Proliferating trichilemmal cyst with spindle cell carcinoma.

We report a 58-year-old woman with proliferating trichilemmal cyst (PTC), from which a spindle cell carcinoma arose. The tumor on her scalp had been removed at another hospital. Histological examination had revealed almost typical features of PTC. However, the case showed a partial transformation to spindle cell carcinoma, and transition zones between squamous epithelium and spindle cells were present. Three months after histologic examination, the patient came to us for the treatment of recurrent tumor. Despite surgical resection, the patient died as a result of distant metastases. Histologically, the recurrent tumor was composed of only spindle-shaped tumor cells. We describe the first example of this uncommon condition.