Case of Carcinoma Breast with Unusually Large Tumor Thrombus in Superior Vena Cava Detected on ¹⁸F-Fluorodeoxyglucose Positron Emission Tomography Computed Tomography Scan

A 60-year-old female diagnosed with carcinoma breast (left) in 2015 underwent a modified radical mastectomy followed by neoadjuvant chemotherapy and radiotherapy. She completed her treatment in early 2016 and was on regular follow-up as she had the triple negative disease (estrogen, progesterone, and Herceptin receptor). She complained of facial puffiness and giddiness. On examination, she was found to have mildly enlarged left supraclavicular lymph nodes. She was referred for ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) scan for recurrence evaluation. ¹⁸F-FDG PET/CT showed evidence of right intramammary, mediastinal and bilateral supraclavicular lymph nodal metastases, brain metastases, lung metastasis, and metastatic soft tissue deposits. Figure 1 shows representative sections of a few of these lesions. In addition, ¹⁸F-FDG PET/CT scan also showed evidence of a large filling defect measuring 4.5 cm × 6.6 cm in size in the superior vena cava (SVC) extending from its origin up to the right atrium [Figure 2]. The filling defect was seen extending into the right brachiocephalic vein and the adjoining parts of right jugular vein. An area of heterogeneous contrast enhancement was noted in the medial aspect of the filling defect with intense FDG uptake suggesting it to be a tumor thrombus (TT). Extensive venous collaterals were evident along the right anterior chest and abdominal wall suggestive of SVC obstruction.

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Figure 1 Intensely FDG concentrating brain metastases (yellow arrow a – fused PET/CT, b – CECT) and intensely FDG concentrating intra-abdominal soft tissue deposit in the left hypochondrium (c – fused PET/CT, d – CECT), soft tissue deposit in the left inguinal region (e – fused PET/CT, f – CECT), and in subcutaneous tissue in posterior aspect of left thigh (red arrow, g – fused PET/CT, h – CECT) were also noted. FDG: Fluorodeoxyglucose, PET/CT: Positron emission tomography/computed tomography, CECT: Contrast-enhanced computed

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Figure 2 ¹⁸F-FDG PET/CT (a – maximum intensity projection) showed multiple abnormal tracer concentrating lesions in the brain, neck, thorax, left upper abdomen, and left thigh. Representative axial sections (b – fused PET/CT, c – contrast-enhanced CT [CECT]) and sagittal sections (d – fused PET/CT, e – CECT) shows a large filling defect measuring 4.5 cm × 6.6 cm in size in the SVC extending from its origin up to the right atrium. FDG: Fluorodeoxyglucose, PET/CT: Positron emission tomography/computed tomography, CECT: Contrast-enhanced computed, SVC: Superior vena cava

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The role of ¹⁸F-FDG PET/CT in staging, restaging, prognostication, and suspected recurrence evaluation of breast cancer especially triple negative disease is well established.[1234] It has been identified that patients with malignancy are at a 4–7-fold higher risk of venous thromboembolism (VTE) than nononcology patients.[5] VTE is not uncommon in breast cancer patients, and it most commonly affects the lower extremities and is more common during the first 6 months after diagnosis. The higher incidence of VTE in the early treatment period may be related to surgical procedures and systemic treatment strategies.[6] However, these are normally bland thrombus, and the incidence of TT is relatively rare. TT is more commonly associated with hepatocellular carcinoma, renal cell carcinoma, and gonadal tumors.[7] Among the sites of TT, most common is inferior vena cava, followed by portal and renal veins.[8] SVC is a relatively rare site of TT although few case reports exist.[910] The ability of ¹⁸F-FDG PET/CT in identifying TT and differentiating it from bland thrombus is studied.[11] This case of unusually large TT in SVC detected on ¹⁸F-FDG PET/CT scan highlights the ability of ¹⁸F-FDG PET/CT scan to identify TT and clearly demonstrate the pattern of disease in suspected recurrence in triple negative breast cancer patients.