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mediastinal leiomyosarcoma

Sunday 18 March 2018

Definition: Mediastinal leiomyosarcoma is a very rare tumour with less than 40 cases until 2015.

Mediastinal leiomyosarcoma occurs in adult patients (26–88 years) of either sex.

A disproportionate number of cases arise in the posterior mediastinum, where tumours are often clinically asymptomatic.

Resected tumours measured up to 18 cm, often without clear relationship to neighbouring anatomic structures. In some cases, an origin from major vessels seemed likely, whilst in others, major vessels appeared rather entrapped within the tumour.

Mediastinal leiomyosarcoma is typically a non-encapsulated, circumscribed mass, which may infiltrate the heart, lungs, thoracic vertebrae or spinal canal.

Patients were treated by surgical resection, sometimes combined with chemo- and/or radiotherapy.

Local recurrence and distant metastasis occur in a significant proportion of patients.

The differential diagnosis of leiomyosarcoma comprises other spindle cell sarcomas, in particular synovial sarcoma and malignant peripheral nerve sheath tumours (MPNST).

Whilst well-differentiated leiomyosarcoma will generally stain for both smooth muscle actin and desmin, less differentiated cases may show diminished staining or even absence of muscular markers, requiring additional investigations (e.g. calponin, caldesmon, TLE, S-100 protein and/or nestin immunohistochemistry or fluorescence in situ hybridisation (FISH) analyses) to rule out MPNST or synovial sarcoma.

Rare cases of liposarcoma may contain a smooth muscle component (‘lipoleiomyosarcoma’). In these cases, the lipomatous and smooth muscle components are admixed, and the dual differentiation is obvious.

Leiomyosarcoma as a secondary non-germ cell sarcoma is extremely rare, and leiomyosarcoma has not been described as the sole mesenchymal component.

Open references

- Mesenchymal tumours of the mediastinum—part II
. 2015. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4656710/