Mucinous tubular and spindle cell carcinoma

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Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare type of kidney cancer. It is usually considered a low-grade tumor and may be a variant of papillary renal cell carcinoma (RCC). It can occur at any age from 17 to 82 years and is more common in women.

MTSCC does not have the typical chromosomal changes seen in papillary RCC, such as gains of chromosomes 7 and 17 and loss of the Y chromosome. Clinically and on imaging, it can look similar to papillary RCC.

Microscopically, MTSCC has three main components: mucin (a gel-like background), tumor cells forming tubules, and spindle cells. The tumor shows cuboidal and spindle cells arranged in tubular or sheet-like patterns on a mucinous or myxoid background. Immunohistochemistry usually shows CK7-positive, AMACR-positive, and CD10-negative staining.

Diagnosing MTSCC can be challenging because the tumor can look different in different areas (morphologic heterogeneity). Some variants have little mucin and are mostly tubular or spindle in appearance. Small papillary structures or foamy histiocytes can also make it resemble papillary RCC.

Helpful diagnostic clues include bland (non-aggressive) cell appearance and the mix of tubular and spindle components. Some areas may contain clear cells or oncocytic cells.

MTSCC is generally a low-grade cancer, but rare instances of lymph node metastasis and recurrence have been reported. There are a few cases with sarcomatoid change, which can be more aggressive and may spread to distant organs such as the lungs or bones. If necrosis is present in the tumor, it should be noted, though its significance is not fully understood.