Papillae

Papillae are small, finger-like projections of tissue that can be seen in many different parts of the body. Each papilla has a central core, usually made of connective tissue and small blood vessels, and is covered on the outside by a layer of cells. Papillae are a normal structure in certain organs, but they can also be observed in specific types of noncancerous growths and cancers.

Where are papillae normally found?

Papillae are part of the normal structure of many tissues and organs. For example, they are found in the skin (dermal papillae), tongue (taste buds sit on papillae), and kidney (renal papillae help drain urine). In these settings, papillae increase the surface area of tissue, provide structural support, and allow blood vessels to reach cells on the surface.

What do papillae look like under the microscope?

When seen under the microscope, papillae appear as projections of tissue that extend outward like tiny fingers. They contain a central supporting structure called a fibrovascular core, which includes fibrous tissue and small blood vessels. The outside of each papilla is lined by epithelial cells, which are the cells that cover surfaces and line glands. The exact appearance of papillae depends on the organ and the type of cells covering them.

Why are papillae important in pathology?

Pathologists describe papillae in pathology reports because their presence can help identify the type of growth or tumour. For example:

• Benign papillomas are noncancerous growths made up of papillae covered by normal or mildly abnormal cells.

• Papillary carcinomas are cancers where the tumour cells grow around papillae. Papillary thyroid carcinoma, papillary renal cell carcinoma, and papillary adenocarcinoma of the lung are examples.

The presence of papillae, along with other microscopic features, helps pathologists determine whether a growth is benign or malignant.

Do papillae mean cancer?

Not always. Papillae can be found in both noncancerous and cancerous conditions. In benign growths, the cells lining the papillae look normal or only slightly abnormal. In cancers, the cells covering the papillae show changes that suggest aggressive or uncontrolled growth. Your pathology report will explain whether papillae were found in a benign setting (such as a papilloma) or in a cancer.

Questions to ask your doctor

• Why did my pathology report mention papillae?

• Were the papillae seen in a benign growth or a cancer?

• How does the presence of papillae help confirm my diagnosis?

• Does this finding affect my treatment or follow-up plan?