Dr Philip Jayasurya (University Hospital Plymouth) and Dr Tim Bracey
A 62-year-old female presented to the ENT outpatient department with a history of discomfort in the back of the throat. Examination revealed nodularity in the right and left post nasal space with tongue base asymmetry. Biopsies from the post nasal space showed extracellular eosinophilic deposits with characteristic apple green birefringence under polarized light, confirming amyloidosis. The amyloid deposits were accompanied by submucosal glands showing abundant eosinophilic granular cytoplasm, consistent with oncocytic metaplasia. Superficial biopsy of the tongue base was unremarkable.
Immunohistochemical staining of the amyloid deposits was performed using mono specific antibodies reactive with serum amyloid A protein (SAA), and with Kappa and Lambda immunoglobulin light chains. The amyloid did not stain with any of these antibodies. Extensive clinical workup including bone marrow biopsy, and cross-sectional imaging showed no evidence of systemic amyloidosis. There were no features to suggest lymphoma, or plasma cell neoplasia.
Amyloidosis is a group of disorders characterised by various insoluble protein subunits identifiable by light microscopy as amorphous eosinophilic material, and can be most broadly classified as systemic and localised. Localised nasopharyngeal amyloidosis is extremely rare, and the combination of this with oncocytic metaplasia appears to be novel in the literature at this anatomical site. Since both AL and AA amyloid were excluded in this case, by a process of elimination, and given the age of the patient it is most likely that this is a case of wild type transthyretin (TTR) localised amyloidosis. Oncocytic metaplasia in a pathological context is a degenerative phenomenon, where an accumulation of mitochondria is thought to compensate for an uncoupling of oxidative metabolism secondary to cellular aging, and can itself present as a mass lesion in the nasopharynx and other head and neck sites. Lesions containing a high concentration of oncocytic cells are often identified as intensely avid for their size on positron emission (PET) scans. Despite the rarity of this combination of features therefore, and with the nasopharynx being a site specifically targeted in endoscopic biopsies searching for unknown primary cancers, pathologists should be aware of both of these lesions, both individually and in our rare case combined in the same mass lesion.
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