Fine-needle Aspiration Biopsy of Pilomatrixoma (Cytological Features of Six Cases Histologically Approved)

Abstract

Background and Objective: Pilomatrixoma is a rare, benign, slow-growing tumor of the hair matrix. Excisional biopsy is often the preferred method of diagnosis for cutaneous masses including pilomatrixoma. However, fine-needle aspiration is also performed on these lesions. There are very few reports on the cytologic features of pilomatrixoma in fine-needle aspiration. In this study, we aimed to evaluate the clinical and cytological features of six cases of pilomatrixoma, which were confirmed histopathologically. Materials and Methods: The study includes six cases of pilomatrixoma, which were diagnosed by two cytopathologists in 2019 and 2022. A detailed cytological analysis was done by a semiquantitative method. Cellularity, basaloid cells, squamous cells, giant cells, shadow cells, naked nuclei, calcium deposits, inflammation, and debris were semiquantified from 0 to 3+. Results: The ages of patients ranged from 8 to 63 years old. The male-to-female ratio was 2:1. All cases occurred in the head and neck area. The cytological diagnosis was pilomatrixoma in five cases and epidermoid/dermoid cyst in one case. The surgical excision was performed in all patients. The diagnosis of pilomatrixoma was confirmed histologically in all cases. Conclusıon: Fine-needle aspiration biopsy (FNAB) of pilomatrixoma can be a diagnostic challenge. There are very few reports on the cytologic features of pilomatrixoma in FNAB smears. The presence of ghost cells and basaloid cells should suggest the possibility of pilomatrixoma. The presence of giant cells, fibrillary matrix, calcium deposits, squamous cells, naked nuclei, inflammation, and debris are cytological findings supporting the diagnosis.