Mucinous Tubular and Spindle Cell Carcinoma (Kidney), from the CureRays guide library.

Mucinous tubular and spindle cell carcinoma is a rare, usually low-grade kidney cancer with an excellent outlook, treated primarily with surgery — with radiation reserved for the uncommon cases that spread.

What it is.

Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare type of kidney cancer named for what it looks like under the microscope: small tube-like (tubular) structures, spindle-shaped cells, and a background of mucin (a gel-like substance). It is most often found in middle-aged adults and more commonly in women. The great majority of these tumors are low-grade and slow-growing, with an excellent long-term outlook — most patients are cured by surgery alone. MTSCC is usually discovered incidentally, when a scan done for another reason finds a kidney mass. Because it can resemble another kidney cancer (papillary renal cell carcinoma) under the microscope, expert pathology and sometimes molecular testing are used to confirm the diagnosis. A small minority of cases are higher-grade or 'sarcomatoid' and behave more aggressively, but these are the exception.

How radiation treats it.

Radiation damages the DNA inside cancer cells so they can no longer divide. For mucinous tubular and spindle cell carcinoma, surgery is the main treatment and usually cures the disease, so radiation is not part of routine care for tumors confined to the kidney. Where radiation helps is in the uncommon situations where the cancer spreads or surgery isn't possible: focused stereotactic radiation (SBRT) can precisely treat a small number of metastatic spots, such as in bone or lung, and palliative radiation can relieve symptoms like pain. Kidney cancers were once thought resistant to radiation, but modern high-dose, tightly focused techniques control tumors more effectively than older methods. Radiation is painless during delivery, given over one or a few sessions for focused treatment, and external-beam treatment leaves no radioactivity in the body.

The ways we can treat it.

Stereotactic body radiation (SBRT). Focused high-dose radiation can precisely treat a small number of metastatic spots (for example in bone or lung) or, occasionally, a kidney tumor in a patient who can't have surgery.

Palliative external-beam radiation. Shaped beams relieve symptoms such as pain from areas of spread, improving comfort in advanced disease.

Image-guided radiation. Daily imaging confirms the target's position so the dose is delivered accurately while sparing the remaining kidney and nearby organs.

Questions we hear often.

Is mucinous tubular and spindle cell carcinoma dangerous? Most cases are low-grade and slow-growing, with an excellent outlook — the majority of patients are cured by surgery alone. A small minority are high-grade or 'sarcomatoid' and behave more aggressively, needing more intensive treatment and close follow-up. Your team bases the plan on your tumor's grade and stage.

Why does it need expert pathology? Under the microscope, MTSCC can resemble papillary renal cell carcinoma, a different kidney cancer. Telling them apart — sometimes with molecular testing — matters because it confirms the generally favorable outlook and guides the right treatment and follow-up.

Will I need radiation? Probably not for a tumor confined to the kidney, since surgery is the main treatment and usually curative. Radiation is reserved for the uncommon situations where the cancer spreads or surgery isn't possible — for example, focused radiation to treat a metastatic spot or relieve symptoms.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.