Melanoma is a rare neoplasm in small ruminants, particularly in sheep, and is uncommon in young animals. This study describes the clinical, cytological, histopathological, and immunohistochemical findings of a melanoma in a lamb. A three-month-old female sheep presented with a progressively growing mass in the left periauricular region, first observed at 45 days of age. Cytological evaluation revealed atypical cellular proliferation with marked pleomorphism and mitotic figures, suggesting a malignant neoplastic process. Imaging examinations demonstrated increased soft-tissue volume without evidence of bone involvement. Surgical excision was performed for both diagnostic and therapeutic purposes. Histopathological examination revealed a non-encapsulated, densely cellular, infiltrative neoplasm predominantly composed of epithelioid cells, with marked anisocytosis and anisokaryosis, a high mitotic index, intracytoplasmic melanin pigment, and areas of necrosis. Immunohistochemical analysis showed positive immunostaining for S100 and Melan-A, confirming the melanocytic origin of the neoplasm. Despite surgical removal, rapid local recurrence and clinical deterioration were observed, culminating in death within 30 days, indicating aggressive biological behavior and possible metastatic dissemination. This report demonstrates that, although rare in sheep, melanoma can occur in young animals and may progress rapidly, with a poor prognosis, highlighting the importance of an integrated diagnostic approach and its inclusion in the differential diagnosis of cutaneous masses in lambs.
Germ cell tumors can be classified as teratoma, embryonal carcinoma, yolk sac carcinoma, dysgerminomas and seminomas. Teratomas are composed by well-differentiated cells from at least two of the three embryonic layers, and are more commonly in ovaries or testicles, but can occur extragonadal. This case describes a subcutaneous mature teratoma in a 6-month-old kitten. Macroscopically, the tumor was multilobulated and firm, measuring 11 x 6,5 x 5cm; on cut surface, multiple cystic cavities, solid white areas and hard portions. Histologically, cells derived from the three layers were present – hair follicles and glands, nervous tissue, odontogenic epithelium, respiratory epithelium, and different mesenchymal cells (bone, adipocytes, muscle fibers and fibrous tissue). Immunolabeling for pancytokeratin, vimentin, GFAP and p40 were strong in the different types of cells, and no immature tissue was seen. So, the tumor was classified as a mature extragonadal teratoma. The mass was completely excised and no recurrence was seen.
This report describes the first known spontaneous case of B. coridifolia poisoning in a domesticated llama. In August 2023, the death of a 10-month-old female llama was reported on a farm in the Santa Catarina Plateau, Brazil. The affected llama had been acquired 2 months earlier from Paraná and initially kept with sheep on ryegrass pasture. One day before death, it was moved to a native field heavily invaded with B. coridifolia. Clinical signs included polydipsia and muscle tremors, progressing rapidly to death approximately 14 h after the onset of clinical signs. At necropsy, the 1st and 2nd gastric compartments (C1 and C2) contained abundant fibrous ingesta and exhibited mild mucosal congestion. In the 3rd gastric compartment (C3), mild to moderate congestion, predominantly affecting the caudal region, was observed. Histopathology revealed marked diffuse mucosal necrosis with inflammatory infiltrates predominantly composed of neutrophils and macrophages, and mild edema in the aglandular portions of C1 and C2. In C3, mild to moderate congestion was observed. Additional findings included pulmonary congestion and edema, renal congestion, and centrilobular hepatocellular degeneration. Specimens of B. coridifolia collected from the property were submitted to the Herbarium Lages of the State University of Santa Catarina (LUSC) for botanical confirmation. The epidemiological, clinical, and pathological findings supported the diagnosis of B. coridifolia (mio-mio) toxicosis.This case underscores the importance of proper pasture management and careful monitoring when relocating animals to areas containing known toxic plants.
Penile and preputial squamous cell carcinomas are among the most common tumors in horses, and inflammation of the external genitalia caused by Halicephalobus gingivalis is an important differential diagnosis. H. gingivalis is a free-living nematode that causes fatal parasitic encephalitis in horses and humans and can eventually be diagnosed in the kidneys, lymph nodes, lungs, genital and ocular mucosa. The objective was to characterize clinical and pathological lesions caused by H. gingivalis infection in the prepuce with concomitant involvement of penile squamous cell carcinoma in an equine. A 15-year-old male Pampa horse with prepuce and penis ulcerated lesions had these surgically excised. Histopathological analysis revealed granulomatous posthitis with H. gingivalis intralesional and ulcerated penile squamous cell carcinoma. The animal had a satisfactory clinical and surgical evolution, and there was no recurrence of the lesions after a six-month follow-up period. Considerations regarding the route of infection, treatment, and zoonotic potential were highlighted, showing the importance of including this pathogen in the differential diagnosis of nodular lesions affecting the preputial and penile areas in horses.
Diffuse immunoexpression of Preferentially Expressed Antigen in Melanoma (PRAME) is an ancillary diagnostic tool for distinguishing human melanoma from melanocytic nevi. Canine melanocytic neoplasms are common in veterinary diagnostic practice; however, no established immunohistochemical biomarkers of malignancy are currently available. This case series study aimed to investigate the immunoexpression of the anti-PRAME (EPR20330) antibody in canine melanocytic tumors. Two cutaneous melanocytomas and six melanomas from distinct anatomical sites (haired skin, oral cavity and feet) were submitted to immunohistochemistry protocol with anti-PRAME antibody (clone EPR20330, dilution 1:100, Abcam) overnight at 4°C. Nuclear immunolabeling was scored on a 5-point scale based on the percentage of positive tumor cells (0: none; 1: 1–25%; 2: 26–50%; 3: 51–75%; 4/diffuse: ≥76%). The two evaluated melanocytomas were PRAME-negative. All melanomas were PRAME-positive and diffuse nuclear immunolabeling was observed in 4/6 cases. To the best of our knowledge, this is the first study to demonstrate the immunohistochemical expression of the anti-PRAME antibody (clone EPR20330) in canine melanomas. Our preliminary findings, based on a limited sample size, suggest that PRAME may represent a promising ancillary diagnostic marker for these tumors, similar to its use in human samples. However, further studies with larger cohorts are needed to better characterize its labeling patterns in canine melanocytic neoplasms and to confirm its diagnostic value in veterinary pathology.
