DP26 Cutaneous Ewing sarcoma in an 89-year-old patient

Abstract

An 89-year-old woman presented with a progressively enlarging mass on her right hip. The exact duration is uncertain but it is likely to have been present for 3–4 months before odour was noted, with intermittent bleeding. She was otherwise well, with controlled comorbidities. Examination showed a large 17-cm purple, firm, malodorous nodule with several areas of ulceration. The tumour appeared to be predominantly cutaneous based on palpation. There was no axillary, inguinal or cervical lymphadenopathy. Histology showed a poorly differentiated basaloid partly cohesive and epithelioid-appearing tumour infiltrating through the dermal collagen, with no involvement of the overlying epidermis. An extensive immunohistochemical panel was undertaken, with negative staining for AE 1/3, EMA, p40, GATA, synaptophysin, chromogranin, CK7, CK20, SOX10, melan-A, CD45, CD20, CD3, CD31, BerEp4, desmin, SMM, MNF, TDT, CD30 and CD138. S100 highlighted dendritic cells only. CD99 was positive, and in the context of a small round blue cell tumour, EWSR1 and fluorescence in situ hybridization testing was undertaken. This showed an EWSR1::FLI1 fusion transcript, in keeping with Ewing sarcoma. Imaging via computed tomography and magnetic resonance imaging revealed a large, subcutaneous, pelvic mass with no bony involvement or distant metastasis, but with infiltration into the right sartorius muscle and right inguinal lymph node. Multidisciplinary review confirmed tumour involvement with surrounding myofascia, and staged the disease as pT4N1M0. Palliative radiotherapy (8 Gy, single fraction) was administered 3 months after dermatology referral. The tumour has since regressed, and the patient’s quality of life has improved. Ewing sarcoma is a malignant small, round, blue cell tumour typically affecting bones in children and adolescents. Cutaneous presentations in adults are extremely rare, usually as small solitary lesions. Diagnosis is complex and relies on histopathology, immunohistochemistry and molecular analysis. This case highlights an exceptionally rare presentation in an older patient.