Congenital and acquired melanocytomas (benign melanomas) in eighteen young horses.

In a retrospective study, cutaneous melanocytic tumors from 18 horses, less than 2 years old, were examined histopathologically and clinical follow-up requested. Melanocytomas (benign melanomas) occurred in a variety of breeds and in horses of varied coat color. The age of the horses at the time of biopsy ranged from 3 weeks old to 2 years old. Four melanocytomas were congenital, 11 melanocytomas were acquired by 1 year of age, and three were acquired prior to 2 years of age. Of the 18 horses, five were male, and 13 were female. All tumors were solitary and located on the legs or trunk; none were in the perineal region. Ulceration of the overlying epidermis was common. Tumors were generally localized and were not encapsulated. The tumors had a variety of cell patterns ranging from sheets, to streams, or nests of melanocytes. Cellular morphologic findings also ranged from epithelioid, to a mixture of epithelioid and spindle cells or to a spindle pattern. The nuclei were large and euchromatic, especially in the epithelioid cells. Several tumors had moderate cellular pleomorphism and binucleate cells. Mitotic activity was generally low (less than 1/high-powered field), but was readily detected (1-2/high-powered field) in bleached sections of four cases. Melanin pigmentation varied from mild to heavy. Melanophages were admixed with the tumor cells or in the adjacent tissue. Follow-up information was obtained on 15/18 horses and revealed that 14/15 horses were free of recurrence following excision. One neoplasm, that was poorly demarcated and had a spindle cell pattern, was not completely resected and continued to grow. These melanocytic tumors in young horses are distinct from melanomas in aged horses in their location, epithelial involvement, and age of horses affected. The majority of these tumors appear to be benign and share features of melanocytic nevi of human beings.     

Clinical electromyographic studies of canine X-linked muscular dystrophy

Clinical electromyographic studies were performed in dogs (6 weeks to 5.5 years old) with a degenerative myopathy analogous to Duchenne muscular dystrophy. Spontaneous activity, consisting primarily of complex repetitive discharges (pseudomyotonic discharges), was found in all dogs tested, but was most prominent in dogs greater than or equal to 10 weeks old. Myotonic discharges also were found, but were less frequent. Motor unit potentials were generally abnormally brief and frequently polyphasic. Ulnar nerve conduction velocities determined in two 4-month-old dogs were similar to those of unaffected littermates. It was concluded that canine X-linked muscular dystrophy is a primary myopathic process in which complex repetitive discharges and myotonic discharges are a prominent feature. The basis for this spontaneous activity is not known.     

Diagnostic comparison of needle and wedge biopsy specimens of the liver in dogs and cats

OBJECTIVE: To compare morphologic diagnoses determined from needle biopsy specimens obtained from the livers of dogs and cats with morphologic diagnoses determined from wedge biopsy specimens. DESIGN: Prospective study. ANIMALS: 124 dogs and cats. PROCEDURE: 2 needle biopsy specimens were obtained from each animal; wedge biopsy specimens were obtained from the same liver lobe during laparotomy or postmortem examination. Histologic features were scored independently by 3 individuals; a morphologic diagnosis was rendered after histologic features were scored. Cases were included only if at least 2 of the 3 examiners agreed on the morphologic diagnosis; the definitive diagnosis was considered to be the morphologic diagnosis rendered for the wedge biopsy specimen. Physical characteristics (length, width, surface area, degree of fragmentation, and number of portal triads for needle biopsy specimens and surface area for wedge biopsy specimens) were determined. RESULTS: Definitive diagnoses included hepatic necrosis (n = 10), cholangitis-cholangiohepatitis (13), chronic hepatitis-cirrhosis (12), canine vacuolar hepatopathy (11), portosystemic vascular anomaly-microvascular dysplasia (17), neoplasia (10), miscellaneous hepatic disorders (18), and no hepatic disease (33). For individual examiners, the morphologic diagnosis assigned to needle biopsy specimens agreed with the morphologic diagnosis assigned to wedge biopsy specimens for 56 and 67% of the specimens. All 3 examiners agreed on the morphologic diagnosis assigned to needle and wedge biopsy specimens for 44 and 65% of the specimens, respectively. Morphologic diagnoses assigned to needle biopsy specimens concurred with the definitive diagnosis for 59 of 124 (48%) animals. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that needle biopsy specimens of the liver from dogs and cats must be interpreted with caution.     

Severe diaphragmatic necrosis in 4 horses with degenerative myopathy

Severe diaphragmatic necrosis occurred in horses with degenerative myopathy due to polysaccharide storage myopathy (n = 2), nutritional myopathy (n = 1), and vasculitis (n = 1). Blood gas analysis performed in 1 horse indicated development of respiratory acidosis. Respiratory muscle necrosis can be severe in horses with degenerative myopathy and can lead to respiratory failure.     

Renal failure, laminitis, and colitis following severe rhabdomyolysis in a draft horse-cross with polysaccharide storage myopathy.

A Thoroughbred-Percheron crossbred gelding developed a fulminant cascade of sequelae following a severe episode of rhabdomyolysis. Complications may occur with rhabdomyolysis of any etiology. In warmblood horses with Percheron bloodlines, rhabdomyolysis may be secondary to polysaccharide storage disease, and aggressive therapy should be undertaken promptly to avoid the complications.     

Bilateral cystic rete testis in an alpaca (Lama pacos).

A 9-year-old intact male alpaca (Lama pacos) was examined because of marked enlargement of the left scrotum. Ultrasound examination revealed a thin-walled anechoic structure in the area of the left testis. Aspirated fluid contained spermatozoa, many of which had abnormal morphology. Castration was performed and the left testis was markedly enlarged with a clear fluid-filled cyst. The cyst was lined by a single layer of squamous to cuboidal epithelial cells consistent with those originating from rete testis. The right testis was of a comparable size and shape to that of normal alpaca testis, but the rete testis was mildly to moderately dilated. Additional findings included chronic inflammation of the right testis and epididymis and epididymal fibrosis with ductal hyperplasia on the left. The diagnosis was bilateral cystic rete testis, most likely secondary to chronic inflammation.