Incidental finding in an enucleation specimen
I took a little break from pathology last week and shared a fiction reading post from my other website. Back to some interesting (I hope!) cases now.
This low power image is centred on the ciliary body and adjacent sclera. It also shows the limbus (on the right) with a small portion of the iris and lens (bottom). This part of the ciliary body is the pars plicata, so called because of the finger-like ciliary processes which overlie the ciliary (smooth) muscle. On a histology note, we can see the pigmented epithelium on the posterior iris surface which merges with the pigmented epithelium of the ciliary body. However, the ciliary body has a second epithelial layer: the nonpigmented epithelium. This covers the internal (I’d say “vitread” as in closer to the vitreous as opposed to “sclerad”) surface of the ciliary body. The abnormality in this field is the irregular nodule attached to one of the ciliary processes.
In the annotated image, I’ve outlined the ciliary muscle in green, with the trabecular meshwork/Schlemm’s canal in blue. The abnormality of interest is outlined in red (or orange, my colour discrimination isn’t great with this monitor!)
On medium power, we can better appreciate the ciliary body’s double layer of pigmented and nonpigmented epithelium. The nodule does not appear to be pigmented.
In the annotated image, I’ve marked the pigmented epithelium in green and the nonpigmented epithelium in red.
On higher power of the nodule, we see a proliferation of the nonpigmented epithelium, embedded in rather solid-looking homogeneous matrix. There’s a very light focal dusting of melanin pigment, but I wouldn’t then call this pigmented epithelium.
PAS stain (of another case) is positive in the matrix, as well as nicely highlighting the thickness of the native epithelial basement membrane.
This is a Fuchs adenoma. Despite the name, it is due to hyperplasia rather than neoplasia of the nonpigmented ciliary epithelium. It is relatively common and harmless. I’ve seen quoted figures ranging from 1% to 31% of eyes. Given that they are usually around 1 mm in diameter, I suspect it depends on how hard you look! They are usually an incidental finding, but they have been described as causing sectoral cataract or being misdiagnosed as a tumour.
I haven’t found any open access articles reviewing the entity. Here are a couple of more unusual manifestations:
Fuchs’ Adenoma of the Choroid Simulating a Choroidal Hemangioma by Razzaq et al (2012)
Optical coherence tomography angiography of a pigmented Fuchs’ adenoma (age-related hyperplasia of the nonpigmented ciliary body epithelium) masquerading as a ciliary body melanoma by Nagarkatti-Gude et al (2018)