Metastatic Malignant Proliferating Trichilemmal Tumor Detected by Positron Emission Tomography

Abstract

BACKGROUND: Whole-body 18F-fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) was introduced in 1990s, and its efficacy for cerebral mapping and for selective detection of various malignancies is now being recognized. OBJECTIVE: To report on the usefulness of whole-body 18F-FDG-PET for detecting a metastatic lesion in a rare case of malignant proliferating trichilemmal tumor. METHODS: A malignant proliferating trichilemmal tumor on the occipital scalp of a 69-year-old female recurred on the margin of the surgical scar after an initial wide excision, and it was removed by Mohs micrographic surgery. 18F-FDG-PET was done to detect any remaining tumor tissue, and it showed a hot uptake on the lower left occipital area, where a pea-sized nodule formed 2 months later. Dissection and wide excision of the nodule showed metastatic malignant proliferating trichilemmal tumor cells in the lymph nodes. RESULTS: We were able to take advantage of the high resolution of the 18F-FDG-PET in detecting a metastatic lesion despite its proximity to the central nervous system. CONCLUSION: The 18F-FDG-PET can be used in future malignant proliferating trichilemmal tumor cases to study the metastatic characteristics of this rare tumor.