Your pathology report for papillary adenoma of the kidney

Jason Wasserman MD PhD FRCPC
June 14, 2025

A papillary adenoma is a small, non-cancerous (benign) kidney tumour. It arises from tiny tubes inside the kidney called tubules. Papillary adenomas typically measure less than 15 millimeters (about 0.6 inches) in size. They often exhibit a pattern of growth described as papillary, meaning they develop in small, finger-like projections. Sometimes the growth pattern is tubular or a combination of tubular and papillary (tubulopapillary). Papillary adenomas typically do not cause any health problems and never spread to other parts of the body.

What are the symptoms of papillary adenoma?

Almost all papillary adenomas are discovered by chance and do not cause noticeable symptoms. Typically, doctors discover them incidentally during imaging tests or examinations performed for other purposes. Because of their small size, they generally do not cause pain, blood in the urine, or other symptoms commonly associated with larger kidney tumours.

What causes papillary adenoma?

The exact cause of papillary adenomas is not known. However, certain factors increase the likelihood of developing them. These include:

• Older age: Papillary adenomas are more common in older adults and become increasingly frequent with age.

• Long-term kidney conditions: Individuals on long-term dialysis or those with kidney disease affecting blood vessels or glomeruli (the filtering units in the kidneys) are more likely to develop papillary adenomas.

• Acquired cystic kidney disease: People who develop cysts in their kidneys, especially after being on dialysis, have a higher chance of having papillary adenomas.

• Genetic conditions: Papillary adenomas can also occur in individuals with inherited conditions such as hereditary papillary renal cell carcinoma, although this is less common.

How is papillary adenoma typically diagnosed?

Papillary adenomas are usually discovered by accident during imaging tests like ultrasounds, CT scans, or MRI scans done for other reasons. On these imaging tests, they appear as small masses or growths in the kidney.

If your doctor finds a small kidney tumour, they may recommend removing the tumour without performing a biopsy first. Once removed, the tumour is examined by a pathologist under the microscope. The pathologist confirms the diagnosis of papillary adenoma based on its appearance and features.

What does papillary adenoma look like under the microscope?

Under the microscope, papillary adenomas are made up of small, round cells arranged into finger-like structures (papillae), tubes (tubules), or both (tubulopapillary). The cells have pale, clear-looking interiors and are uniform in size and shape. There is minimal variation in the size or shape of the cells, and they rarely divide. Special features, such as foamy macrophages (immune cells) and small calcium deposits called psammoma bodies, can sometimes be present.

Papillary adenomas do not have a clear capsule around them, meaning they blend gradually into the surrounding normal kidney tissue.

What is the difference between papillary adenoma and papillary renal cell carcinoma?

Although papillary adenoma and papillary renal cell carcinoma sound similar, they are very different conditions.

• Papillary adenoma is a small, non-cancerous tumour measuring 15 millimeters or smaller. It has a very low risk of growing larger, spreading, or causing health problems.

• Papillary renal cell carcinoma is a cancerous (malignant) tumour. It tends to grow larger, may spread to other parts of the body, and usually requires treatment.

The main differences between these two types of tumours are the size, cell appearance, and their behavior. Doctors carefully examine tumour size and microscopic features to make a clear distinction between them.

Prognosis and treatment for papillary adenoma

Papillary adenomas are benign tumours that do not spread or turn into cancer. They are not life-threatening and have an excellent outlook. Once surgically removed, papillary adenomas generally do not recur, and additional treatments are usually not needed.

Importantly, having a papillary adenoma in a kidney does not typically interfere with kidney function. Even if found in a kidney intended for donation and transplantation, a papillary adenoma usually does not prevent successful transplantation.

What is a surgical margin and why is it important?

When doctors remove a tumour, they also remove some healthy tissue surrounding it—this tissue is called a margin. Pathologists examine these margins closely under the microscope to see if any tumour cells remain at the edges.

• Negative margins: No tumour cells are seen at the edges. This usually means the tumour was completely removed.

• Positive margins: Tumour cells are found at the edges, suggesting some tumour may still remain.

With papillary adenomas, because they are benign tumours, a positive margin typically does not pose a serious risk. However, your doctor will discuss the margin status and determine if any further action is needed.

Questions to ask your doctor

• Do I need any further tests or treatments?

• What are the chances of my tumour coming back?

• How often should I have follow-up imaging or check-ups?

• Should my family members consider screening or genetic counselling?

• Can you explain what the surgical margin means in my case?

• What symptoms should prompt me to contact you in the future?