Radioiodine whole body scan pitfalls in differentiated thyroid cancer.

PURPOSE: whole body scan (WBS) performed following diagnostic or therapeutic administration of I-131 is useful in patients with differentiated thyroid carcinoma. However, it can be falsely positive in various circumstances. We aimed to report a series of pitfalls in a clinical perspective. METHODS: A search in the database PubMed utilizing the following terms: "false radioiodine uptake" and "false positive iodine 131 scan" has been made in January 2023. Among the 346 studies screened, 230 were included in this review, with a total of 370 cases collected. Physiological uptakes were excluded. For each patient, sex, age, dose of I-131 administered, region and specific organ of uptake and cause of false uptake were evaluated. RESULTS: 370 cases of false radioiodine uptake were reported, 19.1% in the head-neck region, 34.2% in the chest, 14.8% in the abdomen, 20.8% in the pelvis, and 11.1% in the soft tissues and skeletal system. The origin of false radioiodine uptake was referred to non-tumoral diseases in 205/370 cases (55.1%), benign tumors in 108/370 cases (29.5%), malignant tumors in 25/370 cases (6.7%), and other causes in 32/370 cases (8.7%). CONCLUSIONS: WBS is useful in the follow-up of patients with differentiated thyroid carcinoma, however it can be falsely positive in various circumstances. For this reason, it is critically important to correlate the scintigraphic result with patient's medical history, serum thyroglobulin levels, additional imaging studies and cytologic and/or histologic result.

Case report: Dramatic response to pralsetinib in an elderly patient with advanced RET-fusion positive papillary thyroid carcinoma.

We are recently faced with a progressive evolution of the therapeutic paradigm for radioiodine refractory differentiated thyroid cancer (RAI-R DTC), since the advent of tissue agnostic inhibitors. Thus, tumor genotype assessment is always more relevant and is playing a crucial role into clinical practice. We report the case of an elderly patient with advanced papillary thyroid carcinoma (PTC) harboring RET-CCDC6 fusion with four co-occurring mutations involving PI3KCA, TP53, and hTERT mutations, treated with pralsetinib under a compassionate use program. Despite the high histological grade and the coexistence of aggressive RET co-mutations, an impressive metabolic and structural tumor response has been obtained, together with a patient's prolonged clinical benefit. A timely comprehensive molecular testing of those cases wild-type for the common thyroid carcinoma BRAF V600E-like and RAS-like driver mutations may uncover actionable gene rearrangements that can be targeted by highly selective inhibitors with great potential benefit for the patients.

FDG PET/CT in malignant eccrine porocarcinoma arising in a pre-existing poroma.

In a 61-year-old man with known poroma of right lower abdomen, malignant transformation to porocarcinoma was suspected and confirmed by biopsy. PET/CT was requested for tumor staging, which revealed high FDG uptake in the known skin nodules located in the right side of abdominal and chest wall and identified further some adenopathy in the right axillary. All nodules and axillary lymph nodes were removed, and diagnosis of eccrine porocarcinoma was confirmed. The primary tumor and secondary lesions of porocarcinoma show a high glucose metabolism; thus, PET/CT could be useful for staging, follow-up, and detection of recurrence of patients with eccrine porocarcinoma.

Imported visceral leishmaniasis - unexpected bone marrow diagnosis in a patient with fever, pancytopenia, and splenomegaly.

Leishmaniasis is spreading from mediterranean countries to the north of Europe. The Alps are not an endemic region and there are only few reports of sporadic cases. We report the case of a 72 year old male who presented after a syncope with fever, cough and a sacral skin rash. Clinical examination revealed splenomegaly, elevated liver enzymes and pancytopenia; differential diagnosis included myeloproliferative or lymphoproliferative disorders, infections and auto-immune conditions that cause enlargement of the spleen and liver diseases, however, all tests were negative. In (18)FDG PET computerized tomography, pathological and diffuse uptake in the spleen was seen, with mild and homogeneous FDG uptake in the bone marrow and normal tracer uptake elsewhere in the body. Bone marrow aspiration revealed the presence of numerous intra- and extracellular Leishmania amastigotes. Travel history indicated that he had been in Sardinia for a 7-day vacation several months ago. The patient promptly responded to treatment with liposomal amphotericin B. Imported visceral leishmaniasis is likely to be seen more frequently in non-endemic regions and fever, pancytopenia and splenomegaly are diagnostic clues, whereas diagnostic confirmation may be done by detection of Leishmania spp. amastigotes in the bone marrow.

Clinical significance of axillary findings in patients with lymphoma during follow-up with 18F-fluorodeoxyglucose-PET.

PURPOSE: The aim of this study was to evaluate the clinical significance of positive axillary findings in patients with Hodgkin's disease and non-Hodgkin's lymphoma during follow-up with 18F-fluorodeoxyglucose-PET. MATERIALS AND METHODS: We retrospectively reviewed PET scans carried out in 543 patients during follow-up. Patients with reports describing any increased fluorodeoxyglucose uptake at the axillary level were selected (106 cases) and final assessment of the findings was available in 78 patients (17 Hodgkin's disease, 51 non-Hodgkin's lymphoma). PET scans were performed after standard procedure and reports were interpreted as positive or negative on the basis of visual analysis. At the moment of the scan all patients had no clinical or laboratory sign of relapse, and had not received therapy for at least 6 months. All PET results were compared with other diagnostic procedures (ultrasonography and computed tomography), biopsy and/or follow-up data. RESULTS: Of 78 patients, 24 were PET positive in one axilla, 23 had axillary findings and one or more other extra axillary sites, five patients were positive in both axillas and 26 were positive in both axillas and one or more other sites. Of the 24 patients with single axillary finding, the result for five was true positive and for 19 it was false positive. Sixteen cases of the 23 patients with PET positive at one axilla and other sites had a true positive result, whereas seven had a false positive result. Only one of five patients with both axillas being positive at PET turned out to be true positive; finally, 23 cases from the 26 patients with both axillas and other findings had a true positive result and three of 26 had a false positive result. Overall, 45 out of 78 patients were true positive and 33 were false positive. CONCLUSION: Axillary findings are relatively frequent and can be isolated or in association with other findings. In patients with axillary involvement only the frequency of false positivity results is elevated and therefore these cases need to be evaluated carefully. In contrast, axillary findings associated with other pathological localizations show true positive results in most cases, thus indicating a high likelihood of disease recurrence. Standardized uptake values showed a limited role for discriminating true-positive and false-positive findings.