Immunohistochemistry Flashcards
4 steps of IHC staining
- Fixation and processing
- Blocking non-specific background staining
- Detection systems
- Antigen retrieval
Purpose of Fixation in IHC
To optimize preservation because this affects morphologic and immunohistologic results.
Qualities of a good fixative
- Should preserve antigenic integrity
- Should limit extraction, diffusion or displacement of antigen during processing
- Should give good preservation of morphology
Coagulant fixative
Ethanol
Produce fewer changes in intermediate filaments and immunoglobulins, than cross-linking fixative
Cross-linking fixative
Formaldehyde
Alter the IHC results for a significant number of antigens
Advantages of formalin as fixative
(Fixation time dependent)
- Preservation of morphology
- Economical
- Sterilize tissue specimen
- Carbohydrate antigens are better preserved
- Low molecular weight antigens are well-preserved
2 aspects to blocking of background staining of tissues
- Nonspecific antibody binding
2. Presence of endogenous enzymes
Methods of blocking nonspecific background staining
- Quenching endogenous peroxidase by an H202 methanol solution
- Blocking endogenous biotin by using the avidin-biotin blocking agent, or skim milk
- Normal serum will act as a secondary Ab to block nonspecific binding sites
2 types of detection system
- Direct
2. Indirect
Principle of detection system
Attach certain labels or flags to antibodies in order to visualize the target ab-ag localization in the tissue sections
Properties of direct conjugate-labeled antibody method
Uses one labelled ab, which binds directly to ag.
Purity or specificity.
Rapid, easy.
Monoclonal.
Sensitivity is low due to low signal amplification.
Properties of indirect or sandwich detection system
Versatility is increased.
The primary ab can often be used at a higher working dilution to achieve successful staining.
The secondary ab is prepared with high order of specificity and affinity.
More sensitive due to signal amplification through several secondary ab reactions with different ag sites in the primary ab.
Streptavidin-peroxidase complex as detection system
Peroxidase enzyme oxidizes DAB, turning it into a brown pigment.
This pigment precipitates out of solution as a brown solif, located at the site of the antigen.
2 types of antigen retrieval or epitope unmasking
Enzyme (trypsin, pepsin, pronase, ficin, prot K, protease 24, saponin.
HIER (WB, Pressure-cooker, microwave, autoclave, etc)
HIER retrieval solutions / buffers
Na Citrate pH 6
EDTA pH 8
citric acid buffers
Tris buff pH 9.5
Consistent results in terms of ag preservation
10% NBF
10% zinc formalin
10% formal saline
The first antigen retrieval method to enhance staining
Enzymatic digestion
Light to Med at 37C for AE1/AE3, B72.3, Factor XIIIa, HAM-56
Trypsin
Strong at 37C for CK7, CK20, Pan CK, Lu-5(7’)
Pepsin
Extra strong at room temp for EGFR (5’)
Protease 24
Very very strong.
Conc x time study necessary
Protinase K
3 broad categories with respect to the importance of pH in Ag Retrieval
- Most ag showed no sig variation using AR solutions with pH ranging 1-10.
- Nuclear ag (ER) showed dramatic decrease in intensity at mid-range pH but optimal at low pH.
- Some ag (HMB 45) are weak at low pH (1-2) but excellent in the high range.
IHC staining steps (shortcut)
Deparaffinization Ag retrieval Block unoccupied sites Add primary abs Add secondary abs Add substrates for color development
IHC staining Steps (Long steps)
Deparaffinization and rehydration Rinse with buffer Target retrieval - cool Rinse in tap water and distilled water Block endogenous peroxidase Rinse with buffer Primary ab Rinse with buffer Secondary ab Rinse with buffer DAB Rinse with distilled water Hematoxylin Rinse with tap water Coveralip with aqueous resin
Deparaffinization and rehydration (time)
- Xylene - 5mins
- Xylene - 5mins
- Absolute ethanol - 3mins
- Absolute ethanol - 3mins
- 95% ethanol - 3mins
- 95% ethanol - 3mins
- Distilled water (30 secs to 1 min)
Target retrieval
Total: 15-18mins plus 20 mins cooling time = 35-38 mins
High - 5mins Med High/Low - 5mins Med - 5mins Med - 3mins Cooling time - 20mins
In 700-800 watts microwave oven
Hydrogen peroxide blocking (time)
5 minutes
Primary ab (time)
20 mins
Washing in buffer (time)
- Dip 10 times
- Dip 10 times
- Dip 1 min
Labelled secondary ab (time)
15 minutes
Chromogen (time)
10 mins
Types of chromogen
Peroxidase AEC DAB (diaminobenzidine) Vector S-G Vector - VIP Vector Nova Red Alk Phos New Fuchsin Fast Red BCIP/NBT Vector red Vector black
Wash in distilled water (time)
1 min
Counterstaining
Hematoxylin, Light green, methyl green for 30 sec to 1 min
False negative causes
Antigen loss Inadequate ag retrieval Method not sensitive enough Expired ab Wrong reagents or wrong reagent sequence
A method for localizing specific ags in tissues or cells based on ag-ab recognition.
Immunohistochemistry
A pair of light chains and a heavy chain
Antibody
Any molecule that is sufficiently complex to induce ab formation
Antigen
Antigenic determinant.
The exact site on the molecule with which the ab combines.
Epitope
Heterogenous mix of abs that recognize several epitopes on an antigen
Polyclonal
Recognizes a single type of epitope
Monoclonal
Unconjugated (unlabelled) antibody, raised against the ag of interest
Primary ab
Ab raised against the primary abs, conjugated either to biotin or to an enzyme or to fluorescent agents
Secondary antibodies
Applications of IHC
Diagnostic
Theranostic
Genomic
Used to describe the proposed process of diagnostic therapy for individual patients - to test them fir possible reactions to a new medication or to tailor a treatment based on the test resultr
Theranostic
IHC as theranostic
HER2/neu analysis
c-kit testing for GISTS
CD20 in B cell lymphomas
Facilitate recognition of specific genomic aberrations in the patient’s tissues by identifying (or not identifying) the presence or absence of specific aberration or gene signature
Genomic
Examples of IHC as genomic
Testing for microsatellite stability in colorectal CA (MLH1, MSH2, MSH6 or PMS2).
Identification of basal-like breast CA (high grade, ER/PR/HER2 (-), CK5/CK14/CK17 (+), variable EGFR expression.
ER (+)
PR (+)
HER2 (-)
Luminal A
ER (+)
PR (+)
HER2 (+)
Luminal B
ER (-)
PR (-)
HER2 (+)
HER2
ER (-)
PR (-)
HER2 (-)
Basal-like
Perform CK5/6 and EGFR to define more precisely tumors in basal-like group.
Molecular category of Breast CA with high expression of hormone receptors and associated genes (luminal A > luminal B)
Luminal
Molecular category of breast CA with high expression of HER2 and other genes in amplicon. Low expression of ER and associated genes.
HER2
Molecular category of breast CA with high expression of basal epithelial genes, basal cytokeratins; low expression of ER and associated genes; low expression of HER2.
Basal-like
BRCA1-associated cancers
Basal-like
Therapy for luminal type Breast CA
Endocrine therapy (response may be different for luminal A and luminal B) Chemotherapy variable (luminal B > luminal A)
Therapy for HER2 type breast CA
Trastuzumab (herceptin)
Anthracycline-based chemotherapy
Therapy for basal-like breast CA
Platinum-based chemotherapy
Prognosis: luminal type breast ca
Favorable
Prognosis: HER2 type breast ca
Poor
Prognosis: Basal-like breast ca
Poor
Cornerstone in tumor diagnosis
Morphology
Uses of IHC
Unknown tumor type (ie carcinoma vs lymphoma)
Metastatic CA of unknown primary
Further classification of CA and lymphomas
Identification of in situ lesions vs invasive carcinomas for breast and prostate cancers
Grading of gliomas ie Ki-68
Predictive factors to guide specific therapy ie c-Kit, ER/PR, Her2/neu
Identification of extacellular material
Identificatiin of infectious agents
PanCK (+) LCA (-) S100/HMB45/MART-1 tyrosinase (-) Desmin (-) Vimentin (-)
Carcinoma
PanCK (-) LCA (+) S100/HMB45/MART-1 tyrosinase (-) Desmin (-) Vimentin (-)
Lymphoma
PanCK (-) LCA (-) S100/HMB45/MART-1 tyrosinase (+) Desmin (-) Vimentin (+)
Melanoma
PanCK (-) LCA (-) S100/HMB45/MART-1 tyrosinase (-) Desmin (+) Vimentin (+)
Sarcoma
Mesenchymal
Vimentin
CK, EMA
Epithelial
Desmin, HHF35, SmActin
Smooth muscle
Myoglobin
Skeletal muscle
CD68, Factor XIIIa
Fibrohistiocyte
Leu7, GFAP
Nerve sheath
HMB45
Melanocyte
Neurofilament
Neuronal
Factor VIII, CD34, CD31
Endothelial, perivascular
LCA, CD3, CD20
Hematopoietic
NSE, Chromogranin
Neuroendocrine
MIC-2(O-13), CD99
Ewing’s sarcoma/PNET
Transbronchial FNA of a lung lesion showing mostly isolated small cells with pyknotic nuclei. Ddx?
Small cell CA: CK(+) LCA(-)
Lymphoma: CK(-) LCA (+)
Patients having no identifiable primary site, despite a careful clinical hx, PE, radiologic imaging and biochemical and histologic investigations
Metastatic Carcinoma of Unknown Primary (MCUP)
Diagnostic approach to MCUP
Det the cell line of differentiation using major lineage markers
Det the CK type or types of distribution in tumor cells
Det if there is co-expression of vimentin
Der if there is expression of supplemental ag of epithelial or germ cell derivation (CEA, EMA, PLAP)
Det if there is expression of cell-specific products, cell-specific structures or receptors that are unique identifiers of cell types (GCDFP, PSA, TTF-1)
CK7+/CK20+
Transitional cell carcinoma
Pancreatic carcinoma
Ovarian mucinous carcinoma
50% of gastric CA
CL7-/CK20+
Colorectal adenoCA
Merkel cell carcinoma
CK7+/CK20-
Non-small cell CA of the lung Small cell CA of the lung Breast CA, ductal and lobular Nonmucinous ovarian CA Endometrial adenoCA Mesothelioma Squamous cell CA of the cervix
CK7-/CK20-
Squamous cell CA of the lung Prostate adenoCA Renal cell CA Hepatoma Thymus
Prostate (MCUP)
PSA
Se 100
Sp 99
Lung (MCUP)
TTF-1
Se 91
Sp 98
Colon
CDX-2
Se 83
Sp 96
CK20
Se 68
Sp 91
Colon and stomach
CDX-2
Se 56
Sp 98
Colon, stomach, pancreas
CK20
Se 36
Sp 97
Breast
GCDFP-15
Se 54
Sp 96
Breast and ovary
ER
Se 74
Sp 95
Ovary and pancreas
CA 125
Se 88
Sp 88
Mesothelin
Se 85
Sp 85
Stomach and pancreas
Lysozyme
Se 65
Sp 69
CK 7
Se 72
Sp 96
FNA of a cervical lymph node in a patient with no known primary cancer.
Cytology is suggestive of a low grade adenoCA, lung (bronchoalveolar type) or thyroid origin
Metastatic thyroid CA: TTF-1(+) nuclear
TGB(+) cytoplasmic, membranous
Lung adenoCA:
TTF-1(+) nuclear
TGB(-)
Poorly differentiated non-small cell CA in bronchial brushings
Lung Squamous cell CA:
p63 (+)
TTF-1 (-)
Lung AdenoCA:
p63 (+)
TTF-1 (+)
Pleural fluid in a 79yo male. The ddx includes reactive mesothelium, malignant mesothelioma, and adenoCA of lung
Malignant mesothelioma:
Calretinin (+)
TTF-1 (-)
Reactive mesothelium:
EMA- isolated reactive mesothelial cells are highlighted
Pleural fluid cytology from a 64yo female with no prior hx of malignancy. The ddx includes adenoCA and mesothelioma.
Metastatic adenocarcinoma:
Calretinin (-)
TTF-1 (+)
IHC in Hematopathology
Distinguishing reactive conditions from lymphomas.
Distinguishing lymphomas from other malignancies
Classification of lymphomas
Prognosis and staging of lymphoma
Assay of the therapeutic targets
Work-up lineage for lymphoma
CD20+: B cell lymphoma
CD3+: T cell or NK cell lymphoma
CD20-/CD3-: nonhematolymphoid, plasmacytoma, anaplastic lymphoma, t cell lymphoma, lymphoblastic lymphoma
Important markers for classifying lymphomas:
Precursor lymphoblastic lymphoma
TdT
Important markers for classifying lymphomas:
Chronic lymphocytic lymphoma
CD5, CD23
Important markers for classifying lymphomas:
Mantle cell lymphoma
Cyclin D1 (aka BCL-1 and PRAD): nuclear positivity
Important markers for classifying lymphomas:
Follicular lymphoma
CD10 (or BCL-6)
Important markers for classifying lymphomas:
Burkitt lymphoma
Ki67 (~100% proliferation index)
Important markers for classifying lymphomas:
Angioimmunoblastic T cell lymphoma
CD10, follicular dendritic cell markers (extrafollicular meshworks)
Important markers for classifying lymphomas:
Anaplastic large cell lymphoma
CD30, ALK
Biomarkers in prostate CA
PSA - cytoplasmic expression in glandular epithelium
Basal cell markers - p63, HMW-CK
Alpha-methyl-CoA racemase (AMACR) - recently identified as being overexpressed in prostatic adenocarcinoma (80%)
GCDFP-15 meaning
Gross cystic disease fluid protein - 15
IHC panel of small round cell tumors in children
CK - carcinoma
LCA - lymphoma
Desmin - rhabdomyosarcoma
CD99 - Ewings sarcoma/PNET
IHC panel of small round cell tumors in adults
CK - carcinoma
LCA - lymphoma
Vimentin, S100 - sarcoma
Chromogranin/Synaptophysin - PNET
IHC panel of endometrial and endocervical, primary
Both: CK7(-)/CK20(+)
Endocervical: p16, CEA
Endometrial: vimentin, ER
IHC panel in subclassification of the most common lung cancers
SCCA: p63, CK5/6, CK7(-)
AdenoCA: TTF-1, CK7(+)
Small cell: chromogranin/synaptophysin, variable CK positivity
IHC panel of atypical small acinar proliferation in prostate biopsy cases.
AMACR
Myoepithelial markers: p63, 34BA12 or HMWCK, SMA
IHC panel of DCIS vs Invasive Ductal Carcinoma breast biopsy cases
Myoepithelial markers: p63, actin, SMA
CK5/6: (+)ADH with low grade DCIS
IHC panel of mature B cell neoplasm
Follicular lymphoma: Bcl-2 MALT: cytokeratin 3 4 5
IHC panel in differentiating HL from NHL
LCA CD30: golgi and cytoplastmic membrane CD15: golgi and cytoplasmic membrane CD20 CD3 Fascin (cytoplasmic expression in HL)
IHC panel in differentiating lung, thyroid, hepatocellular, primary.
Thyroid:
CK7+/CK20-
TTF-1(+): nuclear
TGB(+): cytoplasmic
Lung:
CK7+/CK20-
TTF-1(+): nuclear
TGB(-): cytoplasmic
Liver:
CK7-/CK20-
AFP: poorly diff hepatocellular CA
Hepar-1: well to mod diff hepatocellular CA
Pattern of bcl-2 expression in reactive lymphadenopathy
Interfollicular and paracortical
Pattern of bcl-2 expression in follicular lymphoma
Within the follicles
Olfactory neuroblastoma
CD56 (NCAM)
NSE
Medium-sized lymphoma
Lymphoblastic lymphoma: TdT
Follicular lymphoma
Positive for HMB-45
Epitheloid angiomyolipoma
Melanoma
Renal cell CA
RCC, CD10