Pulmonary hamartoma: Cytological study of a case and literature review.

Pulmonary hamartomas are the most common but rare benign tumor-like lesions of the lung arising from the embryonic rest. They are more common in males and in aged. Majority are asymptomatic and seen as coin lesions with popcorn calcification in the chest radiograph. Fine needle aspiration cytology (FNAC) helps to diagnose and distinguish them from the cancerous lesions of the lung. The cytological material is characterized by fibromyxoid stroma, cartilage, bronchial cells, adipose tissue and bone. Bronchial cells with reactive atypia may be a source of false-positive result. Symptomatic cases need surgical intervention such as enucleation or segmental resection. We report a case of a 74-year-old male who had a lung mass that did not progress over 4-year on chest radiograph. The CT-guided FNAC smears showed benign bronchial epithelial cells, fibro-myxoid spindle cell stroma and fat spaces that aided the diagnosis of pulmonary hamartoma avoiding surgical intervention.

Introduction

Pulmonary hamartomas are rare but the most common benign mass lesions of the lung. They were first described by Albrecht in 1904.[1] They are more common in males, with a peak incidence at the age of 50 years. Majority are found accidentally as coin lesions with popcorn calcification in the chest radiograph.[2] Cancerous growth is a differential and fine needle aspiration cytology (FNAC) helps to diagnose these lesions. Cytological material is composed of fibromyxoid stroma, bronchial cells, adipose tissue and rarely bone. Atypical reactive bronchial cells can lead to a false positive diagnosis for malignancy.[3] Malignant change in pulmonary hamartoma is not reported. A preoperative cytological diagnosis can avoid surgical intervention. Such cases can be followed up with regular chest radiographs. Enucleation or segmental resection is required for symptomatic cases and large lesions.[2] We report a case of pulmonary hamartoma diagnosed on FNAC in a 74-year old patient that helped the clinician to make appropriate therapeutic decisions.

Case Report

A 74-year-old male patient presented with cough with expectoration of 2 months duration. He was a chronic cigarette smoker for 45 years and had on and off cough with expectoration of 20 years duration. General physical examination revealed clubbing. There was no pallor, lymphadenopathy or organomegaly. Chest radiograph showed a mass lesion in the mid-zone of left lung.

His past history revealed hospital admission elsewhere for similar complaint 4 years back and chest radiograph showed a mass lesion in the left lung mid-zone and was diagnosed as tuberculosis or fungal infection. He was treated for chronic obstructive pulmonary disease (COPD). The previous and present radiograph were compared and showed no significant change in the size of the mass in the lung. Sputum was negative for malignant cells and acid-fast bacilli.

The patient was subjected to chest computed tomography (CT) scan. CT scan showed a well defined heterogeneous, enhancing mass lesion in the superior segment of left lower lobe with internal hypodense fat areas (Hounsfield Unit: from – 15 to – 30) measuring 6.5 cm × 6 cm [Figure 1].

Figure 1

CT chest showing well-demarcated coin lesion with internal hypodense fat areas

The lesion was aspirated under CT guidance using 23G, 11 cm spinal needle by transthoracic approach. The aspirate yielded blood-mixed sticky material. The smears prepared were fixed in 95% ethanol and stained by Papanicolaou stain. A few air dried smears were prepared and stained by May-Grünwald–Giemsa stain.

The stained smears revealed good cellularity. Clusters of epithelial cells were seen with moderate amount of cytoplasm and a round central nucleus with granular chromatin. A few of the cells displayed prominent nucleoli. No cellular atypia or mitoses were seen. Background showed abundant chondroid and fibromyxoid element with benign spindle cells and numerous fatty spaces [Figure 2]. A cytological diagnosis of pulmonary hamartoma was offered.

Figure 2

Cytological aspirate showing (a) fibromyxoid stroma with spindle cells, fat spaces and (b) sheets of bronchial epithelial cells with benign cytological features (Pap, ×400)

Patient was advised surgical excision in view of the large mass; however, patient declined surgery. He was treated for chronic obstructive pulmonary disease (COPD) and is presently under follow-up.

Discussion

Pulmonary hamartoma was first described by Albrecht in 1904 and is defined as “tumor-like malformations in which occurs only an abnormal mixing of the organ. The abnormality may take the form of a change in quantity, arrangement or degree of differentiation, or may comprise all three”.[12] They are rare but most common benign tumor-like lesions of the lung and also termed as hamartochondroma, chondromatous hamartoma, adeno-chondroma and mesenchymoma.[14] A classical lesion is non-organized mixture of epithelial and mesenchymal components such as of fibromyxoid stroma, adipose tissue, cartilage, smooth muscle cells and respiratory epithelium. Occasionally bone and bone marrow can be present.[35] They arise from embryological rests that are present from fetal life, but are seldom visible before adulthood.[25]

Being more frequent in the sixth decade of life, they are more common in males.[12] They are generally asymptomatic and accidentally found in chest radiograph during routine evaluation. They are usually small, vary from 1 to 6 cm in size (average 2 cm), and are well demarcated. In chest radiograph, they are termed as “coin lesion,” and although rare, a classical popcorn calcification is diagnostic.[12]

Most of the hamartomas are peripheral and are asymptomatic. Central hamartomas may obstruct a bronchus causing atelectasis, pneumonitis, cough, expectoration and chest pain.[12]

Majority of the lesions are solitary, but rarely are multiple posing as metastasis to the lung.[2]

They may cause diagnostic difficulty for both the radiologist and the clinician. Malignant change is practically non-existent; therefore, identification before the definitive management is of utmost importance. FNA can confidently distinguish them from the lung malignancy, avoiding surgery.

The fine needle aspirate material is characterized by fibromyxoid-stroma, cartilage, bronchial cells, adipose tissue and rarely bone marrow.[4] Identification of fibromyxoid stroma is more reliable than the cartilage. Although distinctive, cartilage is present in minority of cases.[6] Bronchial cells with reactive atypia may be a source of false-positive result. In such cases, immunocytochemical stain for S-100 protein can help to highlight the chondroid and fibromyxoid stroma.[4]

Long-term follow-up of cytologically proven pulmonary hamartoma for 5 years did not reveal any evidence of malignancy.[2] In the present case, chest radiographs taken at 4 years interval did not reveal any change in the size.

In their review of 19 cases of cytologically diagnosed pulmonary hamartoma, Hughes et al.[5] showed 78% specificity and 22% false-positive rate in FNA diagnosis. Most common false-positive diagnoses were carcinoid tumor, adenocarcinoma and small cell carcinoma. Paucity of stroma and prominent epithelial component led to high false-positive rate in their study.

In the cases of confident diagnosis of pulmonary hamartoma by cytology, it needs no treatment and in more that 50% cases surgery can be avoided. These cases need regular follow-up by chest radiograph. Symptomatic cases, large lesions and rapid growth of the lesion need surgical interventions that may be limited to enucleation or segmental resections and rarely lobectomy.[27]

Conclusion

Pulmonary hamartomas are rare tumor-like masses of the lung seen as coin lesion in the chest radiograph, causing diagnostic difficulty. FNA can help to diagnose these cases, avoiding the surgery. Regular follow-up is advised in small and asymptomatic cases. Symptomatic and large lesions may need surgical resection.