Introduction Primary thyroid lymphoma is rare accounting
Primary thyroid lymphoma is rare, accounting for <5% of thyroid malignancies. The two distinct histological types of primary thyroid lymphoma are diffuse large B cell lymphoma (DLBCL) and mucosa-associated lymphoid tissue (MALT) lymphoma. Because DLBCL is sensitive to chemotherapy and radiotherapy, the general consensus is to avoid extensive surgery. By contrast, radiotherapy or thyroidectomy is typically used as the initial treatment for localized MALT lymphoma. Fine-needle aspiration cytology, the most common initial diagnostic tool used in thyroid malignancies, is difficult to use for diagnosing tumor type, which is necessary for treatment planning. However, core-needle biopsy, which is less commonly used in thyroid-gland biopsies, may serve as a substitute to surgical biopsy. This study investigated the efficacy of various biopsy procedures and explored indications for thyroidectomy in patients with primary thyroid lymphoma.
Results Ten patients with primary thyroid lymphoma were identified. Of these, eight had DLBCL, and two had MALT lymphoma. Patient demographics, pathological diagnoses, and disease stages are listed in Table 1. In total, six women and four men were identified. The mean age at onset was 67.9 years (range, 54–83 years). All patients developed rapidly growing neck masses over months, with mean tumor size of 7.1 cm (range, 3.8–11.4 cm). Table 2 lists treatment types, major treatment-related complications, initial disease stages, and their corresponding outcomes. All patients with DLBCL underwent chemotherapy with a platinum-based regimen. Three patients also received adjuvant radiotherapy. Two patients with MALT lymphoma underwent thyroidectomy as the primary treatment. Patient five initially underwent a lobectomy, after which the frozen tissue section indicated benign disease, and he Rimonabant had subsequent completion of a thyroidectomy and adjuvant radiotherapy, because the final pathological assessment revealed Hashimoto\'s thyroiditis with marginal cell lymphoma (MALT lymphoma). Patient 8 underwent subtotal thyroidectomy. Neither Patient 5 nor Patient 8 underwent chemotherapy. In Patients 4, 6, 7, and 10 with DLBCL, systemic steroid therapy immediately relieved airway compression and precluding the need for tracheostomy. Additionally, remarkable tumor shrinkage was observed after chemotherapy. A comparison of the neck CT scans of Patient 6 before and after treatment is presented in Figure 1.
Discussion Primary thyroid lymphoma is rare, accounting for only 5% of thyroid malignancies and 2% of extranodal lymphomas. Thyroid lymphoma typically presents as a rapidly growing neck mass that is sometimes accompanied by respiratory compression symptoms. Thyroid lymphoma is more predominant in women and has a peak onset age of 50 to 70 years. The risk of thyroid lymphoma is high in individuals with a history of chronic thyroiditis, such as Hashimoto\'s thyroiditis. Similar to other lymphomas, subtypes in thyroid lymphoma are classified according to histological and immunological features. B cell non-Hodgkin\'s lymphoma is the most common subtype, whereas DLBCL and marginal-zone B cell lymphoma of MALT type (MALT lymphoma) are other common subtypes that may also co-occur in a single patient; follicular, small lymphocytic, and T cell-origin lymphoma are other less common subtypes of the disease. Ultrasound is a common diagnostic tool for measuring the thyroid mass, because it reveals hypoechoic masses intermingled with echogenic structures and enhances posterior echoes. FNAB is often used as an initial tool for the pathological diagnosis of the thyroid nodule and can provide a suggestive diagnosis of lymphomas. Microscopically, large-cell lymphomas are observed as atypical large lymphocytes with frequent mitosis and reveal positive B cell markers (CD20 and CD79a) on immunohistochemical staining. By contrast, low-grade lymphomas are observed as a mixture of small and large lymphocytes, mimicking Hashimoto\'s thyroiditis. In uncertain diagnoses, adjuvant tests, such as immunophenotyping, flow cytometry, and polymerase chain reaction-based detection of the immunoglobulin heavy chain gene, may be helpful; however, because of the rarity of the disease, availability of these adjuvant tests varies among institutions, and no universal standard is available.