Excerpt from Adenoma, Bronchial

Synonyms, Key Words, and Related Terms: endobronchial neuroendocrine tumor, Kulchitsky tumor, bronchial carcinoid, bronchial gland tumor, mucous gland carcinoma, mucous gland adenomas, mucoepidermoid carcinoma, adenoid cystic carcinoma, cylindromas, small cell undifferentiated carcinoma, malignant lung neoplasms

Please click here to view the full topic text: Adenoma, Bronchial

Background: Bronchial adenoma is a descriptive but misleading term for a histologically and clinically diverse group of respiratory tract neoplasms. This group includes bronchial neuroendocrine tumors (carcinoids), adenoid cystic carcinomas (cylindromas), mucoepidermoid carcinomas, mucous gland adenomas, and other mixed seromucinous tumors arising from mucous glands and ducts of the tracheobronchial tree. The term is misleading because these tumors are of widely variable malignant potential, although low-grade malignancies predominate. Only mucous gland adenomas are truly benign, lacking malignant potential.

When these tumors were originally described in the 1800s, the term was used to describe only the carcinoid variant. Initial classification of bronchial adenomas arose from a description in a 1930 article in Annals of Otolaryngology by Krane et al of a group of tumors with a better prognosis and less aggressive behavior than bronchogenic carcinoma. In 1952, mucoepidermoid carcinomas were first described. In 1907, Oberndorfer introduced the term karcinoide to indicate "resembles carcinoma." In 1972, after recognizing a subset of lesions with a more rapid course, Arrington et al reclassified the tumors, with carcinoid varieties termed either typical or atypical.

The latest reclassification differentiates bronchial adenomas (eg, adenoid cystic carcinomas, mucoepidermoid carcinomas, mucous gland adenomas) from neuroendocrine tumors (eg, carcinoids, large cell carcinoma). In current practice, carcinoid tumors fall into a separate category because their cells of origin are now recognized to be Kulchitsky cell types I and II. Bronchial carcinoid actually represents the low end of a spectrum of neuroendocrine tumors, with the high end being small cell lung carcinoma.

In 1932, Bigger performed the first bronchoplastic procedure, a bronchotomy for removal of a left mainstem endobronchial lesion. In 1939, Eloesser performed a bronchotomy with simple excision and fulguration of an adenoma of a left lower lobe orifice. In 1947, Price-Thomas performed the first sleeve resection for an adenoma originating in the right mainstem bronchus.

Etiology

As noted above, bronchial carcinoids are thought to arise from Kulchitsky cells. These cells are characterized by amine precursor uptake and decarboxylation, which characterizes cells that produce and store active peptide hormones. Typical carcinoids originate as clusters of monotonous polyhedral cells in a fibrovascular stroma. Ultrastructurally and immunoreactively, carcinoids share characteristics with small cell neuroendocrine carcinoma of the lung.

True oncocytomatous bronchial mucous gland adenoma originates from salivary gland tissue, having close similarity to its salivary counterpart. True oncocytomatous bronchial mucous gland adenoma must be distinguished from oncocytomatous bronchial gland carcinoid tumor, the cells of which possess dense-core neurosecretory granules. This tumor also must be distinguished from the common oncocytomatous change that affects normal bronchial mucous glands in adults.

Adenoid cystic carcinoma originates from salivary gland tissue. Occasionally, some tumor cells in this variant are of myoepithelial origin. These tumors have several other names, including cylindromas, adenoid cystic basal cell carcinomas, adenomyoepitheliomas, and pseudoadenomatous basal cell carcinomas.

Mucoepidermoid carcinomas originate from tracheal and proximal bronchi. These tumors are of squamous and intermediate elements, with intercellular bridges or cytoplasmic membranes. They have the same microscopic appearance as mucoepidermoid carcinoma of the salivary glands, arise in glandular submucosa, and manifest as submucosal lesions. Mucous gland adenoma (ie, bronchial cyst, papillary cystadenoma) is a rare submucosal tumor arising from mucous glands. Mucous gland adenomas .....