Sclerosing epithelioid fibrosarcoma of the kidney

Abstract

A woman in her 20s presented with headache and back pain and was found to have a left renal mass with bony metastases. She underwent nephrectomy, and on histopathology was initially diagnosed with stage 4 clear cell sarcoma of the kidney. She underwent palliative radiation and chemotherapy; however, the disease progressed and she came to our centre. We started her on second-line chemotherapy and submitted her tissue blocks for review. Due to her age and lack of sclerotic stroma in the tissue, we had our doubts about the diagnosis and hence, tissue sample was submitted for next-generation sequencing (NGS). NGS detected an EWSR1::CREBL1 fusion, clinching the final diagnosis of sclerosing epithelioid fibrosarcoma of the kidney, a singular diagnosis rarely reported in the literature. Currently, the patient is post her third line of chemotherapy, is on maintenance, and is doing well and has resumed her daily activities.

Keywords: Pathology; Urological cancer.

Figure 1

Photomicrographs show a tumour with pushing (A; HE, ×20) and infiltrative (B; HE, ×40) borders, with entrapped tubules at the periphery (C; HE, ×100). Tumour cells are polygonal epithelioid (D; HE, ×200) and spindle-shaped (E; HE, ×200), embedded in a variable collagenous to oedematous stroma (F; HE, ×100). Cells have pale eosinophilic to clear cytoplasm and nuclei with inconspicuous nucleoli (G; HE, ×200; H; HE, ×400), show moderate BCOR staining (I; IHC, ×200), and are negative for keratin (J; IHC, ×200) and PAX8 (K; IHC, ×200); Ki-67 labelling is low (L; IHC, ×200). IHC, immunohistochemistry.