Article Type : Case Report
Title : Histopathological Benign Transformation of Atypical Meningioma at Recurrence: A Rare Case Report
Abstract : Background: Atypical meningiomas (WHO grade II) are characterized by aggressive behavior and a high recurrence rate. Paradoxical benign transformation to a lower histological grade at recurrence is exceedingly rare.
Case Presentation: We report a case of a 56-year-old female initially diagnosed with atypical meningioma, who underwent gross total resection. On recurrence five years later, imaging revealed a regrown lesion. Surprisingly, histopathological evaluation demonstrated a benign transformation to WHO grade I meningioma. This rare phenomenon prompted a detailed review of the pathological and clinical course, highlighting the possible biological mechanisms and clinical implications.
Conclusion: This case emphasizes the importance of re-evaluating recurrent meningiomas histopathologically, as grade reversal may occur. Further studies are needed to elucidate the underlying mechanisms driving such transformations.
Introduction : Meningiomas are the most common primary intracranial tumors, comprising approximately 30% of cases. They are graded by the WHO into three categories: grade I (benign), grade II (atypical), and grade III (anaplastic). Atypical meningiomas account for 15-20% of cases and exhibit aggressive behavior with a higher recurrence rate than grade I lesions [1-3].
While malignant progression is well-documented, the reverse phenomenon—benign transformation upon recurrence—is rarely described [4]. This report details such an occurrence, exploring potential mechanisms, clinical implications, and the need for cautious interpretation of recurrence.
Case Presentation : Clinical History
A 56-year-old female presented with headaches and episodic seizures. MRI revealed a dural-based lesion in the right parietal region, suggestive of a meningioma. She underwent craniotomy with gross total resection. Histopathological analysis confirmed an atypical meningioma (WHO grade II), characterized by increased mitotic activity (6 mitoses per 10 HPFs), brain invasion, and high Ki-67 index (15%). Postoperative follow-up with annual MRI scans showed no residual disease.
Recurrence
Five years later, the patient presented with similar symptoms. MRI revealed a recurrent lesion in the same location.
Imaging
Preoperative MRI showed a well-demarcated, enhancing lesion with surrounding edema. No signs of aggressive growth or infiltration were noted.
Surgery and Pathological Examination
The patient underwent re-resection of the recurrent tumor. Histopathological evaluation surprisingly revealed features of a WHO grade I meningioma. The tumor was characterized by spindle cells arranged in whorls, with no mitotic activity, necrosis, brain invasion, or increased cellularity. The Ki-67 index was reduced to 3%.
Postoperative Course
The patient experienced an uneventful recovery. At two years of follow-up, no further recurrence was noted.
Discussion : This case underscores a rare histopathological transformation of an atypical meningioma to a benign grade I lesion upon recurrence. Such transformations defy the general progression model and suggest dynamic tumor biology [5].
Findings in Literature: [4-7]
Most studies report malignant progression of meningiomas at recurrence. However, isolated reports of benign transformation exist, often attributed to tumor heterogeneity, selective survival of indolent clones, or the influence of adjuvant therapies.
In a study by Louis et al., benign transformation was linked to effective immune modulation post-surgery.
Epigenetic changes, such as promoter methylation of tumor suppressor genes, have been hypothesized as a potential mechanism.
Clinical Implications:
The phenomenon necessitates routine histopathological reassessment of recurrent meningiomas. It also raises questions about optimal management, as recurrence in benign lesions may not always warrant aggressive therapy [3-5].
Benign transformation of atypical meningioma at recurrence is an extremely rare phenomenon. This case highlights the dynamic nature of tumor biology and underscores the need for further research to understand its clinical and biological implications. Routine histopathological evaluation of recurrent tumors remains essential.
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5. Oya, S., Kim, S. H., Sade, B., et al. (2011). The role of the Ki-67 index as a prognostic factor in meningiomas. Journal of Neurosurgery, 114(2), 643-649.
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