Pitfalls and solutions in neuroblastoma diagnosis using radioiodine MIBG: our experience about 50 cases.

We have been among the first authors to point out that false negative cases could be observed with 131I-MIBG scintigraphy for neuroblastoma. We have observed until now ten of such false negative cases, 7 with primary tumor and 3 with bone metastases. Fifty 131I-MIBG scans were performed in 35 children with histologically proven neuroblastoma (24 grade IV) and compared to bone scans, CT and NMR images, ultrasound and clinical results. The visualization of the primary tumor shows a higher sensitivity with MIBG (79%) than with bone scans (47%) and a 100% specificity with each method. MIBG and bone scans, for bone metastases, are similar in the sensitivity (87.5%) but MIBG is much more specific (100%) than bone scan (81%). These results clearly confirm the superiority of MIBG scan for detection of primary tumor as well as bone metastases. However, MIBG is not always the most appropriate investigation, as shown by 11 observed pitfalls. Ten false negative cases have been observed and must be considered: in five out of 10 cases, bone scans performed with 99m Tc-HMDP made the diagnosis (3/7 cases of primary tumor and 2/3 cases of bone metastases). Moreover, one case was not usable due to a large digestive uptake. Our aim is to understand the reasons of the false negative by a meticulous analysis of every single case. The optimal procedure for neuroblastoma diagnosis, extent and follow up clearly seems to be the following strategy: MIBG scan must be firstly performed; in case of non-demonstrative scan the bone scan, which is complementary, will greatly contribute to the diagnosis.

Radionuclide bone imaging in diaphyseal aclasis with malignant change.

Chondrosarcoma is a rare complication in hereditary multiple exostoses. The six patients in this study have had a complete follow-up and constitute the largest group of such cases to have been studied so far. Five patients had histologic evidence of malignancy. Since histologic examination can be very difficult, any other diagnostic features, may it be clinical, radiologic, or scintigraphical, should be taken into account for early surgical treatment. Bone scintigraphic examination is a valuable adjunct to early diagnosis of malignant change by showing highest uptake in malignant areas. It is also very useful for posttherapeutic follow-up.

The hyperactive halo as a sign of renal graft death in 99mTc-DTPA studies.

In scintigraphic studies of renal transplants the absence of renal perfusion and clearance have been demonstrated to have many possible pathologic etiologies, vascular obstructions, and rejections. Increased perinephric activity was suggested as a sign of renal infarction and its absence may indicate potential renal viability. A case is presented in which a hyperactive halo was seen when the graft was dying.