Journal of the New Zealand Medical Association, 02-June-2006, Vol 119 No 1235
Extramedullary plasmacytoma of the thyroid
Sheng-Fong Kuo, Hung-Yu Chang, Chuen Hsueh, Jen-Der Lin
A 19-year-old female visited the Metabolic Clinic at Chang Gung Memorial Hospital (CGMH) due a right neck mass persisting for about 6 months. Physical examination revealed a 3.5-cm nodule in the thyroid gland. The mass was non-tender, elastic in consistency, and movable after swallowing.
All other physical examination findings were normal. Thyroid function; haemoglobin, serum calcium, phosphate, total protein (7.6 g/dl) and albumin (4.9 g/dl) levels; immunoelectrophoresis; and chest X-ray results were normal. Thyroid ultrasonography with fine-needle aspiration cytology (FNAC) was performed.
Figure 1 shows the results of real-time thyroid ultrasonography with the 10 MHz transducer probe. There was a 3.5×2.8×1.6 cm hypo-echo mass in the right thyroid.
Figure 2 presents the patient’s cytological data. Tentative diagnosis by FNAC was thyroid lymphoma. The patient underwent surgery and lobectomy for the right thyroid tumour to obtain a histological diagnosis.
Figure 3 shows the histology of the tumour, composed of diffuse infiltration of sheets of plasmacytic cells in mature and immature forms.
The final diagnosis of thyroid plasmacytoma was made and further confirmed by immunohistochemical stains for IgA, IgG, IgM, light chains-kappa (κ), and lambda (λ).
Figure 4 shows the positive staining result with a striking intracytoplasmic staining for the IgA antibody. The light chains were negative immunohistochemically. A diagnosis of extramedullary plasmacytoma of the thyroid gland was therefore made.
The patient was well and had no bone pain. She did not undergo bone marrow examination or further treatment, and has been well for 3 years without tumour recurrence.
Plasma cell neoplasm is a malignancy typically afflicting elderly populations. In contrast to multiple myeloma, plasmacytoma is a localised proliferation of plasma cells in the bone marrow and less frequently in extraosseous organs.1,2 Primary plasmacytomas and plasma cell granulomas are unusual thyroid disorders.3–5
A review of primary plasmacytoma cases identified similar gender distribution in Western nations and Japan. In an average 5-year follow-up period, over 70% of the patients were alive with no evidence of disease.6 Long-term follow-up is recommended due to possible progression to multiple myeloma.6,7
Although FNAC has been widely used in diagnosing nodular thyroid disorders,8,9 limited experience exists for preoperative diagnosis of thyroid plasmacytomas.5,6,10 A thyroid plasmacytoma can be mistaken as thyroid lymphoma and even medullary carcinoma by FNAC;5,6,10 in this case, the thyroid plasmacytoma was mistaken for thyroid lymphoma.
In contrast to extramedullary thyroid plasmacytoma, multiple myelomas with thyroid involvement are rarer. Multiple myelomas have reportedly involved the thyroid in its advanced stage.11 Fewer than 10 reported cases have the thyroid as the first presenting site of multiple myelomas.11
In our case, the possibility of multiple myeloma with thyroid involvement could not be completely excluded, however, a literature review revealed that all patients diagnosed with primary thyroid plasmacytoma were over 35 years old, as was the patient with multiple myelomas with thyroid involvement. Our case is the youngest patient reported with thyroid plasmacytoma.
Author information: Sheng-Fong Kuo, Hung-Yu Chang, Jen-Der Lin, Endocrinologists, Division of Endocrinology and Metabolism, Department of Internal Medicine; Chuen Hsueh, Department of Pathology; Chang Gung Memorial Hospital and University, Taoyuan, Taiwan
Correspondence: Dr Jen-Der Lin, Division of Endocrinology and Metabolism, Department of Internal Medicine, Chang Gung Memorial Hospital, 5 Fushing St, Gueishan Shiang, Taoyuan, 333, Taiwan. Fax: +886 3 3288257; email: einjd@.adm.cgmh.org.tw
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