A Plasmacytoma of the Lateral Pharyngeal Wall: A Diagnostic Enigma

Abstract

Plasmacytoma is a rare plasma cell dyscrasia that grows in bones or soft tissues such as the pharynx. Soft tissue plasmacytomas are rare, and a higher burden has been reported in the upper aero-digestive tract, often manifesting as hoarseness, dysphagia, or odynophagia. Due to their rarity, extramedullary plasmacytomas (EMPs) have unknown prognostic factors, and guidelines for optimal management are still lacking. However, radiation therapy and surgery have been used with positive outcomes. Herein, we describe a unique case of plasmacytoma of the pharyngeal tissue in a male patient with a history of HIV disease. The patient completed 28 sessions of radiation therapy, resulting in an improvement in his throat pain and hoarseness. Given the patient's age and lack of traditional risk factors for head and neck cancers, his hoarseness and odynophagia proved to be a diagnostic conundrum. Although infrequent, soft tissue plasmacytomas should be considered in the differential diagnosis of head and neck tumors.

Keywords: dysphagia; extramedullary plasmacytoma; hoarseness; multiple myeloma; pharyngeal plasmacytoma; radiotherapy; surgery.

Figure 1.

Biopsy slides show a polypoid mass lined by benign squamous mucosa with underlying extensive proliferation of plasma cells. The plasma cells are mostly mature in appearance, but some plasma cells are mildly enlarged, and occasional plasma cells show plasmablastic morphology. Mitotic activities are present, but not risk.

Figure 2.

Immunostains demonstrated CD138 positivity (A), highlighting plasma cells. On in situ hybridization, the plasma cells were monotypic for immunoglobulin light chains kappa (B) and negative for lambda (C).