Malignant transformation of struma ovarii is a rare event observed in about 5% of cases. We present here an unusual case that closely simulated highly differentiated follicular carcinoma, an entity with a relatively similar appearance to malignant struma ovarii. In our case, peritoneal and systemic dissemination occurred 18 y after excision of struma ovarii, which had been reported as histopathologically benign. There were 3 noteworthy features in the case: the highly functioning nature of the lesions (evidenced by a low level of thyroid-stimulating hormone even without thyroxine suppression); the low to minimal 18 F-FDG avidity of the foci, which reiterates the well-differentiated nature of these lesions, as expected in highly differentiated follicular carcinoma; and prominent involvement of rare sites such as spleen and liver, in addition to usual sites such as lungs, peritoneum, and bilateral adnexae.

[¹³¹I]MIBG therapy can be of significant value in the treatment of patients with chemotherapy-resistant stage III and IV neuroblastomas who demonstrate good tracer uptake in diagnostic scans. MIBG therapy has the potential to stabilize the disease and provide symptomatic improvement in patients with metastatic/recurrent pheochomocytoma/paraganglioma and medullary carcinoma thyroid and carcinoid in which there is evidence of tracer accumulation in the tumor. Both single high dose or multiple fractionated doses are equally effective in improving the quality of life in metastatic/recurrent pheochomocytoma/paraganglioma.

Although FDG PET/CT evaluation of liver nodules still has limited application in routine clinical practice compared with the conventional imaging modalities (US, CT and MRI), it nevertheless seems to have certain potentially useful roles in this setting. Two major determinants of the diagnostic sensitivity of PET/CT in hepatocellular carcinoma (HCC) are (1) the degree of differentiation (related to varying levels of glucose transporters and glucose-6-phosphatase activity, with well-differentiated tumors being suggested to show low expression of GLUT and high dephosphorylating enzyme activity and undifferentiated tumors to show high expression of glucose transporters and low dephosphorylating enzyme activity), and (2) the size of the lesion. The diagnostic efficacy of FDG PET/CT could be enhanced on delayed imaging. An inverse correlation has been described between FDG PET/ CT and choline/acetate PET. The literature underlines the role of choline and acetate in detecting and staging well-or moderately differentiated HCC, in which these PET tracers demonstrate better efficacy compared with FDG. The dualtracer approach using tracers like FDG and acetate is suggested to provide the best diagnostic accuracy. Disease prognostication and staging of extrahepatic metastasis both benefit from whole-body staging with FDG PET/CT. In cholangiocarcinoma, the major factors determining the sensitivity of FDG PET/CT are (1) hilar versus peripheral subtype and (2) nodular versus infiltrating morphology. FDG PET/CT can serve an adjunct to conventional imaging in differentiating benign from malignant lesions, with hemangioma, FNH, and hepatic adenoma usually showing tracer accumulation similar to, or lower than, the background physiological liver activity although a small number of false positives are observed. The non-FDG tracers have been investigated in this setting in a limited number of patients and have been found not to be of incremental value.