Immunohistochemistry Techniques

The following table gives an indication of the use of various antibodies to characterize different types of carcinomas. The antibodies include those raised against low molecular weight cytokeratin (LMW-CK), high molecular weight cytokeration (HMW-CK), cytokeratin 7 (CK-7), cytokeratin 20 (CK-20), carcinoembryonic antigen (CEA), and vimentin.

The following table gives an indication of the use of various antibodies to characterize different types of sarcomas. The antibodies include those raised against vimentin, smooth muscle cell specific actin (smc-Actin), desmin, S-100, CD-34 (an endothelial marker), CD-31 (an endothelial marker), and high molecular weight cytokeratin (HMW-CK).

The following table gives an indication of the use of various antibodies to characterize different types of hematologic malignancies. The antibodies include those raised against CD-45 (common leukocyte antigen), CD-3 (a T-cell marker), CD-45RO (a T-cell marker), CD-20 (a B-cell marker), CD-15 (a marker for Reed-Sternberg cells and their variants), CD-30 (a marker for Hodgkin's disease and Ki-1 lymphoma), CD-68 (a marker for macrophage-like cells, or histiocytes, and mast cells), and CD-99.

Examples of Immunohistochemical Stains

A wide variety of antibodies to different tissue antigenic components are commercially available. These antibodies can be utilized to aid in diagnosis of neoplasms, infections, and other conditions. Examples of these uses are given below. The specificity of some antibodies for certain neoplasms is shown in the table. Click on the antibody for an image and description:

Antibody	Specificity
LMW-CK	Carcinomas (neoplasms of epithelial origin)
Vimentin	Sarcomas (neoplasms of mesenchymal oriigin)
GFAP	Gliomas (neoplasms primary to the CNS)
HMB-45	Melanomas (a malignant skin neoplasm that may metastasize widely)
S-100	Neoplasms of neural origin (schwannomas, neurofibromas)
CD-68	Proliferations of mast cells
CD-45	Neoplasms of lymphoid origin
CD-20	Neoplasms of B-cell lymphocytic origin
CD-45RO	Neoplasms of T-cell lymphocytic origin
CD-3	Neoplasms of T-cell lymphocytic origin
CD-15	Hodgkin's disease (non-lymphocyte predominant type)

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In addition, immunoperoxidase staining can aid in determination of therapy for breast carcinoma. This is accomplished via staining for the presence of nuclear estrogen and/or progesterone receptor. The presence of such receptors suggests that the neoplasm may respond to chemotherapy agents such as Tamoxifen that interact via the hormonal millieu of the neoplastic cells. Additionally, staining for cathepsin D and C-erbB2 may indicate biologic behavior of the breast carcinoma.

• Estrogen receptor staining
• Progesterone receptor staining
• Cathepsin-D staining
• C-erbB2 (C-neu) staining

Not only breast carcinomas may show positive staining for estrogen and progesterone receptors. Ovarian, endometrial, thyroid, and some neuroendocrine carcinomas may on occasion also show positivity. Normal breast tissue is positive and serves as an internal control in many biopsies. Other normal tissues may also be positive.

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Immunoperoxidase staining can aid in diagnosis of infectious agents in tissue sections. This can be helpful when the organisms are difficult to see and the inflammatory reaction is not characteristic.

• Toxoplasma gondii
• Epstein-Barr virus (EBV)

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