Clinicopathologic Findings of Metastatic Skin Cancer

Background: The incidence of metastatic skin cancer has been reported to be relatively low. Because the diagnosis is not so difficult, cutaneous metastasis could be an important clue to discover the hidden internal malignancy, if found before recognizing primary cancer, or play a significant role to determine therapeutical plans and prognosis if found after diagnosis of primary cancer. Material and methods: This study was made upon the 68 cases of metastatic skin cancer, which had been confirmed histopathologically in the department of dermatology, Kosin University Gospel hospital from January, 1986 to August, 2003. Age and sex distributions, sites of primary cancer, time of detection, localization of the lesions, morphologic and histopathologic findings were examined by the review of medical records, clinical photographs, and pathologic slides. Results: 1. The mean age at the time of diagnosis was 56.6 years and most patients were distributed over 5 decades. The male to female ratio was 1:1.3. 2. Metastasis from breast carcinoma consisted of 19 cases, this was the most common primary cancer, followed by lung cancer, melanoma, and stomach cancer. In men, lung cancer and stomach cancer were the most common primary neoplasm, while breast cancer was the most frequent in women. 3. 50 of the cases were detected after diagnosis of primary cancer and during therapy. The other 18 cases were detected before the internal malignancy was recognized. 4. The localization of metastatic skin cancer was widespread over the whole body. The majority of cutaneous metastasis was predisposed to the surface near primary cancer, but distant metastases such as alopecia neoplastica on the scalp were also observed. 5. The most common morphologic features were single or multiple nodules, while inflammatory and indurated plaques were also found. 6. Histopathologic examination revealed that adenocarcinoma was the most common pathologic type, followed by squamous cell carcinoma and melanoma. The histopathologic features of cutaneous metastasis generally mimicked that of primary tumors. Conclusion: Generally, metastatic skin cancer is detected after the diagnosis of primary cancer showing subsequent treatment failure and poor prognosis. In some cases, however, cutaneous metastasis can be the earliest sign to recognize internal malignancy. Especially in the cases of metastatic skin cancer originating from the kidney, liver and thyroid gland, cutaneous features are the most significant evidences to presume the site of origin without any other findings. Therefore, it is important to recognize the clinical and histopathologic findings of metastatic skin cancer for the most successful diagnostic, therapeutic and prognostic determination.