Cytological and Immunohistochemical Analysis of Human Fetal Brain across Different Gestational Ages.

Introduction: Human fetal brain development involves complex processes of cellular proliferation, neuronal migration and differentiation. Although several studies have independently evaluated cytology or immunohistochemistry in fetal brain development, integrated analyses using both approaches remain limited. Methods: This descriptive observational study was conducted on brain tissues obtained from nine aborted human fetuses of different gestational ages distributed across the first, second and third trimesters. Fetuses with visible congenital anomalies, autolysis, or damaged brain tissue were excluded. Histological evaluation was performed using Masson's trichrome and reticulin stains. Immunohistochemical analysis was carried out using Ki-67, c-myc and Ber-H2 (CD30) antibodies. Immunostaining intensity was graded semi-quantitatively on a scale from 0 to 4+ according to the percentage of immunoreactive cells. Results: Developing neuronal cells and pyramidal neurons were observed predominantly in later gestational stages, along with scattered oligodendrocytes and reticular fibers. Immunopositive cells were mainly localized in the white matter and ventricular regions, whereas comparatively lower staining was observed in the granular layers. Progressive increases in immunoreactivity were observed with advancing gestational age, particularly in the ventricular zone, cortical plate and white matter. Among the markers studied, Ki-67 demonstrated the highest immunopositivity, followed by c-myc and Ber-H2 (CD30). Conclusion: The present study demonstrates gestation-related variations in the immunohistochemical expression of Ki-67, c-myc and Ber-H2 (CD30) in the developing human fetal brain. These findings contribute baseline developmental data that may assist future studies investigating fetal neurodevelopment and neuropathological conditions.