[175] Clinicopathologic Evaluation of Apocrine Carcinoma of the Breast

Yuna Gong, Shirin Sioshanshi, Shaolei Lu, Dina Kandil, Ashraf Khan. University of Massachusetts Medical School, Worcester, MA; Rhode Island Hospital, Providence, RI

Background: Apocrine carcinoma of the breast is a rare histologic subtype accounting for 0.4 to 4% of all breast cancers. Limited data exists in literature regarding these tumors due to the rarity of the subtype. The goal of this study is to evaluate the immunohistochemical (IHC) expression pattern of a series of apocrine carcinomas and to correlate the findings with the clinical outcome.
Design: A search in the medical records at our institution from 1998-2012 yielded 77 malignant cases of breast surgical specimens with apocrine differentiation. The tumors included 24 cases of ductal carcinoma in-situ (DCIS) and 53 cases of invasive ductal carcinoma (IDC). IHC study was performed on paraffin sections of the cases, including markers for estrogen (ER), progesterone (PR), HER2/neu, androgen receptor (AR), insulin-like growth factor II mRNA-binding protein 3 (IMP3), epidermal growth factor receptor (EGFR) and cytokeratin 5/6 (CK 5/6). Clinical follow-up (FU) was available on 17/24 of DCIS and on 31/51 of IDC patients, with a median follow-up period of 64 and 56 months, respectively.
Results: Of the total of 5698 breast carcinomas diagnosed between 1998-2012, 24/1388 (1.7%) DCIS and 53/4310 (1.2%) IDC were identified to have apocrine differentiation. 3/18 (15%) of apocrine DCIS and 18/53 (34%) of apocrine IDC exhibited a triple negative (TN)* profile; and of the TN cases, 100% of DCIS and 93% of IDC were AR positive. However, there was a poor correlation between TN profile and basal phenotype markers, with 0/3 DCIS positive for EGFR, CK 5/6 and IMP3 and with only 7/18, 4/18, and 2/18 IDC cases positive for EGFR, CK5/6 and IMP3 respectively. Of the 17 DCIS patients with FU, 1 patient developed concurrent invasive metaplastic carcinoma and died from the disease. The remaining 16 patients have no evidence of local recurrence or metastases. Of the 31 IDC patients, 3 developed metastatic diseases, 4 died from unrelated causes and the remaining 24 are disease-free to date.
*Triple negative (TN) = ER, PR and HER2 negative

Summary of IHC Study
DCIS58% (14/24)42% (10/24)67% (12/18)5% (1/20)10% (3/21)0% (0/20)91% (19/21)
IDC38% (20/53)21% (11/53)40% (21/52)13% (6/47)26% (12/47)17% (8/47)85% (39/46)
% positive (# positive/total # tested)

Conclusions: Apocrine carcinoma of the breast is a distinct subset of ductal carcinoma with a largely indolent behavior. While >1/3 of IDC were TN, only a minority of these showed markers associated with basal-like breast cancer. No prognostic impact was observed with TN profile or the basal phenotype markers.
Category: Breast

Wednesday, March 6, 2013 1:00 PM

Poster Session VI # 1, Wednesday Afternoon


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