Enucleation specimen. Intractable raised intraocular pressure due to an iris mass.
This is a low power view of the anterior segment (cornea, anterior chamber, iris, ciliary body and a piece of lens). The section is off-centre, and so the iris is continuous rather than having a central gap where the pupil is. The iris is irregularly thickened, particularly on the left. Even at low power, you can see a cellular proliferation across its anterior surface.
In the annotated image, I’ve indicated the anterior iris surface with a blue line and the posterior iris (pigment epithelium) with a green line. The yellow line indicates the cellular proliferation coating the original iris anterior surface. I’ve indicated the ciliary processes (cp) of the pars plicata. There is a fragment of lens: the disruption is artefactual.
Technical note: Because the lens is quite solid compared to other intraocular structures, and because it is suspended by the delicate zonules, it can easily become dislodged from the rest of the specimen. So if you see a lens lying in the vitreous, don’t get too excited about spontaneous luxation!
This is another low power view, including cornea, one iris leaflet (this section includes the pupillary aperture), lens and both the pars plicata and pars plana of the ciliary body. The iris is markedly thickened by a spindle cell tumour, which extends into the ciliary body as well as the angle and partway through the sclera.
In the annotated image, I’ve indicated the normal cornea (c) and lens. The iris, angle (a), ciliary body (cb) and sclera (s) all contain tumour.
Here’s a higher power image of the angle, which is bounded by cornea, trabecular meshwork and iris. The tumour is composed of nests of spindle cells with mild nuclear pleomorphism and very few mitoses. It infiltrates the trabecular meshwork and probably Schlemm’s canal as well as the iris and ciliary body.
In the annotated image, I’ve indicated Descemet’s membrane in blue, the location of the trabecular meshwork in yellow, and the probable Schlemm’s canal in green. The tumour obliterates the normal structures, and it’s difficult to precisely identify the anatomy.
This image is slightly further back, with (presumably) Schlemm’s canal on the left. The smooth muscle of the ciliary body is involved by tumour, as are the ciliary processes.
Anatomy note: The posterior surface of the iris is covered by a layer of pigment epithelium. The ciliary processes are covered by a double layer of epithelium: an inner layer of pigmented epithelium and an outer layer of non-pigmented epithelium. I’ve indicated the pigment epithelium with a yellow line and the non-pigmented epithelium in blue.
This is an iris melanoma. In this case it has spread circumferentially around the iris, and so we can call it a ring melanoma. Because of the relationship of the iris to the drainage angle, the tumour has blocked the trabecular meshwork and compromised outflow of aqueous from the eye. This has caused secondary glaucoma.
Here’s a bonus image of the retina. Glaucoma leads to optic nerve damage, which manifests in the retina as loss of ganglion cells. I took this photomicrograph of the posterior retina, where we would expect to see a continuous layer or multilayer of ganglion cell nuclei (with the latter histologically defining the macula). Instead, there are only occasional ganglion cell nuclei. Additionally, the nerve fibre layer is gliotic (the retinal equivalent of fibrotic). The remainder of the retina is relatively well preserved.
In the annotated image, I’ve labelled the inner nuclear layer (inl), outer nuclear layer (onl) and photoreceptors (p: the rods and cones). I’ve marked a couple of ganglion cell nuclei with asterisks. I’ve outlined the gliotic layer in yellow.
Further reading
Here are a few open access articles about iris melanoma and how it can give rise to secondary glaucoma
PRIMARY TUMOURS OF THE IRIS by Normal Ashton. I’ve included this 1964 article for historical interest.
Factors associated with elevated intraocular pressure in eyes with iris melanoma by Shields et al (2001). This case series review concludes that the mechanism of raised intraocular pressure in these cases is predominantly infiltration of the trabecular meshwork rather than rubeosis.
Primary iris melanoma: diagnostic features and outcome of conservative surgical treatment by Conway et al (2001). This case series review from Australia concludes that local resection can be an effective treatment for iris melanoma.
Surgical treatment of iris and ciliary body melanoma: follow‐up of a 25‐year series of patients by Klauber et al (2012). Similar to the Australian paper above, this retrospective review from Denmark concludes that local resection can be a safe and effective treatment, as long as preoperative intraocular pressure is normal.
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