Microscopy September 2017

A quiet session this month, which gave us a chance to start by reviewing some technical aspects of macroscopy (grossing) and compare macroscopic impressions with the corresponding slides before moving on to discussion of recent interesting cases.

Case 1

Globe with choroidal tumour.
The actual diagnosis isn’t a challenge here, but there are a couple of interesting features related to the surgery.

Low power of globe

This is a low power image of the optic nerve head, with the (surgeon’s) cut end of the optic nerve inked green. The nerve has been cut very close to the globe, displacing myelin anteriorly as “toothpasting” artefact and distorting the optic nerve head and adjacent retina.
You can see normal and cupped optic nerve heads for comparison at my retinoblastoma post here.

Low power of globe

This low power view shows a spindle cell melanoma within the choroid (lower part of the screen) and two clusters of tumour cells within the sclera. The cluster on the right is within a blood vessel.

High power of sclera

However, the second cluster lies within a track which is most probably from needle sampling of the tumour (for cytogenetics). If it were present on the outer scleral surface, I wouldn’t regard it as extrascleral tumour extension (which would upstage the tumour by TNM classification). The difficulty is that melanoma can extend directly through the sclera, and in this case it is only the straightness and narrowness of the (presumed) track that leads me to think this is artefactual.


Case 2

Globe with choroidal tumour

Low power of globe

In contrast, this low power view of another eye with a choroidal melanoma (top right) has a distinctly defined deposit of tumour outside the eye, close to the optic nerve (bottom left).

Higher power of extrascleral tissue

On higher power, the deposit is within a blood vessel, which also contains fresh blood and is lined by endothelial cells

Vortex vein

The vortex vein sampled separately at macroscopy also contains tumour.

As noted above, extrascleral tumour extension increases the TNM classification. Currently, extrascleral extension within vortex veins is not categorised separately from that outside veins (ie directly within the periocular soft tissue). My current pragmatic approach while reporting these cases is to specify if the extrascleral tumour is inside the vortex veins.


Case 3

This cornea is from a patient with previous blunt trauma to the eye

Low power cornea

The epithelium is missing from this specimen. Even at low power, granular material can be seen throughout the stroma.

Higher power cornea

Higher power shows tiny red granules within the stroma. The distribution of keratocyte nuclei is close to normal, and the endothelial density is normal too.

The red granules have been deposited following breakdown of red blood cells following a hyphaema.


Case 4

Orbital biopsy from a patient with a recurrent tumour.

Low power of orbital mass

This low power view shows a confluent sheet of tumour cells with no particular architecture (not forming eg nests or ducts). On the right is a blood vessel with an irregular “staghorn” profile.

Higher power of orbital mass

Higher power shows spindled cells with plump oval nuclei, ill-defined borders and an occasional mitosis.

 

CD34 immunohistochemistry

Immunohistochemistry for CD34 (which is positive in a variety of tumours) is strongly and diffusely positive

STAT-6 immunohistochemistry

Immunohistochemistry for STAT-6 shows strong nuclear positivity throughout.

This tumour is a recurrent solitary fibrous tumour. Typically these tumours are positive for CD34 and bcl-2, but both of these markers can be positive in other entities. STAT-6 has relatively recently been found positive in solitary fibrous tumour, and so far appears to be more specific than CD34 and bcl-2. Recent articles about STAT-6 include this and this.

My next teaching session will be on Wednesday 11 October. Additionally, I will be hosting the annual meeting of the British Association for Ophthalmic Pathology in London on 12-13 April 2018 (booking open as of 26/9/17), which is open to anyone interested in eye pathology. Feel free to contact me if you have any questions.

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