Microscopy March 2019

For yesterday’s teaching session, we welcomed Moorfields Fellows from medical retina and vitreoretinal services as well as Olivia, who is doing a PhD in corneal genetics.

We had a case-based discussion around macular and Fuchs’ dystrophy and a chat about parasitic diseases in ophthalmology including Loa loa – long story!

Over the last month, I’ve see more uveal melanomas than usual, so they formed the bulk of yesterday’s cases. Here are a few examples with contrasting features.

Case 1

Melanoma of ciliary body.

PAS low power

This low power view of a PAS section shows tumour within the ciliary body and extending into the iris. Interestingly, the lens has a squared-off profile suggesting that it’s distorted due to the tumour.

H&E high power

The higher power H&E section shows tumour in the iris and encroaching on the trabecular meshwork as well as in the ciliary body.

Case 2

This is a previously treated melanoma which has recurred and now needs enucleation.

H&E low power

This low power view shows a relatively small choroidal tumour. It extends into the optic nerve as well as forming an extrascleral nodule.

H&E medium power

Further away from the tumour, there is a broad area of chorioretinal scarring. This field shows atrophic retina on the left. Towards the right, there is scar formation reminiscent of a disciform. In this case, the scarring is secondary to transpupillary thermotherapy.

Case 3

This is a nice example of an epithelioid melanoma.

H&E medium power

The medium power view includes a mitosis. There is little melanin pigmentation.

H&E high power

High power shows discohesive tumour cells with plenty of cytoplasm and distinct cell borders.

PAS of uveal melanoma

PAS stain demonstrates loops and networks, which are a prognostically adverse finding.

If you’re interested in TNM classification of uveal melanomas, I went over some aspects of it in my October 2018 post.

See you at my next session on 10 April!

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