Myoepithelial carcinoma arising in recurrent pleomorphic adenoma in maxillary sinus

Abstract

Myoepithelial carcinoma is characterized by nearly exclusive myoepithelial differentiation and evidence of malignancy. It may arise de novo or in preexisting benign tumors including pleomorphic adenoma and benign myoepithelioma. A 39-year-old lady presented with painless progressive swelling on the right cheek and right side of palate. On surgery, there was a mass in right maxillary sinus which was surgically excised and diagnosed on histopathology as pleomorphic adenoma. Subsequently, there were two recurrences. The first recurrence was in the right maxilla after 2 years that was removed surgically and diagnosed as pleomorphic adenoma. One year later, she came with rapidly progressive swelling in bilateral cheeks and face. Intraoperatively, there was a large tumor in both maxillary sinuses with extensive local infiltration. Histologically, it was diagnosed as myoepithelial carcinoma. Carcinoma ex pleomorphic adenoma is usually a high grade malignancy. It occurs most commonly in parotid gland followed by submandibular glands, minor salivary glands and occasionally in sublingual gland. To the best of our knowledge, this is the first case of myoepithelial carcinoma arising in a recurrent pleomorphic adenoma in the maxillary sinus.

Keywords: Carcinoma ex-pleomorphic adenoma; maxillary sinus; myoepithelial carcinoma.

Figure 1

(a) Pleomorphic adenoma: sheets of myoepithelial cells and ductular structures lined by epithelial cells set in chondromyxoid stroma (H&E stain, ×100). Myoepithelial carcinoma: Cellular tumor with infiltration of adjacent bone (b) and areas of geographic necrosis (c) (H&E stain, ×100). (d) Cells arranged in lobules, nests, trabeculae and cords with hyperchromatic, pleomorphic, mitotically active nuclei (H&E stain, ×200); (e) Immunoprofile of myoepithelial carcinoma displaying positivity for S-100 (IHC stain, ×100), (f) Cytokeratin (IHC stain, ×100) and (g) Focally SMA (inset, IHC stain, ×400)