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.
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
The term adenochondoma implies a benign
mixed neoplasm but the role played by the epithelial components may also
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.
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.
Most are lobulated and the predominant
tissue is cartilage, which may calcify or undergo osseous change.
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 –
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
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
gastric epithelioid leiomyosarcomas
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