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Primary ectopic meningiomas: Report of 6 cases with emphasis on atypical morphology and exploratory
Hao Ni1, Qianqian Yang1, Chenxi Shi1
1Department of Pathology, the First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China.
Aims:
To investigate the histological and immunohistochemical features of primary ectopic meningiomas (PEMs), especially those of primary ectopic atypical meningiomas (PEAMs).
Methods And Results:
We examined 6 cases of PEM, including 2 PEAM cases, which occurred separately in left nasal cavity, left lower lung, right neck, left orbit, right upper lung, and left upper lung by histological and immunohistochemical analysis. In general, of the 6 PEM cases analyzed, 4 cases exhibited morphology of Grade Ⅰ, including 1 fibrous, 1 meningothelial, and 2 transitional variant. The remaining 2 cases shared similar atypical morphology of Grade Ⅱ. The tumors were distributed in sheet-like patterns with loss of architecture of classic meningiomas. Significant hypercellularity, multi-focal necrosis, and thin-walled blood vessels were identified. The mitotic figures were estimated at 6 per 10 high-power fields in one case, and 8 mitotic figures in another. Immunohistochemically, the 6 PEM cases were all positive for Vimentin and EMA, while none showed immunostaining for CKpan, S-100, CD34, STAT6, SMA, Syn or Bcl-2. 4 PEM cases of Grade Ⅰ were immunoreactive for PR but negative for P53, while the 2 PEAM cases displayed negative staining for PR but positivity for P53. As for Ki-67, the positive staining of 4 Grade Ⅰ cases was no greater than 2%, while the positive rates of the 2 PEAM cases were 10% and 20%.
Conclusions:
Our study has expanded cases of PEMs, especially the 2 PEAM cases in rare sites. Our study has also further summarized the pathological features of PEMs, focusing on the histological features of PEAMs, and the immunohistochemical features worthy of further investigations.
Insights
This study details the histological and immunohistochemical characteristics of primary ectopic meningiomas (PEMs), including rare atypical variants (PEAMs) found in unusual locations. Findings highlight distinct molecular markers differentiating typical PEMs from atypical PEAMs, aiding in diagnosis.
Area of Science:
- Pathology
- Oncology
- Histology
Background:
- Primary ectopic meningiomas (PEMs) are rare tumors occurring outside the central nervous system.
- Investigating their histological and immunohistochemical profiles is crucial for accurate diagnosis and understanding their behavior.
Observation:
- Six PEM cases were analyzed, including two primary ectopic atypical meningiomas (PEAMs), located in the nasal cavity, lungs, neck, and orbit.
- Histological analysis revealed sheet-like growth, hypercellularity, necrosis, and varying mitotic rates.
- Immunohistochemistry showed consistent Vimentin and EMA positivity, with distinct PR and P53 expression patterns differentiating Grade I PEMs from PEAMs.
Findings:
- Grade I PEMs (4 cases) showed low Ki-67 (<2%) and positive PR staining.
- Atypical PEAMs (2 cases) exhibited higher Ki-67 (10-20%) and negative PR with positive P53 staining.
- PEMs lacked S-100, CKpan, CD34, STAT6, SMA, Syn, and Bcl-2 expression.
Implications:
- This research expands the case series of PEMs, particularly rare PEAMs in extraneural sites.
- The distinct immunohistochemical markers identified can aid in differentiating benign from atypical ectopic meningiomas.
- Further investigation into these pathological features is warranted for improved clinical management.
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