Presentation
Presented with a slowly enlarging, painless lump in the parotid gland. A superficial 'lumpectomy' was performed - the specimen was 45mm in greatest dimension and well-circumscribed - macroscopically visible non-lesional salivary gland tissue was not identified.
Patient Data
The specimen was composed wholly of this fully circumscribed, nodular lesion with a thin fibrous capsule, comprising a central region of fibrosis and a cellular periphery formed by islands, tubules and anastomosing trabeculae of cytologically bland basaloid cells, set within an occasionally blue-tinged, variably cellular and somewhat loose fibrous stroma. There is no necrosis and mitotic figures are scarce. Perineural invasion is not present. There is no evidence of chondromyxoid stroma. Benign salivary gland parenchyma is not seen.
Case Discussion
Basal cell adenomas are benign tumors that tend to arise within the parotid glands of adults. Just like in this case, tumors are well-circumscribed, non-infiltrative and may be encapsulated. They often are composed of both basaloid epithelial cells, along with myoepithelial cells.
Differential diagnosis:
- Pleomorphic adenoma: They differ from pleomorphic adenomas in that they don't have a chondromyxoid stroma component - this may be somewhat subjective - one pathologist's pleomorphic adenoma may be another's cellular pleomorphic adenoma.
- Canalicular adenoma: The same cellular components as in basal cell adenoma, however, these differ from BAs in their distinctive architecture - strands and ribbons of cells with a columnar appearance and a loose stroma.
- Adenoid cystic carcinoma: Invasive front with no capsule, predilection for perineural invasion, cookie-cutter cribriform structures, can have similar matrix material, may have more mitotic activity and cytological atypia.
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