Abstract: 【Abstract】 Objective To investigate the clinical and pathological characteristics of solitary fibrofolliculoma. Methods This was a case series study. Clinical data were collected from 15 patients with histopathologically confirmed solitary fibrofolliculoma at Nanjing Drum Tower Hospital from April 2008 to December 2023. Clinical characteristics, histopathological features, immunohistochemical findings, and follow-up information were collected and analyzed. Results The 15 patients were aged from 22 to 71 years, including 9 males and 6 females. Skin lesions mostly presented as solitary yellowish or white papules or nodules measuring 0.2 ? 1.2 cm in diameter. The lesions were located on the nose （8 cases）, ear （4 cases）, periocular region （2 cases）, and occipital region （1 case）. Histopathologically, the lesions were centered on well-developed hair follicles within the dermis and exhibited reticular and lobulated architectures; cytologic atypia was generally absent, although outer root sheath hyperplasia was observed in some cases. Immunohistochemical study of 7 cases showed that the neoplastic epithelial cells were diffusely positive for p63 and p40, positive for smooth muscle actin （SMA）, focally positive for S100 and epithelial membrane antigen, but negative for carcinoembryonic antigen; peritumoral mesenchymal cells were positive for CD10 and focally positive for CD34, but negative for SMA and desmin; intratumoral mesenchymal cells did not express CD10. All patients underwent surgical excision of the lesions. During a follow-up period of 4 - 192 months, no recurrence was observed. Conclusions Solitary fibrofolliculoma most commonly presents as papules or nodules on the face, head, and neck, and is immunohistochemically characterized by CD10 positivity in peritumoral mesenchymal cells and CD10 negativity in intratumoral mesenchymal cells, which may be helpful for the diagnosis.

Key words: Hamartoma, Fibrofolliculoma, Single, Organizational pathology, Immunohistochemistry