Apocrine epithelium of the breast: does it result from metaplasia?

Apocrine Variant of Pleomorphic Lobular Carcinoma In Situ: Further Clinical, Histopathologic, Immunohistochemical, and Molecular Characterization of an Emerging Entity

To date, the apocrine variant of lobular carcinoma in situ (AP-LCIS) has been cursorily described as a subtype of lobular carcinoma in situ (LCIS). We retrospectively reviewed 34 cases of AP-LCIS (including 23 associated with invasive lobular carcinoma) to fully characterize it. AP-LCIS typically presented with screen-detected calcifications in older women (mean age: 65 y) and was characterized by distended terminal duct lobular units with relatively large "pleomorphic" cells, central necrosis, and calcifications. AP-LCIS cells exhibited abundant eosinophilic occasionally granular cytoplasm, hyperchromatic nuclei, and prominent nucleoli. Synchronous classic and/or florid LCIS was identified in 24/34 (70%) AP-LCIS, and in 9/11 (82%) pure AP-LCIS. Most (68%) cases of AP-LCIS were estrogen receptor-positive (50% strongly), 35% were progesterone receptor-positive, 26% were human epidermal growth factor 2-positive, 18% demonstrated high-proliferation rate (Ki67: >15%), and 90% were androgen receptor-positive. Aurora kinase A, immunoreactive in 38% of AP-LCIS cases, was not significantly associated with recurrence, development of invasion, or nodal positivity (P>0.05). Compared with conventional (nonapocrine) pleomorphic lobular carcinoma in situ (P-LCIS), aurora kinase A was expressed in a significantly greater proportion of P-LCIS (100%). AP-LCIS and P-LCIS did not otherwise differ in clinicopathologic features. Next-generation sequencing utilizing the Oncomine Comprehensive Panel v2, performed on 27 AP-LCIS cases, showed no specific molecular findings. In a mean follow-up of 57 months, 2 (of 11, 18%) pure AP-LCIS cases recurred (2 both in situ and invasive) and none metastasized or proved fatal. AP-LCIS should be regarded as another high-grade LCIS similar to P-LCIS in many respects, and pending additional studies should be managed similarly.

Atypical Apocrine Adenosis: Diagnostic Challenges and Pitfalls

Apocrine change in the breast is an extremely common finding. In most cases, the benign or malignant nature of the lesion is easily recognized. Apocrine adenosis is used to describe sclerosing adenosis with apocrine change. The term apocrine atypia is used when there is significant cytologic atypia in apocrine cells, characterized by a 3-fold nuclear enlargement, prominent/multiple nucleoli, and hyperchromasia. Atypical apocrine adenosis is diagnosed when apocrine adenosis and apocrine atypia are superimposed. However, there are no definite criteria to distinguish atypical apocrine adenosis from apocrine ductal carcinoma in situ. Immunohistochemical markers can be confounding and may lead to erroneous diagnoses. Atypical apocrine features in sclerosing lesions may be misinterpreted as invasive carcinoma if the underlying lesion is not recognized. In the absence of definite features of malignancy, the diagnosis of apocrine ductal carcinoma in situ may be extremely difficult. In the present article, we review atypical apocrine adenosis focusing on diagnostic challenges and their implications on clinical management.

Apocrine adenoma of the breast coexistent with invasive carcinoma

We describe a case of apocrine adenoma with simultaneous occurrence of invasive ductal carcinoma in the breast of a 53-year-old woman. Apocrine adenoma affecting the breast is very rare. The lesion is composed of back-to-back ducts and papillary fronds covered with apocrine cells, and it is sharply demarcated from the surrounding breast tissue. The patient presented with a palpable nodule with skin retraction in her right breast, where ultrasound examination identified a 5-mm hypoechogenic nodule. The ultrasound also revealed in the surrounding breast parenchyma an additional abnormal finding suggestive of carcinoma. Histologic examination of the excised specimen showed that the hypoechogenic nodule represented an apocrine adenoma in proximity to the invasive ductal breast carcinoma. This is the first report that describes the simultaneous occurrence of these two lesions in the same breast.

Molecular pathology of breast apocrine carcinomas: A protein expression signature specific for benign apocrine metaplasia

Breast cancer is a heterogeneous disease that encompasses a wide range of histopathological types including: invasive ductal carcinoma, lobular carcinoma, medullary carcinoma, mucinous carcinoma, tubular carcinoma, and apocrine carcinoma among others. Pure apocrine carcinomas represent about 0.5% of all invasive breast cancers according to the Danish Breast Cancer Cooperative Group Registry, and despite the fact that they are morphologically distinct from other breast lesions, there are at present no standard molecular criteria available for their diagnosis. In addition, the relationship between benign apocrine changes and breast carcinoma is unclear and has been a matter of discussion for many years. Recent proteome expression profiling studies of breast apocrine macrocysts, normal breast tissue, and breast tumours have identified specific apocrine biomarkers [15-hydroxyprostaglandin dehydrogenase (15-PGDH) and hydroxymethylglutaryl coenzyme A reductase (HMG-CoA reductase)] present in early and advanced apocrine lesions. These biomarkers in combination with proteins found to be characteristically upregulated in pure apocrine carcinomas (psoriasin, S100A9, and p53) provide a protein expression signature distinctive for benign apocrine metaplasias and apocrine cystic lesions. These studies have also presented compelling evidence for a direct link, through the expression of the prostaglandin degrading enzyme 15-PGDH, between early apocrine lesions and pure apocrine carcinomas. Moreover, specific antibodies against the components of the expression signature have identified precursor lesions in the linear histological progression to apocrine carcinoma. Finally, the identification of proteins that characterize the early stages of mammary apocrine differentiation such as 15-PGDH, HMG-CoA reductase, and cyclooxygenase 2 (COX-2) has opened a window of opportunity for pharmacological intervention, not only in a therapeutic manner but also in a chemopreventive setting. Here we review published and recent results in the context of the current state of research on breast apocrine cancer.

The enigmatic nature of apocrine breast lesions

Epithelial cells of fetal breast glandular structures, at the third trimester of pregnancy (28 weeks), produce GCDFP-15, in the absence of specific apocrine morphology. Apocrine epithelium of the breast may be a normal process of differentiation rather than a result of metaplasia, and it has been demonstrated that it is estrogen-receptor, progesterone-receptor and bcl-2 negative, but androgen-receptor (AR) positive. The significance of AR expression in apocrine epithelium is uncertain. Apocrine epithelium is seen in a wide spectrum of breast entities, ranging from benign lesions to invasive carcinoma. Breast cancer accounts 32% of all cancer cases among women and is the most common type of cancer in women. Little is known about breast carcinogenesis. Widely, it is accepted that breast cancer, like most other type of cancer, is being developed through the accumulation of genetic aberrations. Apocrine epithelium may reflect instability of the breast epithelium, creating an environment favouring further oncogenic alterations. In the last decade, several lines of evidence support the idea that some breast benign epithelial apocrine lesions are clonal lesions and may be considered as truly pre-malignant or precursors of breast carcinoma. Apocrine changes in many cases do not present any diagnostic difficulty; on the other hand, apocrine proliferations with cytologic atypia can be particularly difficult and challenging. The purpose of this study is to collect and highlight the areas of consensus in the literature as well as the controversial areas concerning the apocrine epithelium of the breast.

Apocrine cysts of the breast: biomarkers, origin, enlargement, and relation with cancer phenotype

Up to one-third of women aged 30-50 years have cysts in their breasts and are presumed to be at increased risk of developing breast cancer. Here we present an extensive proteomic and immunohistochemistry (IHC) study of breast apocrine cystic lesions aimed at generating specific biomarkers and elucidating the relationship, if existent, of apocrine cysts with cancer phenotype. To this end we compared the expression profiles of apocrine macrocysts obtained from mastectomies from high risk cancer patients with those of cancerous and non-malignant mammary tissue biopsies collected from the same patients. We identified two biomarkers, 15-hydroxyprostaglandin dehydrogenase and 3-hydroxymethylglutaryl-CoA reductase, that were expressed specifically by apocrine type I cysts as well as by apocrine metaplastic cells in type II microcysts, terminal ducts, and intraductal papillary lesions. No expression of these markers was observed in non-malignant terminal ductal lobular units, type II flat cysts, stroma cells, or fat tissue as judged by IHC analysis of matched non-malignant tissue samples collected from 93 high risk patients enrolled in our cancer program. IHC analysis of the corresponding 93 primary tumors indicated that most apocrine changes have little intrinsic malignant potential, although some may progress to invasive apocrine cancer. None of the apocrine lesions examined, however, seemed to be a precursor of invasive ductal carcinomas, which accounted for 81% of the tumors analyzed. Our studies also provided some insight into the origin, development, and enlargement of apocrine cysts in mammary tissue. The successful identification of differentially expressed proteins that characterize specific steps in the progression from early benign lesions to apocrine cancer opens a window of opportunity for designing and testing new approaches for pharmacological intervention, not only in a therapeutic setting but also for chemoprevention, to inhibit cyst development as both 15-hydroxyprostaglandin dehydrogenase and 3-hydroxymethylglutaryl-CoA reductase are currently being targeted for chemoprevention strategies in various malignancies.

Identification of molecular apocrine breast tumours by microarray analysis

Previous microarray studies on breast cancer identified multiple tumour classes, of which the most prominent, named luminal and basal, differ in expression of the oestrogen receptor alpha gene (ER). We report here the identification of a group of breast tumours with increased androgen signalling and a 'molecular apocrine' gene expression profile. Tumour samples from 49 patients with large operable or locally advanced breast cancers were tested on Affymetrix U133A gene expression microarrays. Principal components analysis and hierarchical clustering split the tumours into three groups: basal, luminal and a group we call molecular apocrine. All of the molecular apocrine tumours have strong apocrine features on histological examination (P=0.0002). The molecular apocrine group is androgen receptor (AR) positive and contains all of the ER-negative tumours outside the basal group. Kolmogorov-Smirnov testing indicates that oestrogen signalling is most active in the luminal group, and androgen signalling is most active in the molecular apocrine group. ERBB2 amplification is commoner in the molecular apocrine than the other groups. Genes that best split the three groups were identified by Wilcoxon test. Correlation of the average expression profile of these genes in our data with the expression profile of individual tumours in four published breast cancer studies suggest that molecular apocrine tumours represent 8-14% of tumours in these studies. Our data show that it is possible with microarray data to divide mammary tumour cells into three groups based on steroid receptor activity: luminal (ER+ AR+), basal (ER- AR-) and molecular apocrine (ER- AR+).

The histologic spectrum of apocrine lesions of the breast

New data on apocrine carcinoma of the breast, especially on its unusual pathogenesis, are the facts that justify this study. The aim of this study was to describe the morphological features in both benign apocrine lesions and invasive apocrine carcinomas of the breast. The following apocrine lesions were pointed out: cysts, metaplasia, adenosis, adenoma, borderline malignant lesion, intraductal carcinoma and invasive apocrine carcinoma. Surgical specimens of breast benign and malignant lesions were fixed in formalin, embedded in paraffin blocks and the slides were stained with HE, PAS and immuno- histochemical ABC complex methods, using primary antibodies against: p53, Ki-67, androgen receptor, and GCDFP-15. The criteria of apocrine lesions, as well as classification of apocrine carcinoma were pointed out also. In the discussion we cited literature data about incidence of apocrine lesions in the breast, immunohistochemical, ultrastructural and molecular characteristics of apocrine lesions focusing on differential diagnostic problems between apocrine and nonapocrine lesions, and benign versus malignant apocrine lesion. The authors have suggested that apocrine carcinoma represents unusual type of the breast carcinoma and which may origin from the following precancerous lesions: apocrine hyperplasia, apocrine adenosis, atypical apocrine adenosis and adenoma. Immunohistochemical markers for apocrine differentiation are: GCDFP-15 and androgen receptors. Ki-67 and p53 may be good markers for differentiation between benign and malignant breast apocrine lesions. Positively staining for androgen receptors, not only in apocrine carcinoma of the breast, but also in benign lesions, has led some authors to postulate a possible role of androgens in the stimulation of breast epithelium and the development of apocrine cells and apocrine carcinomas. However, in this stage the clinical significance remains uncertain and follow-up studies will be required to evaluate this issue.

Extramammary Paget Disease of the Axilla Associated With Comedo-like Apocrine Carcinoma In Situ

Extramammary Paget disease of the axilla with underlying apocrine carcinoma has been reported only in six cases until now. This report deals with a seventh case characterized by the unique finding of comedo-like features evocative of large cell ductal breast carcinoma within an otherwise typical in situ apocrine carcinoma. This is characterized by spiral-shaped foci of epithelial proliferation with decapitation secretion and central masses of necrotic debris. A possible connection between the solid neoplasm and the overlying Paget disease is illustrated by a few apocrine-follicular units colonized by both the Paget cells and the structured adenocarcinoma. Here, although they display the same immunohistologic pattern of glandular differentiation, the two populations seem to be cytologically different and do not show signs of gradual transition to one another. Thus, they give the impression of parallel but distinct processes, which is consistent with the hypothesis of proliferative induction of a preexisting intraepidermal scattered population from the underlying adnexal carcinoma. The observed resemblance between apocrine carcinoma and comedo carcinoma of the breast, with its ontogenetic and phylogenetic implications, links not only the two neoplasms and the corresponding glands of origin but also mammary and extramammary Paget disease. This reinforces the unifying conception of Paget disease.

Immunohistochemical localization of gross cystic disease fluid protein-15, -24 and -44 in ductal carcinoma in situ of the breast: relationship to the degree of differentiation

AIMS

Three major proteins present in breast gross cystic disease fluid and expressed by the cyst lining apocrine epithelium are gross cystic disease fluid protein-15 (GCDFP-15), apolipoprotein-D (APO-D; GCDFP-24) and zinc alpha2-glycoprotein (ZnGP; GCDFP-44). The aim of this study was to investigate the expression of these proteins in ductal carcinoma in situ (DCIS) of the breast and to relate their expression with the degree of differentiation of DCIS.

METHODS AND RESULTS

An immunohistochemical study of these proteins was performed in 57 cases of DCIS and nine cases of morphologically apocrine DCIS. Positivity was seen in 24/57 (42.1%) cases with anti-GCDFP-15, 20/57 (35.1%) cases with anti-GCDFP-24 and 22/57 (38.6%) cases with anti-GCDFP-44. GCDFP-15 positivity was noted in 5/13 (38.5%) of the well-differentiated, 11/19 (57.9%) intermediately differentiated and 8/25 (32.0%) of the poorly differentiated cases (P=0.217). GCDFP-24 positivity was seen in 3/13 (23.0%) well-differentiated, 9/19 (47.4%) intermediately differentiated and 8/25 (32.0%) poorly differentiated cases (P=0.336). GCDFP-44 was detected in 5/13 (38.5%) of well-differentiated cases, 11/19 (57.9%) intermediately differentiated and 6/25 (24.0%) poorly differentiated cases (P=0.074). In the nine cases of apocrine DCIS, GCDFP-15 positivity was detected in seven (77.8%), while five (55.6%) and six (66.7%) cases were positive for GCDFP-24 and GCDFP-44, respectively.

CONCLUSIONS

The results indicate that there is no significant association between the expression of the studied proteins and the degree of differentiation of DCIS of the breast. Moreover, some morphologically apocrine DCIS cases appear to lose expression of these proteins.

Cell turnover in apocrine metaplasia of the human mammary gland epithelium: apoptosis, proliferation, and immunohistochemical detection of Bcl-2, Bax, EGFR, and c-erbB2 gene products

Apocrine metaplasia is considered to be a benign lesion of human mammary epithelium. However, it is not known how apocrine differentiation develops, and whether there is a relationship with particular subtypes of mammary carcinoma. In order to investigate cell turnover in apocrine metaplasia, apoptosis was detected by terminal transferase nick-end-labelling, and Ki-67 was used as proliferation marker. Bcl-2, Bax, epidermal growth factor receptor (EGFR), and c-erbB2-encoded protein were detected by immunohistochemistry. The proliferative activity was low (<1%). Frequency and intraepithelial localization of apoptotic cells resembled those of normal mammary epithelium. Bax immunostaining was inconstant and weak, and Bcl-2 was not detectable in apocrine metaplasia. Immunoreactivity of the c-erbB2 gene product was membrane-bound and showed a moderate to strong intensity, whereas staining for EGFR was weak and inconsistent. When compared with normal breast epithelium, apocrine metaplasia shows a regular cell turnover at a low rate, although the expression patterns of regulatory proteins are clearly altered. Our data suggest that changes in the expression of Bcl-2 or c-erbB2 protein do not result in a significant imbalance of apoptosis and proliferation, and thus should not be interpreted as indicator for increased risk of neoplastic transformation.

Molecular cytogenetic comparison of apocrine hyperplasia and apocrine carcinoma of the breast

The relationship of apocrine metaplasia to invasive breast cancer is controversial. Different authors have reported that apocrine differentiation in proliferative lesions may be a risk factor, a precursor lesion, or have no association with malignancy. The aim of this study was to compare the genetic alterations in benign apocrine hyperplasia with apocrine ductal carcinoma in situ (DCIS) and invasive apocrine carcinomas of the breast using comparative genomic hybridization. The mean number of alterations in apocrine hyperplasia was 4.1 (n = 10) compared to 10.2 in apocrine DCIS (n = 10) and 14.8 (n = 4) in invasive carcinoma. The most common alterations in apocrine hyperplasia were gains of 2q, 13q, and 1p and losses of 1p, 17q, 22q, 2p, 10q, and 16q. Apocrine DCIS and invasive carcinomas showed gains of 1q, 2q, 1p, and losses of 1p, 22q, 17q, 12q, and 16q as their most common DNA copy number changes. Apocrine hyperplasia is considered to be a benign lesion and its relationship to invasive carcinoma remains unclear. Our data suggest that some apocrine hyperplasias may be clonal proliferations. The mean number of alterations are lower in apocrine hyperplasia, however the changes show considerable overlap with those identified in in situ and invasive apocrine carcinoma. These alterations are also commonly seen in nonapocrine breast cancer. The data are consistent with apocrine hyperplasia as a putative nonobligate precursor of apocrine carcinoma.