18F-FDG PET/CT Findings in a Patient With a Proliferating Trichilemmal Cyst

Case report: Malignant proliferating trichilemmal tumor of the thumb

Proliferating trichilemmal tumor is a very rare benign tumor that has the potential to transition into a malignant tumor. PTT most commonly affects the scalps of women above 60 years old and is frequently misdiagnosed due to its rarity. Herein, we present a case of a 68-year-old man with a malignant proliferating trichilemmal tumor on his right thumb. X-ray image showed a soft tissue mass on his thumb accompanied by bone destruction, while ¹⁸F-FDG PET revealed a hypermetabolic mass in the first index with axillary lymph node metastasis.

The Proliferating and Malignant Proliferating Trichilemmal Cyst: An Anatomo-Clinical Study of Three Cases

Background

The proliferating and malignant proliferating trichilemmal cysts (MPTC) are rare adnexal tumors. We report 3 cases through which we will detail the anatomo-clinical characteristics of these tumors.

Cases

Two patients, 60 and 56 years old, consulted for multiple scalp nodules, one of which had changed with the appearance of a central ulceration. The removal of the remaining scalp nodules was in favor of PTCs. The third patient presented with an ulcerative lesion occupying the vertex. Skin biopsy found trichilemmal-type keratinization associated with areas of necrosis concluding with a MPTC.

Discussion

The PTC is a transitional form between the trichilemmal cyst (TC) and the MPTC. The increase in the size of a TC and ulceration are sufficient signals to suspect this evolution.