Chondroid “hamartoma” (adenochondroma, mixed mesenchymoma).
Despite their most popular name (chondroid hamartoma), it is likely that these lesions are benign connective tissue neoplasms rather than tumour-like malformations. Image Link
They are generally regarded as hamartomas because they consist of a disorganized proliferation of various connective and epithelial tissues normally found in the lung.
However, their rarity in childhood and continued growth in adult life favour their interpretation as benign neoplastic lesion .
The term adenochondoma implies a benign mixed neoplasm but the role played by the epithelial components may also be questioned.
It is now appreciated that epithelial structures are commonly entrapped in many lung tumors, both primary and metastatic and is likely that this is how the epithelial clefts of the so-called adenochondroma or chondroid hamartoma should be regarded. Image1 ; Image2
A name that reflects a purely mesenchymal nature appears appropriate and, since these tumours display a variety of connective tissues, the term mixed mesenchymoma has been recommended.
These lesions are fairly common, constituting about 10% of all ‘coin’ lesions in chest radiographs.
The age range is wide but they are rare in children and the peak age incidence is the sixth decade.
Sequential radiographs show that most first develop in adult life and slowly increase in size thereafter.
Most are parenchymal and asymptomatic but about 8% are endobronchial and cause coughing, dyspnoea or haemoptysis.
There are no significant pathological differences between parenchymal and endobronchial growths.
Most measure 1 to 3 cm in diameter but they range up to 9 cm.
They are sharply circumscribed but lack in capsule and shell out easily at operation, after which there is little risk of recurrence. Image
Other connective tissues commonly found include fat, fibrous tissue and loose mesenchyme with a myxoid appearance.
These various components are usually present in combination. All are well differentiated and show no feature of malignancy.
Intersecting the connective tissue lobules are clefts lined by ciliated pseudostratified columnar epithelium, which is quite normal cytologically.
The retention of cilia is notable as these are usually lost when such epithelium becomes neoplastic.
These tumours have no malignant potential.
The differential diagnosis includes metastatic testicular teratome from which the malignant elements have been ablated by chemotherapy.
If the proposed nature of chondroid hamartomas (mixed mesenchymomas) outlined above is accepted, they are obviously closely related to benign connective tissue neoplasms composed of a single tissue – lipomas , chondromas ,and fibromas for example – none of which is common in the lungs.
Like the mixed mesenchymomas, all these neoplasms may either lie entirely within the lung substance or protrude into major bronchi.
Epithelial clefts are not found in single tissue benign mesenchymal tumours, which resemble in every way their counterparts that occur more commonly in other parts of the body.
Like chondroid hamartomas, they appear to have no malignant potential. In this context it should be noted that the rare primary pulmonary fibrosarcomas , liposarcomas , chondrosarcomas and osteosarcomas are believed to be sarcomatous from their onset.
Carney’s triad is a rare combination of three unusual neoplasms that affects young women. The patients are generally in the second or third decade, the youngest recorded being a girl aged 9 years. The condition is not familial. The three tumours are extra-adrenal paraganglioma (chemodectomas), gastric epithelioid leiomyosarcomas (Gastrointestinal Stromal Tumour) and pulmonary chondromas. All are generally multiple and early recognition of the syndrome is important in view of the malignant potential of the gastric lesions and paragangliomas. The chondromas have no malignant potential.
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