Abstract
BACKGROUND: Mucinous tubular and spindle-cell carcinoma (MTSCC) is a rare kidney cancer subtype with limited cases reported in the literature. We report on outcomes of 25 patients with this variant who were managed at our institution. MATERIALS AND METHODS: The institution database was queried, and clinical data extracted for patients with MTSCC. Molecular features examined included next-generation sequencing with Memorial Sloan Kettering Integrated Mutation Profiling of Actionable Cancer Targets and allele-specific copy number analysis using the Fraction and Allele-Specific Copy Number Estimates from Tumor Sequencing (FACETS) algorithm in a subset of patients. RESULTS: All patients underwent primary tumor-directed therapy (nephrectomy = 23, cryoablation = 2). Metastases were diagnosed in 6 patients (24%), 3 (12%) of whom had de novo metastatic disease. Five of 6 patients with metastatic disease had high-grade histological features compared with 0 of 19 nonmetastatic patients (83% vs. 0%; P < .001, Fisher exact test). Three-year overall survival from diagnosis was 84.8% (95% confidence interval, 59.6-94.9) with a median follow-up time of 3.9 years (range, 1 month to 10.3 years). Three deaths occurred, all from metastatic disease. Four patients received systemic therapy with time to treatment failure ≤6 months across different agents with the exception of 1 patient with prolonged response with sunitinib treatment (30.6 months). The most frequent molecular alterations were neurofibromin 2 mutations (n = 2; 40%), germline alterations (n = 2; 40%) including checkpoint kinase 2 and BRCA2 DNA repair associated mutations, multiple chromosomal copy number losses, and mismatch repair deficiency in 1 patient. CONCLUSION: MTSCC is characterized by localized tumors treated successfully with primary tumor-directed therapy. However, patients with high-grade histological features were more likely to develop metastatic disease with limited responses to standard therapies.