The diagnosis of AFST depends on its presentation (particularly its location), histopathology (particularly the expression of certain proteins by its tumor cells), and the presence of specific fusion genes (e.g. AGRR-NCOA2) in its tumor cells. Among benign tumors, cellular<unk>  and solitary fibrous tumor may be confused with AFST. Cellular<unk>  differs from AFTS in its typical location (i.e. inguinal, scrotal, and vulva areas), its distinct histology of rounded, non-branching vessels, high cellularity, and cells with small nuclei, and its tumor cells' loss of the RB1 gene. Solitary fibrous tumors differ from AFST tumors in their common location in the lungs' pleurae, their characteristic branching dilated, staghorn-shaped blood vessels, and their tumor cells' expression of CD34 and STAT6 proteins in the majority of the cases. AFTS tumors may also be confused with three malignant tumors, low-grade fibromyxoid sarcoma, myxofibrosarcoma, and myxoid liposarcoma. Low-grade fibromyxoid sarcomas tend to be less cellular and have less prominent blood vessel than AFST; they also differ from AFST in that their tumor cells commonly express the MUC4 protein and FUS-CREB3L1, FUS-CREBL2, or, EWSR1-CREB3L1 fusion genes. Myxofibrosarcoma tumors commonly show overt malignant features such as highly infiltrating margins, tumor cells with eosinophilic cytoplasm, atypical nuclei, and rapid proliferation rates as evidenced by their high mitotic indexes. Myxoid liposarcoma tumors consist of round or slightly fusiform cells in a myxoid matrix, vacuolated lipoblasts (i.e. cells that are precursors to fat cells), and arborizing networks of thin-walled capillaries. In all of these cases, the presence of one of the AFST-associated fusion genes cited in the previous section lends support for the diagnosis of AFST.
Angiofibroma of soft tissue
Cellular angiofibroma
Juvenile hyaline fibromatosis
Lymphangioma
Lymphohemangioma
Peripheral ossifying fibroma
Cavernous hemangioma
Aponeurotic fibroma