Myoepithelial Carcinoma Ex Pleomorphic Adenoma of the Maxillary Sinus: A Case Report and Review of Literature

Abstract

Myoepithelial carcinoma ex pleomorphic adenoma is defined as a malignant epithelial neoplasm arising from a primary or recurrent benign pleomorphic adenoma. This type of tumor comprises 3.6% of all salivary gland tumors and 12% of malignant ones. Clinically, it most commonly presents as a firm mass in the parotid gland. The development of this neoplasm in the sinonasal and nasopharyngeal regions is extremely rare and only few cases are reported in the literature. The prognosis of myoepithelial carcinoma is variable. Marked cellular pleomorphism, high mitotic rate, and high proliferative activity correspond to a poor prognosis. In this article, the authors report the histopathological features of a clinical case of a 64-years-old patient with a large median maxillary neoplasm diagnosed as myoepithelial carcinoma/ex-pleomorphic adenoma. The tumor was resected and subjected to secondary reconstruction using a revascularized free fibula flap. The myoepithelial derivation of neoplastic cells was demonstrated by immunohistochemical positivity for S-100 protein (strong and diffuse), cytokeratin 14 (strong and diffuse), and GFAP (focal).

Keywords: Craniofacial surgery; Ex pleomorphic adenoma; Free flap; Maxillary sinus; Microvascular surgery; Myoepithelial carcinoma.

Fig. 1

a Microscopic image of the previous pleomorphic adenoma diagnosed three years earlier (H&E, × 400). b Sections showing a residual component of pleomorphic adenoma on the border of tumor (H&E, × 200)

Fig. 2

a Cut surface of the specimen after formalin fixation. b Histologically, sections show a tumor with infiltration into adjacent bone. Multiple nodules with hypercellular areas and myxoid stroma are seen (H&E, × 100)

Fig. 3

a Microscopic examination showing sheets of polygonal cells with moderate amounts of cytoplasm and hyperchromatic nuclei with mild to moderate pleomorphism and inconspicuous nucleoli (H&E, × 400). b A smaller component exhibits plasmacytoid features with abundant eosinophilic cytoplasmic inclusions (H&E, × 400). c Immunohistochemical analysis shows strong and diffuse positivity for S-100 protein (× 400)