Unusual Metastatic Malignant Lesions Involving the Parotid Region: A Cytopathological Case Series

Abstract

Background: The parotid gland is predominantly affected by benign neoplasms; however, a broad spectrum of malignant lesions may present as parotid or periparotid masses. Secondary involvement of the parotid gland by metastatic malignancies and hematolymphoid neoplasms may closely mimic primary salivary gland neoplasms. Fine-needle aspiration cytology (FNAC) serves as a valuable initial diagnostic modality for recognizing these unusual secondary lesions and is important for guiding appropriate ancillary investigations, identifying the primary tumor, and facilitating subsequent clinical management. Materials and Methods: We retrospectively reviewed unusual malignant lesions diagnosed on cytological specimens from the parotid at a tertiary oncology centre. Clinicopathological details, cytological diagnosis, available immunohistochemical findings and correlation with histopathological specimens from other anatomical sites were reviewed where ever available. Results: Seven unusual malignant lesions involving the parotid region were identified. The patients ranged in age from 42 to 72 years, with a mean age of 55.9 years. Five patients were male and two were female. The lesions comprised four cases of metastatic squamous cell carcinoma, one case of metastatic neuroblastoma, one case of metastatic gastrointestinal stromal tumor (GIST), and one case of plasmablastic multiple myeloma with extramedullary parotid involvement. Conclusion: Fine-needle aspiration cytology (FNAC) is a rapid, safe and minimally invasive first-line investigation for any masses. It can identify unusual cytomorphological patterns, when combined with cell-block preparation and targeted immunohistochemistry—help establish tumor lineage. Combined with clinical and radiological correlation, FNAC can guide the search for a primary tumor, avoid unnecessary surgery and facilitate appropriate management.

Keywords: parotid gland; fine-needle aspiration cytology; metastatic carcinoma; squamous cell carcinoma; neuroblastoma; gastrointestinal stromal tumor; extramedullary plasmablastic disease; cytopathology