Histologic Findings NOT Characteristic of Meningiomas
"Orphan Annie eye" nuclei are NOT a characteristic histologic finding of meningiomas—this feature is classically associated with papillary thyroid carcinoma, not meningiomas.
Classic Histologic Features of Meningiomas
The characteristic microscopic features of meningiomas include 1:
- Meningothelial whorls (whorl formation of cells): Concentric arrangements of meningothelial cells forming characteristic whorled patterns 2, 3
- Psammoma bodies: Laminated calcified structures that develop within meningocytic whorls, formed through calcification of collagen fibers synthesized by meningothelial cells 1, 4, 5
- Nuclear pseudoinclusions: Invaginations of cytoplasm into the nucleus creating inclusion-like appearances 2
- Nuclear holes: Clear spaces within nuclei 2
Why Each Option Matters
Psammoma Bodies (PRESENT in Meningiomas)
Psammoma bodies are definitively characteristic of meningiomas, representing calcified structures within meningocytic whorls 1. Ultrastructural studies demonstrate these form through matrix vesicles produced by meningothelial cells that serve as initial calcification nidi, with collagen and elastic fibers playing crucial roles in crystal deposition 4, 5.
Whorl Formation (PRESENT in Meningiomas)
Whorled architectural patterns are a hallmark feature, with cells arranged in concentric layers 1, 2. These whorls can be paucicellular or acellular collagen whorls in certain variants like whorling-sclerosing meningioma 6.
Pseudorosettes (PRESENT in Meningiomas)
While not mentioned as prominently as whorls and psammoma bodies in the provided evidence, pseudorosette formation can occur in meningiomas as part of their diverse morphological spectrum 3.
Orphan Annie Eye Nuclei (NOT PRESENT in Meningiomas)
This is the correct answer. Orphan Annie eye nuclei—characterized by optically clear nuclei with peripheral chromatin condensation—are pathognomonic for papillary thyroid carcinoma, not meningiomas. The nuclear features of meningiomas include pseudoinclusions and nuclear holes, which are distinctly different morphologic findings 2.
Clinical Pitfall
A common diagnostic error would be confusing nuclear pseudoinclusions (which ARE present in meningiomas) with Orphan Annie eye nuclei (which are NOT). Nuclear pseudoinclusions represent cytoplasmic invaginations, while Orphan Annie eyes represent true nuclear clearing with a different pathophysiologic basis 2.