Bronchial "Hamartoma"

(Adenochondroma, pulmonary mesenchymoma)  This entity is probably a neoplasm rather than a hamartoma.  It may be either endobronchial or, more commonly, parenchymal.

Epidemiology  

Hamartomas account for 1% to 2% of all pulmonary neoplasms and are the most common benign tumour³. The incidence in a series of 8000 post-mortems was 0.25%.   The average age is 55 years.  Endobronchial lesions more commonly occur in men.  Cytogenetic abnormalities are common, indicating that this is probably a true neoplasm.

Clinical features

These lesions are usually asymptomatic, but may present with haemoptysis.  Multiple bronchial hamartomas have been reported.  In a series from Finland, the incidence was higher in smokers.  Carney's triad consists of gastric epithelioid leiomyosarcoma, pulmonary chondroma and functioning extra-adrenal paraganglioma:  the syndrome is usually seen in women below the age of 35 years.

Radiology

The tumours form homogenous peripheral round or lobulated opacities. Calcification is variable.

Macroscopic appearances

Endobronchial lesions are sessile or pedunculated.   The cut surface is grey, or yellow if there is much fat.  Parenchymal lesions are often sub-pleural and may show cystic foci.

Histopathology

These lesions consist of a combination of epithelium and connective tissue.  In the endobronchial lesions, the epithelium lines cleft and is usually of ciliated columnar type:  seromucinous glands may be present. In parenchymal lesions, it is usually non-ciliated. There are foci of cartilage merging with loose myxoid tissue, bone (with marrow), fibrosis, fat, smooth muscle and lymphoid tissue.   The parenchymal lesions show more cartilage and less fat.  Non-caseating granulomata have been reported, without evidence of micro-organisms or sarcoid.

Immunohistochemistry

The expression of steroid receptors by hamartomas differs between male and female patients.

		Fibromyxoid stroma	Chondroid cells	Epithelial cells
Oestrogen receptors	Male	3/153	6/153	12/153
	Female	9/153	12/153	9/153
Progesterone receptors	Male	14/153	0/153	0/153
	Female	13/153	0/153	0/153
Androgen receptors	Male	14/153	9/153	9/153
	Female	0/153	0/153	0/153
Vimentin		positive
GFAP		positive	also in cartilage nodules
S-100		positive	also in cartilage nodules and adipocytes
Calponin		positive	also in smooth muscle bundles
SMA		positive	also in smooth muscle bundles
p63				focally positive
TTF-1				positive
AE1/AE3 or MNF116				positive

Differential diagnosis

• Benign chondroma

• Fibroma

• Bronchial lipoma

• Metastatic teratoma after chemotherapy

Prognosis

Malignant change has been reported, albeit extremely rarely; malignancies developing within a hamartoma include carcinomas, sarcomas and salivary-gland type tumours³. There is reportedly an increased risk of concurrent pulmonary carcinoma, in particular of adenocarcinoma in the same lobe³.

¹ Gjevre JA, Myers JL,Prakash UB Pulmonary hamartomas. Mayo Clin Proc 1996; 71:14-20

² Tomashefski JF, Jr. Benign endobronchial mesenchymal tumors: their relationship to parenchymal pulmonary hamartomas. Am J Surg Pathol 1982; 6:531-40

³ Pelosi G, Rosai J,Viale G Immunoreactivity for Sex Steroid Hormone Receptors in Pulmonary Hamartomas. Am J Surg Pathol 2006; 30:819-827

 This page last revised 14.7.2006.

©SMUHT/PW Bishop