Pleomorphic adenoma with bizarre myoepithelial cells: A diagnostic challenge on cytologic smear

Abstract

The diagnosis on fine needle aspiration of salivary gland tumors with a myoepithelial component is challenging because myoepithelial cells can have a wide cytomorphologic spectrum. The authors report a case of a pleomorphic adenoma of the parotid gland that expands the spectrum of appearances that myoepithelial cells can show with this tumor. A 55-year-old female was found to have a right parotid gland mass. FNA showed hypercellularity, with loosely cohesive fragments of spindle-shaped myoepithelial cells admixed with small nests of epithelial cells. Interspersed may occasional bizarre cells possessing severely pleomorphic nuclei with hyperchromasia. The cytologic diagnosis was "suspicious for carcinoma ex pleomorphic adenoma." A total parotidectomy was performed with complete resection of the tumor that was confirmed to be a pleomorphic adenoma. The pleomorphic cells noted on FNA were scattered throughout the tumor, and were positive by immunostaining for keratin, S-100 protein and p63, identifying them as myoepithelial cells.These cells did not show mitotic activity and were negative for Ki67. The pleomorphic adenoma showed extensive degenerative changes including central cyst formation, stromal hyalinization and hemosiderin deposition. On the basis of the combined light microscopic and immunohistochemical findings, there was no evidence to support a malignant change in the pleomorphic adenoma. It was concluded the pleomorphic myoepithelial cells were a degenerative change, reminiscent of what is seen in "ancient" schwannoma and some uterine leiomyomata. Our case expands the spectrum of appearances that can be seen in myoepithelial cells in the salivary gland. K E Y W O R D Sfine needle aspiration, myoepithelial cell, pleomorphic adenoma

Fine needle aspiration of spindle cell lipoma—Lochkern cells as a clue for diagnosis: A case arising in the parotid gland

“…As expected for an adipose tumor, the Lochkern cells in our case were immunohistochemically positive for S100 protein in a nuclear staining pattern. However, cells of similar unusual nuclear morphology that might resemble Lochkern cells, and which would also be S100 protein‐positive, might be seen in other tumors, including myoepithelial tumors, pleomorphic adenoma, 13 Schwannomas, 14 and melanoma. This is especially relevant for cases of SCL in unusual locations, such as parotid gland for our case.…”

Pleomorphic adenomia of lower lip: A case report

“…However, the myoepithelial cells are difficult to diagnose accurately even on cytology, given their mimicking behavior and the heterogenous appearance of the tumor. 11 Thus, histopathology is warranted.…”

Molecular testing in salivary gland cytopathology: A practical overview in conjunction with the Milan system

“…2 Moreover, myoepithelial cell-rich PA can be easily misdiagnosed because myoepithelial cells have a wide spectrum of cytomorphological features. 22 In fact, myoepithelial cells can be highly pleomorphic-a feature that can lead to a diagnosis of myoepithelial carcinoma arising within PA. 23 Several diagnostic cytomorphological pitfalls have been described in PA salivary gland FNA. Among them are cellularity with epithelial atypia, epithelial predominance and cystic patterns.…”