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.

(68)Ga-DOTANOC PET/CT detection of multiple extracranial localizations in a patient with anaplastic meningioma

We report herein a case of a 65-year-old male with intracranial recurrence of atypical meningioma initially treated with a combination of surgical resection and gamma knife radiotherapy. Afterwards, he underwent a (68)Ga-DOTANOC PET/CT scan in order to evaluate the feasibility of peptide receptor radionuclide therapy (PRRT). The scan identified multiple pulmonary, pleural and lymph node localizations. Histological diagnosis was consistent with intracranial atypical meningioma with diffuse metastatic spread. In our case, we have shown that meningioma with extracranial locations may present high uptake of somatostatin receptor analogues. Among other radionuclides, we believe that (68)Ga-DOTANOC PET/CT may be particularly useful for staging, detection of recurrence, evaluation of disease extension and alternative therapeutic approaches.

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.