CONTEXT: Recent investigations have demonstrated the utility of CD10 as a marker for renal cell carcinoma (RCC). Cutaneous metastases occur in up to 11% of patients with RCC and may be the presenting sign of widespread disease. The differential diagnosis in histopathologic evaluation of these cases includes cutaneous adnexal neoplasms, and describing the expression of CD10 in these tumors may be helpful in delineating the differential diagnosis. OBJECTIVE: To determine CD10 expression in a variety of adnexal lesions and to determine the diagnostic utility of CD10 in an immunohistochemical panel differentiating metastatic cutaneous renal cell carcinoma from cutaneous adnexal neoplasms. DESIGN: We studied 57 primary adnexal neoplasms of eccrine (n = 31), apocrine (n = 16), and sebaceous (n = 10) differentiation as well as normal skin (n = 3) and RCC metastatic to the skin (n = 4). A CD10 monoclonal antibody was applied to formalin-fixed, paraffin-embedded tissue. Specimens were randomized and categorized as immunopositive or immunonegative by a pathologist with expertise in immunohistochemistry who was blinded to the diagnoses. RESULTS: Two (6.5%) of 31 eccrine, 1 (6%) of 16 apocrine, and 4 (40%) of 10 sebaceous neoplasms demonstrated CD10 immunopositivity. Four (100%) of 4 RCC were CD10 immunopositive. CD10 expression was significant for eccrine and apocrine neoplasms (P < .001) compared to metastatic RCC, but not for sebaceous neoplasms (P = .08). CONCLUSION: Based on these results, CD10 is a useful additional immunostain for the discrimination of RCC metastatic to the skin and cutaneous adnexal neoplasms with eccrine and apocrine differentiation, but not with sebaceous differentiation.
CONTEXT: Recent investigations have demonstrated the utility of CD10 as a marker for renal cell carcinoma (RCC). Cutaneous metastases occur in up to 11% of patients with RCC and may be the presenting sign of widespread disease. The differential diagnosis in histopathologic evaluation of these cases includes cutaneous adnexal neoplasms, and describing the expression of CD10 in these tumors may be helpful in delineating the differential diagnosis. OBJECTIVE: To determine CD10 expression in a variety of adnexal lesions and to determine the diagnostic utility of CD10 in an immunohistochemical panel differentiating metastatic cutaneous renal cell carcinoma from cutaneous adnexal neoplasms. DESIGN: We studied 57 primary adnexal neoplasms of eccrine (n = 31), apocrine (n = 16), and sebaceous (n = 10) differentiation as well as normal skin (n = 3) and RCC metastatic to the skin (n = 4). A CD10 monoclonal antibody was applied to formalin-fixed, paraffin-embedded tissue. Specimens were randomized and categorized as immunopositive or immunonegative by a pathologist with expertise in immunohistochemistry who was blinded to the diagnoses. RESULTS: Two (6.5%) of 31 eccrine, 1 (6%) of 16 apocrine, and 4 (40%) of 10 sebaceous neoplasms demonstrated CD10 immunopositivity. Four (100%) of 4 RCC were CD10 immunopositive. CD10 expression was significant for eccrine and apocrine neoplasms (P < .001) compared to metastatic RCC, but not for sebaceous neoplasms (P = .08). CONCLUSION: Based on these results, CD10 is a useful additional immunostain for the discrimination of RCC metastatic to the skin and cutaneous adnexal neoplasms with eccrine and apocrine differentiation, but not with sebaceous differentiation.