Metastasizing pleomorphic adenoma of parotid gland: Case report

Abstract

Pleomorphic adenoma is a benign tumor and the most common salivary gland neoplasm. Metastasizing pleomorphic adenoma shares histological characteristics with pleomorphic adenoma but exhibits malignant behavior, including local lymph node involvement and/or distant metastasis. Several potential risk factors for metastasizing pleomorphic adenoma have been identified, some of which are associated with incomplete tumor clearance due to inadequate surgical techniques used in the treatment of primary pleomorphic adenoma. Here, we present a rare case of metastasizing pleomorphic adenoma originating from the parotid gland and describe its clinical features. The patient was a 75-year-old female with a surgical history of enucleation of a pleomorphic adenoma in the left parotid gland. Total parotidectomy and left neck dissection were performed for the left parotid tumor this time, and the patient attended one postoperative outpatient visit but subsequently was lost to follow-up.

Keywords: Pleomorphic adenoma; benign tumor; metastasis; parotid; salivary gland.

Figure 1.

Contrast CT: (a) enhancing soft tissue involving the left parotid with extension along the left sternocleidomastoid muscle and skin (green arrows); (b) one heterogeneously enhancing nodule over the left neck level II, suspected metastatic lymph node (green arrow); ((c) and (d)) two enhancing nodules (green arrows) over the left parotid gland, suspected metastases or reactive lymph nodes.

Figure 2.

(a) Left total parotidectomy and neck dissection were performed, and the left facial nerve and its branches (yellow arrows) were well preserved. (b) The sternocleidomastoid muscle rotation flap (yellow arrow) filled the defect after the parotidectomy.

Figure 3.

Microscopic examination of the specimen of the parotid gland showed (a) multiple nodules; (b) stromal components containing myxoid areas (green arrow); ((c) and (d)) positive immunohistochemical staining for calponin and CK 14 respectively, indicating myoepithelial cells.

Figure 4.

Microscopic examination of the specimen of the lymph nodes from the left neck level II showed (a) stromal components containing myxoid areas (green arrow); (b) positive PLAG1 immunohistochemical staining suggesting pleomorphic adenoma; (c) positive SOX-10 IHC staining suggesting myoepithelial cells.