RESUMO
Context: Diagnosis of primary NETs (neuroendocrine tumors) is challenging and often late due to tumor heterogeneity, and a wide variety of general symptoms. Low grade NETs are often indolent and have a good prognosis, especially in the early stages. Even so, some tumors are diagnosed using SPECT/CT either in the metastatic stage or directly as a metastasis with an unknown primary tumor. Objective: This study aims to characterize well and moderately differentiated NETs, using Tektrotyd SPECT/CT imaging as well as from the viewpoint of NET immunohistochemical biomarker expression. Design: Patients diagnosed with low grade neuroendocrine tumors (carcinoids) investigated over a period of 2 years, using SPECT/CT with 99mTc-EDDA/HYNIC-Tyr3-Octreotide (Tektrotyd) and confirmed through at least two immunohistochemical neuroendocrine markers were evaluated. Subjects and Methods: Twenty-seven cases with neuroendocrine tumors were analyzed. Four patients met the inclusion criteria. Staining intensity was scored using a weak, moderate, or strong scoring system. CD56 was quantified using criteria derived from Her2 cell membrane staining evaluations. Results: Patients included in the study had two well differentiated (G1) NETs and two moderately differentiated (G2) NETs. SPECT/CT with Tektrotyd showed variable intensity ranging from discreet to strong. All tumors expressed chromogranin A with at least moderate intensity, weak to moderate intensity for synaptophysin and variable CD56 intensity. Conclusions: Chromogranin A and synaptophysin staining patterns may aid in primary tumor identification. CD56 stain intensity showed an inverse correlation with Tektrotyd uptake in carcinoids. Additional studies merit further investigation for use in clinical settings.