Course of Multimodal Therapy and Genetic Profile of Hereditary Leiomyomatosis and Renal Cell Carcinoma with Early Recurrence during Adjuvant Therapy after Radical Nephrectomy: A Case Report.

Fumarate hydratase-deficient renal cell carcinoma is a rare and aggressive subtype associated with hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome, characterized by germline mutations in the fumarate hydratase (FH) gene. Here, we report a case of HLRCC with early recurrence during adjuvant therapy following radical nephrectomy. A 34-year-old woman with FH-deficient RCC presented with fever, right flank pain, and a large renal mass with a tumor thrombus. Open radical nephrectomy and IVC tumor thrombectomy were performed. Pathological findings and genetic analyses confirmed the diagnosis of HLRCC. Despite adjuvant pembrolizumab therapy after nephrectomy, bone metastases were detected within 9 weeks. The patient was treated with stereotactic body radiotherapy (SBRT), followed by systemic therapy with nivolumab and cabozantinib. After 16 months since the recurrence, no further disease progression was observed. Genetic counseling revealed the same FH mutation in her daughter, prompting annual surveillance. This case highlights the potential efficacy of combining tyrosine kinase inhibitor therapy with SBRT in managing aggressively progressive HLRCC.