Microscopy September 2019

We were a bit short of attendees at yesterday’s microscopy session—it seems that the dreaded lurgy is going around, now that summer has drawn to a close. Still, we had an interesting discussion about various aspects of eye pathology including the two cases below. I’ll post a few of my “diagnostic process” thoughts while going through each one.


Case 1

Orbital mass in a middle aged patient

Low power H&E of orbital mass

The low power view shows fibroconnective tissue with a dense infiltrate of small round blue cells. Top of my list would be lymphoma although other tumours (eg metastatic small cell carcinoma, Merkel cell carcinoma, even melanoma) could also be considered. Obviously, it’s helpful to know any relevant clinical history.

Medium power of orbital mass

On higher power, we can see that the tumour cells are quite uniform and monotonous, and that they don’t form structures such as rosettes or nests. This still supports my impression of lymphoma. I requested a lymphoma immunohistochemistry panel to cover the diagnoses most commonly encountered in our practice.

CD3

This is CD3, which highlights T cells. There aren’t very many.

CD5

This is CD5. Usually, CD5 also highlights T cells. In normal lymphoid tissue, we’d expect it to be expressed in about the same pattern as CD3. However, in this case it’s much more widely expressed. Two types of B cell lymphoma characteristically have aberrant CD5 expression: small lymphocytic lymphoma/chronic lymphocytic leukaemia, and mantle cell lymphoma.

Cyclin D1

This is cyclin D1, which is expressed by mantle cell lymphoma as well as various neoplastic and non-neoplastic epithelial tissues. In contrast to the CD3 and CD5 above, it is expressed in the cell nucleus rather than cytoplasm/membrane.

The immunoprofile—combination of different antibodies—favours mantle cell lymphoma. There are very few tumours where a single antibody is enough to clinch a diagnosis. Sometimes with an unknown tumour, we might need to cast a wide net with an initial immunopanel, and then home in on a more specific diagnosis. That’s one reason that it can sometimes take several days (or even longer) to provide a meaningful report.

In this case, and at this site, I wasn’t seriously expecting a non-lymphoma pathology. In a different context, you might need consider a wider range of pathologies.

Here’s a recent (2017) open access article by Sharma and colleagues on approaching small round blue cell tumours: Round cell tumors: classification and immunohistochemistry.


Case 2

Eye with longstanding disease

Low power view

This is a low power view of the anterior segment (cornea, angle, iris and lens). The full thickness folds in the cornea are artefactual. This eye was large enough to be processed into a megablock, and preparing sections from megablocks can be tricky.

Low power view with annotations

Here are some annotations for the same image:
c = cornea
i = iris
a = angle
L = lens (sort of!)

Medium power of iris

This view of the iris shows a very flat anterior profile. When I see this at low power, it makes me suspect traction: either from a rubeotic membrane or from neodescemetisation.

Iris and angle

A higher power view of the iris and cornea shows a rubeotic (neovascular) membrane coating the anterior iris surface. Additionally, the iris is stuck to the back of the cornea at the periphery (peripheral anterior synechiae), obliterating the true angle.

PAS of peripheral cornea, iris, angle and lens capsule

PAS shows the iris adherent even anteriorly to Descemet’s membrane. Additionally, there are fragments of lens capsule in the lower part of the image. The patient has also had cataract surgery and placement of an intraocular lens.

This eye has extensive rubeosis iridis leading to intractable glaucoma.

My next microscopy session will be on 16 October. Sign up details will be circulated to Moorfields trainees and fellows nearer the time.

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