To investigate the clinicopathologic and genetic features, pathologic diagnosis and differential diagnosis of angiofibroma of soft tissue(AFST).

The clinicopathologic characteristics of 24 cases diagnosed at Fudan University Shanghai Cancer Center from 2011 to 2017 were analyzed; immunohistochemical staining and interphase fluorescence in situ hybridization (FISH) were performed, and the literatures were also reviewed.

There were 15 male and 9 female (male∶female=1.7∶1.0) patients with age of onset ranging from 8 to 68 years (mean, 45 years). Fourteen cases occurred in extremities, including upper limbs (n=3) and lower limbs (n=11); seven cases were in the trunk, and 1 case each was in the temporal region, retroperitoneum and liver, respectively. Clinically, the tumors usually presented as a slowly growing painless mass. Tumor sizes ranged from 0.8 to 14 cm (mean 4.6 cm). Microscopically, most lesions were well-circumscribed, with fibrous capsules. Few cases infiltrated the surrounding fibrofatty tissue focally. The tumors were mainly composed of sparse short spindle cells and numerous small, branching, thin-walled blood vessels distributed in amyxoid, fibromyxoid or collagenous matrix, often accompanied by medium-sized, round or irregular and ecstatic vessels at the tumor periphery.By immunohistochemistry, all tested cases expressed vimentin (5/5), and showed variable positivity for EMA (2/4), ER (1/2), PR (2/3), α-SMA (1/18)and desmin (1/10). Ki-67 proliferation index were all less than 5%. CD34, CD31 and ERG staining clearly outlined the contours of blood vessels in the stroma. Four cases were tested for NCOA2 gene rearrangement by FISH, of which three were positive. Follow-up data was available in 17 patients (range, 3 to 69 months; mean, 30 months) were all free of disease.

Soft tissue angiofibroma is a benign fibroblastic neoplasm characterized by a prominent and complex vasculature set in a myxoid-to-collagenous stroma, and cytogenetically a distinctive NCOA2 gene rearrangement. Caution should be exercised for the possibility of potentially misinterpretation of AFST as vascular tumors and other myxoid soft tissue tumors.

Angiofibroma; Immunohistochemistry; In situ hybridization, fluorescence; Diagnosis, differential