Brain raspberries: a microvascular finding, seen with anti-collagen 4 staining.

INTRODUCTION: A brain raspberry is a microvascular formation of yet insufficiently known origin and significance, defined histologically as three or more transversally sectioned vascular lumen surrounded by a common perivascular space. Previous reports on the prevalence of this structure have been based mainly on histopathological routine staining with haematoxylin-eosin (HE). The aim of this study was to compare the detectability of raspberries between HE and immunohistochemical vessel staining with anti-collagen 4 (col4). MATERIALS AND METHODS: We used 50 pairs of tissue sections from the cerebral cortex of 40 deceased individuals who had undergone a diagnostic neuropathological examination at the Department of Pathology, Lund, Sweden, during 2019-2022. Raspberries were manually quantified on digitally scanned cortical sections stained with HE and col4, respectively. RESULTS: Staining with col4 showed a higher detectability of cortical raspberries than staining with HE, with an absolute difference of 12.1 raspberries/cm2 and a relative difference of 252.1%. The difference between the two staining methods was statistically significant (P < 0.001). CONCLUSIONS: This study reveals that staining with col4 provides a substantially higher detectability of raspberries compared with HE staining. Immunohistochemical detection is recommended for future studies on the pathogenesis and prevalence of brain raspberries.