Abstract: Objective To analyze histopathological and clinical features of dermatofibroma, and to explore the relationship between them. Methods Clinical and histopathological data were collected from 150 patients with histopathologically confirmed dermatofibroma in Department of Pathology, Shanghai Skin Disease Hospital from September 2017 to August 2018, and analyzed retrospectively. Results Among the 150 patients, 65 were males, and 85 were females. Their age was 42 ± 13.8 years, and the course of disease ranged from 3 months to 30 years. Some of the patients had concomitant symptoms, mainly manifesting as itching, some had spontaneous pain and mild tenderness, and 18 patients had a history of injury, insect bite or infection at lesion sites. Skin lesions mainly occurred on the extremities（107 cases, 71.3%）, and most were solitary（105 cases, 70%）. Before pathological examinations, 102 cases were clinically diagnosed as dermatofibroma, 16 as epidermoid cyst, 13 as pigmented nevus, 3 as keloid, 12 as skin mass, 1 as malignant melanoma, 1 as xanthogranuloma, 1 as prurigo nodularis, and 1 as neurofibroma. Among 169 hematoxylin and eosin （HE）? stained sections, 25 （14.8%） appeared to be consistent with aneurysmal dermatofibroma, 66（39.1%）with cellular dermatofibroma, 36 （21.3%） with sclerosing dermatofibroma, and 22 （13.0%） with epithelioid dermatofibroma. Coexistence of two or more subtypes could be seen in 12 sections. There were also a few new variants, such as dermatofibroma with hyperplastic sweat duct （1 case）, deep dermatofibroma （3 cases）, dermatofibroma with epithelioid cells intermingled with hyperplastic collagen （1 case）. The duration of aneurysmal dermatofibroma varied from 7 months to 30 years, and most manifested as skin masses on the lower extremities. A relatively short course of disease was observed in patients with cellular dermatofibroma, who often visited a hospital several months after the onset, and cellular dermatofibroma was commonly observed on the extremities and frequently accompanied with itching and pain. The duration of sclerosing or atrophic dermatofibroma was usually long for years or decades, and it commonly occurred on the upper limbs without concomitant symptoms. Epithelioid dermatofibroma of varied durations had various clinical manifestations, frequently occurred on the lower limbs without concomitant symptoms. Conclusions The clinical and pathological manifestations of dermatofibroma are diverse. Different dermatofibroma lesions can share similar typical histopathological manifestations, and atypical pathological features can interfere with the diagnosis of dermatofibroma.

Key words: Histiocytoma, benign fibrous, Skin manifestations, Pathological processes