[Two cases of squamous cell carcinoma arising from erythema ab igne]

This report describes two female patients, 69 and 79 years old, with squamous cell carcinoma (SCC) developing from erythema ab igne (EAI) due to thermal irradiation from a sunken hearth (irori in Japanese) or an underfloor brazier covered with a quilt (kotatsu in Japanese). EAI on the knees and lower thighs showed reticular pigmentation at its periphery and poikiloderma in the center with many keratotic nodules. In both cases, the SCCs were located almost symmetrically on an anterior site 1/3 of the way down both lower thighs. They were surrounded by many keratotic nodules. Histologically, these nodules showed an atypia of the epidermal cells, indicating carcinoma in situ resembling actinic keratosis ro Bowen's disease. It was also strongly suggested that the SCCs in these patients had developed from the keratotic nodules. EAI appeared to have played a pathogenetic role in the cutaneous carcinoma.