Triple-negative apocrine carcinoma: A rare pathologic subtype with a better prognosis than other triple-negative breast cancers

BACKGROUND AND METHODS

Apocrine adenocarcinoma is a rare subtype of breast cancer. We sought to compare the characteristics and survival of patients diagnosed with triple-negative apocrine adenocarcinoma to those of patients diagnosed with triple-negative invasive ductal carcinoma. Utilizing data from the National Cancer Database between 2004 and 2013, 70 524 eligible female patients with triple-negative breast cancer were identified including 566 patients with apocrine adenocarcinomas and 69 958 patients with invasive ductal carcinoma. Descriptive statistics for each variable were reported. A comparison of each covariate between the study cohorts was assessed in univariate and multivariate analysis. Cox proportional models were used to calculate hazard ratios. Additionally, the propensity score matching method was implemented to reduce treatment selection bias.

RESULTS

Patients with triple-negative apocrine tumors were more likely to be older, Caucasian, and have smaller, moderately to well-differentiated tumors. Multivariable analysis noted a significantly improved survival for patients with triple-negative apocrine carcinoma (TNAC) vs triple-negative invasive ductal carcinoma (TNBC) (hazard ratio [HR] 0.65 [95% confidence interval [CI] [0.53-0.81], P = 0 < .001). Propensity score matching analysis confirmed a significant difference in overall survival for patients with TNAC in comparison to TNBC (HR 0.79 [95% CI [0.63-1.00], P = .05).

DISCUSSION

Triple-negative apocrine adenocarcinomas have a modestly improved long-term survival when compared with triple-negative invasive ductal cancers.

A Rare Case of Invasive Apocrine Carcinoma of the Breast with Unusual Radiologic Findings

Invasive apocrine carcinoma (IAC) of the breast is a rare subtype of breast malignancy. Its incidence is not well known, but it is approximately less than 1% to 4%. For these reasons, there are few reports and little information on the radiologic appearance of IAC. Furthermore, most of the case reports show malignant features which are similar to invasive ductal carcinoma (IDC). We present a rare case of IAC without typical malignant feature on mammography, and ultrasonography (USG). Imaging findings on computed tomography (CT), magnetic resonance imaging (MRI), and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT are also presented. The nodule in our case showed a relatively benign feature on USG and it is the first case of IAC with unusual findings. Therefore, this report may encourage radiologists to consider the malignant potential and perform pathologic correlation even if a newly developed nodule does not present with a typical malignant feature on USG.

Aberrant Expression of Napsin A in Breast Carcinoma With Apocrine Features

An incidental finding of napsin A-positive breast carcinoma with apocrine features during workup for metastatic cancer in an axillary lymph node led to our investigation of the incidence of napsin A expression in breast carcinomas, focusing on those with apocrine features. We included 97 cases of breast carcinomas and performed immunohistochemistry with napsin A, GATA-3, thyroid transcription factor-1, and GCDFP-15. There was a statistically significant difference between apocrine and nonapocrine cases with respect to polyclonal napsin A H-scores (P < .00152), monoclonal napsin A H-scores (P < .00631), GATA-3 H-scores (P < .00029), and GCDFP-15 H-scores (P < .00251). Of the 49 cases of apocrine carcinoma, monoclonal napsin A antibody was positive in 66.7% of cases, including in 7 (14.6%) that showed 3+ staining. The majority of nonapocrine cases were negative (62.5%) or weakly (1+) positive (29.2%), with none exhibiting 3+ strength. It is important for pathologists to be aware that breast carcinomas with apocrine features can express napsin A.

A rare presentation of triple-negative apocrine breast carcinoma with metastases

Apocrine breast carcinoma is a rare subtype of the invasive ductal carcinoma and accounts for as little as 0.3–1% of all breast cancers. It is usually positive for human epidermal growth factor receptor 2 (HER-2) and negative for both estrogen receptor and progesterone receptor. Here we present an exceptionally rare case of apocrine breast carcinoma that is a triple receptor negative with metastases and to our knowledge this is the first published case. This is a significant finding because it implies that the tumor would not respond to the typical hormonal agents. This case highlights the need for studies to elucidate better treatment strategies for these types of patients.