Malignant aneuploid spindle-cell transformation in a proliferating trichilemmal tumour.

A case of spindle-cell carcinoma developed on a proliferating trichilemmal tumour (PTT) is presented. The tumour on the scalp of an 84-year-old white woman was excised and histological examination showed typical features of PTT, but with a coexistent malignant spindle-cell tumour with a sarcomatoid appearance. There were some areas of transition between squamous trichilemmal epithelium and the neoplastic mass composed of atypical spindle-shaped cells. Two years later, the patient was well, and neither recurrence nor metastases were observed. We report the second case of PTT with a malignant spindle-cell transformation with a sarcomatoid appearance (spindle-cell carcinoma), and a proven aneuploidy, demonstrated with DNA-flow cytometric analysis.