A Rare Case of Extramedullary Plasmacytoma Presenting With Critical Airway Compromise

Introduction/Background/Significance: Plasmacytoma is a rare malignancy of monoclonal plasma cells, with tracheal involvement being exceptionally uncommon. Its indolent course can delay diagnosis, which may lead to serious complications. We report a case of solitary tracheal plasmacytoma causing critical central airway obstruction successfully treated by bronchoscopic tumor removal, laser ablation, and radiation.

Materials and Methods/Case Presentation/Objective: A 66-year-old woman with a history of late-onset asthma presented with a six-month history of intermittent hemoptysis, wheezing, and globus sensation. CT scan of the neck revealed a 1.0 x 1.0 x 1.2 cm polypoid soft tissue tumor in the upper trachea.. Flexible bronchoscopy identified an exophytic mass causing 70% luminal obstruction. Partial resection using an electrocautery snare, followed by laser ablation and cryotherapy, restored 90% airway patency. Histopathology confirmed a plasma cell neoplasm with Lambda light chain restriction, CD138, partial CD56, and rare B-cell marker expressions. Immunohistochemistry surveillance showed elevated Kappa free light chains, normal range Lambda free light chains, and mildly increased Kappa/lambda ratios. A bone marrow biopsy revealed polyclonal plasma cells. A PET scan showed no evidence of a hypermetabolic tumor. The patient was successfully treated by radiation therapy and continues to be monitored with no recurrence in 1 year.

Results/Description/Main Outcome Measures: Solitary tracheal plasmacytoma is extremely rare and may cause critical airway obstruction when luminal narrowing exceeds 50%. In our case, tracheal plasmacytoma was diagnosed after a prolonged course of unexplained respiratory symptoms. Bronchoscopic tumor debulking and laser therapy are effective in reducing obstruction and optimizing the airway for definitive treatment with radiotherapy. Given its high radiosensitivity, radiation therapy is the standard treatment for solitary extramedullary plasmacytoma. Ruling out multiple myeloma is essential when evaluating plasmacytoma. In our case, tissue biopsy confirmed a plasma cell neoplasm, a PET scan revealed no hypermetabolic lesions, and bone marrow biopsy showed polyclonal plasma cells, excluding multiple myeloma. The kappa/lambda ratio and CD56 glycoprotein help detect monoclonal plasma cell proliferation. In our case, an elevated serum kappa/lambda ratio and normal range free Lambda light chain did not align with the biopsy-confirmed lambda restriction. The partial CD56 expression, often seen in multiple myeloma, highlights the need for close follow-up, as its atypical patterns may carry a risk of progression. Prognosis for solitary extramedullary plasmacytoma is favorable, with 10-year progression rates to MM between 25–35%, significantly lower than the 65–84% risk of solitary bone plasmacytoma.

Conclusions: Our case highlights the importance of early diagnosis and surveillance in tracheal plasmacytoma, a rare malignancy with potential progression to airway compromise and multiple myeloma. It emphasizes the role of bronchoscopy, laser ablation, radiotherapy, and the need for further investigation into biomarkers of plasmacytoma.