Solitary Extra-Medullary Plasmacytoma of the True Vocal Cord
Solitary plasmacytoma is a rare plasma cell neoplasm, accounting for only 5% to 10% of all plasma cell neoplasms. It is categorized into two types based on location: solitary bone plasmacytoma (SBP), which occurs in bone, and solitary extra-medullary plasmacytoma (EMP), which arises in soft tissue. SBP is approximately 40% more common than EMP. While EMP can develop in various parts of the body, 90% of cases occur in the head and neck region, particularly in the nasal cavity, paranasal sinuses, and pharynx. However, EMP of the larynx is exceptionally rare, representing only 0.04% to 0.19% of all malignant laryngeal lesions. The diverse appearances of laryngeal EMP make accurate diagnosis challenging without definitive pathological confirmation.
This case report describes a 42-year-old male who initially presented with acute hoarseness and a persistent cough following a cold. His primary physician treated him with antibiotics for suspected laryngitis, but the symptoms persisted for six months. Upon referral to Peking University Third Hospital, the patient denied any history of pharyngalgia, dysphagia, dyspnea, fever, or weight loss. However, he had a significant smoking history of more than 20 years, consuming two packs of cigarettes daily.
Indirect and flexible laryngoscopy revealed a pink exophytic mass with a narrow base located on the middle third of the right vocal fold. The lesion had a smooth surface and measured approximately 10 mm in diameter. The vocal fold movement was normal, and no abnormalities were observed in the nasopharynx or oropharynx, aside from non-specific signs of chronic inflammation. No palpable superficial lymph nodes were detected. Based on the clinical presentation, the lesion was initially presumed to be a benign vocal cord polyp. Consequently, a direct suspension laryngoscopy was performed under general anesthesia, and the lesion was resected using a CO2 laser following phonomicrosurgery principles.
Pathological examination of the resected lesion revealed diffuse and dense infiltration of plasma cells. Immunohistochemical tests confirmed the diagnosis of plasmacytoma. To rule out multiple myeloma (MM), a comprehensive work-up was conducted. Serum electrophoresis, serum immunoglobulins, and β2-microglobulin levels were all within normal ranges. Complete blood count (CBC), serum calcium, uric acid, and renal function tests were also normal. Bone marrow aspirate and biopsy from the right iliac crest showed normal hematopoiesis with less than 1% plasma cells. A skeletal survey, including X-rays of the long bones and spine, revealed no abnormalities. A whole-body positron emission tomography scan showed no evidence of metastatic disease. Urine examination for light chains indicated slightly elevated kappa and lambda light chains. Based on these findings, the diagnosis of laryngeal EMP was established.
Current guidelines for solitary plasmacytoma recommend radiation therapy to the involved field as the primary treatment, with surgery serving as an adjunct when necessary. However, the patient declined radiation therapy and opted for close follow-up. Every six months, flexible laryngoscopy was performed to monitor for local recurrence, while CBC and urinalysis were conducted to detect systemic recurrence. At the five-year follow-up, the patient remained asymptomatic, with no signs of local or systemic recurrence.
EMP accounts for less than 1% of head and neck tumors, with the majority occurring in the upper respiratory tract. It predominantly affects male patients aged 40 to 70 years. Laryngeal EMP, which comprises 4.5% to 18.0% of all EMP cases, is rare but has been increasingly reported in recent years. The primary clinical manifestation is hoarseness, although other symptoms such as dyspnea, dysphagia, stridor, a sensation of a foreign body, hemoptysis, and dry cough may occur depending on the lesion’s location and size. Some patients may present with a neck mass, while others may be asymptomatic. Laryngeal EMP can vary in appearance, ranging from small lesions of 0.3 cm to larger masses up to 3.0 cm. Lesions may present as solitary granulation polyps, diffuse mucosal thickening, or masses within the larynx. The supraglottic region is the most commonly affected site, followed by the glottic and subglottic regions.
In this case, the lesion was located in the glottis and was small, causing only hoarseness. Its smooth and polypoid appearance led to an initial misdiagnosis of a vocal cord polyp. This case underscores the importance of recognizing that plasmacytoma, though rare, can mimic benign lesions, making accurate diagnosis challenging based solely on laryngoscopy.
Advances in the treatment of MM have been significant in recent years, but the treatment paradigm for solitary plasmacytoma has remained relatively unchanged. Surgery combined with radiotherapy is considered superior to unimodal treatment in preventing local recurrence, with radiotherapy remaining the mainstay of treatment. Guidelines from the International Lymphoma Radiation Oncology Group suggest that definitive surgical excision alone may be acceptable for small tumors in anatomic locations where clear margins can be achieved with minimal morbidity. Examples include cutaneous lesions and solitary lung lesions. In this case, despite the clear margin being uncertain, the patient declined radiotherapy. Fortunately, no signs of local recurrence or progression to MM were observed at the five-year follow-up, possibly due to the sealing effect of the CO2 laser, which can extend up to 2 mm deeper than the visible margin.
Factors associated with the risk of local relapse and myeloma progression in EMP include the treatment type, disease site, patient age, lesion size, and the presence of bony erosion. Non-sinonasal EMP has a better prognosis than sinonasal lesions. Patients over 65 years of age, those with lesions larger than 5 cm, or those with bony erosion have a worse prognosis. The patient in this case was a 45-year-old male with a localized laryngeal lesion and no evidence of bony erosion, placing him in a lower-risk category. Despite the relatively favorable prognosis of EMP, 10% to 15% of cases progress to MM. Therefore, lifelong follow-up and surveillance are essential, including regular blood and urine tests.
In summary, laryngeal EMP is a rare disease with varied and often confusing presentations. Radiation therapy should be prescribed whenever possible, and close follow-up is necessary for patients at high risk of recurrence and myeloma progression. This case highlights the diagnostic challenges and the importance of considering plasmacytoma in the differential diagnosis of laryngeal lesions, even when they appear benign.
doi.org/10.1097/CM9.0000000000000303
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