Previous reports regarding the rates at which various internal tumors metastasize to the skin have been limited and have only included the Caucasian population. Moreover, the mechanisms that predispose certain internal malignancies to metastasize to the skin have rarely been discussed in the scientific literature.

We determined the frequencies with which various internal malignancies metastasize to the skin in patients from a Taiwanese medical center. We also evaluated whether expressions of chemokine receptors CCR10 and CXCR4 by tumor cells correlate with cutaneous metastatic ability.

Clinical records from Kaohsiung Medical University Hospital, Kaohsiung, Taiwan, during 20 years (1986-2006) were reviewed and cases of biopsy-proven primary internal malignancies and cutaneous metastases were identified. Immunohistochemical staining with antibodies to CCR10 and CXCR4 was performed on a selected number of internal malignancies with and without skin metastases.

From 12,146 patients with internal malignancies, we found 124 cases (1.02%) with cutaneous metastases. The highest rates of skin metastases were found to occur from carcinoma of the breast, followed by the lung, oral mucosa, colon and rectum, stomach, and esophagus. However, the rate of cutaneous metastasis from breast cancer was much lower compared with previous studies involving Caucasians. In general, adenocarcinomas gave rise to cutaneous metastases at a higher frequency compared with other histologic subtypes. In addition, the expressions of CCR10 and CXCR4 by tumor cells did not correlate well with the presence or absence of skin metastases.

This study is retrospective in nature.

Different internal malignancies metastasize to the skin with different frequencies, and the rates at which different malignancies metastasize to cutaneous sites differ between the Taiwanese and Caucasian populations. The mechanisms responsible for the cutaneous metastatic ability of certain malignancies likely involve factors other than chemokine receptors CCR10 and CXCR4, because their expressions by tumor cells are neither necessary nor sufficient for the formation of skin metastases.