Page 1327 - Clinical Small Animal Internal Medicine

138 Tumors of the Eye and Ocular Adnexa 1265

optic nerve, and orbit. Although usually considered pupil (Figure 138.3). Secondary glaucoma may occur.
VetBooks.ir benign, such invasion warrants a more cautious Diffuse iris melanoma is differentiated from chronic
anterior uveitis with iridal hyperpigmentation by the
prognosis. Small tumors are typically asymptomatic
although larger tumors frequently present with chronic
course.
uveitis, secondary glaucoma, retinal detachment, absence of other signs of uveitis and a more protracted
intraocular hemorrhage, or blindness. Ocular ultra- Diffuse iris melanoma has the potential to distantly
sonography may be required to identify the mass in metastasize, especially to the liver and lungs. Iris hyper-
these patients. Therapy is usually enucleation if the pigmentation, however, is typically very slowly progres-
mass is progressive or the eye is painful. Diode laser sive, often requiring months to years to progress to the
ablation is an alternative treatment for small masses point at which the eye must be enucleated, and an addi-
that do not involve the optic nerve. tional 1–3 years after that before metastatic disease may
become evident. No single morphologic feature is pre-
Feline Diffuse Iris Melanoma dictive of outcome, but metastasis has been linked to a
Diffuse iris melanomas are the most common primary greater mitotic index, larger tumors, extension through
intraocular tumor in cats. Although the prodromal the iris into the ciliary body stroma, and involvement of
period may be quite long, most cats are 9 years of age or the scleral venous plexus.
older at the time of diagnosis. The treatment of diffuse iris melanoma is controver-
The most common clinical sign is slowly progressive sial. Because these eyes initially retain vision and are
diffuse iridal hyperpigmentation. Occasionally, a pig- comfortable, in the ideal setting, enucleation would be
mented iridal nodule or amelanotic mass is seen. The delayed until just prior to malignant transformation,
diagnosis is generally made clinically, and is based on invasion into other ocular structures, secondary glau-
the presence of progressive iridal hyperpigmentation coma, or metastasis. Such precise timing; however, is
and thickening or irregularity of the iris surface or seldom possible. Enucleation is recommended if iris
hyperpigmentation progresses to involve virtually all
of the iris surface, pigmented cells are present in the
(a) aqueous humor and trabecular meshwork, the pupil
is distorted (indicating iridal stromal invasion), inva-
sion into the ciliary body or scleral appears imminent,
or intraocular pressure is elevated. However, it is
unknown whether early enucleation leads to increased
survival.
As an alternative to enucleation, some veterinary
ophthalmologists have attempted to ablate small,
focal, hyperpigmented foci with a diode laser in an
effort to preserve vision and the eye. The long‐term
(b) success rate and side‐effects of this procedure, however,
are unknown.
In practice, slowly progressing lesions, especially in
older cats with other life‐limiting disorders, are often
simply monitored, ideally by comparison to baseline
photographs. In many cats, the progression may be so
slow that the patient can be followed for many years to a
decade or more without apparent metastasis.

Iridociliary Epithelial Tumors
Primary iridociliary epithelial tumors (e.g., ciliary body
adenomas, adenocarcinomas, pleomorphic adeno-
carcinomas) are occasionally observed in middle‐aged
Figure 138.3 (a) Feline diffuse iris melanoma. The right iris is to older dogs and cats. Most are benign, fairly well‐
diffusely and heavily pigmented and the pupil is slightly more delineated, slow‐growing masses that originate from
dilated due to stromal invasion of neoplastic cells (anisocoria). The the ciliary body or the posterior iris epithelium
left iris has multifocal nevi (freckles). (b) Exfoliated pigment from (Figure 138.4). They are often nonpigmented, although
the iris is present on the anterior lens capsule. Source: Courtesy of
University of Wisconsin‐Madison Comparative Ophthalmology some epithelial tumors are pigmented and clinically
Service Collection. indistinguishable from anterior uveal melanocytomas.