False-Positive Asymmetrical Tongue Muscle 18F-FDG Uptake in Hypoglossal Nerve Paralysis Following Lymph Node Dissection in a Pediatric Patient with Malignant Rhabdoid Tumor of the Neck.

A 5-year-old male patient with a malignant rhabdoid tumor originating in the left neck underwent primary tumor resection concurrently with ipsilateral lymph node dissection after receiving neoadjuvant chemotherapy consisting of cyclophosphamide, carboplatin, etoposide, vincristine, and doxorubicin. He later received the same adjuvant chemotherapy as well as proton therapy for the primary tumor. Sixteen months after completing the initial therapy, follow-up PET-CT revealed a novel area of glucose hypermetabolism in the right side of the tongue, which was suspected of being a recurrence. However, a physical examination and magnetic resonance imaging (MRI) demonstrated no evidence of tumor recurrence. The patient had a significant leftward deviation of the tongue, suggesting left hypoglossal nerve paralysis. Denervation of the ipsilateral intrinsic tongue muscles secondary to the treatment had caused atrophy in the ipsilateral muscles and compensatory hypertrophy in the contralateral muscles, which increased FDG uptake. Physicians should carefully confirm any diagnosis of a locally recurrent tumor because PET-CT often produces ambiguous findings.