[Semi-malignant pitch-acanthoma on the hand of a coke oven worker]

We experienced a case of pitch-acanthoma which had developed on the hand of a coke worker after 15 years from his retirement. The patient was a 75-year-old male, who had worked mainly as a coke-oven worker for 24 years. In the spring of 1988, after 15 years from his retirement, he noticed a small nodule on the dorsal aspect of his right hand. He visited our clinic on June 1988 because the nodule was rapidly growing larger. The diagnosis of pitch-acanthoma was obvious from his occupational history and the characteristic poikilodermatous outlook of his skin. The tumor was removed surgically. Histological examination showed hyperkeratosis and acanthosis with horn-pearl formation. Moreover, a pack of atypical cells was observed within the lesion, suggesting an early malignant change. The patient was heavily exposed to a tar-gas-containing atmosphere in his workplace for quite a long period. As tar or pitch remains within the skin in spite of careful cleansing, workers in this atmosphere have a relatively high risk of developing skin cancer. Our present case shows that such malignant change can occur after long years and we would emphasize the necessity of a long term follow-up, perhaps throughout the lifetime of these workers.