A rare case of a solitary extramedullary plasmacytoma of the palatine tonsil

A 48-year-old man, without a past medical history, was admitted to the emergency department due to a spontaneous bleeding from the pharynx. Coagulation parameters were normal. Dental examination excluded bleeding from periodontal tissue. Ear, nose, and throat examination revealed bleeding from the tumor of the left palatine tonsil. Histopathologic examination of the biopsy specimen showed infiltrate composed of plasma cells (Figure 1A). Immunophenotyping demonstrated a positive reaction to CD38, CD56, and CD138 (Supplementary material, Figures S1–S3), and κ light-chain restriction (Figure 1B). Additionally, a few c-Myc–positive cells were observed (Figure 1C). The result of Epstein–Barr virus–encoded small RNA in situ hybridization was negative (Figure 1D). No monoclonal protein was found on serum protein electrophoresis and immunofixation. No protein was detected on urinalysis. Radiograms showed no osteolytic lesion. Bone marrow trephine biopsy findings were typical for normal hematopoiesis (Figure 1E), with dispersed CD138⁺ plasma cells representing 1% of total bone marrow cells, and no light-chain restriction (Supplementary material, Figures S4­–S6). Magnetic resonance imaging of the head and neck showed an exophytic lesion communicating with the left palatine tonsil, attached tightly to the upper esophageal sphincter and longus colli muscle (Figure 1F). A focal increase in ¹⁸F-fluoroethyl-tyrosine (¹⁸F-FET) uptake in the left palatine tonsil was observed on positron-emission tomography–computed tomography (PET-CT) (Figure 1G). Based on those findings, the patient was diagnosed with solitary extramedullary plasmacytoma. Considering the locally advanced neoplastic process, the patient was not considered eligible for tonsillectomy but underwent radiotherapy with a total dose of 54 Gy in 27 fractions. Currently, 5 months after the radiotherapy, the patient remains without progression. No increase in the standardized uptake value was found on follow-up PET-CT (Figure 1H).

Solitary extramedullary plasmacytoma (EMP) is a rare plasma cell tumor involving soft tissues, with no sign of a systemic disease.¹ EMPs are found primarily in the head and neck region, especially in the sinonasal area; however, any other site can be affected as well.² EMPs are more common in men, with a peak incidence in the sixth decade of life.³ In differential diagnosis, reactive processes, carcinoma, and lymphoma should be considered. Diagnostic criteria include clonal plasma cell infiltration in the biopsy specimen, lack of clonal plasma cells in trephine biopsy, normal skeletal survey, and no features of end-organ damage.⁴ Imaging studies should include magnetic resonance imaging to determine the extent of local disease and PET-CT to exclude systemic involvement.⁴ During the latter examination, ¹⁸F-FET should be used as a tracer as it exhibits no uptake in inflammatory cells, which makes it a more specific marker of neoplastic cells than ¹⁸F-fluorodeoxyglucose.⁵ Treatment is local. Radiotherapy has been considered a cornerstone, but the essential role of surgical treatment has been also highlighted.³ Surgery combined with irradiation was shown to be associated with a survival benefit when compared with either surgical treatment or radiotherapy alone. In patients with unresectable tumors, radiotherapy (at least 45 Gy) should be the treatment of choice. Considering the risk of local progression and myeloma relapse, a follow-up is required.³