Keywords

FormalPara Objective

  • Learn the importance of immunohistochemistry as an adjunct study in surgical pathology.

Introduction

Immunohistochemistry is a technique based on antigen–antibody binding reaction. It visualizes the distribution and localization of specific antigen or cellular components in tissue sections.

Based on the affinity of mono- or polyclonal antibodies produced in variable species (mostly mouse, rabbit, or goat) to specifically recognize protein epitopes, it helps in recognizing tissue- or cell-specific proteins and can be applied as a direct, an indirect, or a multistep assay. Most of the time a combination of antibodies (“immunohistochemical profile”) is used to confirm a diagnosis.

Diagnostic Use

Organ Diagnosis

  • Intestinal differentiation

    CDX2

  • Thyroid and lung

    TTF-1

  • Prostate

    PSA, PSA-P

  • Lymphoid cells

    CD45

  • Melanocytic cells

    Melan-A, HMB45, S-100

  • Germ cells and liver

    Alpha-fetoprotein

  • Thyroid gland, parathyroid glands, C-cells, beta-islets of the pancreas

    Hormones, hormone receptors and secretory vesicles of neuroendocrine (respectively thyroglobulin, parathormone, calcitonin, insulin, glucagon…).

  • Syncytiotrophoblast

    Beta-HCG

Differentiation

  • Epithelial

  • Cytokeratin (CK1 to CK20, numerated inversely depending on their molecular weight and basic or acidic character). A combination of CK of low- and high-molecular weight will give an idea on the organ systems from where a tumor might come from (e.g., CK7− and CK20+: gastrointestinal tract or CK7+ and CK20−: endometrial origin, biliary tract, mesothelioma).

  • Hematopoietic

  • Cluster of differentiation (CD): broadly present types of antigen at the surface of different hematopoietic cells or subtypes of lymphoproliferative disorders (e.g., CD45 is the common marker of leukocytes). A profile of cluster of differentiation is specific to certain subtypes of leukocytes; Pan-T-cells antigens: CD3, CD5; Pan-B-cells antigens: CD20, CD79a. Clonality of B-cells: kappa and lambda light-chains. Clusters of differentiation are not only present in hematopoietic cells (e.g., CD56 (or NCAM) is expressed in some lymphomas but also neuroendocrine tumor cells).

  • Mesenchymal

  • Vimentin: a common marker of mesenchymal differentiation. It can be encountered in other neoplasms such as melanoma, renal cell carcinoma, and mesothelioma.

  • Neural

  • S-100, GFAP.

  • Muscular

  • Smooth muscle actin; desmin (striated fibers).

  • Vascular

  • Endothelial (CD31, CD34, Factor VIII).

  • Melanocytic

  • Melan-A; HMB45 (naevus cells or melanoma).

  • Neuroendocrine

  • Hormones, hormone receptors, and secretory vesicles of neuroendocrine organs or (sometimes secreting) tumors (thyroglobulin, parathormone, calcitonin, insulin, glucagon, or ACTH …), tumors with neuroendocrine differentiation (chromogranin A, synaptophysin, CD56).

Inflammation

  • Immune deposits

    Immunoglobulins and complement in inflammatory diseases (e.g., IgG4 in IgG4-associated inflammatory diseases).

  • Subtyping of infiltrating leukocytes

    CD3 or CD5: T-cells

    CD20: B-cells

    CD38 and CD138: plasma cells

Tumor Subtypes

  • Mammary carcinoma

    E-Cadherin (+: ductal; −: lobular).

  • Lung/Pleura malignant tumor

    CK7, napsin, EMA, Ber-EP4, TTF-1 (adenocarcinoma) versus CK5/6, p63 (squamous cell carcinoma) versus calretinin, CK5/6, mesothelin, thrombomodulin, WT-1 (mesothelioma).

  • Ovarian carcinoma

    CA125.

  • Gastrointestinal and biliopancreatic carcinoma

    CA19-9.

  • Intestinal adenocarcinoma

    CDX-2.

  • Adenocarcinoma (vs. other carcinomas)

    CEA.

  • Squamous cell carcinoma

    CK5/6, p63.

  • Prostatic carcinoma

    PSA, PSA-P.

  • GIST

    cKIT, DOG1.

  • Adipocytic tumors

    MDM2; CDK4 in well-differentiated and dedifferentiated liposarcoma.

Infections

  • Bacterial

  • Helicobacter pylori; Mycobacterium tuberculosis; Tropheryma whipplei; rickettsia sp.; bartonella sp.; borellia sp.; Treponema pallidum; staphylococcus sp.; streptococcus sp.; clostridium sp.; Escherichia coli.

  • Viral

  • HSV 1 and 2 (herpes simplex viruses); CMV (cytomegalovirus); EBV (Epstein–Barr virus); BK-virus (Polyomavirus); HPV (human papilloma viruses); HHV (human herpes viruses); adenovirus, parvovirus B19; VZV (varicella zoster virus); Hepatitis B or C viruses.

  • Fungal and parasitic

    Candida sp., Aspergillus sp.; Cryptococcus neoformans; Pneumocystis carinii

  • Protozoan

    Leishmania; Toxoplasma gondii; trichomonas Vaginalis; Trypanosomia sp.; Entamoeba histolytica; Giarda lamblia

Theranostic Use

The immunohistochemical detection of the following proteins supports the decision for hormonal deprivation or targeted therapy.

  • Lung adenocarcinoma

  • EGFR, ALK, cMET, ROS1, PD-L1

  • Breast carcinoma

    Estrogen and progesterone receptors, BRCA1&2, HER2, PI3K/AKT, androgen receptor

  • Colon adenocarcinoma

    EGFR, VEGF, VEGFR, KRAS, NRAS, BRAF

  • Gastric adenocarcinoma

    HER2, VEGF, VEGFR, EGFR, c-MET, mTOR

  • Prostatic adenocarcinoma

    PDGFR, HER2, VEGF

  • Melanoma

    BRAF V600E, NRAS, PD-L1

  • Ovarian carcinoma

    VEGFR, PDGFR, BRCA1&2, PD-L1

  • Renal cell carcinoma

    VEGFR, EGFR; PDGFR, HER2, PD-L1

  • GIST

    cKIT, PDGFR-A

Prognostic Use

  • Proliferation marker

    Ki-67 is in many tumors a marker of poor prognosis (gastric, pulmonary; prostatic adenocarcinoma)

  • Cell cycle markers

    Cyclin D-1, p16INK4 in melanoma

  • Oncogenes

    HER2 in mammary, pulmonary or colorectal carcinoma

    Bcl-2 in melanoma

    cKIT in GIST, lung adenocarcinoma, melanoma

    BRAF in thyroid papillary carcinoma, melanoma, colorectal carcinoma, lung carcinoma

    cMET and HGF in testicular tumors

  • Tumor suppressors

    p53 is in many tumors a marker of poor prognosis (gastric carcinoma; lung adenocarcinoma; prostate carcinoma)

    BRCA1 and 2 in breast carcinoma

    PTEN in prostatic adenocarcinoma

  • Vascular and lymphatic markers

    CD31, CD34, podoplanin in melanoma (better detection of angio- or lymphangioinvasion)

  • DNA mismatch repair

    Microsatellite instability syndrome in colon carcinoma (MSH6, MSH2, MLH1, PMS2)

    Neuroendocrine differentiation

    Worse prognosis for prostatic adenocarcinoma

  • Hormone receptors

    Androgen receptor for prostatic carcinoma

    Estrogen- or progesterone receptors in breast cancer