Case 100

Diagnosis: Mucoepidermoid Carcinoma

Radiologic Findings

Chest PA shows complete atelectasis of right lower lobe.

Contrast-enhanced chest CT scans reveal a well-defined ovoid endobronchial mass with distal atelectasis of right lower lobe.

 

Brief Review

Mucoepidermoid carcinoma of the tracheobronchial tree is a rare airway tumor, comprising only 0.1 - 0.2 percent of the primary lung malignancies [1 - 5].
The tumor is believed to originate from the minor salivary glands lining the tracheobronchial tree [6].

The term "bronchial adenoma" has been used to describe a group of slow-growing neoplasms, many of which arise from the bronchial glands, including adenoid cystic carcinomas, mucoepidermoid carcinomas, and mixed tumors, and carcinoid tumors [1].
Since these tumors are usually low-grade malignancies rather than benign neoplasms, the term "bronchial adenoma" is a misnomer and should be discarded.

Histologically, mucoepidermoid carcinoma of the tracheobronchial tree consists of variable proportions of mucus-secreting cells, squamous cells, and so-called intermediate cells that show no particular differentiating characteristics [1]. The tumor is pathologically classified into low- and high-grade malignancy.

Radiographic manifestations of 58 cases of tracheobronchial mucoepidermoid carcinoma reviewed by Yousem and Hochholzer consisted of a solitary nodule or mass in 41 (70%) and "pneumonic consolidation" in 16 (29%) (one case showed no abnormality on chest radiograph) [6, 7].

According to a review of twelve cases of mucoepidermoid carcinoma by Kim et al (8), it is more commonly seen in the segmental bronchus rather than in the trachea or the main bronchus. (distal trachea [n = 1], main [n = 2], lobar [n = 1], or segmental [n = 8] bronchus)  

On chest radiographs, the tumor appears as a central mass with or without postobstructive pneumonia/ peripheral atelectasis or solitary pulmonary nodule.

Prediction of endoluminal location of the tumor is plausible at CT, even when the tumor is located within the segmental bronchus.

  1. It appears as a sharply-marginated ovoid or lobulated intraluminal mass adapting to the branching features of the airways.

  2. Postobstructive pneumonia or distal bronchial dilatation with mucoid impaction is frequently associated.

  3. Punctate calcification within the tumor is seen in about half of the patients.

  4. The tumor shows mild enhancement after contrast enhancement.

  5. Metastasis to the regional lymph node is rare, and the prognosis is excellent.


 

References
  1. Colby TV, Koss MN, Travis WD. Tumors of salivary gland type. In: Tumors of the lower respiratory tract, Atlas of tumor pathology, 3rd series, fascicle 13. Washington D.C., Armed forces institute of pathology, 1995; 65-89.

  2. Heitmiller RF, Mathisen DJ, Ferry JA, Mark EJ, Grillo HC. Mucoepidermoid lung tumors. Ann Thorac Surg 1989; 47:394-399.

  3. Leonardi HK, Jung-Legg Y, Legg MA, Neptune WB. Tracheobronchial mucoepidermoid carcinoma: clinicopathological features and results of treatment. J Thorac Cardiovasc Surg 1978; 76:431-438.

  4. Miller DL, Allen MS. Rare pulmonary neoplasms. Mayo Clin Proc 1993; 68:492-498.

  5. Turnbull AD, Huvos AG, Goodner JT, Foote FW Jr. Mucoepidermoid tumors of bronchial glands. Cancer 1971; 28:539-544.

  6. Yousem SA, Hochholzer L. Mucoepidermoid tumors of the lung. Cancer 1987; 60:1346-1352.

  7. Fraser RS, Pare JAP, Fraser RG, Pare PD. Neoplastic disease of the lungs. In: Synopsis of diseases of the chest. 2nd ed. Philadelphia, Pa: WB Saunders, 1994; 445-539.

  8. Kim TS, Lee KS, Han J, et al. Mucoepidermoid carcinoma of the tracheobronchial tree: radiographic and CT findings in 12 patients. Radiology 1999 Sep;212(3):643-8


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