Simple SummaryRhabdomyosarcoma is the most common malignant soft tissue sarcoma in childhood and adolescence, with one-third of cases occurring in the head and neck region. A patient with a soft tissue mass on their tongue presented to our clinic. After an excisional biopsy, histology revealed an embryonal type of rhabdomyosarcoma, an extremely rare diagnosis in the adult population. An extension study was performed, followed by appropriate margin-free surgery with reconstruction using a buccinator flap and subsequent neoadjuvant chemotherapy. After 42 months, the patient remains free of disease. A thorough literature search for similar cases and treatments yielded only three comparable cases. The rarity of this pathology in adults necessitates the application of children’s treatment protocols, although the prognosis is worse than in childhood cases.Abstract(1) Background: Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in the first two decades of life. One third of cases appear in the head and neck, with 60% of these being embryonal type. RMS is extremely rare in adults, comprising only 1% of adult malignancies, and of those, only 3.3% are rhabdomyosarcomas. (2) Case report: A 46 y.o. male presented with a 1 cm exophytic pediculated painless lesion on the dorsum of his tongue, with progressive growth for 3 months. An excisional biopsy revealed an “embryonal rhabdomyosarcoma with fusocellular areas, with negative rearrangement for gen FOXO1A, negative MDM2 (only focal positivity), and positive INI-1”. Subsequent contrast-enhanced MRI concluded the presence of a lesion with imprecise margins in the right half-tongue, 15 × 8 × 7 mm (longitudinal × transverse × craniocaudal), compatible with a sarcoma. The patient underwent a partial centrolingual glossectomy followed by reconstruction with a buccinator muscle local flap. After surgery, he received chemotherapy with eight cycles of VAC (vincristine, actinomycin, and cyclophosphamide) protocol. The patient is now disease free after 42 months, with good tongue function. (3) Discussion and conclusions: Embryonal RMS is an extremely rare sarcoma in adults, and the location in the tongue is even more exceptional (only two more similar cases are reported in the literature). The prognosis in adults is significantly poorer than in children. A complete margin-free resection with an adequate chemotherapy protocol is the treatment of choice in cases such as these.