Unveiling Rarity: A Case Report of a Poorly Differentiated Synovial Sarcoma Mimicking a Plunging Ranula.

Synovial sarcomas are uncommon and highly aggressive sarcomas. Typically, they start in the soft tissues of the extremities, although they may develop in the head and neck region in rare cases. When they do, they usually present with localized symptoms in the affected area. Our patient is a 20-year-old man without a medical history who complained of a three-month history of submental swelling of the left side with a non-tender, palpable 5 cm mass. Initially believed to be a plunging ranula, the patient underwent transoral excision of the left submandibular soft tissue mass in the neck by the ear, nose, and throat (ENT) specialist. The pathological analysis of the mass confirmed the presence of a poorly differentiated synovial sarcoma. A postoperative neck imaging was performed, which showed a significant decrease in mass size compared to the previous imaging; however, the mass was still present. This is one of the few described cases of a poorly differentiated synovial sarcoma located on the floor of the mouth. Therefore, it highlights the importance of considering it as a possible differential diagnosis of head and neck pathologies.