A 52-year-old woman presents with progressive headaches and mild cognitive decline over 6 months. MRI brain shows a well-demarcated, homogeneously enhancing mass arising from the dura with a broad-based attachment and perilesional edema. Histopathology reveals meningothelial cells arranged in the characteristic pattern marked **A** in the diagram. Which of the following best describes the biological significance of this histological finding in meningioma?

Explanation

## Why option 1 is correct The characteristic whorl-like arrangement of meningothelial cells (marked **A**) is the classic histological hallmark of benign meningioma, typically WHO Grade 1. This organized, orderly growth pattern reflects the slow-growing, extraaxial nature of the tumor, which arises from arachnoid cap cells of the meninges and compresses rather than invades the adjacent brain. According to Robbins 10e Ch 28, approximately 80% of meningiomas are benign (WHO Grade 1) and present with this characteristic histology, often accompanied by psammoma bodies. The whorled arrangement is a direct expression of the tumor's benign biological behavior and favorable prognosis. ## Why each distractor is wrong - **Option 2**: Whorl formation is NOT indicative of high-grade malignancy. WHO Grade 3 (anaplastic) meningiomas show sarcoma-like features, high mitotic rates, and loss of organized architecture—not whorls. Whorls are seen in benign tumors with 10–30% recurrence over 10 years, not the 60–70% recurrence of Grade 3 tumors. - **Option 3**: Whorl-like cell arrangement indicates an extraaxial tumor that compresses the brain (as shown by structure **D** in the diagram), not invasion. Meningiomas are characteristically non-invasive; brain invasion is actually a feature of atypical (Grade 2) meningiomas and raises the grade classification. - **Option 4**: While NF2 is a risk factor for multiple meningiomas and is associated with bilateral vestibular schwannomas, the presence of whorls alone is not pathognomonic for NF2. Most sporadic benign meningiomas also show this histology. NF2 diagnosis requires genetic testing and imaging surveillance, not histological whorls alone. **High-Yield:** Whorls of meningothelial cells = benign meningioma (WHO Grade 1), slow-growing, extraaxial, ~80% of all meningiomas; Grade 2–3 tumors lose this organized architecture. [cite: Robbins and Cotran Pathologic Basis of Disease, 10th edition, Chapter 28]