Microscopy April 2017

Despite the imminent Easter closure of UCL Institute of Ophthalmology, this month’s session was well attended. A warm welcome to Zerin (from the Institute), and also to Lucia (from Gran Canaria). Dr Mandeep Sagoo, Consultant Ocular Oncologist, was present for the early part of the session, and we had an interesting discussion on the difficulties of diagnosing ring melanomas, as well as the difficulties in differentiating iris naevi from melanomas – both clinically and histologically. See case 4 below.

Here are some highlights from today’s session.

Case 1
Full thickness corneal graft

Low power view of cornea, H&E

Lower power shows full thickness cornea, lacking epithelium (which would be at the top) and with a coating of inflammatory cells along Descemet’s membrane (at the bottom). Even at this low power, the stroma appears “busier” than usual with scattered rounded structures.

High power view of cornea, H&E

At higher power, we can see large numbers of Acanthamoeba trophozoites and cysts. I can’t always differentiate between the two with confidence, but, as a guide, the trophozoites contain eosinophilic (pink) structures while the cysts appear more “empty”.

This is Acanthamoeba keratitis.

Case 2
Conjunctival fornix biopsy

Conjunctival biopsy, low power view

The epithelium is on the top right of the image. The stroma is markedly abnormal, with deposits of eosinophilic material, particularly around blood vessels. The appearance is “pink” rather than “blue”, suggesting that there is little cellular infiltrate (ie little inflammation).

Conjunctival biopsy, medium power
2b. This is not a haematoxylin and eosin stain.What is it?
*Click here for more detail*
This is a Congo Red stain. In this field, it is markedly positive (red) around blood vessels.
Conjunctival biopsy…
This is the above stain viewed using polarised light.
*Click here for more detail*
This polarised Congo Red stain demonstrates the classic apple-green appearance of amyloid.

This is amyloid deposition.

Case 3
Evisceration of an eye with longstanding disease.

Evisceration specimen, low power

This low power view shows markedly disorganised intraocular contents and blood. Of note, there is calcification and bone formation, particularly on the left of the image. The remainder of the tissue is quite fibrotic.

Evisceration specimen, medium power

A medium power view of the bone metaplasia shows fat spaces (the rounded empty structures) within an area of high cellularity…

Evisceration specimen, high power

… and on high power, the hypercellular area includes a wide mixture of cell types. Some cells have multiple huge nuclei – these are megakaryocytes. Others have bilobed or apparently fragmented nuclei – these are early-stage eosinophils and neutrophils (polymorphs). Still other cells have small round nuclei and little cytoplasm – lymphocytes.

This is trilineage haematopoiesis within metaplastic bone in an eye with longstanding disease. I don’t have information about the original problem.

Case 4
Enucleation for melanoma. Globe melanomas are fairly common specimens in this department (we get one or two per week), but this specimen has some interesting features.

Low power of iris leaflet

This low power view of the anterior part of the eye shows diffuse iris thickening. The melanoma involves the whole iris leaflet and extends into the angle, trabecular meshwork and the anterior part of the ciliary body.

Low power of opposite iris leaflet

The opposite iris leaflet has a hypercellular area on the anterior stroma, close to the pupillary margin.

Opposite iris leaflet, high power

On higher power, the cells have irregular hyperchromatic enlarged nuclei. Similar cells extend along the iris surface to the angle in other sections (not shown). This distribution is consistent with a ring melanoma of the iris.

Another iris for comparison

For comparison, this is a different case showing increased melanocytes on the anterior iris surface. Here, they are quite uniform slender spindle cells with bland nuclei. This is a coincidental iris naevus in a globe with a posterior choroidal melanoma. It is not always easy to differentiate histologically between iris naevi and melanomas.

My next teaching session will be on 17 May. If you are an ophthalmologist, histopathologist or scientist interested in eye pathology, and interested in attending my teaching sessions, please drop me a note using the contact form below.

See you next month!

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