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

Iridial melanocytoma in a ferruginous hawk (Buteo regalis): A case report and review of avian melanocytic neoplasia

A 21-year-old, suspected female captive ferruginous hawk (Buteo regalis) was followed for 3 years due to an iridial mass of the left eye (OS) that progressively increased in size. Enucleation of OS was eventually recommended due to the iridial mass taking up approximately 75% of the anterior chamber, and the bird seemed less active. A complete physical examination, complete blood cell count, biochemistry, and survey radiographs were performed pre-surgery with no findings indicating metastasis. A subconjunctival enucleation was performed and the globe was submitted for histopathology through the Comparative Ocular Pathology Lab of Wisconsin. The histopathologic evaluation determined the mass to be consistent with an iris melanocytoma, which has not been previously reported in this species. The patient recovered well from surgery and has remained comfortable and active for 117 days post-surgery. This case report aimed to review the current available information on avian ocular neoplasms as well as describe the clinical presentation, medical management and surgical procedure, and long-term follow-up for this patient to enhance clinical understanding of the behavior of iris melanocytic tumors in avian species.

Use of a canine melanoma vaccine in the management of malignant melanoma in an African penguin (Spheniscus demersus)

CASE DESCRIPTION

A 25-year-old 4.4-kg male aquarium-hatched African penguin (Spheniscus demersus) was evaluated because of a raised 1.5 × 0.5-cm pigmented mass extending from within the right naris noted 2 days earlier.

CLINICAL FINDINGS

The penguin had a raised pigmented mass extending out from the right naris and onto the upper beak. Histologic examination of excisional biopsy specimens confirmed a diagnosis of malignant melanoma. A treatment plan including administration of meloxicam, radiation therapy, and immunotherapy was initiated.

TREATMENT AND OUTCOME

Treatment with meloxicam (0.2 mg/kg, PO, q 24 h) was initiated and continued for a total of 45 weeks; however, the medication was discontinued for a period of 6 weeks because of the risk of toxic effects in the chick that the penguin was feeding at that time. The penguin underwent local hypofractionated radiation therapy and received 4 once weekly 8-Gy fractions of radiation (total radiation dose, 32 Gy). The penguin was administered a canine melanoma vaccine transdermally every other week for 4 doses, with a booster injection given 7 months after the first dose. Treatment with the vaccine appeared to have no adverse effects. The penguin's pre- and postvaccination tyrosinase-specific antibody titers were measured with an anti-human tyrosinase-specific ELISA, and a 3-fold titer increase indicated a positive humoral immune response to the canine melanoma vaccination. The penguin died of unrelated causes 54 weeks after initial diagnosis, and there was no evidence of metastasis on necropsy.

CLINICAL RELEVANCE

These case findings suggested that vaccination with a canine melanoma vaccine may be a safe and useful adjunct treatment for management of malignant melanoma in penguins.

Uveal Malignant Melanoma in a Hybrid Macaw Parrot (Ara chloropterus × Ara militaris)

An adult male green-winged (Ara chloropterus) × military (Ara militaris) hybrid macaw of unknown age was presented to the Texas A&M Veterinary Medical Teaching Hospital for evaluation of left periocular swelling, blepharospasm, and ocular discharge. Complete ophthalmic examination and B mode ocular ultrasonography were performed to evaluate the affected eye. Ocular examination revealed a blind left globe with exophthalmos, periocular swelling, diffuse corneal edema, and severe anterior fibrinous uveitis obscuring visualization of the intraocular structures. An ultrasound examination revealed a hyperechoic mass that filled the posterior segment of the globe. Focal discontinuity of the posterior sclera suggested scleral rupture. Enucleation with histopathology was recommended and performed 1.5 months later. Intraoperatively, a heavily pigmented and friable soft tissue mass extruded through the posterior sclera and extended into the orbit. Histologically, the mass was consistent with a malignant melanoma. The patient died 18 hours after the surgical procedure because of unknown complications. Postmortem examination did not identify evidence of metastasis. This study described the clinical appearance and histopathologic findings of a rare ocular neoplasm with extrascleral extension in a hybrid macaw. Although uncommon in psittacine birds, primary ocular melanocytic neoplasms may display features of malignancy with scleral or orbital invasion, or both.

Rhabdoid melanoma in a harpy eagle (Harpia harpyja)

A 28-year-old male harpy eagle (Harpia harpyja) with a history of anorexia, hyporexia, lethargy, and progressive weight loss was found dead and submitted for post-mortem examination. Gross findings include dark brown discolouration of testes and lungs; the testes were bilaterally enlarged, glistening brown-grey to blackish in appearance, firm, smooth, and multilobulated. The lungs contained a mass with similar features to the testicles, irregularly shaped with multiple nodules. Histology of testis showed round, polygonal and pleomorphic cells, containing melanin pigments and a typical eosinophilic vacuole in their cytoplasm and with severe pleomorphism. An immunohistochemistry panel with Melan-A, vimentin, CK AE1/AE/3, MUM-1 and CD-68 were performed, yielding a positive reaction for Melan-A and vimentin. The morphology of the tumour cells, the presence of melanin pigment and the immunoreactivity for Melan-A and vimentin by the cells led to a diagnosis of rhabdoid melanoma. This is the first case of this pathology in the testis with lung metastasis in a harpy eagle.

Malignant Melanoma in a Long-legged Buzzard (Buteo rufinus): Characterization of Clinical and Histologic Lesions

A 17-year-old, male long-legged buzzard (Buteo rufinus) presented for acute lethargy and black gelatinous tissue in both nostrils. Despite intensive care, the bird died within 2 days. A postmortem computed tomographic scan of the head revealed a complete obstruction of the rostral infraorbital sinus, later confirmed by necropsy. Postmortem examination also highlighted multifocal, black, infiltrating nodules of various sizes (2 mm to 2 cm in diameter) in almost all internal organs: lungs, heart (pericardium, myocardium, endocardium), kidneys, pancreas, adrenals, muscles, and bones (periosteum and medulla). Histologically, the nodules were composed of anaplastic cells containing abundant melanin pigment, consistent with a disseminated melanoma. Malignant melanomas are aggressive neoplasms frequently reported in mammals but rarely found in avian species. In Accipitridae and Falconidae, only 2 cases have been reported.

Malignant Melanoma of the Syrinx and Liver in an African Grey Parrot ( Psittacus erithacus erithacus)

A 20-year-old, female African grey parrot ( Psittacus erithacus erithacus) was examined because of ataxia and weakness. Radiographs were unremarkable, and results of a complete blood cell count revealed leukocytosis and heterophilia. Because of poor response to therapy with meloxicam, doxycycline, and enrofloxacin; deteriorating condition; and poor prognosis, the parrot was euthanatized. Postmortem examination revealed 2 dark red nodules in the liver. No grossly visible mass was observed in the syrinx. Histologic examination of the liver and syrinx revealed similar foci of round, oval, and polygonal cells exhibiting severe pleomorphism, with poorly demarcated cytoplasmic borders and moderate amounts of eosinophilic cytoplasm containing brown to black granules (melanin). The mitotic index was 15. The presence of melanin pigment is consistent with a diagnosis of melanoma at both sites. The multifocal distribution and intravascular invasion indicate metastasis; however, the site of origin was unknown. To our knowledge, this is the first recorded case of melanoma in an avian syrinx.

Metastatic melanomas in young broiler chickens (Gallus gallus domesticus)

Four young broiler chickens affected by multiple melanotic tumors are described. Grossly, there were multiple tumors composed of melanocytes within the skin, skeletal muscle, and multiple visceral organs. Tumors ranged from flattened macules to masses that extensively replaced viscera. Microscopically, melanocytes were often well pigmented, and while there was moderate nuclear anisokaryosis, mitotic rates were low. Immunohistochemical staining of some melanomas with antibodies to S100 proteins, Melan-A, vimentin, or neuron-specific enolase after bleaching of tumor cells with potassium permanganate revealed lack of immunostaining of tumor cells with antibodies to S100, strong positive staining of tumor cells for neuron-specific enolase, moderate staining with antibodies to vimentin, and faint staining for Melan-A. Only neuron-specific enolase staining was evident in unbleached tumor cells. Attempts to identify exogenous avian leukosis viruses in these tumors were unsuccessful.

Malignant melanoma in a seagull (Larus fuscus): morphological and immunohistochemical approach

A common seagull (Larus fuscus) was found near the southern coast of Italy by the veterinarians of the local wild animal rescue center. Physical examination of the bird revealed an ulcerated mass involving a majority of the oral cavity; the mass did not allow for normal feeding. After the bird died necropsy was performed and the mass was histologically and immunohistochemically examined. The morphology and the immunoreactivity for Melan-A and S-100 antigens led to a diagnosis of malignant melanoma. This is the first case of malignant melanoma described in a seagull, and herein we compare the characteristics of the present case with malignant melanoma already described in domestic animals.

Malignant melanoma of the subcutaneous tissues in an umbrella cockatoo (Cacatua alba)

A 24-year-old female umbrella cockatoo (Cacatua alba) was examined because of a subcutaneous swelling of the left shoulder. Radiographs of the left wing revealed boney proliferation of the left proximal humerus. At surgery, an unencapsulated infiltrative nonpigmented mass within the subcutaneous tissue and skeletal muscle was identified overlying the left humerus. The mass was surgically excised and submitted for histologic examination; however, the cockatoo died after excision. Histologically, the mass was composed of nests and sheets of pleomorphic neoplastic cells with a high mitotic index and extensive necrosis. Rare neoplastic cells contained fine brown cytoplasmic granules that stained black with Fontana-Masson, confirming the presence of melanin pigment. The histomorphologic diagnosis was consistent with an anaplastic malignant melanoma of subcutaneous tissues.