Clinical Analysis and Literature Review of 18 Cases of Children Pulmonary Mucoepidermoid Carcinoma

  

    
Pathology
    
Number (%)
  
  

    
Low grade
    
9(52.9)
  
  

    
Intermediate
    
2(11.8)
  
  

    
High grade
    
2(11.8)
  
  

    
Ungraded
    
4(23.5)
  
  

    
Treatment
    

  
  

    
Surgery
    

  
  

    
Sleeve resection
    
7(41.2)
  
  

    
Lobectomy
    
6(35.3)
  
  

    
Endoscopic excision
    
3(17.6)
  
  

    
Radiotherapy
    
1(5.9)
  
  

    
Metastasis
    

  
  

    
Yes
    
1(5.9)
  
  

    
No
    
16(94.1)
  

Table 3: Pathology, Treatment and Metastasis.

Metastasis

1 case of invasion of the visceral pleura, metastatic cancer in parabronchial lymph nodes; 1 case developed a second tumor (thyroid micropapillary carcinoma) 11 years later.

Prognosis

6 cases in this group were lost to follow-up, and the remaining 12 cases were followed up by telephone, except for 2 cases with decreased exercise tolerance compared with the same age, the remaining 10 cases were asymptomatic.

Discussion

Mucoepidermoid carcinoma was first proposed by Smetana and Liebow in 1952 [1], and is the most common malignancy of the salivary glands, occurring in children and young adults, but can be seen in people of all ages (3-78 years old) [2], and the smallest reported case to date is a 2-year-old boy in the United States [3]. Bronchial Mucoepidermoid carcinoma is rare, with an incidence of about 0.1-0.2% of primary lung cancer [4]. It has been reported that there is no gender preference for the onset of men and women in patients with MEC [5-7], the number of male children in our group of cases is about 1.6 times of female children, which is consistent with the study of Lily et al [8].

Primary bronchial mucoepidermoid carcinoma usually presents as an endobronchial tumor with polypoid growth, with no specific clinical manifestations, mostly bronchial irritation and obstruction symptoms (depending on the tumor site). Patients may have cough, hemoptysis, wheezing [9] and post-obstructive pneumonia, some children have no clinical symptoms (about 9%-28%) [10], but even some children will have carcinoid syndrome, Cushing syndrome and acromegaly and other manifestations [2], the disease is easy to be misdiagnosed as tuberculosis, pneumonia, right middle lobe syndrome, asthma and other diseases in clinical work [11]. According to the statistics of Lili et al [8], about 88.9% of children's MEC is misdiagnosed as tuberculosis and treated according to tuberculosis. As previously shown, the delay in diagnosis of tracheal MECs ranged from 3 months to 2 years [12-15], with the longest time from symptom onset to diagnosis in our group of cases being more than two years. Tsuchiya [16] and Dinopoulos [17] summarized the clinical manifestations of 84 children with MEC, concluded that cough, hemoptysis, fever and recurrent pneumonia were the most common manifestations. Looking back at our group of 18 cases, the first symptom of the children was cough as the most common, followed by hemoptysis and fever, which were consistent with the relevant literature reports, and one child even had no clinical symptoms, only found swollen lung nodules during body check, and then further biopsy confirmed bronchial mucoepidermoid carcinoma.

MEC is mainly manifested as a round-like or lobulated mass with a smooth inner edge of the bronchi and clear boundaries, and is often accompanied by obstructive atelectasis, obstructive pneumonia and other manifestations [18], and some children with smaller tumors do not even have clump-like masses on CT or chest radiograph, but only show pneumonia or atelectasis [19]. In general, tumors appear as isolated masses and do not have any specific segment or lobar predisposition [20]. The literature points out that tumors can be found in the trachea and each lobe, and segment bronchi [21], but more often occur in the main bronchi, middle and lobe bronchi. According to literature statistics, about 10% of tumors are confined to the trachea, about 15% are located in the main bronchi, about 75% are located in the lobes and segment bronchi [22], invasion of trachea and carina is rare [23], according to the data reviewed, less than 10 cases of tracheal MEC have been reported in the literature. Most of them are located about 2~4cm above the carina [12-15,24]. In our group of cases, there is no significant preference of the location of the masses (one case violated the tracheal carina), and distal pneumonia, atelectasis as well as pleural effusion may also occur. However, although the imaging of MEC is diverse and nonspecific, Li X, and Yi W believe that well-circumscribed oval or lobulated intraluminal or peripheral lung masses with significant heterogeneous contrast enhancement may suggest a diagnosis of mucoepidermoid carcinoma [25-27]. An analysis shows a centrally located or hilar mass with clear margins, regular shape, no necrosis, and moderately enhanced findings were associated with bronchial MEC [28]. However, in our cases, patients presenting with uneven enhancement are rare and may be limited by small sample sizes.

Mucoepidermoid carcinoma often covers the surface of normal mucosal epithelium, and there are usually no positive findings on bronchoscopic brushing or lavage, and in the case reported by Zhou X, et al, the patient did not find tumor cells on three smear examinations, but TCT (Thin-layer cytology test) showed a large number of atypical cells [29], so TCT may suggest the diagnosis of MEC, but its diagnosis still depends on tissue biopsy. The histologic findings of MEC typically show a mixture of squamous cells, mucin-producing cells, and intermediate cells, lacking keratinization and overlying epithelium (Figure 6-7). Though they are all composed of these cells, MEC has a different biological behavior clinically. According to histopathology, MEC can be divided into low, intermediate, and high grades, with the low grade (48% of 75 cases) being more common than the high grade (38.7% of 75 cases), and the intermediate grade (13.3% of 75 cases) being the least common [30]. Low-grade tumors are more common in children, with well-defined lesions, often presenting as endobronchial polypsoids. High-grade tumors are large, often invade adjacent lung parenchyma, and occur with lymphatic or hematogenous spread. All children in our group of cases underwent pathological biopsies, more than half of them showed low-grade malignancy, which with good differentiation was mostly only locally aggressive, while distant metastasis was rare. Metastases are mostly associated with tumor grade, with only 2% (in 45 patients) of low-grade MECs and 15% (in 13 cases) of high-grade MECs metastasizing to lymph nodes in a study by Yousem SA et al. [31]. In our cases, only one child had a tumor invading the visceral pleura and distant lymph node metastasis at the time of first diagnosis, and another child found a second tumor (micropapillary thyroid carcinoma) 11 years after the first time of the diagnosis of MEC, and then underwent total thyroidectomy, recovered well after surgery, and now survives asymptomatically.

    

    

    Figure 6: Picture shows squamous cells in MEC, lacking keratin pearls (H and E × 40).
    

    

    

    Figure 7: The histologic findings of MEC typically show a mixture of squamous cells, mucin-producing cells, and intermediate cells. The nucleus of tumor cells are round or oval shapes, with mucus in the cytoplasm (H and E ×200).
    

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Citation: Guo YL, Qiu Y, Deng Y, Gu YY, Huang SK, et al. Clinical Analysis and Literature Review of 18 Cases of Children Pulmonary Mucoepidermoid Carcinoma. Austin J Clin Case Rep. 2024; 11(3): 1326.

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