FNA diagnosis of secondary malignancies in the parotid gland: over 20 years of experience from a single institute.

Introduction: Metastatic solid tumors account for a significant portion of malignancies in the parotid gland. Fine-needle aspiration (FNA) is a primary tool to diagnose these tumors.

Materials and methods: We retrospectively reviewed 134 FNA cases of metastatic solid tumors affecting the parotid gland, spanning from 2000 to 2023 at our institute. We summarized the medical histories, cytology diagnoses, correlations with surgical resections, clinical treatments, and follow-up outcomes.

Results: The patient cohort included 107 male and 27 female patients, with a median age of 71 years (range: 4-96 years). Eighty-five percent of metastases (113 of 134) originated from head and neck (H&N) malignancies, comprising 66% from cutaneous source and 19% from mucosal sites. The most frequent primary sites outside the H&N were lung (4%), kidney (2%), and non-H&N skin (2%). Sixty-eight percent of metastases (92 of 134) were squamous cell carcinoma (SqCC) including 61% conventional type and 7% human papillomavirus-related SqCC. Melanoma is the second most common metastatic malignancy (28 of 134, 21%). The median time from primary diagnosis to metastasis was 10 months (range: 0 to 132 months). During clinical follow-up, 59 (44%) patients died from the disease in a median follow-up of 10 months (range: 2 to 56 months).

Conclusions: This study represents one of the largest series of secondary malignancies in the parotid gland collected from a single institution. Most of these tumors are metastases from H&N malignancies, with cutaneous SqCC being the most prevalent primary site and histology. Accurate diagnosis relies heavily on clinical history, morphologic evaluation, and ancillary studies.