Plasmacytoma in the thyroid.
Extramedullary plasmacytoma is a plasma cell tumor which involves soft tissues without any signs of systemic spread. It may originate in many sites, it although most frequently occurs in the upper respiratory tract and oral cavity. (1-3) It has also been synchronously found in contiguous sites, confirming that the disease tends to spread locally. (4) Extramedullary plasmacytoma afflicts elderly populations and accounts for less than 5% of all plasma cell neoplasms. Histologically, this tumor is composed of sheets of plasma cells at different stages of maturity. (5)
A 60-year-old woman presented to the Tulane University Hospital complaining of compressive symptoms, including dyspnea, dysphagia, and anterior neck discomfort. She had also noted hoarseness. Physical examination revealed an enlarged thyroid with no specific nodule. CT scan of the neck and chest revealed diffuse homogenous enlargement of both thyroid lobes with the gland extending into the mediastinum and causing tracheal compression (Figures 1-3). No cervical or mediastinal lymphadenopathy was detected. The patient was clinically and biochemically euthyroid. Because of the compressive symptoms, total thyroidectomy was performed. There was nothing remarkable about the gland during resection. The postoperative course was uneventful and patient's compressive symptoms resolved completely.
Pathologic examination of the resected thyroid revealed evidence of fibrosis surrounding small nodules of residual follicles with massive infiltration by plasma cells (Figure 4), primarily of the kappa type. Immunoperoxidase stains for polyclonal kappa and lambda revealed cytoplasmic staining for kappa in 99% of the cells with staining for lambda in less than 1%. The findings were consistent with plasmacytoma of the thyroid. Serum protein electrophoresis showed a mildly elevated gamma globulin band of 1.8gm/dL (range, 0.5-1.5gm/dL) indicative of mild polyclonal gammopathy. Bone marrow biopsy was preformed and there was no evidence of systemic multiple myeloma.
Postoperative radioiodine scan was negative for any evidence of residual thyroid tissue, demonstrating complete resection of the thyroid. Additionally, postoperative neck ultrasound scan revealed no evidence of remnant thyroid tissue. Since the plasmacytoma was totally resected, no postoperative radiation therapy was indicated.
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In this patient, thyromegaly was due to the massive infiltration of the gland with plasma cells. Extramedullary plasmacytoma is a rare tumor of the thyroid gland most commonly noted in older women. The exact incidence is not known, but to date, only 46 cases have been reported. (6) Plasmacytoma may be associated with Hashimoto thyroiditis or may mimic medullary cancer. Extramedullary plasmacytoma may be a primary isolated lesion with or without affected lymph nodes or as an extramedullary manifestation of systemic multiple myeloma. Multiple myeloma involving the thyroid is even rarer than extramedullary thyroid plasmacytoma. The thyroid was the first presenting site of multiple myeloma in fewer than 10 reported cases. (2)
The head and neck are the most common sites of isolated extramedullary plasmacytoma, whereas in systemic multiple myeloma, the most frequent extramedullary sites of involvement are the liver, spleen, and lymph nodes. (7) Plasmacytoma may also arise in bone marrow (osseous) and in soft tissues (non-osseous), both of which can be solitary or multifocal. Solitary extramedullary plasmacytomas frequently remain localized, whereas solitary plasmacytomas of bone frequently progress into multiple myeloma. (8) When it originates in the upper respiratory tract, extramedullary plasmacytoma can be a manifestation of multiple myeloma at its initial appearance or precede the development of the systemic disease. Most extraskeletal plasma cell lesions have no typical imaging characteristics, and clinical laboratory, and histology correlations are necessary to differentiate them from other solid lesions. If lymph nodes are involved, their CT appearance is similar to that of lymphoma. Based upon imaging alone, characteristic lesions in the nasopharynx and upper respiratory tract cannot be distinguished from carcinoma. (9) CT and magnetic resonance imaging are the imaging techniques of choice for demonstrating extramedullary manifestations of systemic or isolated plasmacytoma. CT and ultrasound are both useful in guiding biopsies. (9) Although fine needle aspiration has been widely used in diagnosing nodular thyroid disorders (10-11) there has been limited experience with the preoperative diagnosis of thyroid plasmacytoma. (12-14) By cytology, a plasmacytoma of the thyroid may be mistaken for thyroid lymphoma or even medullary carcinoma. (11-13)
In the preoperative staging, it is important to look for soft tissue and long bone metastases. Non-surgical modalities to treat plasmacytoma include chemotherapy with a combination of thalidomide dexamethasone combination treatment or radiation therapy. Plasmacytoma without medullary lesions has a favorable prognosis (15 years survival rate of 78%) when treated locally by irradiation and/or surgery. (6) Surgical intervention is safe and radiation therapy should be considered in these patients, due to the associated complications. Long-term follow-up is required to monitor for possible progression to multiple myeloma. (12, 15)
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Extramedullary lesions occur in less than 5% of patients with multiple myeloma and can involve any organ. Because spleenomegaly is uncommon in patients with multiple myeloma, the possibility of tumor infiltration should be considered when an enlarged spleen is noted. In patients with myeloma, liver involvement generally consists of diffuse sinusoidal infiltration, rather than nodules. (16) Extramedullary lesions usually present in the nasopharynx, upper respiratory tract, lamina propria of the gastrointestinal tract, lymph nodes, and in the central nervous system. (15, 17)
Extramedullary plasmacytomas should be considered in the differential diagnosis of homogenous and unexplained thyromegaly. They are difficult to diagnose with routine imaging studies for thyromegaly. Surgical intervention should be considered for relief of relevant compressive symptoms and in patients in whom radiation is contraindicated or not feasible.
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Emad H. Kandil, MD, FACS; Mohamed S. Abdel Khalek, MD; Haytham H. Alabbas, MD; Tina Thethi, MD; Byron E. Crawford, MD; and Bernard M. Jaffe, MD
Drs. Kandil, Abdel Khalek, Alabbas, Thethi, and Jaffe are with the Department of Surgery, Division of Endocrine and Oncologic Surgery at Tulane University School of Medicine in New Orleans. Dr. Crawford is with the Department of Pathology at Tulane University School of Medicine in New Orleans.
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|Author:||Kandil, Emad H.; Khalek, Mohamed S. Abdel; Alabbas, Haytham H.; Thethi, Tina; Crawford, Byron E.; Ja|
|Publication:||The Journal of the Louisiana State Medical Society|
|Article Type:||Case study|
|Date:||Nov 1, 2010|
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