Three cases of porocarcinoma

Three cases of long‐standing eccrine poromata are described showing a range of histological changes progressing towards malignancy. The duration of the lesions was from 10 to 20 years, finally presenting as raised, non‐pigmented, sessile and pedunculated lobulated tumour masses on the foot, scalp and thigh. Two tumours showed ulceration; none was associated with metastasis. These clinical features are similar to reported series of eccrine porocarcinomata (Shaw et al. , 1982). Two of the patients had prior internal malignancies. The excised tumour tissue was firm and grey‐white in colour. Histology of the tumours showed continuity with the epidermis; one initially presenting as an exclusively intra‐epidermal lesion. Typical appearances of eccrine poromata were demonstrated: closely packed small squamous cells formed broad interlacing trabeculae, with occasional clefts and duct‐like spaces. Cytological evidence of dysplasia was present in the intra‐epidermal lesion at the outset; in the others focal Bowenoid dysplasia has arisen from previously bland and uniform tumour epithelium. The most recent biopsies show a range of appearances from focal Bowenoid dysplasia in an otherwise benign lesion, through to invasive squamous carcinoma. We postulate a spectrum of development of porocarcinomata originating from long‐standing poromata. Histochemistry confirms active glycogen metabolism within the invasive tumour (Sanderson & Ryan, 1963; Hashimoto & Lever, 1964). Immunoperoxidase studies demonstrated carcino‐ embryonic antigen in clefts and duct‐like structures, but not in the main mass of tumour tissue (Penneys, Nadji & Morales, 1982). Electron microscopy was performed on two of the tumours.