Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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July 13, 2015
Isolated Nasopharyngeal Amyloidoma
- Background: Amyloidoma represents 0.2–1.5% of all benign laryngeal tumors. It is typically associated with underlying plasma cell dyscrasia or myeloma. Solitary de novo amyloidoma is vanishingly rare. The larynx is the most common site of involvement of amyloidoma, with the supraglottic larynx being the most common laryngeal subsite in the head and neck, followed by the orbit. Other reported sites include the oral cavity and oropharynx, larynx, and subglottic trachea.
- Clinical Presentation: Presentation can be systemic or localized. Systemic involvement is most common, either familial or found in association with plasma cell dyscrasias or chronic inflammatory/infectious disease. Twenty percent of cases of isolated amyloidomas involve the head and neck. Progression to systemic amyloidosis has not been reported in association with focal amyloidoma. Polyclonal plasma cell proliferation has been found histologically without frank plasmacytoma transformation to date.
- Key Diagnostic Features:
- Hypointense or mixed signal on T2WI, iso- or mild hyperintensity on T1WI, and moderate enhancement is characteristic.
- CT typically shows a relatively hyperdense lesion on NECT, due to the proteinaceous matrix.
- Dystrophic calcification can be seen, ranging from minimally apparent to flocculent with positive, potentially confounding uptake on Tc 99m MDP skeletal scintigraphy.
- Relatively intense metabolic activity mimicking locoregional neoplasia can be seen on FDG PET imaging.
- DDx: Other considerations for mucosal-based head and neck lesions, including inflammatory or metaplastic polyp vs. squamous neoplasm, should be excluded with surgical biopsy/resection. More densely calcified lesions can mimic extraskeletal chondro - or osteosarcoma, calcified metastatic thyroid or adenocarcinoma, or a schwannoma undergoing a degeneration process.
- In this case, biopsy showed chronically inflamed squamous mucosa with underlying amyloid deposition compatible with isolated amyloidoma. Subsequent marrow aspirate was positive for mature plasmacytosis, with elevated light and heavy chain immunoglobulins.
- Treatment: In addition to regional resection, marrow aspiration is warranted to rule out other underlying hematological abnormalities, including plasma cell dyscrasias or myeloma.
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