Learning Objective
By the end of this section, learners should be able to recognize key immunohistochemical stains, understand their diagnostic significance, and identify their associated tissue or tumor types.
Key Points
- Immunohistochemistry (IHC) uses antibodies to detect specific antigens in tissue samples.
- IHC is critical for:
- Classifying tumors (e.g., epithelial vs. mesenchymal origin)
- Identifying tissue of origin in metastatic cancer
- Guiding targeted therapy
Examples of High-Yield IHC Stains
| Stain | Target / Use | Notes / Associated Tumors |
|---|---|---|
| Cytokeratin | Epithelial cells | Carcinomas |
| Vimentin | Mesenchymal cells | Sarcomas |
| S100 | Neural crest derivatives | Melanoma, schwannoma |
| GFAP | Glial cells | Astrocytoma, glioblastoma |
| CD45 (LCA) | Leukocytes | Lymphomas |
| CD20 / CD3 | B and T cells | B-cell and T-cell lymphomas |
| Chromogranin / Synaptophysin | Neuroendocrine cells | Neuroendocrine tumors, small cell lung cancer |
| Desmin / Myogenin | Muscle cells | Rhabdomyosarcoma, leiomyosarcoma |
| ER / PR / HER2 | Breast cancer markers | Hormone receptor status, therapy guidance |
| Ki-67 | Proliferation marker | Tumor growth fraction |
