Mucoepidermoid carcinoma

This low-grade, polypoid tumor of the trachea or bronchus has nests composed of squamous cells and glands. This PAS-D stain shows the scattered glands with red secretion within the squamous nests.

Note: High grade tumors with many mitoses are called adenosquamous cancers. They are usually found peripherally.

Adenoid cystic carcinoma

These are low-grade tracheal or bronchial tumors that resemble bronchial ducts or glands. The nests are composed of epithelial and myoepithelial cells. Tumors have an infiltrative growth that is difficult to eradicate completely.

Adenoid cystic carcinoma

The gland-like pattern develops as tumor surrounds stroma, but some true glands do occur. At the periphery of the nests, flat myoepithelial cells are present (arrow).