Undermining the normal surface bronchial epithelium (left) is an infiltrative tumor with some tubular growth.
There are also small solid nodules and focal cribriform growth as the tumor abuts the bronchial cartilage (right).
As seen in its salivary gland counterpart, perineural (and intraneural) involvement is frequent.
Salivary gland tumors in the lung are uncommon. Because they are virtually identical to salivary gland tumors, it is important to exclude metastasis from the salivary gland primary. Most salivary gland lung tumors arise from the submucosa of the bronchi and present as endobronchial lesions; however, some are peripheral lesion and have no connection to the bronchi (Fletcher). Types of salivary gland tumors in the lung include adenoid cystic carcinoma (ACC), mucoepidermoid carcinoma (MEC), acinic cell carcinoma and mixed types.
Adenoid cystic carcinoma (ACC) can grow in various patterns -- a cribriform pattern (most common), a tubular pattern, and a solid pattern (less common, more aggressive). Perineural invasion is common, but not necessarily an alarming feature.
Most present as endobronchial lesions ranging from 1-4cm in size and symptoms are related to obstruction (e.g. cough, dyspnea). Patients in their 5th decade are most commonly affected.
Complete resection, with radiation is recommended.
Up to 30% of ACC cases have distant metastases (compared to 10.5% in MEC patients). Stage is the most important prognostic factor. The survival rates for surgical MEC cases were 94% at 3 years and 87% at 5 years and 10 years. In comparision, the survival rates for surgical ACC cases were 73%, 57%, and 45% at 3, 5, and 10 years, respectively .
Thus, in terms of salivary gland tumors, ACC are more aggressive than MEC and although indolent tumors, the prognosis is guarded.
Molina JR, et al. Primary salivary gland-type lung cancer: spectrum of clinical presentation, histopathologic and prognostic factors. Cancer. 2007 Nov 15;110(10):2253-9.