CLINICOPATHOLOGICAL FACTORS INFLUENCING SURVIVAL IN RENAL MUCINOUS TUBULAR AND SPINDLE CELL CARCINOMA: A SINGLE CENTER EXPERIENCE FOR 18 YEARS

Objective: Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare, indolent renal cell carcinoma variant, rarely showing unusual histology and aggressive behavior. We aimed to document histopathological and clinical characteristics and their relation to survival.Materials and Methods: We retrospectively identified 20 cases diagnosed as MTSCC between 2007-2024 and documented the relationship between clinicopathological features and follow-up.Results: There were 9 males and 11 females with a mean age of 54.6±11.1 (range: 28-72). Twelve (60%) underwent radical nephrectomy, 5 (25%) partial nephrectomy, 3 (15%) tru-cut biopsy. Eight (40%) were consultation cases, 12 (60%) were in-house material. The median tumor diameter was 70.4 (IQR: 4.88-9.03) mm. The presence of hemorrhage was observed in 2 (10%), necrosis in 4 (20%), sarcomatous transformation in 2 (10%). Median number of tissue blocks per case was 13 (IQR: 8-17.5) and correlated with the presence of sarcomatous differentiation (r=0.561, p=0.019). Mean follow-up time was 82.9±63.9 months. Four patients succumbed to disease with distant metastasis and two to other causes. One showed local recurrence. Remaining patients showed no recurrence or metastasis. Among four patients who died of disease, two showed sarcomatous transformation. Sarcomatous transformation showed worse prognostic significance in univariate analysis for overall survival (p=0.028), although not validated in multivariate Cox regression model (HR: 0.607, 95% CI: 0.030-12.120, p=0.744). Kaplan-Meier analysis showed that survival probability was lower in patients with sarcomatous transformation (0% vs 88.9%, p=0.008).Conclusion: MTSCC is a distinct renal neoplasm typically with an indolent prognosis, though rarely metastasizes, causing death. Meticulous histopathological assessment and close follow-up is essential.