Warthin's tumor distribution within the parotid gland. A feasible etiologic source from lymph nodal tissue

Warthin's tumor (WT) is the second commonest parotid gland neoplasm after pleomorphic adenoma (PA). It mainly arises from the lower pole of the superficial parotid lobe (i.e., tail of gland), a site with the greatest distribution of intra-parotid lymph nodes, and its definitive etiopathogenesis is still unclear. The aim of this study was to support the strict topic and etiologic link hypothesised between this tumor and the intraparotid lymph nodes, as being massively present in the tail, by assessing the WT distribution within the parotid gland.

Seventy-one WTs excised from 64 patients were compared retrospectively with 134 PAs from 133 patients, as controls. In all sample, staging of parotid gland tumors was defined by sonography and magnetic resonance imaging. Furthermore, tumor localization, size, bilaterality and multifocality were assessed according to radiological, intraoperative and histopathological findings.

WTs were mainly detected in the tail (73%), less in the superficial lobe (23%) and the deep one (4%). WT presented with bilateral and synchronous lesions in 10% of cases vs. 0.75% of controls.

Since the tail has been well known to present the greatest distribution of intra-parotid lymph nodes, our clinical findings on WT parotid localization could suggest the possible origin of this tumor from epithelial salivary gland ductal inclusions, as being likely entrapped during embryogenesis within the intra-parotid lymph nodes, and could support the hypothesis of a heterotopy in the pathogenesis of WT. However, this suggestive hypothesis based only on clinical and "topographic" data should be confirmed by histopathological studies about the presence of the salivary ductal elements trapped within the intra-parotid lymph nodes.