18F-FDG PET/CT in a Rare Case of Malignant Proliferating Trichilemmal Cyst Secondary to Trichilemmal Cystic Nevus.

A 52-year-old man with multiple scalp nodules for more than 30 years and a right occipital mass that had been progressively enlarging for the past 2 years and rupturing and draining for more than 6 months was pathologically confirmed to be secondary malignant proliferating trichilemmal cyst (MPTC). 18F-FDG PET/CT showed active glucose metabolism in the scalp lesion and similar hypermetabolism in the dorsal and right iliac spine skin nodules. This case demonstrates the significant advantages of 18F-FDG PET/CT whole-body imaging in evaluating malignant proliferating trichilemmal cyst, a rare disease.