SOLITARY EXTRAMEDULLARY PLASMACYTOMA CAUSING PROXIMAL ENDOBRONCHIAL OBSTRUCTION

TOPIC: Lung Cancer TYPE: Medical Student/Resident Case Reports INTRODUCTION: Extramedullary plasmacytomas can arise in patients with systemic multiple myeloma and should not be confused with solitary extramedullary plasmacytoma (SEP). SEP refers to a solitary non-osseous plasma cell neoplasm in patients without evidence of multiple myeloma. SEP, observed in 3% of all patients with plasma cell neoplasms, is usually located in the upper aerodigestive tract.1 Endobronchial obstruction due to SEP is very rare. CASE PRESENTATION: We report the case of a 50 year old non-smoking male with a history of asthma and left sided pneumonia who presented with a three year history of nonproductive cough and dyspnea. Computerized tomography of the chest showed a 4 cm mass extending into the left mainstem bronchus (LMB), with post-obstructive atelectasis, mediastinal adenopathy and pleural thickening (figure 1). His labs did not demonstrate anemia, hypercalcemia, or renal insufficiency. Bronchoscopy demonstrated 99% occlusion of the proximal LMB by an exophytic tumor (figure 2). He underwent extensive endobronchial debulking. Endobronchial biopsy (figure 3) confirmed a monoclonal plasma cell neoplasm. Mass spectrometry showed kappa immunoglobulin light chains with no evidence of amyloid-associated proteins. Bone marrow biopsy showed a normocellular marrow with mildly increased plasma cells. Serum protein electrophoresis did not show a monoclonal protein spike. Beta-2-microglobulin was normal. Positron emission tomography scan showed FDG uptake in the left endobronchial mass and mild mediastinal uptake. The patient was diagnosed with SEP and received targeted external beam radiotherapy (4500 cGy in 25 fractions) with a favorable response. DISCUSSION: SEP in the lungs, while rare, most frequently presents as lung nodules. Endobronchial involvement is uncommon and can occur proximally in the trachea and mainstem bronchi or distally. Only two other case have shown light chain extracellular deposits.2 Most pulmonary plasmacytomas are treated with surgical resection, radiation therapy, or palliative bronchoscopic interventions.3 Initial reports of aerodigestive SEP suggested that radiation therapy may be superior to surgical resection, however, that assertion has been challenged. Nevertheless, these tumors do appear to be highly radiosensitive. CONCLUSIONS: Endobronchial SEP is a rare neoplasm that can cause proximal endobronchial obstruction. Proper immunohistopathology confirms SEP. While endobronchial and surgical options can be used in some instances, radiotherapy with intent to cure should be considered for proximal endobronchial disease. REFERENCE #1: Dores GM, Landgren O, McGlynn KA, Curtis RE, Linet MS, Devesa SS. Plasmacytoma of bone, extramedullary plasmacytoma, and multiple myeloma: incidence and survival in the United States, 1992-2004. Br J Haematol. 2009 Jan;144(1):86-94. doi: 10.1111/j.1365-2141.2008.07421.x. Epub 2008 Nov 11. PMID: 19016727; PMCID: PMC2610331. REFERENCE #2: Liu HY, Luo XM, Zhou SH, Zheng ZJ. Prognosis and expression of lambda light chains in solitary extramedullary plasmacytoma of the head and neck: two case reports and a literature review. J Int Med Res. 2010 Jan-Feb;38(1):282-8. doi: 10.1177/147323001003800133. PMID: 20233540. REFERENCE #3: Park JI, Lee YY, Lee SS, Ahn JH. A rare case of primary solitary endobronchial plasmacytoma. Thoracic Cancer. 2021;12:958–961. https://doi.org/10.1111/1759-771 4.1385 DISCLOSURES: No relevant relationships by Urbee Haque, source=Web Response No relevant relationships by Randall Harris, source=Web Response No relevant relationships by Sonya Joshi, source=Web Response No relevant relationships by Jason Lane, source=Web Response No relevant relationships by Sujith Modugula, source=Web Response No relevant relationships by Sanjiv Tewari, source=Web Response