Patient 2
A 64-year-old man was referred for right parotid swelling with facial palsy (75/100: Sunnybrook method). Magnetic resonance imaging (MRI) showed a mass (45 × 30 × 26 mm in size) in the right parotid gland with suspected infiltration of the surrounding soft tissue and mandible. Parotid carcinoma stage cT4aN0M0 was diagnosed, and extended parotidectomy, ipsilateral selective neck dissection, facial nerve reconstruction, and anterolateral thigh flap reconstruction were performed. Histopathology of the resected tumor showed a salivary gland carcinoma with biphasic appearance composed mainly of basaloid cells with marked atypia (Fig. 2a). Immunostaining showed positivity for CK AE1/AE3, CK7, p40, DOG1, and p63 (Fig. 2b, c). S-100 protein, α-smooth muscle actin, vimentin, androgen receptor, HER2, CD56, chromogranin, synaptophysin, and β-catenin were negatively stained. The Ki-67 LI was approximately 70% in neoplastic cells. The differential diagnosis included basal cell adenoma (BCA)/basal cell adenocarcinoma (BCAC) and adenoid cystic carcinoma (ACC). Sanger sequencing revealed theHRAS Q61K mutation (no mutation in HRAS codons 12 and 13). Thus, the final diagnosis was EMC. Since histopathology showed a high-grade carcinoma, we suspected EMC with high-grade transformation. The postoperative course was uneventful. The patient was disease-free at the 24-month follow-up.