Salivary gland fine-needle aspiration biopsy: quality assurance results from a tertiary cancer center

Abstract

Introduction: Fine-needle aspiration biopsy (FNAB) plays a critical role in the management of patients with salivary gland lesions. A specific diagnosis can be difficult due to the wide range of lesions with overlapping morphologic features, potentially leading to interpretation errors. We analyzed the cytologic-histologic discrepancies identified in the quality assurance program of a major cancer center in cases of salivary gland FNAB and performed a root cause analysis.

Materials and methods: Salivary gland FNAB specimens performed during a 12-year period at a major tertiary cancer center were reviewed. The inclusion criteria for this study included FNAB cases of salivary glands with subsequent histologic or flow cytometry follow up. The cytologic diagnoses for these cases were recategorized according to the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) based on the original reports. The risk of neoplasm and malignancy based on the cases with subsequent resection or flow cytometry and the most common causes of discrepancy were analyzed.

Results: The risk of neoplasm ranged from 41% to 99% and the risk of malignancy ranged from 22% to 99% among the different MSRSGC categories. Lymphoid and myoepithelial rich lesions were the most common miscategorized lesions using the MSRSGC. Reactive changes due to inflammation were associated with overcalls. The most common malignancy in the atypical category was mucoepidermoid carcinomas.

Conclusions: Myoepithelial and lymphoid rich lesions arising in the salivary gland are associated with a higher risk of misclassification. The use of category IVB in the MSRSGC is appropriate for lesions with abundant myoepithelial cells. Reactive atypia seen in sialadenitis was the most common feature associated with overcall.

Keywords: Cytology; Myoepithelial; Quality assurance; Risk of malignancy; Salivary gland.

Figure 1:

Case initially misdiagnosed as benign neoplasm; Myoepithelial carcinoma ex-pleomorphic adenoma. A) Smear containing abundant myoepithelial cells associated with metachromatic stroma (Modified Giemsa stained slide) B) Surgical resection showing the presence of myoepithelial carcinoma next to a pleomorphic adenoma C) Myoepithelial carcinoma showing myoepithelial cells with varying degrees of atypia.

Figure 1:

Case initially misdiagnosed as benign neoplasm; Myoepithelial carcinoma ex-pleomorphic adenoma. A) Smear containing abundant myoepithelial cells associated with metachromatic stroma (Modified Giemsa stained slide) B) Surgical resection showing the presence of myoepithelial carcinoma next to a pleomorphic adenoma C) Myoepithelial carcinoma showing myoepithelial cells with varying degrees of atypia.

Figure 1:

Case initially misdiagnosed as benign neoplasm; Myoepithelial carcinoma ex-pleomorphic adenoma. A) Smear containing abundant myoepithelial cells associated with metachromatic stroma (Modified Giemsa stained slide) B) Surgical resection showing the presence of myoepithelial carcinoma next to a pleomorphic adenoma C) Myoepithelial carcinoma showing myoepithelial cells with varying degrees of atypia.

Figure 2:

Case initially misdiagnosed as neoplastic A) Clusters of basal cells associated with lymphocytes, which was initially thought to represent a basal cell adenoma. (Modified Giemsa stain) B) Surgical resection demonstrated chronic sialadenitis.

Figure 2:

Case initially misdiagnosed as neoplastic A) Clusters of basal cells associated with lymphocytes, which was initially thought to represent a basal cell adenoma. (Modified Giemsa stain) B) Surgical resection demonstrated chronic sialadenitis.