[IPSILATERAL SYNCHRONOUS MUCINOUS TUBULAR AND SPINDLE CELL CARCINOMA AND CLEAR CELL PAPILLARY RENAL CELL CARCINOMA: A CASE REPORT AND REVIEW OF THE LITERATURE].

Renal cell carcinoma (RCC), the most common solid lesion of the kidney, accounts for approximately 2%-3% of all malignancies among adults. Clear cell carcinoma and papillary cell carcinoma are the most common types of renal tumors. Some case reports have described synchronous benign and malignant tumors in the same kidney. In particular, angiomyolipoma and RCC in patients with tuberous sclerosis (TSC) and non-TSC have been reported many times in the literature. However, unilateral concordance of malignant renal tumors is very rare; thus, only few cases have been reported in the literature.Here we report the case of a 58-year-old male who had ipsilateral synchronous mucinous tubular and spindle cell carcinoma (MTSCC) and clear cell papillary renal cell carcinoma (CCPRCC). Both cancers are rare and relatively recently defined subtypes of RCC. Additionally, both were successfully treated using partial nephrectomy. MTSCC has been a distinct entity in the World Health Organization classification of kidney tumors since 2004. The classic type of MTSCC is characterized by small elongated tubules lined with clear cuboidal or spindle cells with mucinous stroma. Neoplastic cells always exhibit low-grade histological features. However, unclassified variants of MTSCC, such as mucin-poor, papillary, high-grade, and sarcomatoid variants, have also been reported. MTSCC is considered to have a relatively good prognosis, but some patients with poor prognoses have recently been reported. CCPRCC is a recently recognized entity and represents the fourth most common variant of RCC. It has unique morphological and immunohistochemical features and shows indolent clinical behavior. Microscopically, CCPRCC may mimic other RCCs with clear cell features, such as clear cell RCC, translocation RCC, and papillary RCC, with clear cell changes. In 2006, CCPRCC was described as a subtype of renal tumors in patients with end-stage renal disease. However, currently, CCPRCC has also been shown to occur in kidneys with normal function.To the best of our knowledge, this is the first report of ipsilateral synchronous MTSCC and CCPRCC, which we present with a review of the pertinent literature.