Cutaneous Metastasis: a Clinical, Pathological, and Immunohistochemical Appraisal

Background: Cutaneous tumor metastasis may be the first manifestation of cancer, but more often is a harbinger of advanced disease that portends an ominous prognosis. All skin accessions over the past 10 years from a large Veterans Administration (VA) hospital were reviewed.

Methods: Archived histories, glass slides, and the immunohistochemical battery (IHC), were assessed to determine diagnostic accuracy.

Results: Of the 100,453 cases reviewed, there were a total of 77 cases (75 males and 2 females) of cutaneous metastasis from the lungs (28.6%), metastatic melanoma (18.2%), gastrointestinal tract (14.2%), genitourinary tract (10.4%), head and neck (9.1%), hematologic (5.2%), breast (5.2%), and miscellaneous (<2%). Metastasis represented the first indication of an internal malignancy in 7.8% of cases. The cutaneous sites of involvement included the head and neck (28%), the trunk (40%), the extremities (18%), and multiple sites (14%). The age range was 38-83 years, with a mean of 62 years. The average time interval between diagnosis of internal malignancy and cutaneous presentation was 33 months (range: <1 month-22 years), and the average survival following diagnosis was 7.5 months (range: <1 month-8 years). In a cohort of subjects, a truncated immunohistochemical battery consisting of CK-7, CK-20, and S-100 was consistent with the expected staining pattern of the primary source of cutaneous metastasis in 83.33% of the patients.

Conclusions: Excluding the potential for age and gender bias in this study conducted in a VA setting, cutaneous metastases represent an uncommon, deadly, and late-developing occurrence in many patients. Compared with previous studies, lung carcinoma remains the most common of the cutaneous metastases, with a relative rise in the incidence of metastatic melanoma. The immunohistochemical battery of CK-7, CK-20, and S-100 is a helpful adjunct in narrowing the differential diagnosis of the primary site of a large proportion of cutaneous metastases, particularly tumors with an epithelioid appearance such as carcinomas and melanomas.