A case of primary choroidal malignant melanoma in a cat

This report describes the clinical presentation, diagnosis, histological lesions, and prognosis of a primary choroidal malignant melanoma in a 15‐year‐old cat. The animal was presented for unilateral blindness. On ocular examination, a raised pigmented mass protruding from the posterior pole into the vitreous body was observed by diffuse transillumination and indirect ophthalmoscopy. Ocular ultrasound and computer tomography (CT) scan confirmed localization of the tumor to the posterior segment. The diagnosis of primary choroidal melanoma was confirmed by histopathology after enucleation. To our knowledge, this is the first reported case of a feline malignant melanoma with a primary choroidal localization without iris involvement.     

Malignant transformation of a giant congenital pigmented nevus (hamartoma) in a dog

A male Golden Retriever was born with a large area of abnormal skin and hair on the distal pelvic limb. A tumour arose from the proximal margin of this area at 5 years of age. Histopathological examination of the abnormal area of skin revealed an area in which follicles were surrounded by nodular accumulations of densely packed round to spindle-shaped cells with fine granular intracytoplasmic melanin. Similar cells were present within the subcutaneous fat, and clusters of densely pigmented melanocytes were scattered within the basal epidermis, follicular epithelium, and dermis. A diagnosis of giant congenital pigmented nevus (hamartoma) was made. The tumour from the proximal end of this area was composed of densely packed, moderately pleomorphic, poorly differentiated and pigmented, spindle-shaped to epithelioid melanocytes, and was diagnosed as malignant melanoma. Metastasis of the malignant melanoma to the stifle and inguinal regions occurred within 6 months. To date, the authors are unaware of prior reports of a canine giant congenital pigmented nevus (hamartoma) with transformation to a malignant melanoma.     

Melan A and S100 protein immunohistochemistry in feline melanomas: 48 cases

Immunohistochemistry, using a monoclonal antibody to Melan A and a polyclonal antibody to S100 protein, was applied to 48 formalin-fixed, paraffin-embedded specimens of feline melanoma. Forty-two cutaneous, three oral, one mucocutaneous, and two metastatic melanomas comprised the tumors. Thirty-two tumors (67%) were positive for Melan A and 42 (87.5%) were positive for S100. All but one of the tumors that were positive for Melan A were also positive for S100. S100 was detected in 11 of 16 tumors that were negative for Melan A. Seventy-five percent (9 of 12) of amelanotic melanomas were negative for Melan A. Normal adrenal cortex, the cerebellum, and the skin had cells that were positive for Melan A. Sebaceous adenoma was the only nonmelanocytic tumor examined that reacted with antibody to Melan A. Although less sensitive than S100 protein, Melan A is more specific for melanoma and is useful in differentiating feline cutaneous melanoma from the more common pigmented basal cell tumor.     

Spindle B cell melanoma in the choroid of a dog

An 8-year-old Schnauzer bitch developed a placoid pigmented mass in the dorso-nasal quadrant of the fundus. A malignant melanoma was diagnosed on the basis of its ophthalmoscopic appearance and on its A and B scan ultrasonography features. Histopathology revealed that the mass was a heavily pigmented spindle B cell melanoma of the choroid. Bruch's membrane was ruptured and the retina was locally detached. The tumour had features similar to choroid melanomas in man which arise from nevi. A review of the literature and of 16 previously unpublished cases of primary canine uveal melanomas confirmed the prevailing impression that choroidal melanomas are rare in the dog.     

Tail-base mass from a "horse of a different color"

A 14-year-old bay Thoroughbred gelding was presented for evaluation of a mass at the base of the tail. The mass had been present for 1 year, and recently had begun to increase in size. Additional masses were found around the eye and shoulder. A fine-needle aspirate of the tail-base mass revealed highly anaplastic round to polyhedral cells containing dark green to black cytoplasmic granules interpreted to be melanin. Histologically, the mass was composed of pleomorphic, poorly pigmented, round to polyhedral cells interpreted to be neoplastic melanocytes. With immunohistochemistry, the cells were positive for vimentin and S-100, but negative for pancytokeratin and Melan-A. The cytologic and histopathologic diagnoses were amelanotic melanoma. The horse was treated with cimetidine, but the tumor continued to progress. In this report, we describe the cytopathologic features of an aggressive amelanotic melanoma in a non-grey horse and emphasize the unique correlation between cytologic and histologic findings.     

Malignant melanoma in a zebra finch (Taeniopygia guttata): cytologic, histologic, and ultrastructural characteristics

An approximately 3-year-old adult male zebra finch (Taeniopygia guttata) was diagnosed with malignant melanoma. The large darkly pigmented tumor was located in the coelom, extended from the apex of the heart to the cloaca, and was adherent to the intestines and the ventriculus. Dark small masses (likely metastases) were observed in the lungs. Cytologically, the neoplasm consisted mainly of round to oval cells with brown or pale blue to blue-brown pigment. Lesser numbers of cells were stellate to dendritic with abundant amounts of brown pigment granules or were markedly pleomorphic with variable amounts of pigment. Histologically, the tumor consisted of dense sheets and aggregates of infiltrative melanocytes that were negative for S-100 and Melan A. A few cells were consistent with "signet-ring" melanocytes. Melanocytes examined by electron microscopy contained typical structures, mainly premelanosomes and melanosomes, of this cell type. However, melanocytes with marked pleomorphism also contained intracytoplasmic aggregates of filaments, consistent with previously reported ultrastructural findings in signet-ring or rhabdoid melanoma of nonavian species.     

Cosmetic rostral nasal reconstruction after nasal planum and premaxilla resection: technique and results in two dogs

Objective— To describe a novel reconstructive technique after nasal planum and premaxilla resection.
Study Design— Case report.
Animals— Dogs (n=2) with squamous cell carcinoma (SCC) of the nasal planum.
Methods— A 9-year-old neutered female Labrador retriever (dog 1) and an 11–year-old neutered male Golden retriever (dog 2) had resection of the nasal planum and premaxilla for treatment of locally invasive SCC. Reconstruction of a nasal planum facsimile was based on use of the nonhaired pigmented margins of bilateral labial mucocutaneous rotation-advancement flaps.
Results— Reconstruction of the premaxilla by construction of a nasal planum facsimile resulted in uncomplicated wound healing and improved cosmesis. There was no tumor recurrence at 1290 (dog 1) and 210 (dog 2) days after surgery.
Conclusion— Reconstruction of a nasal planum facsimile was successfully performed without complications in 2 dogs with high owner satisfaction with cosmetic appearance.
Clinical Relevance— This technique represents a significant advancement in surgical cosmetic outcome, may potentially reduce postoperative complications, and should be considered for dogs requiring nasal reconstruction after nasal planum resection with premaxillectomy.     

Pigmented epidermal plaques in three dogs

Papillomavirus was identified in pigmented epidermal plaques (PEP) from three dogs: a miniature schnauzer with hyperadrenocorticism and hypoglobulinemia, an American Staffordshire terrier with hypoglobulinemia, and a Pomeranian with unconfirmed hypothyroidism. Squamous cell carcinoma (SCC) arose within several plaques in the Pomeranian. Clinical improvement coincided in the first two cases with treatment of the concurrent disease and the administration of low-dose oral interferon-alpha. This is the first report of PEP in an American Staffordshire terrier and a Pomeranian. The potential for malignant transformation of PEP to SCC emphasizes the need for recognition and clinical management of PEP.     

Unusual presentation of an anterior uveal melanocytoma in a 3-year-old poodle

A poodle was referred for evaluation of a pigmented mass in the right eye. The differential diagnoses included an ocular melanoma or ocular melanosis. The right eye was removed and an anterior uveal melanocytoma was confirmed on light microscopical examination.     

Malignant melanoma of the conjunctiva in a cat

A conjunctival melanoma was diagnosed in an adult domestic cat. The neoplasm was excised without further complications. It is important to differentiate conjunctival melanoma from other types of pigmented ocular neoplasia. In man, conjunctival melanomas are often malignant tumors with potential for metastatic behavior. Although this neoplasm had histologic features of malignancy, no evidence of local recurrence or metastasis has been apparent during the 11-month follow-up period.     

Unusual presentation of a metastatic uveal melanoma in a cat

A 10 year-old, spayed female Domestic Short-Haired (DSH) cat was diagnosed with a large primary uveal melanoma and exenteration was recommended. Thoracic radiographs, abdominal ultrasonography, and complete blood count and serum biochemistry panel did not reveal any abnormality compatible with metastatic disease and surgery was performed. Histopathologic study of the eye confirmed a diffuse iris melanoma. Five months later, the cat presented with a lameness of the right anterior extremity. On physical exam the right elbow was swollen and painful. Radiographs showed a severe osteolysis of the radial head and proximal diaphysis. Fine needle aspiration of the radius head identified a round cell neoplasm with scattered cells containing intracytoplasmatic pigmented granules, compatible with metastatic melanoma. The owners decided not to treat the patient with chemotherapy and declined a biopsy. Two months later, the cat died and necropsy was performed confirming bone metastasis of the uveal melanoma. A diagnosis of generalized metastasis from primary diffuse iris melanoma was made. This report describes, for the first time, long bone metastasis from an uveal melanoma in a cat.     

Canine digital tumors: a veterinary cooperative oncology group retrospective study of 64 dogs

We compared clinical characteristics and outcomes for dogs with various digital tumors. Medical records and histology specimens of affected dogs from 9 veterinary institutions were reviewed. Risk factors examined included age, weight, sex, tumor site (hindlimb or forelimb), local tumor (T) stage, metastases, tumor type, and treatment modality. The Kaplan-Meier product limit method was used to determine the effect of postulated risk factors on local disease-free interval (LDFI), metastasis-free interval (MFI), and survival time (ST). Outcomes were thought to differ significantly between groups when P < or = .003. Sixty-four dogs were included. Squamous cell carcinoma (SCC) accounted for 33 (51.6%) of the tumors. Three dogs presented with or developed multiple digital SCC. Other diagnoses included malignant melanoma (MM) (n = 10; 15.6%), osteosarcoma (OSA) (n = 4; 6.3%), hemangiopericytoma (n = 3; 4.7%), benign soft tissue tumors (n = 5; 7.8%), and malignant soft tissue tumors (n = 9; 14%). Fourteen dogs with malignancies had black hair coats, including 5 of the 10 dogs with MM. Surgery was the most common treatment and, regardless of the procedure, had a positive impact on survival. None of the patient variables assessed, including age, sex, tumor type, site, and stage, had a significant impact on ST. Both LDFI and MFI were negatively affected by higher T stage, but not by type of malignancy. Although metastasis at diagnosis correlated with a shorter LDFI, it did not have a significant impact on ST. On the basis of these findings, early surgical intervention is advised for the treatment of dogs with digital tumors, regardless of tumor type or the presence of metastatic disease.     

Intraocular melanoma in a horse.

Sudden unilateral blindness occurred in a 7-year-old grey gelding Quarterhorse. Ophthalmoscopy revealed a pigmented mass arising from the nasal ciliary body of the right eye and extending around the posterior surface of the lens, and there were pigmented particles in the vitreous. Examination of the enucleated globe showed a circumscribed, black, dense and symmetrically ovoid mass with sessile attachment to the nasal ciliary region and extension to posterior lens capsule, vitreous and along the vitreal face of the detached retina to the optic papilla. The mass was composed of heavily pigmented, plump, polyhedral cells that invaded the vitreous and the inner limiting membrane of peripapillary retina and optic papilla. It was considered to be a primary, malignant, intraocular melanoma arising from a large uveal nevus.     

Feline conjunctival melanoma: histopathological characteristics and clinical outcomes

Purpose  We report on the histopathology and clinical features of 21 cases of feline conjunctival melanoma.
Methods  A total of 18 cases are from the COPLOW collection and three cases from Antech Diagnostics. We tabulated the location of the tumor, pigmentation, cell shape, mitotic index and presence of multinucleated tumor cells. Surveys were sent to referring ophthalmologists to obtain further information about each case.
Results  The mean age of the cats was 12.4 years. A total of 11 cases were neutered males, six spayed females, and one each of intact female and male. Thirteen of the 21 cases were located on the bulbar conjunctiva, three on third eyelid only, three on palpebral conjunctiva. Sixteen tumors were pigmented while five were amelanotic. Seventeen of the cases consisted of round cell only while four cases were mixed populations of round and spindle cell. Fourteen of the cases contained multinucleated cells. The mitotic index ranged from 0 to 45 mitotic figures/10 HPF. Of the 13 cases with adequate follow-up information, four showed local recurrence while three reported metastasis. Eight cats had died at the time of the survey. Survival time post-diagnosis ranged from 0.5 to 36 months. Two cases had metastasized to the submandibular lymph nodes and in a third case, an abdominal mass was detected.
Conclusions  Feline conjunctival melanoma is most frequently found on the bulbar conjunctiva, are mostly round cells and suggest that conjunctival melanoma in cats has a poorer long term prognosis than the same neoplasm in dogs.     

Expression of S100a, vimentin, NSE, and melan A/MART-1 in seven canine melanoma cells lines and twenty-nine retrospective cases of canine melanoma

We evaluated the expression of vimentin, S100a, and Melan A/MART-1 (melanoma antigen recognized by T cells 1) in seven cell lines established independently from dogs with canine melanoma. We also compared routine immunostaining of 29 clinical specimens from melanoma cases using vimentin, S100a, and neuron-specific enolase (NSE) with staining for Melan A/MART-1 as part of a diagnostic panel. All the cell lines were positive for expression of vimentin and S-100a. MelanA/MART-1 expression was seen consistently in only two of the seven cell lines. Staining for Melan A/MART-1 was most intense near areas of heavy melanin pigmentation. All except one of the clinical specimens were positive for vimentin. S 100a was expressed in the majority of both pigmented (15/20, 75%) and amelanotic (8/9, 88.8%) tumors. Seventeen of 29 (58.6%) tumors were positive for NSE. Melan A/MART-1 was expressed in 18/29 (62%) tumors, including 90% of pigmented tumors, but in no amelanotic tumors. Intensity of Melan A/MART-1 staining correlated positively with biologic behavior, with seven malignant tumors showing negative to weak staining and 10 benign tumors showing moderate to strong staining. Three malignant tumors showed moderate to intense staining for Melan A/ MART-1. Our results suggest that expression of Melan A/MART-1 may be unstable in cultured cell lines. Assessment of both S100a and Melan A/MART-1 expression is useful to confirm a diagnosis of canine melanoma, and Melan A/MART-1 may be especially informative regarding the biologic behavior of these tumors.     

A case of conjunctival melanoma in a cat

Since 1985, 5 cases of feline conjunctival melanoma have been reported in the literature. Information on feline conjunctival melanoma epidemiological features, localizations, macroscopic features and histological features is limited. We are describing the clinical, histopathologic features and outcomes in a cat that presented clinically with a slow developing dark brown mass located under the upper eyelid of the left eye. Pertinent literature is reviewed; and the recognizable clinical features and treatment are discussed. The mass was surgically resected. Despite its size, the lesion was easily separated from underlying tissues, making possible a macroscopic complete resection that left intact the adjacent conjunctiva. The tumour histological examination has showed a pigmented melanoma lacking encapsulation, but presenting a clear zone delimiting the lesion. It was exclusively composed of epithelioid cells, and presented mild cellular anaplasia and weak mitotic activity. These features allowed it to be classified as a quite differentiated melanoma with few signs of potential malignancy. In accordance with these histologic features, no recurrence has been registered 34 months after surgery. Thus, a favorable outcome is now reported for two out of six cases of conjunctival melanoma in the cat. This report also confirms the predilection for this neoplasm to arise from the bulbar conjunctiva.     

Squamous cell carcinoma in a digit of the hind limb with systemic metastasis in a 17-year-old female koala

We encountered a case of cutaneous squamous cell carcinoma (SCC) in a 17-year-old female koala at a zoo. A fragile, papillary, elevated mass was found on the third digit of the right hind limb. SCC was identified histopathologically: squamous cell-like polygonal tumor cells showed a nest-like growth pattern with epidermal down growth, central keratinization and necrotic foci, and invaded dermal connective tissues. Metastatic lesions were observed in various organs, including the lung and axillary lymph node: in the lung, multiple metastatic foci similar to the primary lesion, and in the axillary lymph node, individual polygonal tumor cells infiltrated the sinusoids. Immunohistochemistry revealed that the tumor cells were positive for proliferating cell nuclear antigen, which exhibited 32–33% of labeling indices in the tumor cells. To our knowledge, this is the first report of a case of SCC in a digit of a koala.     

Malignant melanoma of the third eyelid in a horse

An 8‐year‐old grey Quarter Horse gelding was referred for evaluation of a rapidly growing mass associated with the third eyelid of the left eye. A pigmented mass of approximately 2 cm in diameter was palpated and visualised associated with the conjunctival lining of the nictitans. It was not possible to palpate normal nictitans deep to the base of the mass. A full dermatological examination revealed no other melanomas in common sites. Based on the size and rapid growth of the mass, surgical excision and one application of local chemotherapy was performed under general anaesthesia. Histopathology confirmed the diagnosis of malignant melanoma and the presence of clean surgical margins. There was no recurrence at 5 weeks post surgery. To our knowledge, this is the first report of a primary malignant melanoma of the third eyelid in a horse.     

Comparison of tyrosinase-related protein-2, S-100, and Melan A immunoreactivity in canine amelanotic melanomas

Tyrosinase-related protein-2 (TRP-2) is a highly conserved melanogenic enzyme expressed in both pigmented and unpigmented melanomas of the mouse. To determine whether TRP-2 would be a good diagnostic marker for amelanotic melanomas of the dog, we performed immunohistochemistry for TRP-2, S-100, and Melan A on 21 canine tumors identified as amelanotic melanomas based on routine histopathologic examination. Thirteen of the tumors were TRP-2 positive, 10 were Melan A positive, and 19 were S-100 positive. TRP-2 was expressed in the cytoplasm of tumor cells in both primary and metastatic melanomas. S-100 staining was positive in all of three schwannomas and two of three gastrointestinal stromal tumors (one fibrosarcoma and one leiomyosarcoma) tested. Neither Melan A nor TRP-2 antibodies reacted with these tumors. Our findings indicate that staining for TRP-2 is a sensitive and specific method for confirming the diagnosis of amelanotic melanoma in dogs.