Mucinous tubular and spindle cell carcinoma of the kidney: Clinical, imaging and pathological features

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Background: Mucinous Tubular and Spindle Cell Carcinoma (MTSCC) is a rare variant of Renal Cell Carcinoma (RCC). MTSCC has been regarded as an indolent subtype of RCC conveying a good prognosis. However, recently some cases of MTSCC have been described presenting or evolving with metastasis, showing an aggressive behaviour. We aim to describe MTSCC clinical characteristics, treatment, prognosis and survival. Methods: We retrospectively reviewed all cases of MTSCC diagnosed at our institution from 1 January 2008 to 31 December 2022. Electronic health records were reviewed, and data were retrieved and analysed. This study was approved by our institution’s ethics committee. Data confidentiality was assured. Results: We identified eight cases of MTSCC among the 15 years of the study timeframe diagnosed in our hospital. The median age at diagnosis was 59 years (range = 32–80 years), and half of the patients were women (n = 4; 50%). In six (75%) of the patients, presentation was incidental, while the remaining two presented with flank pain. One patient had metastasis at presentation, while the remaining cases were localised at the time of diagnosis. Six patients were submitted to radical nephrectomy: four by open approach and two by transperitoneal laparoscopic approach. Two patients were submitted to a partial nephrectomy by an open approach. Mean (SD) postoperative haemoglobin drop was 2.18 (1.12) g/dL. Median follow-up was 36.5 months (range = 2–157). During the study timeframe, no other patients were diagnosed with local recurrence or distant metastasis. Two patients died during follow-up: the one that was metastatic at diagnosis died due to disease progression 2 months after surgery and another died due to a competitive disease (acute lower limb ischaemia). Conclusion: MTSCC is a rare variant of RCC that, despite being initially regarded as an indolent disease with good prognosis, might harbour an aggressive behaviour and grim prognosis. Level of evidence: 2b