Pilocytic Astrocytoma Arising in Ovarian Mature Cystic Teratoma: An Unusual Neuroectodermal Malignant Transformation Occurring in Pregnant Female

Mature cystic teratomas are usually benign, however malignant transformation occurs rarely. It is identified in only 0.17-02% of cases. Malignant cells can arise from cell of any type, but most common malignant transformation found to be squamous cell carcinoma (80% cases) followed by adenocarcinoma. While neural tissue is identified in nearly 80% cases of mature cystic teratomas, neuroectodermal tissue with malignant transformation is the most exceptional event. There is minimal data available on primary neuroectodermal tumours of ovary, majority are astrocytoma of different grades, only few cases were reported in the literature so far. Authors report a extremely rare and unique case of pilocytic astrocytoma arising from a mature cystic teratoma in a pregnant female. A 33-year-old pregnant female in her first trimester came for regular antenatal visit, Ultrasound (USG) abdomen and pelvis single live intrauterine gestation corresponding to 10 weeks and incidental complex right ovarian cyst likely to be mature cystic teratoma. Patient underwent right ovarian cystectomy five months after normal vaginal delivery and provisional diagnosis was given as complex right ovarian dermoid cyst. Final detailed histopathological examination revealed a tumour with glial tissue within the cyst, reported as pilocytic astrocytoma {World Health Organisation (WHO) grade 1} arising in mature cystic teratoma. To the best of authors’ knowledge this is the third case showing pilocytic astrocytoma component in ovarian teratoma and the first case of this entity occurring in a pregnant female. Authors present an unusual case where radiology gave preliminary diagnosis however, extensive histopathological examination, histochemistry and immunohistochemistry helped in definite diagnosis.