Pure Apocrine Carcinomas Represent a Clinicopathologically Distinct Androgen Receptor–Positive Subset of Triple-Negative Breast Cancers

Abstract

Apocrine carcinomas comprise ∼1% of all breast cancers and are characterized by large cells bearing abundant eosinophilic granular cytoplasm, round nuclei, and prominent nucleoli. They are typically estrogen receptor/progesterone receptor/HER2 negative, making them unresponsive to typical hormonal or HER2-based chemotherapy. However, this subtype of triple-negative breast cancers expresses androgen receptor (AR), a feature not shared by most nonapocrine triple-negative cancers (NA-TNCs). AR therefore represents a potential diagnostic tool and therapeutic target for apocrine breast carcinoma. All pure apocrine carcinomas diagnosed during a 10-year period were reviewed, and clinicopathologic characteristics were compared with a control group of 26 NA-TNC cases. Twenty apocrine carcinomas were identified (∼0.8% of all breast cancers). The mean age at diagnosis was 69.3 years for apocrine carcinomas and 56.7 years for NA-TNC. All apocrine carcinomas and no NA-TNC were AR positive. The proportions of apocrine carcinoma grades varied, with G1 being seen in 15% of patients, G2 in 55%, and G3 in 30%. In contrast, 100% of NA-TNC cases were G3. The majority of apocrine carcinomas presented at low T stage (T1: 70%; T2: 20%; T3: 10%; T4: 0%), whereas NA-TNC cases more often presented at T2 or higher (T1: 46.2%; T2: 30.8%; T3: 11.5%; T4: 11.5%). Thirty percent of apocrine carcinomas and 30.8% of NA-TNCs had nodal metastases at presentation. Apocrine carcinomas had a favorable clinical prognosis, with 80% of patients showing no evidence of disease-related morbidity or mortality (mean follow-up: 45.2 mo). Pure apocrine carcinomas represent a clinicopathologically distinct subgroup of triple-negative breast cancer characterized by AR positivity. When compared with NA-TNC, apocrine carcinomas more often present in older women with lower grade and T stage, a group in which a more conservative treatment regimen is often desired.

Prognosis in triple‐negative apocrine carcinomas of the breast: A population‐based study

“…Most of these findings were consistent with previous studies. Mills et al found that patients with AC more often present in older women with lower grade and T stage, which is consistent with our findings. According to two retrospective studies, the proportion of lymph node metastasis was significantly lower in patients with AC than in patients with IDC, while our results showed no difference in N stage.…”

“…An observational study of 46 breast cancer patients showed that AC was more often present in older women with lower grade and T stage compared with TNBC, but some AC patients in this study were non-TNBC. 8 Meattini et al showed that TNAC had a favorable overall survival (OS) outcome when compared with other TNBC tumors. 9 However, this study provided limited information on the prognosis for TNAC due to its small sample size.…”

Apocrine lesions of the breast: part 2 of a two-part review. Invasive apocrine carcinoma, the molecular apocrine signature and utility of immunohistochemistry in the diagnosis of apocrine lesions of the breast

“…Pure apocrine carcinoma is relatively rare accounting for <1% of primary invasive breast tumours 4. It has been defined according to strict morphological and IHC criteria by Vranic et al 3.…”

Androgen Receptor: A Complex Therapeutic Target for Breast Cancer

“…Since AR and androgens increase the proliferation of a molecular apocrine breast cancer cell line, MDA-MB-453, it is widely perceived, albeit falsely, that AR is an unfavorable therapeutic target and prognostic marker in molecular apocrine subtype [33,34]. However, a study compared 20 molecular apocrine cancers with 26 non-apocrine cancers for AR expression and other clinical features [35]. All apocrine carcinomas were AR-positive, while all non-apocrine tumors were AR-negative.…”