case_images: PMC8081108_01
case_images: (a) Noncontrast enhanced computed tomography shows a hypodense nodule (size: 4.1 cm x 3.6 cm x 4.5 cm) in the right lobe of thyroid gland. (b) This nodule shows minimal homogeneous enhancement on contrast enhanced computed tomography imaging. The trachea, vessels and soft tissues in the right neck are under pressure and displaced toward the left side
case_images: JMU-29-60-g001.jpg
case_images: PMC8081108_01_JMU-29-60-g001.jpg
case_images: F1
case_images: The patient had received computed tomography (CT) at hospital outside, which revealed a hypodense nodule with minimal enhancement on the right lobe of thyroid gland [Figure 1].
case_images: (a) Transverse sonogram of the neck reveals a heterogeneous hypoechoic mass with an irregular border in the right lobe of thyroid gland. Note posterior acoustic enhancement under the nodule. (b) The color Doppler ultrasound shows abundant twisted blood flow signals in the tumor. (c and d) Note a nodular goiter in the left lobe of thyroid gland with minimal blood flow signals
case_images: JMU-29-60-g002.jpg
case_images: PMC8081108_01_JMU-29-60-g002.jpg
case_images: F2
case_images: 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 2a and b].
case_images: The fluorodeoxyglucose positron emission tomography computed tomography scan (left) reveals a tumor with high-grade hypermetabolic status in the right lobe of thyroid gland. The whole-body positron emission tomography scan (right) shows no other foci with increased fluorodeoxyglucose uptake out of the thyroid gland. Therefore, the primary thyroid lymphoma is diagnosed based on the pathological result from core needle biopsy
case_images: JMU-29-60-g003.jpg
case_images: PMC8081108_01_JMU-29-60-g003.jpg
case_images: F3
case_images: 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 [Figure 3].
case_images: (a) The gray-scale ultrasonography shows no significant decrease of the tumor size (transverse diameters: 4.79 cm x 4.73 cm   3.95 cm x 3.01 cm; <25% extent). (b) The color Doppler ultrasound shows reduction of twisted blood flow signals in the primary thyroid lymphoma after three cycles of rituximab plus bendamustine. (c) Color Doppler ultrasonographic image of the left thyroid gland is shown
case_images: JMU-29-60-g004.jpg
case_images: PMC8081108_01_JMU-29-60-g004.jpg
case_images: F4
case_images: 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 [Figure 4].
case_images: (a) After three cycles of rituximab, cyclophosphamide, vincristine, prednisone, the primary thyroid lymphoma disappears on the color Doppler and gray-scale ultrasonography. (b) Complete remission of the primary thyroid lymphoma is confirmed on the positron emission tomography computed tomography (left) and whole-body positron emission tomography scan (right) after three cycles of rituximab, cyclophosphamide, vincristine, prednisone regimen
case_images: JMU-29-60-g005.jpg
case_images: PMC8081108_01_JMU-29-60-g005.jpg
case_images: F5
case_images: 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 [Figure 5a]. 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 [Figure 5b].