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Immunohistochemical techniques to compare primary vs. metastatic mucinous carcinoma of the skin
Gillian Levy1, Alexander Finkelstein, Jennifer M McNiff
1Department of Pathology, Yale University School of Medicine, New Haven, CT 06520, USA. gillian.levy@yale.edu
Background:
Primary and metastatic mucinous carcinomas in skin are histologically indistinguishable. Immunohistochemical panels help differentiate primary and metastatic adenocarcinoma of skin, but data regarding mucinous carcinoma is scant.
Methods:
We stained five primary mucinous carcinomas, two mucinous carcinomas metastatic to skin and five primary breast and colon mucinous carcinomas with p63, CD15, CK5/6, CK7, CK20, calponin and D2-40 to identify patterns that might differentiate primary from metastatic disease. We also searched for myoepithelial cells in all cases.
Results:
All cases of primary mucinous carcinoma of the skin were positive for CK7, 40% showed rare cells labeled for p63 and 20% of cases labeled focally for CK5/6. The breast mucinous carcinomas metastatic to the skin were negative for all markers except CK7, although 60% of primary breast carcinomas labeled for p63. Colon mucinous carcinoma labeled only for CK20.
Conclusions:
In a small subset of mucinous carcinomas (20% in this series), positive labeling for CK5/6 indicated primary cutaneous tumor. Staining with p63 also favored primary over metastatic disease. Myoepithelial cell layers were not consistently identified to enable the identification of primary disease.
