Low-grade fibromyxoid sarcoma of acral sites: Case report and literature review.

Low-grade fibromyxoid sarcoma (LGFMS) is a rare soft tissue sarcoma that usually presents as a deep-seated tumor in young adults; however, they can occur on superficial sites, mostly documented in pediatric age groups. LGFMS presenting on acral sites is not highly emphasized in the general pathology or dermatopathology literature. The case presented is that of a 30-year-old man with a foot mass that was removed 15 years earlier and subsequently recurred as two masses, the first occurring between the third and fourth toes/metatarsal region and the second over the lateral tarsal region. An excisional biopsy showed a relatively circumscribed, bland spindle cell proliferation with hypocellular and hypercellular zones. The cells showed minimal pleomorphism and lacked mitotic activity. Immunohistochemical analysis showed immunoreactivity for MUC4 and break-apart fluorescence in situ hybridization was positive for FUS rearrangement, confirming the diagnosis of LGFMS. There are multiple spindle cell tumors that occur on acral sites which usually generates a list of differential diagnoses; however, LGFMS is not usually discussed in that anatomic location. Awareness of the occurrence of LGFMS on acral sites is important to avoid misdiagnosis of this deceptively benign-appearing tumor.