Abstract
We review existing models of the pathogenesis of peritonsillar abscess (PTA) and intra-tonsillar abscess (ITA) and present a novel pathophysiologic model based upon observed histopathology in 2 ITAs and 10 PTAs and acute tonsillitis cases. ITA is rare, and prevailing models are only able to account for a minority of cases. The tonsillar lymphatic ultrastucture and the rapid nature of intratonsillar lymphatic transit, offer the framework for a unifying model of the development and progression of tonsillitis, PTA and ITA.
1
Introduction
Tonsillitis is a common pharyngeal infection affecting young adults and children. Peritonsillar abscess (PTA) is an occasionally identified complication and intratonsillar abscess (ITA) is rarely reported. Prevailing models of the reported pathogenesis of tonsillitis, PTA and ITA are found to be lacking, suggesting that these conditions are either unrelated or the general conceptual framework is inadequate.
The palatine tonsils are located in the tonsillar fossa defined by the palatoglossal muscle anteriorly and the palatopharyngeal muscle posteriorly. Laterally the tonsil is covered by a fibrous connective tissue capsule and medially the tonsillar crypts are covered by nonkeratinized stratified squamous epithelium. Disruption in the crypt epithelium allows for interaction of antigenic stimuli with tonsillar lymphocytes. Contents of the tonsillar crypts are expelled by contraction of the tonsillopharyngeus muscle . A virulent organism that enters the tonsillar crypt and fails to be expelled can proliferate in the base and lead to localized edema and influx of neutrophils: clinically presenting as a red swollen tonsil with exudate .
A PTA is a collection of pus between the tonsil fibrous capsule and the pharyngeal constrictor muscles. The true pathophysiology of PTA formation is unclear. Authors have proposed that drainage failure of suppurative inflammation from crypt blockage in acute tonsillitis leads to coalescence by extension into the peritonsillar space . The collection of pus in the loose areolar tissue behind the superior tonsillar pole leads to tonsillar bulging and uvula and palate deviation. Others have proposed that PTA formation may be a consequence of abscess formation in a group of salivary glands (Weber’s glands) located in the supratonsillar space .
An ITA is defined as focal areas of neutrophils and necrotic debris within the parenchyma of the tonsil . The pathogenesis of this rare presentation is also uncertain. Two mechanisms of ITA formation have been proposed: First, direct extension of acute suppurative inflammation into the crypts is followed by enlargement of the inflamed tonsil, occluding the crypt and containing the abscess. Second, it is proposed that ITA arises from bacterial seeding via the bloodstream or lymphatic system .
2
Case review
Two cases of ITA, and ten representative cases of PTA and acute tonsillitis cases were pulled from the pathology department from The University of Toledo Medical Center by a listed diagnosis of PTA or acute tonsillitis over the years 2007–2013. Institutional review board approval was obtained and all slides were appropriately stripped of all identifiers. The histopathology was then reviewed and classified.
Pathologic examination of acute tonsillitis specimen demonstrated ulceration of the stratified squamous surface epithelium with local invasion of neutrophils (PMN). This commonly extended into the crypts but no inflammation or abscess formation was observed deeper within the parenchyma ( Fig. 1 ).
Microscopic examination of six PTA specimen revealed erosion of the surface epithelium with PMN invasion, as observed in the acute tonsillitis specimen. The tonsillar parenchyma was observed to be uniformly unremarkable throughout, only with hyperplasia of follicles. The PTA itself was represented by a collection of PMN infiltration, tissue necrosis and abscess formation deep between the fibrous tonsillar capsule and the skeletal muscle of the pharyngeal wall ( Fig. 2 ).
Pathologic examination of ITA specimen revealed a similar erosion of stratified squamous surface epithelium, with sheets of PMN extending into the tonsillar crypts. Deep into the epithelium, within the parenchyma, a large abscess was found completely surrounded within unremarkable appearing tonsillar tissue ( Fig. 3 ). A concomitant PTA with abscess collection between the tonsil and pharyngeal skeletal muscle wall was also observed.
