An undifferentiated malignant tumor on immunohistochemical stain shows cytoplasmic positivity of most of the tumor cells for cytokeratin. The most probable diagnosis of the tumor is: (A) Carcinoma, (B) Lymphoma, (C) Sarcoma, (D) Malignant melanoma
Answer is A. Immunohistochemistry is used for making categorization of undifferentiated tumors. The important examples include: Cytokeratin (carcinoma), Desmin (Leiomyoma and Rhabdomyosarcoma) and vimentin (Sarcomas).