Appearance of cutaneous melanoma and subcutaneous metastases in metastatic gastric carcinoma undergoing chemotherapy with oral 5-fluorouracil prodrug.

Metastatic skin lesions of gastric cancers usually appear as nonspecific, firm, and hyperpigmented nodules. However, they occasionally present as unusual skin manifestations that mimic other skin disorders. We describe a case of multiple cutaneous metastases from gastric cancer resembling sebaceous cysts with a synchronous melanoma, in a patient after fluoropyrimidine-based systemic chemotherapy. Melanoma occurring as a second cancer has been recognized in patients having undergone previous chemotherapy or radiation for another cancer. We can assume that the capecitabine-based chemotherapy may have played a role in the development of the melanocytic neoplasm. Our observation adds extra evidence to the link between fluoropyrimidine-based immunosuppression and the induction of melanocytes' proliferation and transformation. For these reasons, it is advisable to require dermatological checkups for patients undergoing chemotherapy treatments in order to identify suspicious melanocytic lesions as soon as possible.