Adrenocortical Carcinoma with Inferior Vena Cava Thrombus on ¹⁸F-FDG-PET-Computed Tomography

A 57-year-old man presented to surgery outpatient department with intermittent abdominal pain in the right hypochondrium for 3 months. Contrast-enhanced computed tomography (CT) of the abdomen was advised which showed a heterogeneous mass with few necrotic areas measuring ~12.2 cm × 11.8 cm × 13 cm in the right suprarenal region with hypodense area in the intrahepatic inferior vena cava (IVC). On suspicion of adrenocortical carcinoma (ACC), biochemical tests were done, which showed elevated serum cortisol and Dihydroepiandosterone DHEA levels, suggestive of secretory activity of the tumor. Considering surgery as the curative treatment option, the patient was referred for ¹⁸F-FDG-PET-CT scan to rule out any distant metastasis. PET-CT findings revealed a large FDG avid heterogenous right suprarenal mass [Figure 1a-j]. Right adrenal was not visualized separately. FDG avid IVC thrombus(Standard uptake volume SUV_max~7.6) extending up to the right atrium was also seen [Figure 1e-j dashed black and white arrows]. Fine-needle aspiration cytology of the mass was consistent with features of ACC. The patient underwent right adrenalectomy with IVC thrombectomy, and the histopathology was consistent with ACC.

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Figure 1 (a) MIP of PET-computed tomography image showing FDG uptake in the right hypochondrium of the abdomen. (b) Axial computed tomography image showing right suprarenal mass and hypodense lesion in inferior vena cava showing increased FDG uptake in PET (c, solid black arrow) and fused PET-computed tomography image (d, solid white arrow). (e) Hypodense lesion in the right atrium showing FDG uptake in the PET (f, dashed black arrow) and fused PET-computed tomography (g, dashed white arrow). (h-j) Coronal images showing FDG avid tumor thrombus extending from the inferior vena cava (solid black and white arrows) to the right atrium (dashed black and white arrows)

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ACC is a rare and aggressive neoplasm with a very poor 5-year survival rate of 15%–44% in a series reported in the literature.[123] These neoplasms tend to grow very rapidly with common sites of metastases being liver, lung, and local invasion into kidneys, renal veins, and IVC.[4] Few case reports have highlighted the pattern of FDG uptake in IVC thrombus in case of ACC.[56] Sharma et al. in their series of 24 patients have demonstrated that avidity of FDG quantitatively assessed by SUV_max can differentiate between a benign and malignant tumor thrombus.[7] Most of the malignant thrombus had a SUV_max of >6.0, and in our case also, SUV_max of 7.6 was suggestive of a malignant tumor thrombus. Our case reiterates the fact that ¹⁸F-FDG-PET-CT can be helpful in the detection of primary tumor with local venous and visceral invasion as well as distant metastases in cases of ACC.