A mesenchymal hamartoma of the chest wall is a very rare benign chest wall tumour. It is sometimes classified as a non-neoplastic developmental anomaly rather than a tumour.
They typically present in neonates or infants 1-3.
Many present with a chest wall mass 2. Some may present with respiratory distress or a chest wall deformity 3.
Macroscopically the tumours are generally well delineated, lobulated, and tan to reddish in colour 3.
Microscopically, they tend to show showed alternating areas of cartilaginous islands and primitive appearing mesenchymal proliferation. There may be also areas of bone formation and blood-filled cystic spaces (secondary aneurysmal bone cyst formation).
Many lesions arise from the ribs. Some can have multifocal disease.
Radiologically they are well-circumscribed masses with solid and cystic components. They may have multiple fluid-fluid levels, in association with single or multiple rib destruction or change.
Plain radiographs may show a well-defined, partly calcified mass involving one or more ribs.
MRI usually shows heterogeneous signal intensities of the mass on both T1- and T2-weighted images. Haemorrhagic cavities (secondary aneurysmal bone cyst regions) are readily detectable in MRI 2.
Treatment and prognosis
Rapid growth may occur but usually is self-limited. While the general rule is that they are they are non-neoplastic, occasional cases of malignant transformation have been reported 8. En bloc resection is curative, but the large residual chest wall defect can frequently result in scoliosis 8.
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