Unusual spindle cell squamous carcinoma in a renal transplant patient.

The histopathological diagnosis of spindle cell tumours is often difficult. We present a patient who developed a painful tumour on his head 6 years after renal transplantation. Histologically, the tumour was first interpreted as scar tissue with an unusual fibrohistiocytic component. Cytokeratins, desmin, CD31, CD34 and S100 could not be detected using conventional immunohistochemistry. After two recurrences and intensive immunohistochemical examinations, cytokeratin-positive tumour areas in direct connection with the epidermis were detected. The final diagnosis was therefore spindle cell squamous carcinoma. The patient finally died from brain metastases after experiencing further painful recurrences that were removed surgically. Our case underscores the importance of refined immunohistochemical methods in establishing the diagnosis of spindle cell squamous carcinomas, methods that should be taken into account especially if painful spindle cell tumours arise on sun-exposed skin in immunosuppressed patients.