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Canine limbal melanoma
A D VA N C E S
CANINE LIMBAL MELANOMA Background Canine limbal melanomas are melanincontaining tumors that arise from the junction of the cornea and sclera. Similar appearing tumors are epibulbar extensions from a canine anterior uveal melanoma (CAUM). Limbal melanomas are usually wellcircumscribed, raised, heavily pigmented tumors that invade the cornea, conjunctiva, and sclera, particularly at the dorsolateral quadrant of the limbus. Their typical behavior is benign, but tumor expansion with intraocular extension may lead to loss of vision and may threaten the globe. Breed predispositions occur in the German shepherd dog, golden retriever, and Labrador retriever.
limbal melanoma, 2 had CAUM, and 1 had diffuse ocular melanosis. In these 8 dogs, there was a pattern consistent with the conditions being caused by genetic mutations. Similar relations were evident in 6 Labrador retrievers. Two Labrador retrievers had limbal melanoma and 4 had CAUM. Histological features suggestive of malignancy were present in 5 of 22 cases (23%). Four of 22 cases (18%) had intratumor necrosis, and cellular atypia was present in 1 of 22 cases (5%).
Author Conclusion In golden and Labrador retrievers, limbal melanomas, CAUM, and ocular melanosis are inheritable and the same genetic mutations may be associated with melanocytic disease at different ocular sites. The same genetic mutations may be present in both breeds. Histologic examination should be performed to identify those with greater malignant potential.
Inclusions Objectives To review the clinical and histological features of canine limbal melanoma, to perform pedigree analysis on breeds predisposed to limbal melanoma to establish if common ancestry exists, and to investigate if any ancestral relationship exists between canine limbal melanoma and CAUM.
Procedure Medical records of 30 dogs with limbal melanoma were reviewed. Follow-up information was obtained by re-examination of patients or interviews with the referring veterinary surgeons or the owners. Pedigrees were analyzed for common ancestry.
Results The mean age at diagnosis was 6.2 years (range, 1 to 11 years) with a bimodal distribution of ages with peaks at 3 to 4 years and 7 to 10 years. There was no eye predilection or predisposition for gender or hair coat color. Twenty-five (83%) of the limbal melanomas occurred within a dorsal arc from the dorsomedial to the ventrolateral limbus. Labrador and golden retrievers were affected 3 and 4 times, respectively, more commonly than other breeds in the melanoma group. Pedigree analysis was performed on 8 golden retrievers. Five of the 8 dogs had
Four figures, 1 table, 6 references.
Editor Annotation Canine limbal melanoma generally present as a smooth, raised, pigmented mass at the limbus that invades the cornea, conjunctiva, and sclera. Typically, the dog’s eye is visual and comfortable at presentation. Limbal melanoma must be differentiated from an intraocular melanoma that has extended from the uveal tract. This can often be done by a good clinical examination, but may also be assisted by ocular ultrasonography. In most situations, referral to a veterinary ophthalmologist for diagnosis and treatments is recommended. I prefer to see these cases as early in the disease process as possible as it increases the therapeutic options that are available. Many therapeutic options are available, including complete surgical resection followed by grafting, partial resection with adjunctive laser treatment, and partial resection with adjunctive cryotherapy. My preference is to perform partial resection followed by adjunctive laser treatment of the deep portion of the mass. Partial resection allows for histopathologic evaluation as well as decreases the amount of mass that must be treated with laser energy. After treatment, the treated site must be monitored carefully for any evidence of regrowth. If regrowth is confirmed, additional laser therapy is usually
PAG E 7
PA G E 8
A D VA N C E S
beneficial. With early referral, we should be able to treat the mass and save vision. (REH) Donaldson D, Sansom J, Scase T, et al. Canine limbal melanoma: 30 cases (1992-2004). Part 1. Signalment, clinical and histological features and pedigree analysis. Vet Ophthalmol 2006;9:115-119.
CANINE LIMBAL MELANOMA Background Canine limbal melanomas are melanincontaining tumors that arise from the junction of the cornea and sclera. Similar appearing tumors are epibulbar extensions from a canine anterior uveal melanoma (CAUM). Limbal melanomas are usually wellcircumscribed, raised, heavily pigmented tumors that invade the cornea, conjunctiva, and sclera, particularly at the dorsolateral quadrant of the limbus. Their typical behavior is benign, but tumor expansion with intraocular extension may lead to loss of vision and may threaten the globe. Breed predispositions occur in the German shepherd dog, golden retriever, and Labrador retriever.
limbal melanoma, 2 had CAUM, and 1 had diffuse ocular melanosis. In these 8 dogs, there was a pattern consistent with the conditions being caused by genetic mutations. Similar relations were evident in 6 Labrador retrievers. Two Labrador retrievers had limbal melanoma and 4 had CAUM. Histological features suggestive of malignancy were present in 5 of 22 cases (23%). Four of 22 cases (18%) had intratumor necrosis, and cellular atypia was present in 1 of 22 cases (5%).
Author Conclusion In golden and Labrador retrievers, limbal melanomas, CAUM, and ocular melanosis are inheritable and the same genetic mutations may be associated with melanocytic disease at different ocular sites. The same genetic mutations may be present in both breeds. Histologic examination should be performed to identify those with greater malignant potential.
Inclusions Objectives To review the clinical and histological features of canine limbal melanoma, to perform pedigree analysis on breeds predisposed to limbal melanoma to establish if common ancestry exists, and to investigate if any ancestral relationship exists between canine limbal melanoma and CAUM.
Procedure Medical records of 30 dogs with limbal melanoma were reviewed. Follow-up information was obtained by re-examination of patients or interviews with the referring veterinary surgeons or the owners. Pedigrees were analyzed for common ancestry.
Results The mean age at diagnosis was 6.2 years (range, 1 to 11 years) with a bimodal distribution of ages with peaks at 3 to 4 years and 7 to 10 years. There was no eye predilection or predisposition for gender or hair coat color. Twenty-five (83%) of the limbal melanomas occurred within a dorsal arc from the dorsomedial to the ventrolateral limbus. Labrador and golden retrievers were affected 3 and 4 times, respectively, more commonly than other breeds in the melanoma group. Pedigree analysis was performed on 8 golden retrievers. Five of the 8 dogs had
Four figures, 1 table, 6 references.
Editor Annotation Canine limbal melanoma generally present as a smooth, raised, pigmented mass at the limbus that invades the cornea, conjunctiva, and sclera. Typically, the dog’s eye is visual and comfortable at presentation. Limbal melanoma must be differentiated from an intraocular melanoma that has extended from the uveal tract. This can often be done by a good clinical examination, but may also be assisted by ocular ultrasonography. In most situations, referral to a veterinary ophthalmologist for diagnosis and treatments is recommended. I prefer to see these cases as early in the disease process as possible as it increases the therapeutic options that are available. Many therapeutic options are available, including complete surgical resection followed by grafting, partial resection with adjunctive laser treatment, and partial resection with adjunctive cryotherapy. My preference is to perform partial resection followed by adjunctive laser treatment of the deep portion of the mass. Partial resection allows for histopathologic evaluation as well as decreases the amount of mass that must be treated with laser energy. After treatment, the treated site must be monitored carefully for any evidence of regrowth. If regrowth is confirmed, additional laser therapy is usually
PAG E 7
PA G E 8
A D VA N C E S
beneficial. With early referral, we should be able to treat the mass and save vision. (REH) Donaldson D, Sansom J, Scase T, et al. Canine limbal melanoma: 30 cases (1992-2004). Part 1. Signalment, clinical and histological features and pedigree analysis. Vet Ophthalmol 2006;9:115-119.