Chromosomal abnormalities of high-grade mucinous tubular and spindle cell carcinoma of the kidney.

Aims: Mucinous tubular and spindle cell carcinoma (MTSC) of the kidney is a distinct entity characterized by bland tightly packed elongated tubules and spindle cells with low nucleolar grade in a basophilic mucinous stroma. Several case studies have reported MTSC with high-grade features and have brought into question whether they represented MTSC or a variant of papillary renal cell carcinoma.

Methods And Results: We searched our pathology database and identified seven cases: six MTSC with high International Society of Urological Pathology (ISUP) nucleolar grade and one MTSC with overall low nucleolar grade but extensive necrosis. DNA samples were extracted from paraffin blocks and analysed using a single nucleotide polymorphism (SNP) array platform. Six of seven patients were female, aged between 46 and 82 years. Tumour sizes ranged from 3 to 7.5 cm. One case showed involvement of renal sinus fat and a second case showed involvement of the perinephric fat. All cases shared common chromosomal abnormalities observed with the more typical MTSC, with monosomy of chromosomes 1, 4, 6, 8, 9, 13, 14, 15 and 22. Trisomy of chromosomes 7, 17 and loss of Y chromosome were not observed in any of the cases. None of the patients showed evidence of recurrence or metastasis.

Discussion: The molecular analysis performed in this study supports that MTSC of the kidney can have high nucleolar grade or extensive necrosis, and that they are not papillary renal cell carcinoma. We support modifying the definition of MTSC to include those with higher nucleolar grade.