A 79-year-old Taiwanese woman came to the otolaryngologic clinic of our hospital due to an enlarging painless mass over the right neck region in the past 3 months. She denied fever, night sweats, dyspnea, hoarseness, dysphagia, dysphasia, or stridor. On physical examination, the right thyroid lobe was noted to be enlarged and firm. There was a palpable mass in the front of her neck, which moved during swallowing. She had no history of Hashimoto's thyroiditis or cervical irradiation, and her thyroid function test was within the normal range (thyroid-stimulating hormone: 2.01 nIU/mL; free T4: 1.24 ng/dL; thyroglobulin: 1.62 ng/mL; anti-thyroperoxidase: 1.03 IU/mL; and thyroglobulin antibody: 1.81 IU/mL).\nThe patient had received computed tomography (CT) at hospital outside, which revealed a hypodense nodule with minimal enhancement on the right lobe of thyroid gland []. Its size was approximately 4.1 cm × 3.6 cm, with a longitudinal dimension of 4.5 cm. The trachea, vessels, and soft tissues in the right neck were under pressure and displaced toward the left side. She underwent fine-needle aspiration (FNA) at that hospital, and the cytologic results were suspicious of lymphoma.\nIn order to obtain more definite results, this woman was referred to the radiological department of our hospital for core needle biopsy. During core needle biopsy, the neck color Doppler ultrasound showed a large heterogeneous hypoechoic mass with an irregular border in the right lobe of thyroid gland. There were twisted and chaotic intranodular vessels, but no defined calcification, hemorrhage, or necrotic portion was observed within the mass, which exhibited indistinct margins and posterior acoustic enhancement [Figure and ]. The pathology revealed diffuse large B-cell lymphoma (DLBCL). For staging the disease, a fluorodeoxyglucose (FDG) positron emission tomography (PET) scan was performed, revealing high-grade hypermetabolic lymphomatous disease, confined in the right thyroid gland, suggesting PTL Ann Arbor stage I [].\nAfter consulting oncology specialists, she started rituximab-based chemotherapy and received serial sonographic follow-up. After three cycles of rituximab plus bendamustine – rituximab (375 mg/m2) and bendamustine (Innomustine®, 90 mg/m2) by intravenous administration on day 1 were administered every 3 weeks for each cycle – neck color Doppler ultrasound showed a significant reduction of twisted blood flow signals in the PTL but no significant decrease (<25% extent) of the tumor size []. Therefore, chemotherapy regimen was adjusted to rituximab, cyclophosphamide, vincristine, prednisone (R–COP). After three cycles of R–COP, i.e., rituximab (375 mg/m2), cyclophosphamide (750 mg/m2), and vincristine (2 mg/m2) by intravenous administration on day 1 and prednisone (100 mg/m2) by oral administration on day 1–5 were administered every 3 weeks for each cycle, the PTL disappeared on the color Doppler and gray-scale ultrasonography []. The patient was treated with R–COP regimen until complete remission of the disease, confirmed on the following FDG PET-CT and whole-body PET examination [].
A 64-year-old man with a history of hypothyroidism and proven Hashimoto's thyroiditis presented with painless progressive asymmetric enlargement of the thyroid gland. Laboratory evaluation revealed an elevated erythrocyte sedimentation rate (ESR), elevated thyroid peroxidase antibody titer of 850 U/mL (normal <30 U/mL), free triiodothyronine (FT3) 2.34, free thyroxine (FT4) 0.97, and thyroid stimulating hormone (TSH) level of 22.11. A contrast enhanced CT (CECT) exam of the neck revealed a large heterogeneous mass lesion predominantly involving the left lobe of thyroid and partly involving the isthmus and anterior part of right lobe. A needle biopsy from the thyroid mass revealed features of non-Hodgkin's lymphoma (DLBCL) with the tumor cells staining positive for CD20, negative for cytokeratin (CK) and having a high proliferative index (MIB-1) of 35-40%. 18F-FDG PET/CT was performed for staging. It revealed a large heterogeneous mass lesion predominantly involving the left lobe of thyroid and partly involving the isthmus and anterior part of right lobe with intense radiotracer uptake in the thyroid mass (SUVmax-18.7) with no other abnormal identifiable areas [Figure –]. The patient underwent four cycles of combination chemotherapy (rituximab-cyclophosphamide, doxorubicin, vincristine, and prednisone) and was reevaluated with 18F-FDG PET/CT. Post therapy 18F-FDG PET/CT [Figure –] done 6 weeks after completion of chemotherapy revealed significant decrease in the size of the enlarged thyroid gland associated with no significant FDG avidity (SUVmax-2.0) of the residual thyroid mass (arrow), suggestive of complete metabolic response. The patient is in complete remission at 18 month follow-up.