Often the distinction of cutaneous apocrine
carcinoma from metastatic mammary apocrine
carcinoma to the skin can be a diagnostic dilemma because both
tumors share similar histologic features and have overlapping immunohistochemical profile. We compared the expression of
adipophilin,
cytokeratin 5/6, p63, GATA3, mammaglobin,
androgen receptor,
estrogen receptor,
progesterone receptor, and HER2 by immunohistochemistry in 14 cutaneous apocrine
carcinomas (11 primary
tumors, 3
metastases) and 26 primary apocrine
carcinomas of the breast. Whereas focal
adipophilin staining was seen in 36% (5/14) of cutaneous apocrine
carcinoma, strong and diffuse
adipophilin staining was seen in 88% (22/25) of mammary apocrine
carcinoma (P = .0013). Differences in
estrogen receptor and
progesterone receptor expression were also statistically significant (P = .018 and .043).
Androgen receptor was strongly positive in all cutaneous and mammary cases. Although there was no significant difference in the frequency of expression of
cytokeratin 5/6, p63, HER2, GATA3, and mammaglobin in cutaneous apocrine
carcinoma versus mammary apocrine
carcinoma, strong and diffuse
cytokeratin 5/6 and/or mammaglobin expression were seen only in cutaneous apocrine
carcinoma. In conclusion, cutaneous apocrine
carcinoma is likely
adipophilin- ER+ PR+/- HER2- and can exhibit strong and diffuse
cytokeratin 5/6 and/or mammaglobin expression. On the contrary, a mammary apocrine
carcinoma is likely adipophilin+ ER- PR- and often exhibit 3+ HER2 with corresponding HER2 gene amplification. A panel of
adipophilin, ER, PR, HER2,
cytokeratin 5/6, and mammaglobin may be helpful in distinguishing cutaneous apocrine
carcinoma from mammary apocrine
carcinoma.