Carcinoma ex pleomorphic adenoma of the submandibular gland: report of a case with an unusual malignant component of clear cell squamous cell carcinoma

A large carcinoma ex pleomorphic adenoma (CXPA) with regional lymph node metastasis occurred in the left submandibular gland of a 64-year-old man. Initially, the patient underwent tumor extirpation and ipsilateral radical neck dissection. Histologic examination revealed the malignant component of CXPA was clear cell squamous cell carcinoma (SCC), which is quite uncommon in head and neck region. In the metastatic regional lymph nodes, aggregates of clear cells were observed. To the best of our knowledge, this is the first case of CXPA of which the malignant component is clear cell SCC. Four months after the postoperative radiotherapy, delayed regional metastasis became evident in the contralateral side of the neck. Radical neck dissection was carried out, and, microscopically, moderately differentiated SCC was identified. The patient recovered well and remained free of disease for 29 months after the second surgery.