Those patients who have an endobronchial mass on endoscopy may have a benign lesion or a malignant lesion. Of the malignant lesions, this can be low grade malignant lesions, one of the more common malignant lesions, or a rare malignant lesion. Benign lesions include such things a plasma cell granuloma (inflammatory pseudotumor). This is a benign tumor that is a post-inflammatory reaction and not a true neoplasia. Other lesions include granular cell myoblastomas or granular cell tumors. These originate from Schwann's cells and are usually found in larger bronchial origins, although they may occur as a peripheral lesion. Leiomyoma, lipoma and fibroma are other benign mesenchymal tumors. The more common malignant tumors include large cell carcinoma, adenocarcinoma, small cell and squamous cell carcinoma. Bronchoalveolar carcinoma can be considered a subset of adenocarcinoma.
The low grade malignant lesions include carcinoid tumor. This is a cancer, albeit a low grade cancer; it is not a benign lesion. There is a continuum histologically of carcinoid up to the level of small cell carcinoma. This series is actually a family of tumors called Kulchitsky cell carcinomas. Other low grade malignant lesions include adenoid cystic carcinoma. This is characterized by submucosal spread and perineural invasion such that even though a lesion may be seen endobronchially, usually in a centrally located bronchus, this may have spread submucosally. Another histologic type of low grade malignancy is mucoepider-moid carcinoma.
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