AJR 2001; 177:1145-1150
© American Roentgen Ray Society
Sialadenoid Tumors of the Respiratory Tract
Radiologic—Pathologic Correlation
Tae Sung Kim1,
Kyung Soo Lee1,
Joungho Han2,
Eun A. Kim1,
Po Song Yang1 and
Jung-Gi Im3
1
Department of Radiology, Samsung Medical Center, Sungkyunkwan University
School of Medicine, 50, Ilwon-Dong, Kangnam-Ku, Seoul 135-710, Korea.
2
Department of Diagnostic Pathology, Samsung Medical Center, Sungkyunkwan
University School of Medicine, Seoul 135-710, Korea.
3
Department of Radiology, Seoul National University College of Medicine, Yongon
Campus, Seoul 140-210, Korea.
Received March 7, 2001;
accepted after revision May 8, 2001.
Presented at the annual meeting of Radiological Society of North America,
Chicago, November 2000.
Address correspondence to K. S. Lee.
Introduction
Because the tracheobronchial mucous glands are pulmonary analogues of the
salivary glands, neoplasms with an identical histologic feature have been
reported in both the respiratory tract and the head and neck regions.
Tracheobronchial sialadenoid tumors have been estimated to account for less
than 0.5% of all lung neoplasms
[1]. Among them, adenoid cystic
carcinoma (80%) and mucoepidermoid carcinoma (5%) are well-known pathologic
entities [2]. Mucous gland
adenoma, pleomorphic adenoma, and acinic cell carcinoma have also been
described pathologically. Other extremely rare salivary gland tumors include
carcinoma ex pleomorphic adenoma, pulmonary oncocytoma, myoepithelioma, and
epithelial—myoepithelial carcinoma
[3]. These tumors
characteristically manifest as intraluminal polypoid masses in the trachea or
major bronchi. Symptoms usually are related to large airways irritation or
obstruction—cough, hemoptysis, fever, and pneumonia. A history of
adult-onset asthma that has become more severe despite adequate therapy should
raise the possibility of a central obstructing lesion
[2].
Adenoid Cystic Carcinoma
Adenoid cystic carcinoma (formerly, cylindroma or adenocystic carcinoma) is
an infiltrative, malignant epithelial neoplasm
[3]. It is the second most
common primary tumor of the trachea (squamous cell carcinoma being most
frequent). Among the subtypes of tracheobronchial gland tumors, it is the most
common one, accounting for 75-80% of reported cases
[2].
Most of these tumors arise in the lower trachea or main stem bronchi, and
peripheral or subsegmental location is uncommon (10% of the cases)
[2,
3] (Figs.
1A,1B,1C,1D,2A,2B,3A,3B).
Adenoid cystic carcinoma has a striking tendency toward submucosal extension,
manifesting as a sessile, polypoid, annular, or diffusely infiltrative nodule
with a heaped-up margin. Pathologically, the tumor narrows the circumference
of the main airway, spreads longitudinally from the main mass, and penetrates
through the bronchial wall to invade the surrounding tissues
[3]. An extraluminal growth
visible on CT scans in the transverse plane is a common feature of adenoid
cystic carcinoma [4] (Fig.
3A,3B).
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Fig. 1C. —36-year-old woman with adenoid cystic carcinoma.
Photomicrograph of biopsy specimen shows typical cribriform pattern with
islands of neoplastic epithelial cells containing several small round
pseudocystic structures. (H and E, x 100)
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Fig. 1D. —36-year-old woman with adenoid cystic carcinoma. CT scan
obtained 16 months later shows multiple metastatic nodules in both lungs, left
pleural space, and liver in addition to malignant pleural effusion.
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Fig. 2A. —62-year-old woman with adenoid cystic carcinoma.
Contrast-enhanced CT scan obtained at level of aortic arch shows diffuse and
eccentric wall thickening of trachea. Subtle irregularity on paramediastinal
lung represents radiation pneumonitis from previous radiation therapy.
Calcified right paratracheal lymph node is also incidentally noted.
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Fig. 2B. —62-year-old woman with adenoid cystic carcinoma.
Two-dimensional sagittal reformation of CT scan shows diffuse irregular wall
thickening with heaped-up margin (arrowheads) in trachea.
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Fig. 3A. —45-year-old man with adenoid cystic carcinoma. CT scan shows
soft-tissue mass (arrow) filling left main bronchus with bronchial
wall thickening, extending into left upper lobar bronchus.
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Fig. 3B. —45-year-old man with adenoid cystic carcinoma.
Photomicrograph of pneumonectomy specimen shows transmural solid mass with
intramural polypoid growth and destruction of bronchial cartilage. (H and E,
x1)
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Mucoepidermoid Carcinoma
Mucoepidermoid carcinoma of the tracheobronchial tree is a rare airways
tumor, constituting only 0.1-0.2% of the primary lung malignancies
[3]. The tumor is believed to
originate from the minor salivary glands lining the tracheobronchial tree
[5] and is pathologically
classified into low- and high-grade malignancy (Figs.
4A,4B,4C,5A,5B,6A,6B,6C,6D).
Although the age of patients with mucoepidermoid carcinoma has been reported
as ranging from 4 to 78 years, nearly half are younger than 30 years
[1,
3,
5]. Mucoepidermoid carcinoma is
more commonly seen in the segmental bronchus than in the trachea or the main
bronchus [6]. It appears as a
sharply marginated, ovoid or lobulated, intraluminal mass adapting to the
branching features of the airways. Prediction of endoluminal location of the
tumor is possible at CT, even if the tumor is located in the segmental
bronchus. A mucoepidermoid carcinoma usually presents as a well-circumscribed,
polypoid endobronchial nodule in the segmental bronchi
[3,
6], whereas an adenoid cystic
carcinoma usually manifests as a tumor in the major airway with a heaped-up
margin and extraluminal infiltration. Postobstructive pneumonia or distal
bronchial dilatation with mucoid impaction is frequently associated with the
disease. Punctate calcification within the tumor is seen on radiologic images
of about half the patients. The mucoepidermoid carcinoma tumor shows mild
enhancement on images after the administration of contrast material.
Metastasis to the regional lymph node is rare, and the prognosis is excellent
[6].
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Fig. 4A. —70-year-old man with mucoepidermoid carcinoma (high-grade
malignancy). Chest radiograph shows mass (arrowheads) in right
lateral wall of trachea, resulting in severe luminal narrowing of tracheal air
column.
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Fig. 4C. —70-year-old man with mucoepidermoid carcinoma (high-grade
malignancy). Photograph of gross specimen shows yellowish tan transmural
myxoid mass with destruction of bronchial cartilage.
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Fig. 6B. —26-year-old woman with mucoepidermoid carcinoma (low-grade
malignancy). Serial contrast-enhanced CT scans show mildly enhancing
endobronchial mass filling ectatic bronchus intermedius, resulting in complete
combined atelectasis of right middle, and lower lobes.
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Fig. 6C. —26-year-old woman with mucoepidermoid carcinoma (low-grade
malignancy). Serial contrast-enhanced CT scans show mildly enhancing
endobronchial mass filling ectatic bronchus intermedius, resulting in complete
combined atelectasis of right middle, and lower lobes.
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Fig. 6D. —26-year-old woman with mucoepidermoid carcinoma (low-grade
malignancy). Serial contrast-enhanced CT scans show mildly enhancing
endobronchial mass filling ectatic bronchus intermedius, resulting in complete
combined atelectasis of right middle, and lower lobes.
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Myoepithelial Tumors
Myoepithelioma and epithelial—myoepithelial carcinoma are
exceptionally rare myoepithelial forms of tracheobronchial sialadenoid tumors.
To our knowledge, only three pathologically confirmed cases of myoepithelioma
[7] and four pathologically
confirmed cases of epithelial—myoepithelial carcinoma of the lung
[8] have been reported in
English literature. Myoepithelial tumors typically manifest as an
endobronchial mass of a lobar bronchus (Fig.
7A,7B,7C),
and a peripheral type of tumor has been reported as well. Although
histologically bland, myoepitheliomas show frequent distant metastasis (Fig.
8A,8B,8C,8D).
Epithelial—myoepithelial carcinoma is pathologically characterized by a
dual-cell population, including an inner layer of cuboidal epithelial cells
that are peripherally bounded by a layer of myoepithelial cells (Fig.
9A,9B,9C,9D).
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Fig. 7A. —38-year-old woman with tracheal myoepithelioma.
Contrast-enhanced conventional (7-mm collimation) CT scan obtained at level of
lower neck shows 10 x 5 mm, well-defined nodule (arrow)
involving proximal tracheal wall and adjacent area.
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Fig. 7B. —38-year-old woman with tracheal myoepithelioma. Photograph of
sliced gross surgical specimen reveals well-circumscribed ovoid nodule with
broad base arising from tracheal ring. Most of tumor shows extratracheal
growth, although some intraluminal growth was noted (not shown). (H and E,
x4)
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Fig. 7C. —38-year-old woman with tracheal myoepithelioma.
Photomicrograph of biopsy specimen reveals spindle cell myoepithelioma, which
is predominantly composed of compactly arranged spindle cells. Some of spindle
cells show clear cytoplasmic change. (H and E, x100)
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Fig. 8B. —36-year-old man with recurrent myoepithelioma in left lower
lobe. Follow-up unenhanced CT scan obtained 12 months after segmental
resection of tumor seen in A shows recurrent mass with minimal amount
of pleural effusion. Mass manifests as homogenous consolidation abutting
pleural surface, hence mimicking pleural-based mass.
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Fig. 8C. —36-year-old man with recurrent myoepithelioma in left lower
lobe. Photomicrograph of biopsy specimen obtained from partial resection of
left lower lobe reveals plasmacytoid myoepithelioma. Tumor is mainly composed
of round or ovoid cells with abundant eosinophilic hyaline cytoplasm and
eccentrically located nuclei. (H and E, x100)
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Fig. 8D. —36-year-old man with recurrent myoepithelioma in left lower
lobe. After second curative operation, large amount of multiloculated left
pleural and pericardial effusion was found on follow-up examination. Diffuse
and nodular pleural thickening (arrows) suggestive of pleural seeding
is seen on follow-up CT scan.
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Fig. 9A. —51-year-old woman with epithelial-myoepithelial carcinoma in
left lower lobe. Left decubitus chest radiograph shows air-space consolidation
or loculated subpulmonic effusion (arrows) in left lower lung
zone.
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Fig. 9B. —51-year-old woman with epithelial-myoepithelial carcinoma in
left lower lobe. Contrast-enhanced conventional (7-mm collimation) CT scan
obtained at level of liver dome shows segmental consolidation in left lower
lobe, mimicking pleural-based mass. Lesion shows slightly heterogeneous low
attenuation.
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Fig. 9C. —51-year-old woman with epithelial-myoepithelial carcinoma in
left lower lobe. Photomicrograph of biopsy specimen obtained from left lower
lobectomy shows epithelial—myoepithelial carcinoma of lung. Tumor is
composed of biphasic cell population: large polygonal myoepithelial cells in
peripheral location (arrow) and slightly cuboidal epithelial cells
forming lumen (arrowhead). Surrounding stromal tissue is hyalinized.
(H and E, x100)
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Fig. 9D. —51-year-old woman with epithelial-myoepithelial carcinoma in
left lower lobe. Photomicrograph of biopsy specimen with smooth muscle actin
immunostaining shows intense immunoreaction of peripherally located
myoepithelial cells in tubular formations. (smooth muscle actin
immunostaining, x100)
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Mucous Gland Adenoma
Mucous gland adenoma (mucous gland cystadenoma, adenomatous polyp) is a
benign tumor arising from bronchial mucous glands in lobar or segmental
bronchi, manifesting as a spherical, polypoid endobronchial nodule (Fig.
10A,10B).
It is one of the rarer epithelial neoplasms of the lung and occurs in both
children and adults, with mild predominance in girls or women
[1,
3]. When viewed through the
microscope, cystic muscus-filled glands are seen as protruding into the
bronchial lumen [3]. Its true
benignity warrants a conservative treatment of surgical excision with sparing
of lung parenchyma.
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Fig. 10A. —65-year-old woman with mucous gland adenoma.
Contrast-enhanced conventional (10-mm collimation) CT scan obtained at level
of aortic arch shows mildly enhancing mass in left upper lobe.
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Fig. 10B. —65-year-old woman with mucous gland adenoma. Lung-window CT
scan shows well-defined, ovoid mass with peripheral tiny radiolucencies, which
suggest residual lumen of segmental bronchus.
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Pulmonary Oncocytoma
To our knowledge, fewer than 10 pathologically confirmed pulmonary
oncocytomas have been reported. The tumors usually manifest as solitary
intrabronchial nodules that are 1.0-3.5 cm in diameter and tend to occur in
men who are smokers [3].
Summary
Most tracheobronchial sialadenoid tumors are found in an endotracheal or
endobronchial location, whereas some myoepithelial tumors manifest as a
peripheral nodule or consolidation. Findings suggestive of airway obstruction
are seen frequently on CT scans of patients with tracheobronchial sialadenoid
tumors. Adenoid cystic carcinoma shows infiltrative growth along the airway.
Mucoepidermoid carcinomas are more commonly seen in the segmental bronchi,
showing frequent tumoral calcification. Myoepithelial tumors show an
infiltrative growth pattern with frequent distant metastasis.
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Introduction
Adenoid Cystic Carcinoma
