Test Details: Immunohistochemical testing is carried out on biopsy/resected tissue specimen. This testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody. CD99 is widely used as a marker for Ewing sarcoma/PNET family exhibiting a membranous stain. Also expressed in T cell and B cell-ALL, solitary fibrous tumor, T-cell lymphoma, anaplastic large cell lymphoma, AML, GIST, various carcinomas.