An undifferentiated malignant tumour on immunohistochemical stain shows cytoplasmic positivity of most of the tumor cells for cytokeratin. The most probable diagnosis of the tumor is?

Immunohistochemistry Immunohistochemistry is a method of analyzing and identifying cell types based on binding of antibodies to specific components of the cell.o Antibody, which is specific for an antigen of a paicular tissue, is labled with a probe (coloured marker) and is run on the tissue specimen obtained from a biopsy.o If the tissue has that paicular antigen, then antibody will get attached to the tissue and the labled antibody can be seen under a microscope.Intermediate filaments of cytoskeleton are the major antigens used in immunohistochemistry. o There are five major types of intermediate filaments -Cytokeratin Carcinoma, mesothelioma, Non-seminoma GCTVimentin Neurofilament Sarcoma (Tumor of mesenchymal), melanoma, seminomas, lymphoma Neural tumorsGnat fibrillary acid proteins (GFAP) Non-neural brain tissue (astroglial origin --> Astrocytoma, ependymomas, medulloblastoma, oligodendroglioma)Desmin Leiomyoma (smooth muscle) & Rhabdomyoma (skeletal ms).