There is a distinct difference in the anatomic areas infected by tumor in ASPS in adults vs children. In adults, ASPS predominantly occurs in the lower extremities with a variety of other reported locations that include the mediastinum, breast, bone, GI tract, female genital tract, and urinary bladder. In infants and children, the tumor often occurs in the head and neck region, most frequently around the orbit and tongue. The histologic differential diagnoses of ASPS include any tumor composed of large cells with eosinophilic/clear cytoplasm in an organoid or pseudoalveolar pattern, which would include, but is not limited to, adrenal cortical carcinomas, hepatocellular carcinoma, malignant melanoma, and renal clear cell carcinoma. Other considerations are paraganglioma and schwannoma. Expression of immunohistochemical markers is variable in ASPS and often not useful in achieving a diagnosis, but they may help to exclude other tumors. The diagnosis depends on morphologic characteristics of the tumor with periodic acid-Schiff (PAS) stain with diastase being the most helpful stain. Coarse PAS-positive diastase-resistant granules with occasional rod-shaped or crystalline structures are the histologic hallmark of the tumor. ASPS has a characteristic cytogenetic abnormality [t(X;17)(p11;q25)], and the diagnosis can be confirmed either by cytogenetics or by molecular testing to identify the fusion product created as a result of the translocation.