Tumor cells forming sinusoids connected to vasculature are involved in hemorrhage of pineal choriocarcinoma.

Intratumor hemorrhage is a poor prognostic factor in pineal choriocarcinoma (PCCC). The aim of this study was to understand the relationship of tumor cells to the blood vessels to gain insights into the formation of intratumor hemorrhage in PCCC. The clinical data indicated that total tumor removal by surgical procedures followed immediately by radiotherapy and chemotherapy improved the prognosis in PCCC. The PCCC tissues removed from the patients were examined by histology and immunohistochemistry. Hematoxylin and eosin staining showed that the tumor stroma mainly consists of hemorrhagic tissues with tumor cells scattered inside. The pattern of distribution suggests that the tumor cells were possibly flushed and compressed by the bleeding. The tumor cells tended to form sinusoids that lacked CD34, but laminin expression provided evidence of vasculogenic mimicry. Interestingly, CD34-positive blood vessels were found connected to these sinusoids, suggesting that blood may flow from the tumor vasculature to the sinusoids. This may subsequently cause the enlargement of the sinusoids, blood clotting, the widening of the blood lakes, and eventually extensive hemorrhagic necrosis. Our study identified the key features of the PCCC vasculature. The findings add to the previous understanding of the formation of vascular channels, blood lakes, and extensive hemorrhagic necrosis. The intimate connections between the tumor-formed sinusoids and the blood vessels might be a major cause of severe hemorrhage in PCCC. The new information may be useful for the development of treatment strategies for managing PCCC.