WHO classification for benign salivary tumors with canalicular adenoma highlighted.
A fibrous capsule (to the right) surrounds the tumor, consistent with a benign epithelial tumor. The tumor is composed of a single row of columnar cells in a hypocellular stroma. Narrow channels are seen between the epithelial elements.
The rows of columnar luminal ductal cells form branching canaliculi in a loose edematous stroma.
Canalicular adenomas, like all monomorphic adenomas, lack the chondroid and myxoid elements of pleomorphic adenomas. "Monomorphic adenoma" was proposed in 1970 by Rauch, Seifert and Gorlin to unite the benign salivary tumors not classifiable as pleomorphic adenomas (Rauch). Basal cell adenoma is another monomorphic adenoma, and in fact, canalicular adenoma used to be considered a variant of canalicular adenoma, but now is considered a distinct entity. Canalicular adenomas derive from the ductal luminal cells, not basal type cells.
Histologically, lines of columnar ductal-luminal cells form double rows that come together intermittently to form a "beading" pattern. Cystic change may be seen. The stroma is hypocellular, vascular and edematous.
Canalicular adenomas typically affect the upper lip, buccal mucosa, palate, and in rare cases the parotid gland (Leiss). By most estimates, these tumors account for less than 1% of all salivary gland tumors. These tumors are typically slow growing masses which seem to form mostly in the lip in elderly white females (Ferreiro).
Complete excision is curative.
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