by Jason Wasserman MD PhD FRCPC
July 1, 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?
Given its benign nature, canalicular adenoma usually causes very few symptoms. 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 tumour. Since these tumours 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 tumours 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 comprises 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.
Immunohistochemistry
Immunohistochemistry (IHC) is a lab test that helps pathologists see certain proteins in tissue samples. Pathologists use this test to determine the types of cells in a tumour, ultimately allowing them to determine the tumour type. Cells that are expressing a protein are described as positive or reactive. Cells that are not expressing a protein are called negative or nonreactive.
The tumour cells in canalicular adenoma are typically positive for the following markers:
The tumour cells in canalicular adenoma are negative for the following markers:
- p40
- Smooth muscle actin (SMA)
- Muscle-specific actin (MSA)
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, that removes 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.
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
Atlas of pathology
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