perivascular rosette
Radial arrangement of tumor cells around blood vessels forming a characteristic architectural pattern. Pathognomonic feature of ependymal tumors.
Full Definition
Perivascular rosettes are highly organized arrangements of ependymal tumor cells that extend radially from central blood vessels, creating a spoke-like pattern. This histological feature is considered pathognomonic for ependymal neoplasms and represents the tumor cells' attempt to recapitulate normal ependymal cell organization around blood vessels. The cells show nuclear-free zones adjacent to the vessel wall, corresponding to the cytoplasmic processes that contact the vessel. Recognition of this pattern is crucial for accurate diagnosis and differentiation from other central nervous system tumors.
Usage
Usage note: Distinguish from perivascular pseudorosettes, which lack the nuclear-free zone and are seen in different tumor types.
In Context
- "The presence of perivascular rosettes in the tumor specimen confirmed the diagnosis of ependymoma." — Histopathology report
- "True perivascular rosettes were identified around multiple blood vessels throughout the neoplasm." — Diagnostic consultation