Primary Pulmonary Salivary Gland-type Tumors

Abstract

Pulmonary salivary gland-type tumors (SGT) comprise a very small proportion of primary lung neoplasms. The most common tumors among this group are mucoepidermoid carcinoma and adenoid cystic carcinoma. Contrary to the head and neck region, benign SGT such as pleomorphic adenomas are exceedingly rare in the pulmonary system. More recently, 2 additional SGT, namely hyalinizing clear cell carcinoma and salivary duct-like carcinoma were recognized as primary lung tumors expanding the spectrum of SGT that have been described to originate in the tracheobronchial system. Primary pulmonary SGT must be clinically excluded from metastatic salivary gland neoplasms as their morphology is indistinguishable from that of their salivary gland counterparts. Little is known about the clinical behavior and best treatment approach for these unusual tumors. In this review, we provide a comprehensive summary of primary pulmonary SGT with particular emphasis on morphologic characteristics and latest developments in terms of immunohistochemical and molecular techniques.

c-Myb Overexpression in Cytology Smears of Tracheobronchial and Pulmonary Adenoid Cystic Carcinomas

“…Although an equal sex distribution was noted previously [17,18] , recent literature shows male predominance, as was seen in our series [3,19] . AdCC spreads commonly by direct extension, perineural invasion, or haematogenous metastasis, whereas lymph nodal metastasis is uncommon [20] .…”

“…Of these, mucoepidermoid carcinoma is the most common, followed by adenoid cystic carcinoma (AdCC). Recently, AdCC has gained attention following the discovery of characteristic tumour-specific translocation t(6; 9) (q22-23; p23-24) generating a fusion of the MYB oncogene (v-Myb avian MYB viral oncogene homolog) with the NFIB (nuclear factor IB) transcription factor gene [2,3] . In addition, cMyb overexpression has been observed on immunohistochemistry (IHC) in cases of AdCC associated both with and without MYB-NFIB fusion [4] .…”

Primary pulmonary sarcomatous and mixed epithelial-mesenchymal neoplasms

“…In contrast to other salivary gland tumours pleomorphic adenoma is very uncommon in the lung [36]. Arising from bronchial glandular tissue it is composed of varying proportions of glandular epithelial elements merging with myoepithelial and myxochondroid stromal elements.…”

Cytology of Primary Salivary Gland-Type Tumors of the Lower Respiratory Tract: Report of 15 Cases and Review of the Literature

“…Primary salivary gland-type tumors (PSGT) arising from the seromucinous submucosal glands of the lower respiratory tract (LRT) (which includes trachea, bronchus and lung) account for <1% of central airway carcinomas (1). They are rare neoplasms morphologically indistinguishable from their salivary gland counterpart; therefore, recognizing them is a challenge, especially on cytology.…”

“…Even though any type of salivary gland tumor that has been described in pathology textbooks can potentially arise in the LRT, published data show that the most commonly encountered primary salivary gland-type tumors in this anatomical site are malignant mucoepidermoid carcinoma (MEC), adenoid cystic carcinoma (AdCC), and epithelial-myoepithelial carcinoma (2–5). In fact, as opposed to the head and neck region, where the vast majority of salivary gland primaries are benign—with pleomorphic adenoma (PA) being the most common type—the contrary applies to LRT primaries (1). …”