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.
Source: International Journal of Surgical Pathology - Category: Pathology Authors: Tags: Original Articles Source Type: research