Low grade fibromyxoid sarcoma: report of a case with epithelioid cell morphology, masquerading as a papillary thyroid carcinoma.

Background Low grade fibromyxoid sarcoma (LGFMS) is a rare tumor with a characteristic histologic appearance. Although the spectrum of histologic features that can be seen in LGFMS are well characterized, their description in the cytology literature is lacking. Case A 5 7-year-old male with a past history of Hodgkin's lymphoma presented with 1-year history of dysphagia. Clinical examination and radiologic imaging studies revealed a neck mass suggestive of a thyroid lesion. Fine needle aspiration cytology of the mass revealed moderately cellular smears with several cohesive clusters. Most of the clusters showed cellular crowding with overlapping nuclei. The nuclei ranged from round to oval or elongated shapes with frequent irregular nuclear membranes, powdery to clear nuclear chromatin and inconspicuous nucleoli. Most notably, several intranuclear inclusions and nuclear grooves were noted, leading to a suggestion of a papillary thyroid carcinoma. Histopathologic examination of the mass revealed an LGFMS. Conclusion This report describes a rare case of LGFMS with epitbelioid morphology. By virtue of its clinical presentation and cytologic features, the case masqueraded as a papillary thyroid carcinoma and should be added to the list of pitfalls in the diagnosis of papillary thyroid carcinoma. The case also serves to add to the spectrum of morphologic changes that can be seen in LGFMS.