The incidence of Aneurismal Bone cyst has increased in worldwide. ABC-like lesions involving Giant (GCTOB) cells, fibrohistiocytic or tumor FD like components can confuse pitfalls of ABC and need to observe and defines. We investigated tissue resources from operative materials of total 28 cases of ABC, selected as primary ABC without any bone pathology (n=17) and ABC-like changes accompanying by Giant cell tumor (n=9) and Fibrous dysplasia (FD) (n=2). Female – 10, male – 18, mean age - 27. Cases were reported according clinical, radiological, histological, localization and recurrence features with special attention to immunohistochemistry (IHC) using different markers: P53, Bcl-2, P63, Ki-67, CD68, Cyclin D1. The results of these assessments were compared for the final histologic diagnosis. Results show that IHC has a positive value in dysplastic and cancerous stroma in GCTOB (P63, Cyclin D1); FD field does not show similar activity, demonstrating improved diagnostic accuracy.