| Summary: | Abstract Background Neuroendocrine tumors (NETs) constitute tumors widely distributed and with heterogeneous biological behavior. For gastrointestinal neuroendocrine tumors (GI-NETs) the following prognostic factors have been identified: location, production of hormones, size and proliferative grade. The latter must be calculated using proliferation index by the number of mitosis or the proportion of tumor cells positive for Ki67 immunostaining. The objective of this study was to use a quantitative tool to calculate the Ki67 index in GI-NETs. Material and methods We reviewed 40 cases of GI-NETs diagnosed at the Department of Pathological Sciences, Santa Casa de Misericórdia de São Paulo Hospital between 2004 and 2014 and compared the Ki67 index by manual count using scanned photomicrographs with semi-automated digital analysis (MC) and eyeball estimation (EE) of the histological slide. After Ki67 immunostaining, the slides were scanned with 3DHistech Pannoramic Scanners. Hot spots were selected and exported in a high-resolution image format and the Ki67 index was calculated with semi-automated image analysis software (AxioVision 3.0). Ki67 immunoreactivity was expressed as the percentage of tumor cells with nuclear staining (number of positive tumor cells/a minimum of 500 total tumor cells). Results We compared the classification of the neuroendocrine tumor by using the two methods in the semi-automated method 26 maintained the same grade, while 14 were re-classified, 4 being upgraded and 10 downgraded. Conclusion In the EE method there was a larger estimate of the percentage of positivity for KI67. As the Ki67 values are the criteria for the classification of neuroendocrine tumors, the semi-automated method can have less error.
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