Low grade fibromyxoid sarcoma: problems in the diagnosis and management of a malignant tumour with bland histological appearance

Abstract

To review the clinicopathological features and highlight the problems in the diagnosis and management of low grade fibromyxoid sarcomas (LGFMS). Three cases of LGFMS were studied with histology and immunohistochemistry, and cytogenetics in one. The features and problems were compared with those in the literature. Two LGFMS had typical fibrotic and myxoid patterns showing abrupt transition from one to the other. Cellularity was low to moderate. Nuclei were medium sized and regular. In one of these the correct diagnosis was not made in the original needle biopsy resulting in inappropriate management. In the third tumour only myxoid areas were seen and the diagnosis was supported by cytogenetics showing a complex previously unreported translocation, t(7;18;16). One tumour recurred, one metastasised, and one has possible metastasis on imaging of the lungs. LGFMS is a tumour with low grade histological features but a high risk of local recurrence and a significant risk of metastasis which can be very late. There should be a high index of suspicion for this rare tumour and a low threshold for sending tissue for cytogenetics and/or molecular genetics. Special precautions should be exercised in the interpretation of small biopsies of a spindle cell lesion with bland cytological features in children. If the diagnosis is unclear there must be a detailed follow up plan with a person responsible for monitoring the plan.