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immunohistochemistry General concepts: 

  • Immunohistochemistry (IHC) describes the process of staining a piece of tissue with various markers to highlight a particular cell type. 

  • Uses:

    • Further classify a poorly differentiated tumor​ (carcinoma vs. lymphoma vs. melanoma etc)

    • Help determine the primary location of a tumor in a patient who presents only with metastatic disease (lung, colon, breast, prostate etc)

    • Distinguish between in-situ vs. invasive lesions by determining whether the tumor invades beyond the basement membrane, basal cell layer or a capsule.

    • Assess the proliferative rate (Ki-67 stain) and establish the overall prognosis (various genetic mutations identifiable).

    • Predict whether a tumor will respond to a particular therapy by determining whether the a mutation targeted by the drug is present.

    • Detect tiny, single, metastatic tumor cells in a lymph node (such as in melanoma or breast cancer cases).

    • Identify viral or other infectious organisms.

  • Tumors typically stain in a very particular way, BUTTTTT "tumors don't read the textbooks" which means not every single squamous cell carcinoma will stain positive with a cytokeratin.

  • Thus, although IHC can aid in the diagnosis, the morphology seen on routine H&E stain trumps IHC nearly every time. Go by morphology and use the IHC stains as pieces of the puzzle to help you come to the most likely diagnosis!! 

Commonly used stains

Stains Used by Organ System

Lung: TTF-1, surfactant, protein B precursor

Thyroid: TTF-1, TGB, Calcitonin

Others: CK19, Galectin3, HBME, AE1/AE3, Bcl2, beta-catenin, BRAF, CD5, CD117, CEA, Chromogranin, Congored, Ki67, Mammaglobin, P53, P63, PAS, PAX8, PPARy, PTEN)

Melanoma: Vimentin, S-100, HMB-45, Melan A, MITP

Lymphoma: CD45, CD3, CD20, CD23, CD43, CD30

Prostate: AR, AMACR, NKX3.1, Prostein (P501S), PSA, PSAP, PSMA

Germ cell: PLAP, AFP, HCG, CD30, CD117

Breast: GCDFP15, ER, PR, Her2, 

Others: AR, CK7, ,  GATA3, Ki67, E-Cadherin, Mammaglobin, P63

Mesothelium: CK5/6, calretinin, thrombomodulin, N-cadherin, WT-1, HBME-1

GI Stains: Arginase1, CD117, CDX2, Chromogranin, DOG1, Gastrin, H.Pylori, HepPar1, IgG4, Iron, Ki67, PAS, Reticulin, Serum amyloid, A/SAA, SMAD4/DPC4, Synaptophysin, Trichrome

Pancreas: EMA, CA19-9, DUPAN-2, B72.3 (ductal); trypsin, lipase (acinar)

Kidney: RCC, CD10

Adrenal gland: Calretinin, Chromogranin, GATA3, Inhibin, MelanA, S100, Synaptophysin

Neuroendocrine: Chromogranin, 

Synaptophysin, NF, peptides

Sarcoma: Vimentin, Desmin, Actin

Others: myoD1, myogenin, CD31, CD34, factor VIII RA, S100, bcl2

Testis: AFP, CD30, CD117/KIT, D2-40, Glypican3, HCG, OCT3/4, PLAP, SALL4

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