SMARCB1-Deficient Renal Medullary Carcinoma: A Case Report Highlighting the Value of History and Race Information.

SMARCB1-deficient renal medullary carcinoma (RMC) is a rare subtype of kidney cancer that predominantly affects young adults with sickle cell trait or disease. It frequently presents with metastasis at diagnosis, displays rapid disease progression, and has a generally poor prognosis. We present the case of a 25-year-old male patient with RMC who sought care for painless, gross hematuria. Imaging workup revealed a hypo-enhancing lobular mass arising from the lower pole of the right kidney. He subsequently underwent a radical right nephrectomy and a lymphadenectomy. Histopathology showed an infiltrative tumor with yolk sac-like and adenoid cystic-like morphology centered on the medulla, adjacent to benign urothelium. The lesional cells had prominent nucleoli and a moderate amount of cytoplasm. Drepanocytes were also identified. Immunohistochemistry revealed positive staining with CK7, PAX-8, and cyclin D1. SMARCB1/INI1 had a loss of staining. Pertinent negative stains included L-ALK, GATA3, CK5/6, CD10, and vimentin. Additional history was sought, and it was revealed that the patient was a person of color, had a family history of sickle cell disease, and was very physically active. The clinical history, combined with loss of SMARCB1/INI1 protein expression, led to a final diagnosis of SMARCB1-deficient RMC. Race data and relevant clinical history, including engagement in vigorous physical activity, can be diagnostically useful, as demonstrated by this case. RMC should be considered in the differential diagnosis of renal tumors in young patients. The patient was managed by the medical oncology team and was treated with chemotherapy and radiation but subsequently developed multiple metastases and passed away three years after the initial disease diagnosis.