TITLE:
Pleomorphic Adenoma Consisting of Multiple Cysts with Squamous Epithelial Lining: Findings on MRI, FNAC, and Histopathological Examination
AUTHORS:
Hiroshi Yamamoto, Sakurako Yamaguchi, Erika Iwai, Yukiko Iizuka, Shu Fushimi, Kunio Hayashi, Takumi Kondo, Satoshi Tokunaga, Masaaki Suemitsu, Takashi Kaneda, Kayo Kuyama, Masamichi Komiya
KEYWORDS:
Salivary Gland Tumor, Pleomorphic Adenoma, Cystic Formation
JOURNAL NAME:
Open Journal of Stomatology,
Vol.11 No.6,
June
18,
2021
ABSTRACT: The incidence of pleomorphic adenoma (PA) of the minor salivary glands is reported to be 10%, and while the histological findings in PA can be diverse, keratin-filled cysts lined by squamous epithelium are rarely reported. The condition can, however, present with cyst formation in some cases. We review a rare case of pleomorphic adenoma in the buccal mucosa that involved the formation of multiple squamous epithelium-lined cysts in a 69-year-old woman. Magnetic resonance imaging (MRI), fine needle aspiration cytology, and histopathological examination were performed. Physical examination revealed a painless, mobile, elastic hard mass in the right buccal mucosa, measuring 2.5 × 1.0 cm. The MRI revealed a well-defined lesion with different signal intensities in the medial and distal regions of the right cheek. The medial side of the lesion showed a low signal intensity on T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI), while the distal side showed a low signal intensity on T1WI, and a high signal intensity on T2WI and short tau inversion recovery (STIR) imaging. Fine needle aspiration of the lesion was performed under local anesthesia and a cytological diagnosis of an epidermoid or dermoid cyst was made. The tumor was completely resected under local anesthesia combined with intravenous sedation. The histopathological examination demonstrated the proliferation of atypical tumor cells with poor atypia and the formation of glandular, alveolar, large, and small cysts. The cysts were lined by keratinized squamous epithelial cells, their cavities were filled with keratinous material, and foreign body reaction was observed after rupture. Histopathological evaluation led to the diagnosis of pleomorphic adenoma. The patient had no evidence of recurrence, 2 years and 3 months after the surgery. In conclusion, the presence of multiple cysts lined by squamous epithelium can pose a significant diagnostic challenge in patients with PA. It is important to make the correct diagnosis in order to avoid unnecessarily aggressive therapy.