EMC is a rare malignant salivary gland tumor that accounts for < 1% of all salivary gland epithelial neoplasms and nearly 2% of malignant salivary gland tumors [
1,
8]. EMC of the salivary gland was first described by Donath et al. in 1972 [
9]. EMC is characterized by a biphasic morphology, with an inner layer of duct-like structures composed of epithelial cells and a surrounding layer of myoepithelial cells immunoreactive for S-100 and smooth muscle actin [
1,
2,
6]. The tracheobronchial glands are considered counterparts of the minor salivary glands in the respiratory tract and can develop similar tumors. Within this type of neoplasia, EMC of the respiratory tract is very rare, and the diagnosis is often difficult [
10,
11]. Salivary gland-type tumors of the lung account for 0.1–1% of all primary lung carcinomas, among which mucoepidermoid carcinoma is the most frequently observed histological subtype, followed by adenoid cystic carcinoma and then EMC [
4,
5]. Recently, Nakashima et al. conducted a literature review of 56 patients (32 females and 24 males; average age [range], 56 [7–81] years) with pulmonary EMC [
6]. Of these, 45 patients had tumors localized in the central airway within segmental bronchi appearing to be endobronchial masses. The size of the tumors varied from 0.7 to 16 cm in diameter (average 2.5 cm). According to the histopathological characteristics, three distinct histological subtypes of pulmonary EMC were reported: (1) EMC with two ductal components, defined as a characteristic feature of this tumor, (2) EMC with a solid component consisting mainly of spindle- and polygonal-shaped myoepithelial cells, and (3) EMC consisting mainly of myoepithelial cells with increased nuclear atypia, referred to as myoepithelial anaplasia [
6,
12‐
14]. Seethala et al. reported that patients with myoepithelial anaplasia had a poorer survival compared with others [
15]. Although our case was diagnosed as adenocarcinoma in the small biopsy, it proved to be typical EMC featuring two ductal components and immunohistochemically.
Several genetic mutations have been detected in EMC of the salivary glands [
7,
16,
17];
HRAS mutations are the most frequently detected, followed by
PIK3CA and
AKT1 mutations. The genetic alterations associated with pulmonary EMC are still unknown because of the rarity of this tumor. Urano et al. are the only ones who described HRAS mutations in all three pulmonary EMC that they analyzed [
7]. However, our case did not show any mutations in
AKT1,
HRAS or
PIK3CA. Although the number of reported cases is very small, the frequency of
HRAS mutations in pulmonary EMC is 75% (3/4 cases). At this time, we cannot conclude whether the genetic alterations in pulmonary EMC are similar to those of other EMC types. Typical cases of pulmonary EMC are easy to diagnose, whereas atypical cases can be difficult to distinguish. Furthermore, because the biopsy specimen is small, the duct-like structure may be misdiagnosed as adenocarcinoma. Determination of the characteristic gene mutations will be useful for differentiating pulmonary EMC from other salivary gland tumors of the lung.