Primary Solitary Intra-thyroid Myofibroma in a Pediatric Patient

Myofibromas are benign soft tissue tumors, mostly seen in young children, and characterized histologically by fibroblasts/myofibroblasts arranged in fascicles. Clinical presentation of this tumor is highly variable, based on the location and extent of organ involvement. Myofibromas most commonly involve skin and subcutaneous tissue, though they may appear in any location and may be multiple. Nearly all thyroid lesions in children are derived from thyroid follicular cells or C-cells. Solitary myofibroma occurring in the thyroid is exceptionally rare. This case report describes a three-year-old male presenting with a right neck mass. Fine needle aspiration (FNA) revealed spindle cells without evidence of malignancy. Resection of the right thyroid lobe and isthmus revealed a myofibroma, which was completely excised. The patient remained healthy without recurrence two years after the surgery. This case highlights that a solitary myofibroma can present as an intra-thyroid lesion in a pediatric patient. Histological evaluation is critical to establish the diagnosis of myofibroma, and ancillary studies may be necessary to differentiate it from other potential differential diagnoses of spindle cell morphology.