Based on the above images only, which of the following combination of immunohistochemical stains would you predict to be POSITIVE✅?
PASD 
CD56
Calretinin
S100
⚕️Diagnosis:
🔬Granular cell tumour
(Colleagues case🙏).
🔬Granular cell tumour
(Colleagues case🙏).
Granular cell tumours (GCT) are thought to be?
Question:
The most common site of a GCT is the?
The most common site of a GCT is the?
1/ This benign tumour can occur at any age (more common ~40s) and si more common in males.
2/ The tongue is the most common site for involvement (but can occur is most places).
3/ They are now considered neuroectodermal, most likely schwannian origin.
tandfonline.com/doi/abs/10.108…
2/ The tongue is the most common site for involvement (but can occur is most places).
3/ They are now considered neuroectodermal, most likely schwannian origin.
tandfonline.com/doi/abs/10.108…
Question:
PASD is often touted as being positive in these tumours.
What does PASD supposedly stain in the tumour cells?
* of Świdwin
**of Milan
PASD is often touted as being positive in these tumours.
What does PASD supposedly stain in the tumour cells?
* of Świdwin
**of Milan
PASD
4/ Depending on the source a proportion of GCT show positive staining for PASD (maybe as low as 1/3 of cases?).
5/ Pustulo-ovoid bodies of Milan, as well as being positive for PASD, can be positive for S100.
6/ ?Maybe these are lysosomes🤷?
onlinelibrary.wiley.com/doi/10.1111/j.…
5/ Pustulo-ovoid bodies of Milan, as well as being positive for PASD, can be positive for S100.
6/ ?Maybe these are lysosomes🤷?
onlinelibrary.wiley.com/doi/10.1111/j.…
Question:
About what portion of GCT can be positive for TFE3 by immunohistochemistry?
About what portion of GCT can be positive for TFE3 by immunohistochemistry?
True or false?
TFE3 expression in GCT is related to underlying Xp11.2 translocation?
TFE3 expression in GCT is related to underlying Xp11.2 translocation?
7/ TFE3 IHC was found to be positive (nuclear expression) in 91% of cases in the below paper.
8/ There was no relation to TFE3 (Xp11) gene rearrangement.
9/ ⚠️Potential pitfall?⚠️
sciencedirect.com/science/articl…
8/ There was no relation to TFE3 (Xp11) gene rearrangement.
9/ ⚠️Potential pitfall?⚠️
sciencedirect.com/science/articl…
10/ Immunohistochemistry shows GCT are often positive for:
✅S100/SOX10
✅CD68
✅Calretinin
✅CD56
✅Inhibin
They are usually negative for
❌Melanocytic markers (HMB45/Melan A)
❌GFAP
pubmed.ncbi.nlm.nih.gov/8878020/
✅S100/SOX10
✅CD68
✅Calretinin
✅CD56
✅Inhibin
They are usually negative for
❌Melanocytic markers (HMB45/Melan A)
❌GFAP
pubmed.ncbi.nlm.nih.gov/8878020/
Last question:
GCT are associated with mutations of genes that encode?
GCT are associated with mutations of genes that encode?
11/ Loss of function mutations for ATP6AP1/2 (which encodes a vacuolar H + -ATPase component(V-ATPase)) are found in ~72% of GCTs.
12/ Lastly, V-ATPase dysfunction may play a role the development of these tumours.
pubmed.ncbi.nlm.nih.gov/30166553/
12/ Lastly, V-ATPase dysfunction may play a role the development of these tumours.
pubmed.ncbi.nlm.nih.gov/30166553/
13/ Supplementary point: please check out this great example of a TFE3 positive GCT from @Cristin28431328
https://twitter.com/Cristin28431328/status/1415915389846917125
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