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IRIS MELANOMA IN CATS
Iuliana Ionașcu, Georgeta Dinescu, Cucoș Cătălina Anca
Faculty of Veterinary Medicine, Bucharest, Romania, ancacucos@gmail.com
Abstract
Iris melanoma is a primary intraocular tumor with a high potential risc for metastasis,
characterized by the presence of a single or a multiple hyperpigmentation focal areas, or
diffuse hyperpigmentation of the anterior epithelium of the iris. This hyperpigmentation is
due to an abnormal growth and proliferation of melanocytes. However, not any
hyperpigmentation should be handled as a melanom, is required differential diagnosis with
melanosis, iris nevi, iris cysts, iridal discoloration due to inflammation, or melanosis
secondary to chronic inflammation process. Depending of the expanding and the size of the
tumor, it may cause complications as glaucoma and uveitis. The enucleation, despite the
metastasis risk, represents the only treatment option that can be considered.
Key words: enucleation, feline, iris, melanoma, Russian Blue.
INTRODUCTION
The most common primary intraocular neoplasm in cats is malignant
melanoma of the anterior uvea, usually is unilateral, is found in cats of all
ages, with no breed predisposition (Boydell and Enache, 2012). A
melanoma is clinically characterized by malignant growth of melanocytes,
cells that are dark in appearance due to the inclusion of the melanin
pigment, or, on the contrary, unpigmented in amelanotic iris melanoma.
The iris involvement is characterized by the presence of one, or more,
golden to dark, brown pigmented foci, that slowly (over months to years)
coalesce to form larger pigmented areas and eventually involve most of the
iris as it becomes diffusely hyperpigmented, thicker, and less mobile.
Iris melanomas in cats usually arise from the front of the iris surface, with
extension to the ciliary body and choroid (Gelatt, 2007).
In the cat, ocular melanomas are more common than oral and dermal ones,
and ocular and oral ones are more malignant that dermal ones, with higher
rates of mortality and metastasis (Pigatto et al., 2010).
Not all iris hyperpigmentation lesions are melanomas or malignant lesions.
Brown hyperpigmentation of the anterior surface of the iris may start out as
single or multifocal pinpoint, flat regions, termed iris freckle or nevus. The
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hyperpigmentation may progress to diffuse iris hyperpigmentation or
coalescing freckles but still without changing the contour of the eye, is
termed iris melanosis. This is considered a benign process, but increasing
darkness and size of pigmented areas can be observed over months to
several years, and the cells may eventually undergo malignant
transformation into iris melanoma. Melanoma must be differentiated from
non-neoplastic lesions, including pigmented cysts, freckles, nevi,
discoloration consequent to granulomatous or nongranulomatous
inflammation; and other intraocular tumors: adenoma or adenocarcinoma,
lymphosarcoma, and metastatic tumors (Peiffer et al., 2002).
MATERIALS AND METHODS
In the Clinics Department of Surgery from the Faculty of Veterinary
Medicine Bucharest, two Russian Blue males had been examined and
diagnosticated with iris melanosis. Periodical ophthalmic examinations
highlighted the transformation of the hyperpigmentation area into tumoral,
nodular masses which spreads and blocks the iridocorneal filtration angle.
Evolution of the cases was different, two years, respectively five months.
Case A, Russian Blue, male, 6 years, in may 2010 the left eye presented a
light-brown hyperpigmentation of the iris root, without changing the
contour of the eye (Figure 1). This is considered a benign process, but
increasing darkness and size of pigmented may eventually undergo
malignant transformation into iris melanoma. Because of that the cat was
closely monitoring through regular medical checks.
After 1 year the brown hyperpigmented area expanded with changing the
contour of the pupil and distortion of the iris root, ring-shaped melanoma.
After performing drug mydriasis, dyscoria was observed (Figure 2).
Ultrasonography was performed, which revealed irregular iris thickening, a
iris mass of 0.48 / 0.52 cm. Enucleation was recommended, but the owner
did not accepted the treatment, thus that surgery was not performed. At the
end of the year the hyperpigmented area is darker, increased in size, and
anisocoria is obvious (Figure 3). The enucleation was performed after 2
years from the first visit.
Case B, a 6 year old cat, male, Russian Blue was examined in may 2012,
presenting a brown hyperpigmentation of the iris root, localized at 3
o'clock”, left eye, diagnosticated with iris melanosis. After 5 months the
hyperpigmented area increased in size, deforming the sclero-corneal limbus.
The complications, glaucoma and buphtalmia occurred, so that the eye is
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painful. Physical examination was normal. As complementary exams had
been realized complete blood cell count and serum chemical profiles, that
were in physiological range. The abdominal ultrasonography did not shown
any evidence of metastasis.
Treatment, the same for the both cases, was the enucleation of the eye,
followed by cytological and histological examinations (Gelatt, 2001).
Surgical treatment, in terms of evolution, was applied differently, the
enucleation was realized after 2 years, for case A, and after 5 months for
case B.
Figure 1. Case A, first medical examination, iris melanosis.
Figure 2. Case A, 1 year after the first medical examination.Dyscoria
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Figure 3. Case A, after 1and a half year from the first medical examination.
Figure 4. Case B, dark-brown hyperpigmentation of the iris root.
RESULTS AND DISCUSSIONS
Case A after 2 years from the first visit the enucleation was performed,
followed by histological and cytological examinations. Histologically,
malignant transformation is characterized by a change in the histological
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features of the cell. Tumor cells are exfoliated into the anterior chamber,
implanted in the iridocorneal angle, and invaded the iridal stroma.
Transformed cells tend to be round, with a large round nucleus and a
proeminent nucleoli. Cytological appearance reveales tumoral melanocytes,
epithelioid cells, with anisocytosis and anisokaryosis, brown
intracytoplasmic granules (Figure 5). Histologically, irido ciliary melanoma
with pleomorphic melanic cells, epithelioid and spindle, with moderate
pigmentation and clear criteria of malignancy (Figure 6).
Figure 5. Case A, tumoral melanocytes, with anisocytosis and anisokaryosis. M-G G stain,
ob. x 100
Figure 6. Case A, irido ciliary melanoma. HE stain, ob. x 20
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Case B presented a rapid, a shorter evolution, for only 5 months, contrary to
the case A, which had a 2 year evolution. The diagnostic in iris melanoma is
estabilished after a complete ophthalmic examination: ophthalmoscopy,
tonometry and eye ultrasound to evaluate thickening of the iris root and
ciliay body, to define the tumor shape and the extent of local invasion.
Depending on the lesion’s size and invasiveness, complications such as
secondary glaucoma, corneal edema, hyphema and anterior uveitis may
occur. When complications like glaucoma and buphtalmia occures, such
eyes fall into the category of the “blind painful eye” (Peiffer et al., 2002).
Cytologically are observed tumoral melanocytes, with anisocytosis,
anisokaryosis, frequent karyomegaly and binucleation, along with numerous
melanophages (Figure 7). The histopathological evaluation confirmed the
tumor as a malignant melanoma with involvement of the iris stroma and the
ciliary body. Predominantly spindle melanocytes, pleomorphic, with evident
melanic pigmentation. Spindle cell tumors are arranged in streams and
interweaving bundles (Figure 8).
Figure 7. Case B, melanophages and binucleated cell. M-G G stain, ob. x 100
Differential diagnosis should include iris freckles or nevi, melanosis,
pigmented uveal cysts, iridal discoloration due to inflammation and other
uveal neoplasia. The diagnosis through of the fine needle aspiration
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cytology of anterior segment is not recommended due to potential
intraocular complications. (Boydell and Enache, 2012)
Figure 8. Case B, spindle melanocytes, pleomorphic. Spindle cell tumors are arranged in
streams and interweaving bundles. HE stain, ob. x 20
Diffuse iris melanomas should be regarded as potentially aggressive
malignant neoplasms with a potential for metastatic disease that can have
long latency periods. They may extend through the sclera into the orbit or
extend to the cranial cavity via the optic nerve and may spread to distant
organs. The tendency of feline uveal melanomas is to metastasize first to
regional lymph nodes and later to all visceral organs and to the skeletal
system. Metastasis to the lungs, pleura, heart, pericardium, mediastinum,
hilar lymph nodes, diaphragm, omentum, liver, spleen, bone, and brain has
been documented (Peiffer et al., 2002).
A systemic examination should also be performed to evaluate and check for
metastatic disease. This may include a complete blood profile, including a
blood count and serum chemistry panel, thoracic and abdominal
radiography or abdominal ultrasonography. This is necessary due to the risk
of metastasis in organs such as regional lymph nodes, lungs and liver, being
the main sites for metastasis. Feline intraocular melanoma is considered to
have a greater metastatic potential than in dogs (Peiffer et al., 2002).
In both cases the treatment was surgically, the enucleation of the affected
eye, and cytology and histopathology exams were performed from the
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excised eye. After enucleation, the definitive diagnosis is confirmed by
histophatology.
CONCLUSIONS
Ocular globe enucleation, despite the metastasis risk, represents the only
treatment option that can be considered for iris melanoma.
The earlier the enucleation is performed, the better is the prognosis.
Iris melanoma represent the most common primary intraocular neoplasm in
cats.
For iris melanosis and small iris freckles the treatment recommendation is
monitoring closely through regular medical checks.
Not any melanosis should be treated as a melanoma, neither as melanoma
should not be treated as melanosis.
Thoracic radiographs and complete blood work should be performed prior
to enucleation.
The globe should always be submitted for histopathology examination in
order to confirm the neoplastic disease.
The cats are alive, returns periodically to the clinic for regular checks.
REFERENCES
Boydell P., Enache A., 2012. Approach to feline iris melanoma. Veterinary practice, 8, 18-
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Robert L. Peiffer , Jr., and Kenneth B. Simons, 2002. Ocular tumors in animals and
humans. Iowa State Press, Iowa
Pigatto J.A.T., Hünning P.S., Almeida A.C.V.R., Pereira F.Q., Freitas L.V.R.P., Gomes C.,
Schiochet F., Rigon G.M. & Driemeier D., 2010. Diffuse Iris Melanoma in a Cat. Acta
Scientiae Veterinariae. 38(4): 429-432.
Gelatt K. Veterinary Ophthalmology, Fourth Edition, Editura Blackwell Publishing, Vol
I-II, USA,
2007.
Gelatt K., Gelatt J.P. - Fundamentals of Small Animal Ophthalmic Surgery, Butterworth-
Heinemann, 2001.
ResearchGate has not been able to resolve any citations for this publication.
  • K. -Veterinary Gelatt
  • Ophthalmology
Gelatt K. -Veterinary Ophthalmology, Fourth Edition, Editura Blackwell Publishing, Vol I-II, USA, 2007.