Soft tissue angiofibroma in a 13-year-old adolescent: case report and literature review

Soft tissue angiofibroma (STA) is a rare, benign soft tissue neoplasm recognized by the World Health Organization in 2013. STA occurs mainly in the lower extremities of middle-aged and elderly patients. Here, we report the case of a 13-year-old adolescent with STA in the left thigh. We focus on establishment of the specific pathological characteristics of STA. Grossly, the tumor was a well-demarcated, soft, painless, large lump and was partial encapsulated with a grayish-white color and firm consistency. Histologically, in areas having high cellularity, the tumor was composed of bland spindle-shaped tumor cells and branching small vessels. Focal tumor cells were vacuolated, including potential erythrocytes, making differential diagnosis challenging. Mitotic counts were 2-3 cells/10 high-powered fields. Occasional tumor cells had irregularly-shaped, large, multinucleate, hyperchromatic nuclei, making it difficult to distinguish between STA and low-grade malignant soft tissue tumor. We used a panel of immunohistochemical markers and showed that the tumor cells expressed FLI-1, Bcl-2, CD31, F8, vimentin and desmin. Additionally, the Ki-67 labeling index was about 5% that higher than that in other cases. STAT6 was negative, which could be used to exclude solitary fibrous tumors. CAMTA1 was negative, which could be used to distinguish STA from epthelioid hemangioendothelioma. In this report, we describe the youngest case of STA to date, broadening the pathological characteristics of STA. Most STAs and aggressive tumors have similar clinicopathological features. Thus, identification of this tumor type may prevent misdiagnosis of a variety of benign or malignant tumors.