Malignant proliferating trichilemmal tumour: a case report.

An 86-year-old man presented with a painless, pea-sized growth over the left angle of his jaw, which had been gradually enlarging over two years. A clinical diagnosis of pilar cyst was made. Histopathological examination of the mass revealed a malignant proliferating trichilemmal tumour. During follow-up 4 months later, a palpable small upper jugular lymph node was noted at the left side of the neck. Biopsy revealed a metastatic malignant trichilemmal tumour. This case illustrates a rare malignant tumour which is a challenge to clinical diagnosis.