Microscopy January 2019

Yesterday we welcomed Simon, Alejandro and Oscar from the Royal Veterinary College for our monthly case discussion as well as Sam and Manuela from our lab.

Alejandro brought a couple of interesting canine globes. The first was a massive intraocular haemorrhage following phacoemulsification surgery for cataract. The second was an iris melanoma. Interestingly, one of the human cases we discussed was also an intraocular melanoma involving the iris. It is quite rare to get iris melanomas as surgical specimens in humans, choroidal melanomas being more common.


Case 1

This is a (human) globe with melanoma within the ciliary body and iris.

Low power of tumour

This low power view shows tumour with areas of necrosis within the anterior part of the ciliary body and extending into the iris and trabecular meshwork. It extends through the sclera (probably within a blood vessel) to form an extrascleral deposit (covered by the green-inked conjunctival cuff). Tumour also dissects just anterior to Descemet’s membrane of the cornea.

Opposite angle, low power

In the opposite angle, floating pigmented cells (probably a combination of tumour and melanophages) clog up the trabecular meshwork. It is likely this patient would have secondary glaucoma.

High power

This higher view shows tumour cells and the collagen beams of the trabecular meshwork.


Case 2

13 year old with proptosis. We received a globe with attached retrobulbar mass, the latter measuring up to 39 mm.

Low power cross section of optic nerve

This low power view shows the optic nerve in cross-section. Unusually, there is fibrous tissue adherent to the nerve (ie loss of the usual space within the dural sheath). The presence of the central retinal artery and vein indicates that this portion of optic nerve is relatively anterior (the artery enters the optic nerve around 12 mm posterior to the globe).

Low power of lesion

This low power view is taken from the more posterior mass. It is reminiscent of the optic nerve, in that it has a fibrous sheath and a lobulated architecture with fibrous septa, but it is markedly expanded.

Medium and high power of lesion

Medium and higher power shows microcysts and cells with fibrillary or clear cytoplasm.

High power

In a few fields, there are brightly eosinophilic aggregates with a corkscrew or tapered shape. These are Rosenthal fibres.

This is an optic nerve glioma (pilocytic astrocytoma).


Case 3

I have to thank the Twitter community for their help on this case. It was an eyelid lesion in a female in her thirties. The specimen measured around 35 mm.

Low power

Dermal proliferation of nested cells with prominent eosinophilic structures (Congo red negative).

Deeper tissue

On the left, there are occasional areas with cribriform architecture in a myxoid stroma.

High power, rather striking architecture

The eosinophilic structures have a spiky/fluffy appearance reminiscent of amianthoid fibres (although we decided they weren’t).

AE1/AE3 immunohistochemistry

This is the AE1/AE3 (pancytokeratin).

S100 immunohistochemistry

And this is the S100.

Rather than replicate the discussion here, I’ll direct you to the Twitter post.


No microscopy session next month as I’ll be doing the Moorfields Half Day Teaching session for ophthalmology trainees. See you again in March!

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