Cellular myxoma is an uncommon type of myxoid benign tumor, predominantly occurring in adult female patients aged >40 years. This report aims to document a case of cellular myxoma that occurred in the buccal mucosa. Compared to intramuscular myxomas, cellular myxoma demonstrates hypercellularity and vascularity. Its manifestation in the soft tissue of the head and neck area is exceptionally rare. Generally, cellular myxoma manifests as a firm and immovable mass covered with normal oral mucosa, with no associated clinical symptoms. Homogenous low signal intensity on T1-weighted scans and high-signal intensity on T2-weighted magnetic resonance scans reveal cellular myxoma, as most lesions show well-defined margins and heterogeneous contrast enhancement. The significant histologic features include a focal or diffuse increase in cellularity with fibroblast-like cells and vascularity with an abundant collagenous matrix. Our presented case reflects these facts examinations, based on which a final diagnosis of cellular myxoma was made. Immunohistochemistry revealed locally and diffusely positive SMA and CD34. The clinical tendency of cellular myxoma with hypercellularity may affect the production of myxoid and collagenous substrates, and if complete resection is not performed, the possibility of local recurrence in the primarily affected region remains. Hence, complete surgical excision was performed under general anesthesia, and follow-up until a year after treatment revealed no observed recurrence. To achieve precise diagnosis and complete treatment without local recurrence, several diagnostic examinations should be considered.

Myxomas are benign, slow-growing, locally invasive neoplasms derived from mesenchymal elements. Infantile myxoma (odontogenic or sinonasal) is extremely rare and usually occur in children older than 10 years of age. A 18-month-old boy presented with a painless, enlarging elevated lesion in left paranasal area. Physical examination revealed a firm, non-tender, bony-like elevation in the left nasal bone- maxilla bone transition zone that extended to the level of the inferior orbital rim, adjacent to the nasal bone. A computed tomography scan of the head revealed a well-defined, hypodense, multilocular lesion with a peripheral hyperdense circumference, involving the anterior wall of the maxilla, from the pyriform aperture to the level of orbital floor, adjacent to the nasal bone. Surgery was performed using an external approach. The microscopic evaluation showed loosely arranged spindle cells spaced in a rich myxoid matrix. Although rare, sinonasal myxoma should be included in the differential diagnosis of slow-growing, well-defined lesions of the face and jaws in infants.