The diagnosis of basosquamous cell carcinoma is controversial. A review of cases of basal cell carcinoma showed 23 cases that had conspicuous areas of squamous cell carcinoma. This was distinguished from squamous differentiation and keratotic basal cell carcinoma by a comparative study of 40 cases of compact lobular and 40 cases of keratotic basal cell carcinoma. Areas of intermediate tumour differentiation between basal cell and squamous cell carcinoma were found. Basal cell carcinomas with areas of squamous cell carcinoma may be called basosquamous carcinoma. Basal cell carcinomas have been described with nuclear atypia,' multinucleate tumour giant cells,' 2 and other unusual or aggressive features.3 Only one case of basal cell carcinoma with areas of squamous cell carcinoma has been reported, and this was termed basosquamous cell carcinoma.4 This controversial diagnosis is accepted by some authors-8 and rejected by others.9-'2 This paper reports a histopathological study of 23 cases of basal cell carcinoma of skin in which there were conspicuous areas of squamous cell carcinoma.

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Two cases of basosquamous cell carcinoma of the skin with lymph node, lung and bone metastases are reported. Metastases occurred 4 and 7 years after identification of the primary tumour. Both the primary and metastatic lesions had areas of typical basal cell carcinoma and squamous cell carcinoma and also intermediate carcinomatous tissue. In the bone metastasis of one case there were rudimentary hair follicles and areas of matrical differentiation. These cases further support the existence of basosquamous cell carcinoma and emphasize its metastatic potential.

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