Warthin Tumor with Signet-Ring Cell Features as a Pitfall in Salivary Gland Cytopathology

Abstract

Background: Warthin tumor (WT) is a common parotid lesion reliably diagnosed by fine-needle aspiration (FNA). Worrisome metaplastic changes may occur in WT. Their interpretation as mucoepidermoid carcinoma represents a diagnostic pitfall. Moreover, WT and mucoepidermoid carcinoma may coexist, making this distinction difficult. So it is worthwhile to report unusual WT features. We describe a WT with signet-ring cells (SRCs). Case: A 61-year-old male presenting with a 3.6-cm right parotid gland mass underwent FNA with rapid on-site evaluation. DiffQuik-stained smears showed groups of oncocytic cells with abundant granular cytoplasm in a background rich with debris, foamy macrophages and lymphoid cells. SRCs were observed on Papanicolaou-stained smears prepared from a second pass. A WT with SRC features was diagnosed. Histology revealed a WT with post-FNA infarctual changes. Conclusion: To avoid false-positive diagnoses, the cytopathologist should be aware that SRC features may occur in WT. The concomitant presence of oncocytes and SRCs is useful to correctly diagnose this unusual WT variant.

Cytomorphological findings in diagnosis of Warthin tumor

“…Benign signet ring cells may be seen in benign salivary gland tumors, and the origins of these cells are salivary gland excretory or striated duct basal cells. They may be differentiated by their capacity for mucus secretion [22]. In one case of our study, we detected an atypical cell with vacuolated cytoplasm (Figure 4d).…”

“…In one case of our study, we detected an atypical cell with vacuolated cytoplasm (Figure 4d). Bellevicine et al pointed out that existence of signet ring cells together with oncocytes supports the diagnosis of WT [22].…”

“…Plasmocytes, mast cells, macrophages, and B lymphocytes constitute the lymphoid stroma in WT [7]. In addition, even reactive follicular germinal center elements may be cell carcinoma or mucoepidermoid carcinoma (MEC) that originated from WT [10,21,22]. Sood et al have stated that diagnostic problems are common in cases that have intermediate-like cells and atypical squamous cells in the mucoid background [7].…”

“…Cytomorphologic findings of 6 cases cytologically suspicious for malignancy had squamous-like cells in 5 (83%), granular debris background in 5 (83%), lymphocytes in 4 (67%), oncocytic cell layer in 3 (50%), mucoid background in 3 (50%), PMN cells in 2 (33%), mast cells in 2 (33%), atypical cells with vacuolated cytoplasm in 1 (17%), and papillae with oncocytic cells in 1 (17%). The presence of squamous or mucoid metaplasia and/or mucoid background are cytological difficulties responsible for misdiagnosis and should be differentiated from primary salivary gland squamous cell carcinoma, mucoepidermoid carcinoma, intraparotid metastasis from head and neck squamous cell carcinoma, and squamous cell carcinoma or mucoepidermoid carcinoma (MEC) that originated from WT [10,21,22]. Sood et al have stated that diagnostic problems are common in cases that have intermediate-like cells and atypical squamous cells in the mucoid background [7].…”

Mucoepidermoid carcinoma: Analysis of 76 cytologic cases and correlation with histologic grade

“…The stroma in our Figure 7B will be interpreted by some observers as mucoid but by others as “watery proteinaceous fluid” reiterating the concern expressed in the prior paragraph by Handa et al 31 in discerning among various types of stroma. Bellevicine et al 52 described a WT with signet‐ring cells, and Hayes et al 53 described one example of MEC containing mucinous sebaceous cells.…”