Microscopic description and IHC:
The mass is a multilocular cystic structure with serosanguineous fluid lined by thin walls. Gelatinous and hardened structures are adherent to the cystic wall throughout the surface. No grossly identifiable mature components (e.g., hair) is found.
Microscopically the mass is composed of numerous neuroepithelial elements merging with a cellular stroma. No other mature tissues is identified.
Discussion:
Immature teratoma is a type of malignant ovarian teratoma seen in children and adolescents. It can be composed of a mixture of embryonal and adult tissues derived from all three germ layers. However, the main component is the neuroepithelial element.
Grossly, immature teratoma can be solid throughout, solid with multiple minute cysts, or predominantly cystic.
The Norris grading system can determine the likelihood of metastatic spread; grade 1: abundant mature tissue, loose mesenchymal tissue with occasional mitoses, immature cartilage and tooth anlage; grade 2, less mature tissue than grade 1, rare foci of neuroepithelium with mitoses, < 4 low power fields in any one slide; grade 3, little / no mature tissue; numerous neuroepithelial elements merging with cellular stroma occupying 4+ low power fields.
Staining for GFAP can be helpful in identification of mature and immature glial tissue.