High-grade Features of Papillary Cystadenocarcinoma of the Parotid Gland.

Papillary cystadenocarcinomas (PCAs) are rare low-grade salivary gland tumors first introduced in the World Health Organization classification in 1991. While classically regarded as a low-grade malignancy, PCAs with more clinically and histologically high-grade features have been reported, reflecting the often-underrecognized morphological diversity of this entity. Although no universally advocated grading system exists, high-grade PCAs tend to demonstrate locally aggressive features, cytologic atypia, high mitotic rate, necrosis, and an absence of papillary features. We present a case of a 51-year-old male with slow-onset, progressive right facial fullness over four years. Contrast-enhanced computed tomography of the neck demonstrated a 3.3 cm peripherally enhancing cystic and solid mass in the right superficial lobe of the parotid gland. Following a superficial parotidectomy and a selective right neck dissection, histopathology demonstrated a large cyst with papillary projections lined with cuboidal cells of mild to moderate atypia and surrounding solid tumor nests. The tumor displayed stromal, lymphovascular, and subcutaneous fibroadipose tissue invasion. One of 12 lymph nodes was positive for metastatic carcinoma without extranodal extension. A diagnosis of intermediate-grade PCA was rendered. This case report summarizes the features typical of high-grade PCAs, the few reported cases of intermediate- and high-grade PCAs within the existing literature and provides a brief overview of the radiological and pathological differential diagnosis when considering a parotid gland PCA.