelocytomatosis oncogene (MYC) proteins and the activation of MYC transcription targets, including those involved in cell growth and metabolism, survival, and tumorigenesis. These results were validated in human mucoepidermoid tumor cells that harbor the t (11, 19)(q21;p13.1) translocation and express the C1/M2 oncoprotein. Notably, the C1/M2-MYC interaction is necessary for C1/M2-driven cell transformation, and the C1/M2 transcriptional signature predicts other human malignancies having combined involvement of MYC and CREB. These findings suggest that such gain-of-function properties may also be manifest in other oncoprotein fusions found in human cancer and that agents targeting the C1/M2-MYC interface represent an attractive strategy for the development of effective and safe anticancer therapeutics in tumors harboring the t (11, 19) translocation.

11q21 rearrangement is a frequent and highly specific genetic alteration in mucoepidermoid carcinoma

Mucoepidermoid carcinoma (MEC) is the most common malignant salivary gland tumor. Translocation t(11;19)(q21;p13) involving the MECT1 and MAML2 genes has been suggested as a diagnostic marker in these tumors. To determine the specificity of 11q21 locus rearrangements for MEC, fluorescence in situ hybridization analysis with specific MEC-I Dual Color Break Apart Probe was performed on a tissue microarray containing samples from almost 1200 salivary gland adenomas and carcinomas. Rearrangements of 11q21 were observed in 40% of 217 MECs. The frequency of rearrangements decreased with tumor grade and was found in 53% of G1, 43% of G2, and 31% of G3 tumors (P=0.015). There were no 11q21 rearrangements found in other salivary gland carcinomas including 142 adenoid cystic carcinomas, 104 acinic cell adenocarcinomas, 76 adenocarcinoma not otherwise specified, 38 epithelial-myoepithelial carcinomas, 15 polymorphous low-grade adenocarcinomas, 18 basal cell adenocarcinomas, 19 myoepithelial carcinomas, 12 papillary cystadenocarcinomas, 6 salivary duct carcinomas, and 10 oncocytic carcinomas. Furthermore, all analyzed salivary gland adenomas, including 39 cases of Warthin tumor and control samples, either from the salivary gland or from other organs were negative for 11q21 rearrangements. It is concluded that MECT1-MAML2 gene fusion is a highly specific genetic alteration in MEC with predominance in low-grade and intermediate-grade tumors.

Combined Epithelial-Myoepithelial Lesions of the Breast

Epithelial-myoepithelial proliferations of the breast are a heterogeneous poorly defined group of lesions characterized morphologically by dual differentiation into ductal (luminal) and myoepithelial cells. They include neoplastic and non-neoplastic entities that have overlapping morphologic features that may give rise to diagnostic difficulty. Many of these entities are low grade or of uncertain malignant potential but the biology of some of these rare lesions remains to be elucidated. This article discusses the differential diagnosis of epithelial-myoepithelial lesions of the breast and highlights the morphologic features of some of these entities.

Salivary gland-type tumors of the breast: a spectrum of benign and malignant tumors including "triple negative carcinomas" of low malignant potential

Salivary gland-type neoplasms of the breast are uncommon and comprise numerous entities analogous to that more commonly seen in salivary glands. The clinicopathologic spectrum ranges from benign to malignant but there are important differences as compared with those of their salivary counterpart. In the breast, benign adenomyoepithelioma is recognized in addition to malignant one, whereas in the salivary gland a histologically similar tumor is designated as epithelial-myoepithelial carcinoma without a separate benign subgroup. Mammary adenoid cystic carcinoma is a low-grade neoplasm compared with its salivary equivalent. It is also important to appreciate that in contrast to "triple negative" conventional breast carcinomas with aggressive course, most salivary-type malignant breast neoplasms behave in a low-grade manner. Most of these tumors are capable of differentiating along both epithelial and myoepithelial lines, but the amount of each lineage-component varies from case to case, contributing to diagnostic difficulties. Well established examples of this group include pleomorphic adenoma, adenomyoepithelioma, and adenoid cystic carcinoma. Another family of salivary gland-type mammary epithelial neoplasms is devoid of myoepithelial cells. Key examples include mucoepidermoid carcinoma and acinic cell carcinoma. The number of cases of salivary gland-type mammary neoplasms in the published data is constantly increasing but some of the rarest subtypes like polymorphous low-grade adenocarcinoma and oncocytic carcinoma are "struggling" to become clinically relevant entities in line with those occurring more frequently in salivary glands.

Unfavorable prognosis of CRTC1-MAML2 positive mucoepidermoid tumors with CDKN2A deletions

The CRTC1-MAML2 fusion oncogene underlies the etiology of mucoepidermoid salivary gland carcinoma (MEC) where it confers a favorable survival outcome as compared with fusion-negative MEC. While these analyses suggested that detection of CRTC1-MAML2 serves as a useful prognostic biomarker, we recently identified outlier cases of fusion-positive MEC associated with advanced-staged lethal disease. To identify additional genetic alterations that might cooperate with CRTC1-MAML2 to promote disease progression, we performed a pilot high-resolution oligonucleotide array CGH (aCGH) and PCR-based genotyping study on 23 MEC samples including 14 fusion-positive samples for which we had clinical outcome information. Unbiased aCGH analysis identified inactivating deletions within CDKN2A as a candidate poor prognostic marker which was confirmed by PCR-based analysis (CDKN2A deletions in 5/5 unfavorable fusion-positive cases and 0/9 favorable fusion-positive cases). We did not detect either activating EGFR mutations, nor copy number gains at the EGFR or ERBB2 loci as poor prognostic features for fusion-positive MEC in any of the tumor specimens. Prospective studies with larger case series will be needed to confirm that combined CRTC1-MAML2 and CDKN2A genotyping will optimally stage this disease.

Enhanced activity of the CREB co-activator Crtc1 in LKB1 null lung cancer

Activation of Crtc1 (also known as Mect1/Torc1) by a t(11;19) chromosomal rearrangement underlies the etiology of malignant salivary gland tumors. As LKB1 is a target for mutational inactivation in lung cancer and was recently shown to regulate hepatic Crtc2/CREB transcriptional activity in mice, we now present evidence suggesting disruption of an LKB1/Crtc pathway in cancer. Although Crtc1 is preferentially expressed in adult brain tissues, we observed elevated levels of steady-state Crtc1 in thoracic tumors. In addition, we show that somatic loss of LKB1 is associated with underphosphorylation of endogenous Crtc1, enhanced Crtc1 nuclear localization and enhanced expression of the Crtc prototypic target gene, NR4A2/Nurr1. Inhibition of NR4A2 was associated with growth suppression of LKB1 null tumors, but showed little effect on LKB1-wildtype cells. These data strengthen the role of dysregulated Crtc as a bona fide cancer gene, present a new element to the complex LKB1 tumorigenic axis, and suggest that Crtc genes may be aberrantly activated in a wider range of common adult malignancies.

Mutation-associated fusion cancer genes in solid tumors

Chromosomal translocations and fusion oncogenes serve as the ultimate biomarker for clinicians as they show specificity for distinct histopathologic malignancies while simultaneously encoding an etiologic mutation and a therapeutic target. Previously considered a minor mutational event in epithelial solid tumors, new methodologies that do not rely on the detection of macroscopic cytogenetic alterations, as well as access to large series of annotated clinical material, are expanding the inventory of recurrent fusion oncogenes in both common and rare solid epithelial tumors. Unexpectedly, related assays are also revealing a high number of tandem or chimeric transcripts in normal tissues including, in one provocative case, a template for a known fusion oncogene. These observations may force us to reassess long-held views on the definition of a gene. They also raise the possibility that some rearrangements might represent constitutive forms of a physiological chimeric transcript. Defining the chimeric transcriptome in both health (transcription-induced chimerism and intergenic splicing) and disease (mutation-associated fusion oncogenes) will play an increasingly important role in the diagnosis, prognosis, and therapy of patients with cancer.

Cutaneous hidradenocarcinoma: a clinicopathological, immunohistochemical, and molecular biologic study of 14 cases, including Her2/neu gene expression/amplification, TP53 gene mutation analysis, and t(11;19) translocation

We present a series of 14 cases of cutaneous hidradenocarcinomas. The patients included 6 women and 8 men ranging in age at diagnosis from 34 to 93 years. All but 1 patient presented with a solitary nodule. There was no predilection site. One patient presented with multiple lesions representing metastatic nodules. Of 12 patients with available follow-up, 2 died of disease, whereas the remaining 10 patients were alive but 3 of them experienced a local recurrence in the course of the disease. Grossly, the tumors ranged in size from 1.2 to 6 cm. Microscopically, of the 14 primary tumors, 9 showed low-grade cytomorphology, whereas the remaining 5 neoplasms were high-grade lesions. The residuum of a hidradenoma was present in 5 of the 14 primaries. The mitotic rate was highly variable, ranging from 2 to 64 mitoses per 10 high-power field. The cellular composition of the tumors varied slightly, with clear cells, epidermoid cells, and transitional forms being present in each case. In 1 case, there was metaplastic transformation into sarcomatoid carcinoma. Glandular differentiation varied from case to case and appeared most commonly as simple round glands or as cells with intracytoplasmic lumens. Necrosis en masse was detected in 8 specimens. One specimen represented a reexcision and was unusual as it showed a well-demarcated intradermal proliferation of relatively bland clear cells accompanied by an overlying intraepidermal growth of clear cells resembling hidradenoacanthoma simplex. Despite the bland appearance, the tumor metastasized to a lymph node. Immunohistochemically, 5 of the 8 specimens studied for Her2/neu expression were negative, whereas 3 specimens from 2 cases yielded score +2, but all the 3 specimens with score 2+ subsequently proved negative for Her2/neu gene amplification by fluorescence in situ hybridization. Of 10 primaries studied, 4 tumors showed positive p53 immunoreaction in more than 25% of the cells comprising the malignant portion of the lesions, in 2 cases, a minority of the neoplastic cells (10%-20%) demonstrated nuclear staining, whereas the remaining 4 cases were negative. Of 9 specimens of hidradenocarcinoma studied for TP53 mutations, 2 harbored mutations, whereas the remaining 7 specimens showed the wild-type sequence. Of 11 specimens studied for translocation t(11;19), 2 cases harbored the translocation. It is concluded that cutaneous hidradenocarcinomas show some microscopic heterogeneity and comprise both low- and high-grade lesions that cytologically are similar to their benign counterpart, the hidradenoma. Within the spectrum of low-grade lesions, there seem to exist tumors almost indistinguishable from hidradenomas but still being capable of regional or distant metastasis. Similar to hidradenomas, hidradenocarcinomas show a t(11;19) translocation, but it is a significantly rarer event. Even rarer is the amplification of the Her2/neu gene. Of note is the relatively low frequency of TP53 mutations despite a high rate of p53 protein expression at the immunohistochemical level.

Skin-type adnexal tumor with trichoblastic germinative differentiation in the breast: a case report

Adnexal tumors with follicular differentiation in the breast parenchyma are rarely encountered. The authors present a unique case arising in a 64-year-old woman, in whom they observed composite differentiation toward follicular germinative cells of the hair follicle with focal areas of outer root sheath differentiation and pilar-type keratinization. The histogenesis of this tumor is analyzed in light of the peculiar pathological, immunohistochemical, and molecular genetic findings.

Nodular hidradenoma of the breast: A case report with literature review

Nodular hidradenoma or clear cell hidradenoma is a rare skin adenexal tumor which arises from eccrine sweat glands. Skin adenexal tumors situated in the breast parenchyma are still very rare and is one of the differential diagnoses of breast tumors. Failure to identify its morphologic features may lead to a mistaken diagnosis and over treatment. We report a case of breast lump, in a 40-year-old lady, which was diagnosed clinically as a malignant breast lump. Final diagnosis of nodular hidradenoma was made only after excision biopsy as fi ne needle aspiration cytology was inconclusive.