PET/CT follow-up

• ~30% malignancy risk — dedicated thyroid US.
• US findings drive FNA per ACR TI-RADS.
• Diffuse uptake suggests thyroiditis — correlate with TSH/antibodies.

Source: Incidental PET/CT thyroid uptake reviews

• High malignancy / adenoma risk — colonoscopy.
• Diffuse uptake is usually physiologic / inflammatory.
• Cecal/right-sided focal uptake especially concerning for adenoma in older adults.

Source: Consensus reviews

• SUV greater than liver: suspicious — dedicated adrenal CT/MRI.
• <10 HU on non-contrast CT correlates with adenoma despite mild uptake.
• In known malignancy, biopsy if imaging features remain indeterminate.

Source: ACR Incidental Adrenal Mass white paper

• Sub-cm nodules can be falsely negative; correlate with Fleischner.
• FDG-avid solid nodule >8 mm → biopsy or short-interval CT.
• Carcinoid and bronchoalveolar carcinoma can be FDG-negative.

Source: Fleischner Society 2017

• Focal uptake → endoscopy to exclude carcinoma or high-grade dysplasia.
• Diffuse linear uptake typically reflects esophagitis or reflux.

Source: SNMMI / consensus reviews

• Solitary focal uptake — dedicated US or contrast-enhanced MRI of the gland.
• Warthin tumor and pleomorphic adenoma are common FDG-avid benign mimics.
• Bilateral symmetric uptake often physiologic; assess for sialadenitis.

Source: EANM head-and-neck guidance

• Focal marrow uptake without CT correlate → MRI to exclude metastasis.
• Diffuse marrow uptake post-G-CSF or chemotherapy is expected (reactive).
• Sclerotic, FDG-negative lesions can still be metastatic (e.g., treated prostate).

Source: EANM/SNMMI FDG PET oncology guideline

• Any focal uptake in a non-lactating breast → diagnostic mammography ± US.
• Biopsy if BI-RADS 4 correlate is identified.
• Bilateral diffuse uptake usually physiologic / lactational.

Source: ACR / EANM consensus

• Focal pancreatic uptake → contrast-enhanced pancreas-protocol CT or MRI/MRCP.
• Autoimmune pancreatitis can mimic malignancy — correlate with IgG4 and morphology.
• Solid mass with uptake → EUS-guided biopsy and oncology referral.

Source: ACR Appropriateness Criteria

• Score 1–2: complete metabolic response.
• Score 3: usually complete response in interim PET (Hodgkin / DLBCL trials).
• Score 4–5: partial / no response — consider biopsy or therapy escalation.

Source: Lugano 2014 / Deauville 5-point scale