Canalicular adenoma

by Jason Wasserman MD PhD FRCPC
April 19, 2024


Canalicular adenoma is a benign (noncancerous) type of salivary gland tumour. It most commonly arises in a minor salivary gland, such as those in the lip and oral cavity (palate, gingiva, floor of mouth). It is a rare tumour, representing about 1% of all salivary gland tumours.

What are the symptoms of a canalicular adenoma?

The symptoms of canalicular adenoma are usually minimal, given its benign nature. Patients might notice a slow-growing, painless mass in the area of the lips, buccal mucosa, or palate. Occasionally, there can be slight discomfort or a feeling of pressure at the site of the tumor. Since these tumors are generally small and slow-growing, they may not cause significant symptoms until they are large enough to be noticed physically.

What causes a canalicular adenoma?

The exact cause of canalicular adenomas is not well understood. These tumors are believed to arise from the ductal epithelium of the salivary glands, but what triggers this abnormal growth is unclear. There is no known association with lifestyle, diet, or environmental factors. The occurrence appears to be sporadic, without any clear genetic predisposition.

Microscopic features

Microscopically, canalicular adenoma is made up of large cuboidal or columnar-shaped cells arranged in 1 to 2 cell-thick layers. The layers of cells grow in long cords, nests, canaliculi, and tubules. Squamoid morules (small round groups of tumour cells that look like squamous cells) may be seen. Rare mitotic figures may be found, but there should be no perineural invasion, lymphovascular invasion, or destructive invasion of surrounding tissues.

The microscopic appearance of canalicular adenoma.
The microscopic appearance of canalicular adenoma.

Immunohistochemistry

The tumour cells in canalicular adenoma are typically positive for S100, SOX-10, and cytokeratin 7. GFAP may show a characteristic peripheral and linear pattern of expression. The tumour cells are negative for p40, smooth muscle antigen, and muscle-specific antigen. Squamous morules may express cytokeratin 5.

Margins

In pathology, a margin is the edge of tissue removed during tumour surgery. The margin status in a pathology report is important as it indicates whether the entire tumour was removed or if some was left behind. This information helps determine the need for further treatment.

Pathologists typically assess margins following a surgical procedure, like an excision or resection, aimed at removing the entire tumour. Margins aren’t usually evaluated after a biopsy, which removes only part of the tumour. The number of margins reported and their size—how much normal tissue is between the tumour and the cut edge—vary based on the tissue type and tumour location.

Pathologists examine margins to check if tumour cells are present at the tissue’s cut edge. A positive margin, where tumour cells are found, suggests that some cancer may remain in the body. In contrast, a negative margin, with no tumour cells at the edge, suggests the tumour was fully removed. Some reports also measure the distance between the nearest tumour cells and the margin, even if all margins are negative.

Margin

About this article

Doctors wrote this article to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

Other helpful resources

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