Large multicystic pulmonary chondroid hamartoma in a child presenting as pneumothorax

Discussion

Hamartoma was first described in the early 1900s.2 It is a common benign tumor of the adult lung seen in the fifth to sixth decade of life, with an incidence of 0.025-0.32%.1 Benign lung tumors are rare in the pediatric age group, of which the relatively common ones are inflammatory pseudotumors, hemangiomas, and adenomas. Pediatric PHs are very rare. The PHs can be parenchymal or endobronchial in location. Parenchymal hamartomas are more common, mostly incidental, and asymptomatic while endobronchial tend to be symptomatic with cough, hemoptysis, and obstructive pneumonia. Awareness of this lesion is necessary as it is a mimicker of primary and metastatic lung tumors, both clinically and radiologically. A CT-guided fine needle aspiration with cytological assessment helps exclude malignancies and other pathologies. Many times PHs are surgically excised either by enucleation or wedge resection, and are diagnosed on histopathology.2 The PHs grow slowly at a rate of 3.2 ± 2.6 mm per year; however, they can double in diameter over time.3 Giant PHs are rare, and most of them have been reported in adults, some as big as 26 cm.4-6 Pediatrics cases of this size have rarely been reported. Ozbudak et al3 reported an 11-year-old with a cystic chondroid PH measuring 18 cm across. Our case measures 11.3 cm in maximum dimension. An endobronchial PH was reported in an 8-month-old infant.7 Our case showed prominent cystic changes. The reason behind the cyst formation is still not clear. Some authors suggest that as hamartomas grow in size, their tendency to become cystic increases. The degenerative changes coupled with the growth leads to formation of cleft-like spaces that ultimately expand into cysts.3 Alternatively, the proximity of a hamartoma to a bronchiole with air-entry and a check-valve mechanism may lead to the expansion of epithelial-lined tubules into resultant cysts.3 We were unable to demonstrate any such connection to any bronchiole in our case.

Initially, hamartomas were considered to be a developmental anomaly, but cytogenetic analyses have shown mutations of high mobility proteins along chromosomal bands 6p21 and 12q13-15, thereby allotting hamartomas the status of a true neoplasm.8 Hamartomas originate from the undifferentiated mesenchymal tissue, which in the case of the lung is the fibrous connective tissue in the bronchial wall. The differential diagnoses for PHs include chondroma, well-differentiated chondrosarcoma, fibroma, and lipoma, all of which are easily excluded by histopathological examination. In our case, due to the age, large size, and multicystic nature, a preliminary diagnosis of CPAMs was made on gross pathological evaluation. In CPAM, an entire lobe of the lung may be replaced by dysfunctional abnormal cysts. A possibility of pulmonary sequestration was also considered. Chondroid cystic malformation associated with trisomy 8 karyotypic anomaly is another close differential diagnosis. Diffuse chondroid malformation was ruled out by the absence of the mesenchymal and adipose tissue typically seen in PHs. In addition, diffuse chondroid malformation has a classical peripheral distribution of cartilage and they tend to be more diffuse. Malignant carcinomatous or sarcomatous transformation of PHs is rare. Complications of large PHs include hemothorax, and pneumothorax.9 Aspergillus colonization of these cysts has also been reported.10

In conclusion, we recommend that despite the rarity of PHs in children, this neoplasm should be considered in the differential diagnosis of any child with a large pulmonary mass, especially since it is benign and surgery is curative. Currently, our patient is being followed up regularly and is doing well.