Microscopy October 2019

During yesterday’s eye pathology session, we chatted about a variety of cases with a focus on benign and malignant tumours.

Cases viewed included an angiosarcoma (rare in our practice) and a choroidal melanoma (very common for us). The latter had previously been treated with radiotherapy, and the eye had developed rubeotic glaucoma. On microscopy, I noticed a prominent Schwalbe’s line, which I interpreted as a posterior embryotoxon. This is an incidental finding, but there was also iris-corneal adhesion (peripheral anterior synechiae). Since there was rubeosis (neovascularisation) of the iris, the PAS might well have been secondary to rubeosis. But I also wondered whether there was a pre-existing Axenfeld syndrome, which is also associated with glaucoma.

Here are a couple of articles about anterior segment dysgenesis, which includes Axenfeld-Rieger syndrome:

From Glaucoma Today

A course excerpt from the American Academy of Ophthalmology

We also had a chat about epithelial ingrowth into the eye. This is a potentially catastrophic consequence of trauma or intraocular surgery, and challenging to treat. Here are a couple of overview articles:

From Glaucoma Today

From the American Academy of Ophthalmology’s EyeNet Magazine

Here are a couple of the cases we viewed.

Case 1

Orbital mass

Low power H&E

The low power view shows an encapsulated tumour with green ink marking its outer aspect. There is varied architecture including epithelial (ductal) structures with some secretions (pink, proteinaceous). The stroma is myxoid and loose.

Medium power H&E

Higher power view shows bland cytology of the epithelial cells. The stroma is hypocellular, with widely spaced stellate and spindled nuclei.

This is a pleomorphic adenoma. Although this is a benign tumour, it is best to excise it completely. If incompletely excised, there is a risk of multiple recurrences, and a risk of malignant transformation.

Here are a couple of reviews on recurrent and malignant change in pleomorphic adenomas. They concern salivary gland rather than lacrimal gland, but we currently tend to extrapolate since the evidence based for lacrimal gland is quite small. I believe the articles are open access—please let me know if they’re not.

From Antony et al (2012) in Head and Neck Pathology: Carcinoma ex Pleomorphic Adenoma: A Comprehensive Review of Clinical, Pathological and Molecular Data

From Kanatas et al (2018) in British Journal of Oral and Maxillofacial Surgery: Current thinking about the management of recurrent pleomorphic adenoma of the parotid: a structured review

Case 2

Evisceration for blind painful eye. This case was an external referral, and there was a history provided of glaucoma. I don’t know the precise reason for the decision to eviscerate, but commonly the eye is painful as well as blind, or it’s unsightly.

Medium power of retina

This image shows retinal atrophy, more pronounced in the inner retina. The middle two portions show preservation of the outer nuclear layer (photoreceptor cell nuclei) and some preservation of photoreceptor inner segments. In contrast, there is nearly total loss of ganglion cell nuclei, and the inner retina is gliotic: especially in the upper portion.

Low powere of cornea

The cornea is thickened, scarred and vascularised. Descemet’s membrane is partly stripped off although this might be perioperative artefact. The epithelium (lower right) overlies sizeable lumpy deposits of acellular material.

High powe of cornea

Higher power demonstrates relatively little inflammation. There is a tongue of epithelium which may reflect gradual accumulation of the deposit.

Congo rev

Congo red stain highlights the deposit…

Congo red (polarised)

… and there is nice apple-green birefringence in polarised light. It is sometimes difficult to decide if the stain is genuinely apple-green or just “shiny”—note the white collagen lamellae towards the top left of the image. Those are not positive.

So we have extensive subepithelial/anterior stromal amyloid deposition in an eye with long-standing glaucoma.

I have occasionally seen corneas with similar deposits where there is a history of glaucoma. We know that chronic inflammation can be associated with accumulation of amyloid, but this cornea is relatively uninflamed. Assuming this patient does not have a dystrophy associated with amyloid (ie gelatinous drop-like dystrophy), I wonder if chronic corneal oedema could allow amyloid to accumulate.

My next microscopy session will be on 20 November. Emails for signing up will be sent out nearer the time. See you then!

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