Atypical Teratoid/Rhabdoid Tumor (AT/RT) shows a variety of histologic patterns and is composed of large cells with or without rhabdoid features. Some cases contain PNET-like areas and epithelial and mesenchymal elements. Brisk mitotic activity, necrosis (seen at upper left in this image), and dystrophic calcification are common findings. Some cases are composed of small round blue cells and resemble medulloblastoma. Others may show cords of cells in a myxoid matrix resembling chordoma, chondroid differentiation, or epithelial cells in a gland-like arrangements. This teratoma-like spectrum accounts for the term "teratoid."