Adamantinoma-like Variant of Ewing Sarcoma in the Metatarsal Bone After Chemotherapy: Report of a Case Successfully Treated with Pedicled Osteocutaneous Fibular Transfer

Abstract

Adamantinoma-like Ewing sarcoma is a rare variant of Ewing sarcoma with histologic and immunohistochemical evidence of squamous differentiation. This variant most commonly occurs in the head and neck region with a few cases reported in the long bones of the limbs. It may be associated with poorer clinical outcome and could pose a diagnostic challenge, particularly if it occurs in older patients or as a metastatic lesion. We present a case of Ewing sarcoma in the metatarsal of an 11-year-old boy that manifested adamantinoma-like morphology after neoadjuvant chemotherapy. Chemotherapy has been reported to induce neuronal maturation and rhabdoid morphology in cases of Ewing sarcoma, but no reports of treatment-induced squamous differentiation with P40/P63 expression have been demonstrated. This is also the first documented case treated with a pedicled osteocutaneous fibular transfer in a metatarsal malignancy, which is usually treated by either ray or below-knee amputation.

Adamantinoma-like Ewing Sarcoma (ALES) May Harbor FUS Rearrangements

“…ALES is a rare subtype of Ewing sarcoma with 56 cases 1–3,6,8,9,14–41 reported to date, including the ones reported in this study and 1 case of Ewing sarcoma with strong nuclear expression of p40 and FUS :: FEV fusion described by Tsuda et al 37 Although they mention the possibility of ALES, Tsuda and colleagues do not clearly separate it out as a unique finding in their cohort of Ewing sarcomas with FEV gene rearrangements. Nevertheless, when included as ALES, the proportion of ALES with FUS rearrangement is around 13% (7/56) of reported cases which is slightly higher than the proportion of FUS rearrangement reported in classic Ewing sarcoma (<10%) 10,13 .…”