Inflammatory myofibroblastic tumour of the lung
Inflammatory myofibroblastic tumours of the lungs are a location-specific type of inflammatory myofibroblastic tumours.
They are very rare with their incidence reported at approximately 0.04-1% of all the pulmonary neoplasms 1. While it can affect any age group, around 25% of cases occur in those under 18 years of age.
It is generally considered to fall within the benign spectrum of tumours.
Microscopically they are characterised by abundant inflammatory infiltrate comprising of predominantly plasma cells, lymphocytes, histiocytes, admixed with a variable proportion of fibroblasts and myofibroblasts.
On immunohistochemistry, the tumour cells can exhibit
- strong diffuse positivity with smooth muscle actin and vimentin
- negativity for cytokeratin, CD34 and S100
They are sometimes divided into two subtypes:
- invasive: usually occurs among younger patients and may reach large sizes
Typically seen as a single (can be multiple in ~5% of cases) peripheral, lobulated mass with lower lobe predominant occurrence. Calcification can occur (commoner in tumours occurring in children). Usually shows heterogeneous enhancement with contrast.
Usually avid on FDG PET-CT.
Treatment and prognosis
Its behaviour is often variable and the overall prognosis is often dependent on tumour size 3. Radical resection with negative margins is often the mainstay of treatment while radiation and steroids may be options in those who cannot undergo surgery. Long-term surveillance is often recommended due to local and distant recurrence as well as possible sarcomatous degeneration.
History and etymology
They were first observed in the lungs and described by Bunn in 1939 2.
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