Clinicopathologic correlation of cutaneous metastases: experience from a cancer center.

OBJECTIVE: To analyze the clinical, histopathologic, and immunohistochemical characteristics of skin metastases.
DESIGN: Retrospective analysis (January 1, 1990, to December 31, 2005).
SETTING: Comprehensive cancer center. PATIENTS: Fifty-one patients (21 men and 30 women) with biopsy-proven skin metastases and correlative clinical data.
INTERVENTIONS: Four dermatopathologists reviewed a random mixture of metastases and primary skin tumors. Immunohistochemical studies for 12 markers were performed on the metastases, with skin adnexal tumors as controls. MAIN OUTCOME MEASURES: Clinical characteristics of cutaneous lesions, clinical outcomes, histologic features, and immunohistochemical markers.
RESULTS: Eighty-six percent (43 of 50) of the patients had known stage IV cancer, and skin metastasis was the presenting sign in 12% (6 of 50). In 45% (21 of 47) of the biopsies, the lesions were not suspected of being metastases owing to unusual clinical presentations. Seventy-six percent of the patients died of disease (median survival, 5 months). On pathologic review, many metastases from adenocarcinomas were either recognized or suspected, but the primary site was not easily identified based on histologic findings alone. Metastases from small cell carcinomas and sarcomas were histologically misinterpreted as primary skin tumors. Immunohistochemical analysis using a panel including p63, B72.3, calretinin, and CK5/6 differentiated metastatic carcinoma from primary skin adnexal tumors.
CONCLUSIONS: Cutaneous metastases can have variable clinical appearances and can mimic benign skin lesions. They are usually seen in patients with advanced disease, but they can be the presenting lesion. Although many metastatic adenocarcinomas can be recognized based on histologic findings alone, immunohistochemical analysis is an important diagnostic adjunct in some cases.