Malignant Transformation of a Hormone Receptor-Positive Benign Intracranial Meningioma During Pregnancy: A Case Report.

Meningiomas are predominantly benign, more prevalent in women, and related to sex hormones. Malignant transformation during pregnancy, however, is exceptionally rare. We report the case of a 22-year-old woman with a WHO Grade I fibrous meningioma that was completely resected. One year later, during pregnancy following ovulation induction therapy, she developed a recurrence, histologically confirmed as a WHO Grade II atypical meningioma. After delivery, a second recurrence occurred, with progression to WHO Grade III anaplastic meningioma. Immunohistochemistry consistently revealed progesterone receptor (PR) positivity and absence of estrogen receptor (ER) expression. This case represents one of the rare documented instances of malignant transformation of a benign meningioma during pregnancy without prior radiotherapy. It emphasizes the potential influence of pregnancy-related hormonal changes in tumor progression and highlights the importance of close surveillance with multidisciplinary management in reproductive-age women with meningiomas.