Microscopy April 2019

For yesterday’s session we welcomed Moorfields ophthalmologists who are currently working in vitreoretinal surgery, medical retina and paediatrics and strabismus. These aren’t subspecialties which generate a lot of specimens, but we included a few archival cases of vitreous cytology and intraocular biopsies.

We started with a quick review of eyelid and globe structure as seen on histology, using two recent exenteration cases. Exenterations are relatively rare—the Department of Eye Pathology receives one a month, on average. The usual indication for exenterations is tumour, but sometimes there is severe orbital inflammatory disease or pain.

Here are a few of the cases we discussed.

Case 1

Cornea from a young adult

Low power of cornea

Low power shows the two halves of the corneal button. Even at this power, the posterior surface appears irregular, suggesting this is anterior lamella rather than full thickness. The epithelium is of irregular thickness with flattened areas over anterior stromal scarring.
Of note, the posterior surface has two distinct rather round “dents” at the periphery.

Higher power of posterior cornea

Here’s one of those dents on higher power. The stroma is a little compressed around it, and it’s larger than we would expect for eg gas injection.

This patient has keratoconus. The posterior dents reflect the position of intrastromal rings used for prior treatment.

Here’s a link to an EyeWiki article on intrastromal corneal ring segments (ICRS) to get you started.

Case 2

This is an exenteration specimen.

Microscope slide of exenteration

This photograph is of the whole section, which is sagittal and roughly in the middle of the globe. I’ve maked upper (UL) and lower (LL) eyelids for orientation. Note the upper lid is longer, and the fornix extends further posteriorly.

Of course, the feature of note is the large tumour mass lying posteriorly.

Medium power of tumour

Microscopy shows nest of basaloid tumour cells with conspicuous necrosis.

Typical feature of this tumour

There is pronounced perineural infiltration.

This is adenoid cystic carcinoma. The tumour architecture is predominantly solid, unlike the classic cribriform (“Swiss cheese”) pattern that features in many textbooks. Necrosis is more a feature of the solid pattern.

There’s an example of cribriform architecture in one of my posts from last year. See Case 3 on the page.

Here’s an open access by van Weert et al in Oral Oncology. It discusses some of the issues around the different patterns of adenoid cystic carcinoma.

Case 3

Here’s some vitreous cytology.

Vitreous cytology. Spot the cells!

First of all, to establish a baseline, this specimen has a fairly typical appearance—hardly any cells at all!

Vitreous cytology

In contrast, this is a cellular clump from a different case. There are cells with large atypical nuclei. Within the background are fragments of debris suggestive of necrosis. The large cells were positive on immunohistochemistry for the B-cell markers CD20 and CD79a. This is consistent with a large B-cell lymphoma.

We also discussed the hazards of microbial contamination and overgrowth in unfixed specimens, especially if they take a few days to get to us. A few years ago, I demonstrated a dramatic case at the Moorfields Medical Retina teaching session.

That’s all the eye pathology teaching for this month. Next session will run on 15 May—I’ll send out a sign-up email in advance.

Off-topic shameless plug. Those of you who attend my teaching or visit my blog regularly probably know I write science fiction as a hobby. If you or your friends/family are interested in light SF adventure stories, please feel free to peruse my books on my M. H. Thaung author website. I rely on word of mouth for promotion, so any sharing is much appreciated.

See you next month!

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