PATH-34. IT NEVER RAINS BUT IT POURS - DIAGNOSING ANAPLASTIC PLEOMORPHIC XANTHASTROCYTOMA TWICE IN A FORTNIGHT - OUR EXPERIENCE IN A RESOURCE CONSTRAINED SETTING

Abstract Grade 3 Pleomorphic Xanthastrocytoma is a rare tumour (less than 1% of all astrocytic glial neoplasms). Present most commonly with seizures. Surgery and Radiation remain the mainstay of treatment with no clear role for traditional systemic chemotherapies; BRAF inhibitors show some benefit. We report two cases who were diagnosed within a month of each other - one was initially diagnosed in 2017- presented with altered smell, headache and diplopia. Found to have a well-defined lobulated heterogeneously enhancing suprasellar parasellar lesion. After Gross Total Resection, was diagnosed from various centers as Anaplastic Ependymoma WHO Grade III; Gllioblastoma WHO Grade IV; Anaplastic Pleomorphic Xanthastrocytoma WHO Grade III. Based on immunohistochemistry, was considered Anaplastic Ependymoma WHO Grade III. Spine screening was negative; received adjuvant Radiation 60Gy in 30 fractions. After a disease free interval of 6 years, developed a recurrence at the post op site. He underwent repeat decompression and the histopathology showed Grade 3 Pleomorphic Xanthastrocytoma. Immunohistochemistry- OLIG2: diffuse positive; R132H p.IDH1: negative; ATRX: intact nuclear expression; Mismatch repair proteins (MSH2, MSH6, MLH1, PMS2); intact nuclear expression; MIB-1 labelling index: 10-12%; H3 p.K27M: negative; GFAP: variable positivity; Podoplanin and p53 shows focal positivity; EMA, CD 34 are negative. He competed Reirradiation in January 2024. He is asymptomatic and on follow up. The second case -15 year old boy presented with episodes of absence seizures. Imaging showed a predominantly extraaxial lesion at tentorial apex. He underwent decompression and histopathology showed Grade 3 Pleomorphic Xanthastrocytoma. Immunohistochemistry - cells positive for S100 and variably positive for GFAP, OLIG2 and vimentin; ATRX: Retained expression, IDH1p.R132H, EMA, Synaptophysin, Neu N: Negative, p53: Focally positive, CD34: Positive in few tumour cells, Ki-67: 14-16 %.V600 mutation detected in the BRAF gene. Had Adjuvant RT 60 Gy in 30 fractions -completed in March 2024. MRI at 1 month - no significant change in overall tumour burden compared to post operative MRI. Was offered Dabrafenib with Trametinib.