Monomorphic adenoma, trabecular basal cell type (40X)

Clinical information: A 65-year-old man presented with a tumor-like lesion in the upper lip.

Clinical diagnosis: Salivary gland tumor

Microscopic examination: Small, solid flakes, trabeculae, buds and curved formations of very uniform (monomorphic) epithelial cells are seen. The cells are cubic / cylindrical and have somewhat indistinct eosinophilic cytoplasm and a fairly lighthtly colored nucleus with fine chromatin grains. The tumor tissue is sharply demarcated from the sparse stroma, which is loose and contains a number of veins. No inductive effect on the stroma is seen.

Comment: Monomorphic adenomas are benign salivary gland tumors that have a predilection for development in the upper lip and parotid gland.