Microscopy January 2020

In yesterday’s session, we covered a lot of topics including eyelid anatomy, differential diagnosis of lymphomas using immunohistochemistry, various tumours with myxoid stroma and a few benign skin tumours.

Here are a few of the case we discussed.

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Case 1

Enucleation for an intraocular tumour

The tumour was anteriorly located, and there was iris rubeosis and angle closure. However, I’d like to concentrate on the optic nerve.

This is a low-power view of the optic nerve and dural sheath, removed from the eye and seen longitudinally. The red ink is to indicate a margin. The obvious abnormality is an area of pallor at the top right.

On medium power, we can see normal architecture towards the left. On the right, the fibrous septa are preserved, but the neural tissue is expanded and pale with cystic cavities.

Higher power shows a continuity between normal and abnormal nerve.

This cross section of the portion of optic nerve still attached to the globe (retina and sclera on bottom left) shows the cystic change to be more widespread.

This is Schnabel cavernous optic degeneration. It is a histological finding with large retrolaminar spaces which contain hyaluronic acid (Alcian Blue positive). The pathogenesis is unclear. Initially it was suggested to occur following an acute rise in intraocular pressure (such as angle-closure glaucoma), but it has also been found in patients with systemic vascular disease and no symptoms or history of glaucoma. There are also reports of associations with uveal melanoma, although this may be indirect and an additional risk factor in patients who already have glaucoma.

I’ve found one open access article which examines the relationship between melanoma, glaucoma and Schnabel cavernous degeneration:

The Occurrence and Proposed Significance of Schnabel Cavernous Degeneration in Uveal Melanoma by Kanavi et al, 2014

There’s a second open access article (pdf format) which looks at morphology of different optic nerve diseases (including Schnabel) and has some nice images for comparison:

Histopathologic studies of ischemic optic neuropathy by Knox et al, 2000

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Case 2

Skin biopsy of yellowish plaque on eyelid

At low power, we can see clusters of pale cells within the dermis. The epidermis looks normal.

On medium power, the the infiltrating cells have well-defined outlines, copious pale cytoplasm and small, roughly central nuclei. There is also a light scattering of lymphocytes.

Higher power shows a slightly foamy or bubbly texture to the pale cytoplasm. There is no necrosis, and eosinophils are not prominent.

This is xanthelasma. It can be associated with serum dyslipidaemia and cardiovascular problems, so it’s wise to consider the possibility of an associated systemic condition. Periocular xanthelasma can also occasionally be associated with orbital xanthogranulomatous disease of various types. If the infiltrate seems deep/posterior, I would suggest that this be considered clinically.

Here are a few open access articles about eyelid xanthelasma (the first one on the list was fun!):

Xanthelasma and lipona in Leonardo da Vinci’s Mona Lisa by Dequeker et al (2004)

Serum lipid profile and clinical characteristics of patients with xanthelasma palpebrarum by Kavoussi etc al (2016)

Cardiovascular profile of xanthelasma palpebrarum by Dey et al (2013)

Case 3

Orbital mass

Low power shows several pieces of fibrofatty tissue. They are infiltrated by tumour with markedly cribriform (sieve-like) architecture. The distinctly punched-out cysts areas might be compared to Swiss cheese.

Higher power shows cohesive strands of basaloid (blue) tumour cells with plenty of pale, acellular matrix within the cystic cavities.

The architecture here is slightly different, with short cords and more tubular elements. There is perineural infiltration in the centre.

This field again demonstrates the cystic cavities.

This is a classic case of adenoid cystic carcinoma with predominantly cribriform architecture and a smaller tubular component.

I’m not running a microscopy session in February as I’ll be going over cases at the Moorfields Half Day Teaching. However, in March, we will have a cornea-themed session with genetics researchers who are also based at the UCL Institute of Ophthalmology.