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Case Reports

Abstract

Myxomas are rare, benign neoplasms originating from primitive mesenchymal cells. They commonly occur in adulthood and are rarely found in the orbit. In this report, we present two unusual cases of infantile orbital myxoma, both associated with a rare MN1::TAF3 fusion. Case 1 involved a male with a right orbital mass, first noticed by parents at 5 months of age and thought to be a dermoid cyst. Clinical monitoring over 10 months revealed progressive growth leading to excision. Pathological examination showed a cellular spindle cell lesion morphologically resembling nodular fasciitis. Case 2 is a 3-month-old male with intermittent left eye drainage and swelling of the eyelid with a rapidly growing orbital mass. MRI showed a 1.7 cm extraocular enhancing mass lesion involving the left superior medial preseptal and postseptal orbital soft tissues. Biopsy showed a tumor composed of mildly atypical spindle cells arranged in short fascicles and focal whorls and scattered cells with large hyperchromatic nuclei and absent nucleoli and infrequent mitosis. In both cases, targeted next-generation RNA sequencing revealed MN1::TAF3 fusion, confirmed by RT-PCR and Sanger sequencing. Case one did not exhibit USP6 and ETV6 fusions. No other fusions were detected. 

These cases highlight the rarity of infantile orbital myxoma and underscore the significance of broad fusion analysis to identify rare MN1::TAF3 fusions. The absence of common fusions linked to other neoplasms suggests distinct molecular mechanisms in the pathogenesis of infantile orbital myxoma, prompting the need for further research and exploring potential targeted therapeutic strategies.