IHC

Question 1

What is GATA3 and what is it used for?

Answer 1

GATA3 is a nuclear TF
High sensitivity for breast ca (expressed > 90%)
Not specific for breast ca.
Also expressed in urothelial ca, many SqCC, salivary gland tumours, skin adnexal tumors et al.

Question 2

What is Desmin and what is it used for?

Answer 2

is a universal marker of muscle cells. It is expressed both in smooth and striated muscle cells; expression is variable in myofibroblasts. Desmin is an intermediate filament (a counterpart to cytokeratins in epithelial cells).

Question 3

What is myogenin and what is it used for?

Answer 3

Myogenin (and MyoD) are transcription factors (thus are nuclear), which are specific to striated muscle; absent in smooth muscle. a-sarcomeric actin is a cytoplasmic marker of striated muscle. These markers are used to differentiate rhabomyosarcoma (positive) from leiomyosarcoma (negative)> The pattern of reactivity can also be helpful as embryonal rhabdomyosarcoma shows focal positivity while alveolar rhabdomyosarcoma is diffusely positive for MyoD/myogenin.

Question 4

What is CD34 used for?

Answer 4

marker of vascular differentiation. Reacts with blood vessels and lymphatics, although lymphatics are variably reactive for CD34. CD34 also reacts with various soft tissue tumours and epithelioid sarcoma.

Normal tissues stained: endothelial cells, fibroblasts, and hematopoietic blasts (stem cells)

Mesenchymal marker

Question 5

What is CD45 used for?

Answer 5

CD45: (46, 59): leucocyte common antigen). Cytoplasmic, membranous. Normal tissues stained -> pan-leukocyte marker (lymphocytes, myeloids, and histiocytes) but absent on plasma cells and nucleated reds. –»

Uses: Screening for haematopoietic origin in an unknown malignancy (part of a standard first-line panel);

Virtually all hematopoietic neoplasms, except some myelomas, R-S cells in classical Hodgkin lymphoma, some lymphoblastic lymphomas, some anaplastic large cell lymphoma, some myeloid sarcomas and follicular dendritic cell sarcoma.

Question 6

Warthin Starry stain

uses

Answer 6

Stains Helicobacter pylori, spirochetes

Question 7

Ck7+/CK20+ ddx

vs

CK7- and CK20-

Answer 7

CK7+/Ck20+: peri-diaphragmatic GI organs (pancreas, biliary tree, stomach) and bladder.

CK7-/CK20- : simple visceral epithelial (except the colon): liver, kidney, and prostate

Question 8

AE1/AE3 - what is this?

Answer 8

AE1 detects the high molecular weight cytokeratins 10, 14, 15 and 16 and the low molecular weight cytokeratin 19
AE3 detects the high molecular weight cytokeratins 1, 2, 3, 4, 5 and 6 and the low molecular weight cytokeratins 7 and 8
Not reactive to cytokeratins 17 and 18