Androgen receptors: a marker to increase sensitivity for identifying breast cancer in skin metastasis of unknown primary site.

Metastatic lesions to the skin may present a dilemma in the identification of the primary site. Breast carcinoma, metastatic to the skin, that is negative for estrogen receptors (ERs) and/or progesterone receptors (PRs) may be mimicked by a number of other metastatic lesions. In the present study, 16 formalin-fixed and paraffin-embedded infiltrating ductal carcinomas metastatic to the skin, which were ER-/PR-, ER-/PR+, or ER+/PR-; 5 metastatic lesions to the skin from primary lesions other than breast cancer; and 5 eccrine tumors were examined for immunoreactivity to the androgen receptor. The majority of the metastatic breast lesions (82%) exhibited immunopositivity for androgen receptor, whereas the metastatic skin lesions from primary lesions other than breast cancer and the eccrine tumors were immunonegative. Thus, androgen receptor immunohistochemistry could serve as a marker to increase sensitivity for identifying breast cancer in skin metastasis of unknown primary sites.