Kidney Mass Biopsy

This article only covers biopsy of abnormal kidney masses. Unlike with most other types of cancer, biopsies are not always needed to diagnose kidney tumors. In certain cases, imaging tests can provide enough information for a surgeon to decide if an operation is needed. The diagnosis is then confirmed when part of the kidney that was removed is looked at in the lab. 

A biopsy might be done to get a small sample of tissue from an area that may be cancer when the imaging tests are not clear enough to permit surgery. Biopsy may also be done to confirm cancer if a person might not be treated with surgery, such as with small tumors that will be watched and not treated, or when other treatments are being considered.

Fine needle aspiration (FNA) and needle core biopsy are 2 types of kidney biopsies that may be done.

In cases where the doctors think kidney cancer might have spread to other sites, they may take a biopsy of the metastatic site instead of the kidney.

Understanding the biopsy results

The biopsy samples are sent to a lab, where they are looked at by a pathologist, a doctor who specializes in diagnosing diseases with lab tests. If kidney cancer is found, an important feature that is evaluated is the grade, specifically called the Fuhrman grade.

The Fuhrman grade is found by looking at kidney cancer cells in the lab. Many doctors use it to describe how quickly the cancer is likely to grow and spread. The grade is based on how closely the cancer cells look like those of normal kidney cells. Renal cell cancers are usually graded on a scale of 1 through 4. Grade 1 renal cell cancers have cells that look a lot like normal kidney cells. These cancers usually grow and spread slowly and tend to have a good prognosis (outlook). At the other extreme, grade 4 renal cell cancer looks quite different from normal kidney cells. These cancers tend to have a worse prognosis.

If a part of/entire kidney is removed, the pathologist will provide additional information such as:

  • Tumor or T-stage
  • Nodal or N-stage
  • Metastatic or M-stage (only if other body parts are removed with the diseased kidney)
  • Lymphovascular invasion or presence of cancer cells in the blood vessels
  • Tumor necrosis, meaning presence of dead cancer cells – this tends to happen if cancer cells divide faster than they get blood supply (usually a bad sign)
  • Sarcomatous and rhabdoid changes, which are abnormal appearance of cancer cells (usually a bad sign)
  • Margins – a “positive margin” can indicate if there was cancer left behind in the body

HOT TIP! This information is extremely valuable in deciding your risk of cancer recurrence and need for additional treatment options, so make sure to pay attention to this conversation.

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