Paraneoplastic Limbic Encephalitis Secondary to SCLC on 18F-FDG PET/CT.

ABSTRACT: A 67-year-old man with rapidly neurologic deterioration and 15 kg weight loss in 2 months was extensively evaluated by several medical specialties and conventional image examinations, with no diagnostic definition. 18F-FDG PET/CT was performed, showing glycolytic hypermetabolism in the hippocampus, cerebral hypometabolism with posterior temporoparietal pattern, multiple cervical and supraclavicular lymph nodes, and mediastinal hypermetabolic and enlarged lymph nodes, suggesting paraneoplastic limbic encephalitis, Alzheimer dementia, and lymphoma. Lymph node biopsy resulted in small cell lung carcinoma. The patient presented rapid clinical deterioration and died.

68Ga-DOTATATE and 18F-FDG in Castleman Disease.

A 35-year-old woman with rectal neuroendocrine tumor, Ki-67 proliferation index less than 2%, and a mediastinal mass on CT postoperatively was referred for restaging with PET/CT Ga-DOTATATE. The examination showed uptake on the pelvic lymph node and mediastinal mass. Because of differences in lesions' SUVs and clinical presentation, the hypothesis of lymphoma for the mediastinal mass was raised, and F-FDG PET/CT was performed, which showed glycolytic hypermetabolism in the mediastinal mass and absence of hypermetabolism in pelvic lymph nodes. Transthoracic biopsy of the mass revealed atypical large-cell lymphoid proliferation, and immunohistochemistry study was compatible with Castleman disease.

Alteração da biodistribuição do MDP-99mTc na cintilografia óssea após o uso de pamidronato: relato de caso / MDP-99mTc Biodistribution Alteration on a Bone Scan after Pamidronate Therapy: Case Report / Alteración de la Biodistribución del MDP-99mTc en la Cintilografía Ósea tras el Uso de Pamidronato: Informe de un Caso

O pamidronato dissódico, bifosfonato utilizado no tratamento de diversas condições, como hipercalcemia oncogênica, osteoporose e Doença de Paget, pode alterar a biodistribuição do MDP-99mTc na cintilografia óssea. Relata-se um caso de importante redução da fixação óssea e aumento da captação em partes moles e pulmões em paciente neoplásico com metástases ósseas e hipercalcemia oncogênica tratado recentemente com pamidronato intravenoso. O provável mecanismo responsável pela alteração descrita seria a competição do MDP pelo mesmo sítio de ligação do pamidronato nos cristais de hidroxiapatita. Já o acúmulo do radiotraçador nos pulmões pode ser atribuído à provável formação de microcalcificações decorrente da hipercalcemia apresentada pelo paciente. Vale ressaltar, portanto, a importância do conhecimento dessas possíveis alterações pelos especialistas em medicina nuclear, a fim de se evitar erros diagnósticos.

Disodium pamidronate therapy is often instituted for the treatment of various conditions, such as oncogenic hypercalcemia, osteoporosis and Paget’s disease, and could interfere in the biodistribution of MDP-99mTc on bone scan. The authors report a case of important decrease of bone uptake and increase of soft tissues and lungs uptake in a neoplastic patient presenting oncogenic hypercalcemia, who had just been treated with intravenous pamidronate. The more likely mechanism to be responsible for these alterations is the competition of MDP for the same binding site as the pamidronate in hydroxiapatite crystals. Increased lung uptake probably resulted from microcalcifications caused by hypercalcemia presented by the patient. Nuclear medicine physicians should, therefore, be aware of this potential pitfall in order to avoid misdiagnosis.

El pamidronato disódico, bifosfonato utilizado en el tratamiento de varias condiciones, como la hipercalcemia oncogénica, la osteoporosis y la enfermedad de Paget, puede alterar la biodistribución del MDP-99mTc en la cintolografía ósea. Se relata un caso de una importante reducción de fijación ósea y aumento de la captación en partes blandas y pulmones, en paciente neoplásico con metástasis óseas e hipercalcemia oncogénica tratados recientemente con pamidronato intravenoso. El probable mecanismo responsable por la alteración descrita sería la competencia del MDP para el mismo sitio de unión del pamidronato en los cristales de hidroxiapatita. Entretanto, la acumulación del radiotrazador en los pulmones puede atribuirse a la probable formación de microcalcificaciones, como consecuencia de la hipercalcemia manifestada por el paciente. Por lo tanto, vale resaltar la importancia del conocimiento de esas posibles alteraciones por los especialistas en medicina nuclear, a fin de evitar errores diagnósticos.