[331] Mammaglobin Distinguishes Cutaneous Metastasis of Breast Cancer from Primary Cutaneous Adnexal Tumors

ME Vergara, TH McCalmont, YY Chen, JT Rabban. UCSF, San Francisco, CA

Background: Distinction between cutaneous metastases of breast carcinoma and primary cutaneous adnexal tumors can be challenging. Immunohistochemistry (IHC) for estrogen and progesterone receptors (ER, PR) or for gross cystic disease fluid protein (GCDFP) offer little value due to overlapping immunophenotypes. Furthermore, a subset of breast cancers with aggressive behavior are negative for ER, PR and HER2 (so-called triple negative cancers). Mammaglobin is also a marker of breast cancer but its specificity in differential diagnosis with primary cutaneous adnexal tumors has not been formally established. It could be of particular value in the setting of triple-negative breast cancers.
Design: Mammaglobin (DAKO, 1:2) IHC was performed on whole sections of 16 cutaneous metastases of breast cancer, on tissue microarray sections of 190 primary breast cancers, including 118 triple negative cancers, and on whole sections of 64 primary cutaneous adnexal tumors (43 female, 21 male) with growth patterns simulating metastatic adenocarcinoma (14 sebaceous carcinoma, 7 microcystic adnexal carcinoma, 18 poroma, 12 syringoma, 5 desmoplastic trichoepithelioma, 3 adnexal adenocarcinomas NOS, 2 adenoid cystic carcinoma, and 3 adenocarcinoma of uncertain origin.) IHC was interpreted without knowledge of the morphologic diagnosis. Membranous/cytoplasmic expression was considered positive. Staining patterns were classified as strong/diffuse or weak/patchy.
Results: Mammaglobin was expressed in 10/16 (62.5%) cutaneous metastases of breast cancer, 23% of triple negative primary breast cancers, and 58% of ER positive primary breast cancers. Strong/diffuse expression was seen in 6/10 cutaneous metastases and weak/patchy in 4/10. Normal eccrine ducts were present in 41 skin specimens and 37 (78%) exhibited luminal/membranous mammaglobin expression. However, only 2/64 primary adnexal tumors were mammaglobin positive (both were male patients): one was an adenoid cystic carcinoma with strong/diffuse expression and one was a glandular neoplasm with poroid features showing weak/patchy expression. Overall, specificity of mammaglobin for breast cancer in this differential diagnosis was 96.9%; sensitivity was 62.5%.
Conclusions: Mammaglobin exhibited high specificity as a marker of cutaneous metastases of breast cancers and positive staining in a cutaneous glandular neoplasm should strongly raise consideration of breast origin even in the absence of ER,PR,HER2 expression. A negative stain result, however, is not conclusive since the sensitivity is moderate at best.
Category: Breast

Monday, March 22, 2010 1:00 PM

Poster Session II # 49, Monday Afternoon


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