In a brain biopsy showing intermediate filaments of the cytokeratin type, from which cell type did the tumor most likely originate?

• A. Astrocytes
• B. Mesenchymal cells
• C. Epithelial cells
• D. Neurons

Answer: (C)

The presence of intermediate filaments of the cytokeratin type in a brain biopsy indicates that the tumor is likely derived from epithelial cells. Cytokeratins are a specific type of intermediate filament that are found in epithelial tissues, which play a crucial role in providing structural support and integrity to cells.

In the context of the brain, the most commonly referenced tumors that originate from epithelial cells are meningiomas, which can exhibit cytokeratin positivity. These tumors arise from the meninges, the protective layers covering the brain and spinal cord, which are composed of epithelial cells.

Other cell types listed, such as astrocytes or neurons, typically contain different types of intermediate filaments. Astrocytes, for example, primarily contain glial fibrillary acidic protein (GFAP), while neurons contain neurofilaments. Mesenchymal cells can give rise to tumors such as sarcomas, which are not characterized by cytokeratins.

Thus, the identification of cytokeratin type intermediate filaments indicates a tumor of epithelial origin, solidifying the conclusion that the tumor most likely arose from epithelial cells.