Sinonasal Myxoma in an Infant: Observations on Its Distinctiveness and a Discussion on Potential Reclassification As Infantile Intraosseous Myxoid Desmoid Fibromatosis.

Myxomas, when they manifest in the paranasal sinuses and/or maxillae of infants, are classified as sinonasal myxomas (SNMs). We present a case of SNM in the maxilla of a 15-month-old infant. Following the initial surgical intervention, the patient unfortunately experienced a recurrence of the condition. However, a subsequent surgery employing marginal excision was performed, and since then, no further recurrence has been reported. SNM exhibits consistent clinical features and histological characteristics that are distinct from those of odontogenic myxomas. Furthermore, in this case, immunohistochemical staining was positive for β-catenin, whereas odontogenic myxomas are generally negative for β-catenin staining. Another study reported that SNMs share genetic mutations with desmoid tumors, which are not observed in odontogenic myxomas. This suggests that this entity is distinct from odontogenic myxomas, leading us to propose that it may indeed represent a separate disease entity. This fact may lead to the reclassification of the disease and, ultimately, to changes in treatment strategies.