Metastatic SMARCB1-Deficient Renal Medullary Carcinoma without Hemoglobinopathy with Durable and Dramatic Response to Pembrolizumab plus Lenvatinib: Case Report.

Introduction: Renal medullary carcinoma (RMC) is a rare form of renal cell carcinoma (RCC) that is typically associated with a loss of function in SMARCB1 and diagnosis of sickle cell or other hemoglobinopathy. In rare cases, this disease can be seen in patients without hemoglobinopathy and is classified as "SMARCB1-deficient RMC without hemoglobinopathy" or referred to as "RCC unclassified with medullary phenotype" in some of the literature. Platinum-based cytotoxic chemotherapy is currently the recommended first-line treatment for this rare disease.

Case presentation: Here we report a 53-year-old male who was diagnosed with metastatic SMARCB1-deficient RMC without hemoglobinopathy after presenting with left flank and abdominal pain. After initiating first-line pembrolizumab and lenvatinib systemic therapy, imaging showed regression at 6 weeks. To date, this patient continues to show a near complete response to this treatment regimen.

Conclusion: To our knowledge, this is the first documented case of SMARCB1-deficient RMC without hemoglobinopathy to receive this treatment regimen and show such a response.