Unusual metastasizing pleomorphic adenoma of the parotid gland involving locoregional lymph nodes

Abstract

Carcinoma ex-pleomorphic adenoma (PA) is a complex group of malignant neoplasms arising in PA. When microscopic features of the neoplastic cells are representative of carcinoma, the pathologist can easily make a definite diagnosis, but when worrisome morphology is replaced by metastatic behavior, the metastasizing PA (MPA) is a diagnostic challenge for the pathologist. Here, we present an unusual MPA to cervical lymph nodes and discuss diagnostic challenges.

Keywords: Cancer of parotid; dissection; lymph node; lymphatic metastasis; mixed salivary gland tumor.

Figure 1

(a) Carcinoma ex-pleomorphic adenoma of the right parotid. Intraoperative view of parotidectomy and radical neck surgery (facial nerve invasion is noticeable); (b) neck region magnetic resonance imaging shows a mass at deep part of right parotid with parapharyngeal extension and cervical lymphadenitis; (c and d) head and neck computer tomography scan showing a well-circumscribed hypoecho mass lesion located in the right parotid gland space; (e) histopathology of the resected specimen reveals an encapsulated PA composed of myxoid, chondroid, and mucoid materials; (f) myoepithelial cells with spindle or stellate cytomorphology in myxochondroid background; (g) there is a rupture of the fibrous capsule and tumor cells are slightly invade the surrounding fat tissues; (h) there is mucinous metaplasia in some areas; (i and j) high magnification of the specimen demonstrates hypocellular areas with scattered various-sized ducts showing no significant cellular atypia in a chondroid stroma.