Myxoid fibroblastic tumor of the maxillary sinus in a 21-month-old child: An unusual diagnosis.

Myxoid tumors of the soft tissue are a heterogeneous group of lesions with significant differences in behavior, from being totally harmless to malignant tumors with metastasizing potential. We describe the unusual case of a 21-month-old boy who developed a paranasal low-grade myxoid neoplasm with recurrent potential. The histological findings showed a proliferation of spindle cells within a vascular and myxoid background. The immunohistochemistry had the features of myofibroblasts and fibroblasts with strong Vimentin and light Smooth Muscle Actin reactivity. Close collaboration between clinician and pathologist is necessary to deal with these unusual lesions to predict their local aggressiveness and long-term behavior. Most of these cellular myxomas have been described in adults, involving primarily the limbs, but this case shows that any localization is possible.