**Question:** Rosenthal fibres in astrocytoma is composed of

A. axons
B. dendrites
C. neurofilaments
D. astrocytic processes

**Core Concept:** Rosenthal fibres are thin, eosinophilic, neurofilamentous processes that extend from the perivascular spaces to the tumor cells and are commonly seen in astrocytomas. These fibres are derived from astrocytes and are associated with the degree of malignancy of the tumor.

**Why the Correct Answer is Right:** Rosenthal fibres in astrocytoma are composed of astrocytic processes (D), which are extensions of astrocytes that surround the blood vessels and extend towards the tumor cells. These fibres are involved in maintaining the blood-brain barrier and providing structural support to the tumor cells. In astrocytomas, the presence of Rosenthal fibres is associated with increased malignancy.

**Why Each Wrong Option is Incorrect:**

A. Axons (option A) are neuronal processes that do not typically extend from the perivascular spaces to the tumor cells.

B. Dendrites (option B) are neuronal processes that receive synaptic inputs and are not associated with astrocytomas.

C. Neurofilaments (option C) are components of neuronal cytoskeleton and are not involved in the formation of Rosenthal fibres.

**Clinical Pearl:** The presence of Rosenthal fibres in astrocytomas indicates a higher degree of malignancy, making it important for medical students and practitioners to recognize these structures during histopathological examination of brain tumors. A better understanding of Rosenthal fibres can help in grading and prognosis of astrocytomas.