Review of mucinous tubular and spindle-cell carcinoma of the kidney with a focus on clinical and pathobiological aspects

Recently, the characterization of mucinous tubular and spindle-cell carcinoma (MTSCC) has been established. MTSCC predominantly occurs in females. This tumor is histologically characterized by eosinophilic cytoplasm, elongated and anastomosing tubules, myxomatous stroma and low-grade nuclear cytology. Proliferation of spindle cells or foci of clear cells are also observed. Histochemically, the myxomatous stroma exhibits a positive reaction for alcian blue and colloidal iron stainings. Ultrastructurally, short microvilli are focally observed and junctional complexes are present. Recently, multiple losses of chromosomes 1, 4, 6, 8, 9, 13, 14, 15 and 22 in MTSCC have been elucidated by using comparative genomic hybridization. The prognosis of MTSCC is generally favorable, but some cases may show local recurrence or metastasis. Some cases with MTSCC seem to show overlapping histology with low-grade collecting-duct carcinoma. Therefore, further investigation will be needed to elucidate pathobiological characteristics of MTSCC.