Each month, this department features a discussion of an unusual diagnosis in genetics, radiology, or dermatology. A description and images are presented, followed by the diagnosis and an explanation of how the diagnosis was determined. As always, your comments are welcome via e-mail at firstname.lastname@example.org.
A 7-year-old girl was referred to our clinic with cough, fever, and recurrent pneumonia. The patient had two episodes of left lower lobe pneumonia (3 months and 1 month before admission) and was treated with oral and intravenous antibiotics, respectively. Clinical examination revealed fever of 102.2°F and diminished breath sounds in the left lower lobe.
Examinations of the other systems were normal. Laboratory tests showed white blood cell count of 19,000/mm3, hemoglobin 10.7 g/dL, platelet count 295,000/mm3. Blood smear demonstrated 84% neutrophils and 16% lymphocytes. C-reactive protein was 45 mg/L (0.1–8.2 mg/L). Blood culture and protein purified derivate (PPD) test was negative. Contrast enhanced computerized tomography (CT), which was performed upon pathological findings (diminished left lung volume, increased density of left lower lobe, and hyperaeration of left lower lobe) demonstrated on chest x-ray, revealed a solid mass within the left main bronchus (see Figure 1).
Figure 1. Contrast enhanced CT examination coronal reformatted (a) and axial scans (b) show hyperdense solid mass within the left main bronchus (arrows). Source: Firinci F.
Bronchoscopy was performed and demonstrated a polipoid tumoural lesion, which was extending to right posterior and lateral wall of the left main bronchus and which obstructed the bronchus. A bronchoscopic biopsy was obtained from this area, which was prone to bleeding. Pathological evaluation was reported to be benign.
Subsequently, the patient underwent a left bronchotomy, and the mass was resected. Additionally, mediastinal lymph node sampling was made. Histopathological examination revealed a solid tumor. The tumor tissue consisted of cytokeratin-positive and synaptophysin-negative cells forming an epithelial pattern with PAS positive mucus. Superficial hemorrhagic areas, comedo necrosis, and calcifications were also present.
Because the glandular areas were sparse, the tumor was considered to be high grade (see Figure 2). The lymph node was not metastatic. The patient had an uneventful postoperative period and was discharged 7 days after the operation. We planned bronchoscopic followup within a 3-month period.
Figure 2. Representative light micrographs showing (a) mucoepidermoid morphology of the tumor, (b) cytokeratin-positive and synaptophysin-negative cells forming an epithelial pattern, (c) PAS positive mucus, and (d) high-grade proliferation. Source: Firinci F.
Mucoepidermoid Carcinoma (MEC)
Mucoepidermoid carcinoma (MEC) of the lung is a rare tumor derived from the minor salivary gland tissue of the proximal tracheobronchial tree, composing only .1% to .2% of the primary lung malignancies. Etiology is unknown.1,2 MEC occurs in patients with a range from 3 to 78 years; males and females are equally affected. Histologic grading separates low- from high-grade mucoepidermoid carcinoma. In childhood, the low grade is more common.3,4 The other tumors comprising this group are the bronchial carcinoid and adenoid cystic carcinoma.
It was first described by Smetana in 1952.5 MEC is believed to arise from excretory ducts of submucosal bronchial glands with an origin of salivary glands.6 Mucoepidermoid carcinoma of the bronchus commonly arises from the large airways, including the trachea and the main or lobar bronchi but occasionally may involve segmental bronchi or, infrequently, the peripheral lung.3 In our patient, tumor localization was in the left main bronchus, which was concordant with the literature.
The clinical symptoms and signs of the MEC are commonly associated with involvement of large airways, including cough, hemoptysis, bronchitis, wheezing, fever, chest pain, and, rarely, clubbing of the fingers.2 The clinical and radiographic differential diagnosis usually includes asthma, pneumonia, atelectasis, aspiration of foreign body, and pleural effusion.7
Recurrent pneumonia in the same region of the lung should raise clinical suspicion of an endobronchial lesion or mass, such as mucoepidermoid carcinoma.3 MEC localized to left main bronchus was diagnosed in a 13-year-old child by the evaluation of 169 children by Kut et al. between 1997 and 2000. The case had presented with recurrent pneumonia.8 Similarly, our patient had a history of recurrent left lower lobe pneumonia.
The radiographic findings are generally normal, or the tumors were seen as an endobronchial nodule, a mass with post obstructive pneumonia, or atelectasis.7,9 CT scan usually shows an intraluminal mass, dissemination of bronchial wall, lymph node involvement, and parenchymal findings associated with obstruction.7 Yousem and Hochholzer reported that among the 58 cases in their group, 41 had a solitary nodule or mass (71%); 16 had pneumonic consolidation (28%); and 1 had no abnormality on chest radiograph.9
In another study of 12 cases, the prevalence of postobstructive pneumonia or atelectasis was 33% on chest radiogram. On CT imaging, the tumors are central, smoothly oval, or lobulated, homogenous, may contain calcification, and may show mild contrast enhancement.7 CT has demonstrated left lower lobe atelectasis.7,10 Chest radiogram of our cases showed atelectasis in left lung, and CT demonstrated either lower lobe atelectasis or mass.
Histopathologically, MEC is classified as low-grade and high-grade. Most tumors are low-grade. High-grade tumors usually demonstrate necrosis, nuclear pleomorphism, active mitosis, and a solid or nested pattern of growth for the intermediate or squamous cells. Low-grade mucoepidermoid carcinoma usually lacks these features.3
The frequency of high-grade MEC increases with advancing age, resulting in worsened prognosis due to recurrences and metastasis.2 A study by Yousem et al. showed that only 2% of low-grade tumor and 15% of high-grade tumors metastasized to the regional lymph node.9 Our case includes histopathological features of high-grade tumors, therefore, we described it as high-grade MEC. Fifty-four cases studied of bronchial MEC indicate that only two children younger than 14 years have had high-grade tumors.2
Bronchoscopic examination of tumor usually shows a partial or complete occlusion of mainstem bronchus by lobulated gray or pink mass, which is firm to touch but prone to bleed. Bronchoscopic examination provides early and accurate diagnosis.10 Bronchospic examination of our patient showed polipoid tumoral mass with bleeding in the left main bronchus.
When the disease is low grade, localized or conservative surgical resection is the best treatment choice. In high-grade tumors, prognosis is usually variable, and lymph node, bone, or cutaneous metastasis can be seen in 25% of cases. High-grade MEC may be surgically treated by sleeve resection, local resection, segmental resection, lobectomy, and pneumonectomy. Lymph node resection is necessary. Surgical approach varies with localization, size, and histopathologic types of tumor.1–3,11 In mucoepidermoid tumors, the use of adjuvant therapy (radiation or chemotherapy) is controversial.12 In our case, the mass was resected from left main bronchus via left posterolateral thoracotomy, and mediastinal lymph node sampling was conducted.
In a review involving 54 patients with disease-free follow-up ranging from 8 months to 21 years, one patient had lymph node metastasis and died, one patient developed lymph node involvement at 5 years of follow-up, and one patient had questionable lymph node metastasis.2 These data suggest that patients with MEC of the lung should be provided with long-term clinical follow-up. Therefore, we decided to follow-up our patient via the bronchoscopic examination.
- Santambrogio L, Cioffi U, De Simone M, Rosso L, Ferrero S, Giunta A. Video-assisted sleeve lobectomy for mucoepidermoid carcinoma of the left lower lobar bronchus. Chest. 2002;121(2):635–636 doi:10.1378/chest.121.2.635 [CrossRef] .
- Dinopoulos A, Lagona E, Stinios I, Konstadinidou A, Kattamis C. Mucoepidermoid carcinoma of the bronchus. Pediatr Hematol Oncol. 2000;17(5):401–408 doi:10.1080/08880010050034346 [CrossRef] .
- Liu X, Adams AL. Mucoepidermoid carcinoma of the bronchus: a review. Arch Pathol Lab Med. 2007;131(9):1400–1404.
- Anton-Pacheco J, Jimenez MA, Rodriguez-Peralto JL, Cuadros J, Berchi FJ. Bronchial mucoepidermoid tumor in a 3-year-old child. Pediatr Surg Int. 1998;13(7):524–525 doi:10.1007/s003830050390 [CrossRef] .
- Smetana HF, Iverson L, Swan LL. Bronchogenic carcinoma: an analysis of 100 autopsy cases. Milit Surg. 1952;111(5):335–351.
- Meran S. Case no. 1. Diagnosis: mucoepidermoid carcinoma of the left bronchus. J Radiology. 1999;80:1714–1715.
- Kim TS, Lee KS, Han J, et al. Mucoepidermoid carcinoma of the tracheobronchial tree: Radiographic and CT findings in 12 patients. Radiology. 1999;212(3):643–648.
- Kut A, Karadag B, Karakoc F, et al. Mucoepidermoid carcinoma of the bronchus: a rare entity in childhood. Pediatr Int. 2005;47(2):203–205 doi:10.1111/j.1442-200x.2005.02027.x [CrossRef] .
- Yousem SA, Hochholzer L. Mucoepidermoid tumors of the lung. Cancer. 1987;60(6):1346–1352 doi:10.1002/1097-0142(19870915)60:6<1346::AID-CNCR2820600631>3.0.CO;2-0 [CrossRef] .
- Sogut A, Yilmaz O, Yuksel H. A rare cause of persistent atelectasis in childhood: mucoepidermoid carcinoma. Tuberk Toraks. 2008;56:325–328.
- Yousem SA, Nicholson AG. Mucoepidermoid carcinoma. World Health Organisation Classification of Tumors Pathology and Genetics of Tumors of the Lung, Pleura, Thymus and Heart. Lyon, Franc: IARC Press; 2004:63–64.
- Matsuzaki Y, Shibata K, Yoshioka M, et al. Successful treatment of bronchial mucoepidermoid carcinoma in an 11-yearold boy by bronchoplasty: report of a case. Jpn J Surg. 1996;26(1):64–67.