Hiroshi Sasai

A collision tumor consisting of granular cell tumor and adenocarcinoma in the uterus of an aged djungarian hamster.

A neoplastic nodular lesion consisting of an admixture of granular cell tumor and adenocarcinoma was found in the uterus of a 26-month-old Djungarian hamster. Neoplastic cells of the uterine adenocarcinoma showed an epithelial nature in their growth patterns and by cytokeratin-immunopositive reaction, exhibiting nuclear pleomorphism. The granular cells had an abundant amount of fine granular eosinophilic cytoplasm and eccentric or central nuclei with no nuclear atypia; the granular structures were positive for periodic acid-Schiff with diastase resistance and were confirmed as lysosomes/autophagosomes by electron microscopy; immunohistochemically, the cells reacted to desmin, vimentin and α-smooth muscle actin and negatively for neurogenic, histiocyte/macrophage or epithelial markers, indicating smooth muscle origin. Because these tumors were generated from different cell origins, a diagnosis of collision tumor was made.

Spontaneous Extraskeletal Osteosarcoma in a Rabbit (Oryctolagus cuniculus): Histopathological and Immunohistochemical Findings

A spontaneously occurring subcutaneous mass in the left forelimb of a nine-year-old rabbit (Oryctolagus cuniculus) was examined histopathologically and immunohistochemically. Clinically, edema and hemorrhage were seen around the mass. No connection of the tumor mass to the appendicular skeleton was found. The tumor was arranged in a solid growth pattern and irregular bundles, and neoplastic cells were polygonal to spindle-shape. Osteoid (positive for osteocalcin) and multinucleated giant cells were diffusely or focally seen. Neoplastic cells were positive for vimentin, osterix and Ki-67, indicating the nature of osteoblasts with proliferating activity, but negative for α-smooth muscle actin, desmin or CD204. Based on these findings, a diagnosis of extraskeletal osteosarcoma was made, a very rare tumor both in laboratory and pet rabbits.

Characteristics of bone fractures and usefulness of micro-computed tomography for fracture detection in rabbits: 210 cases (2007-2013).

OBJECTIVE To characterize bone fractures and the usefulness of micro-CT for imaging fractures in pet rabbits. DESIGN Retrospective case series. ANIMALS 210 client-owned rabbits with bone fractures. PROCEDURES Medical records of rabbits evaluated for bone fractures from 2007 through 2013 were examined. Information was collected on signalment and nature of fractures, and radiographic and micro-CT images of fractures were reviewed. RESULTS Almost half (n = 95 [47.7%]) of fractures were in rabbits < 3 years old. Accidental fall was the most common cause. Vertebral fracture was the most common type of fracture with a nonneoplastic cause (n = 46 [23.2%]) and was most common in the L4-L7 region. The tibia was the most common site for limb fracture among all fractures with a nonneoplastic cause (45 [22.7%]). Twelve (5.7%) fractures had a neoplastic cause, and 7 of these were associated with metastatic uterine adenocarcinoma. Females were significantly more likely to have a fracture caused by neoplasia than were males. Compared with radiography, micro-CT provided more detailed fracture information, particularly for complicated fractures or structures (eg, skull, pelvic, vertebral, and comminuted limb fractures). CONCLUSIONS AND CLINICAL RELEVANCE Findings were useful for understanding the nature of fractures in pet rabbits and supported the use of micro-CT versus radiography for fracture detection and evaluation.

The use of micro-computed tomography in the diagnosis of dental and oral disease in rabbits.

BackgroundThe aim of this study was to investigate the use of a newly developed micro-computed tomography (micro-CT) system for the diagnosis of oral pathologies in small animals, using the rabbit as a model. The diagnosis of dental diseases in rabbits is usually based on oral endoscopy and radiographic imaging, but detailed pathological diagnosis using these methods is frequently difficult. Micro-CT was used in this study to address this challenge.ResultsThis study was conducted using 50 privately owned rabbits, presented to our hospital due to loss of appetite or difficulty feeding. Image recording times were 18 s in normal mode and 120 s in fine mode. The animals were maintained in the required position for scanning via the administration of sedatives. Micro-CT captured with a slice thickness of 60-120 mm has excellent spatial resolution, and is suitable for the clinical diagnosis of dental diseases in rabbits weighing 1-3 kg.ConclusionsMicro-CT can yield more detailed data than radiography or conventional CT. This study determined that this novel imaging modality can be utilized for the accurate assessment of dental and oral diseases in rabbits.

Outcome of limb fracture repair in rabbits: 139 cases (2007–2015)

OBJECTIVE To evaluate outcome of limb fracture repair in rabbits. DESIGN Retrospective case series. ANIMALS 139 client-owned rabbits with limb fractures treated between 2007 and 2015. PROCEDURES Medical records were reviewed for information on fracture location, fracture treatment, and time to fracture healing. RESULTS 25 rabbits had fractures involving the distal aspects of the limbs (ie, metacarpal or metatarsal bones, phalanges, and calcaneus or talus). Fractures were treated in 23 of these 25 rabbits (external coaptation, n = 17; external skeletal fixation, 4; and intramedullary pinning, 2) and healed in all 23, with a median healing time of 28 days (range, 20 to 45 days). One hundred ten rabbits had long bone fractures, and fractures were treated in 100 of the 110 (external skeletal fixation, n = 89; bone plating, 1; intramedullary pinning, 3; and external coaptation, 7). The percentage of fractures that healed was significantly lower for open (14/18) than for closed (26/26) tibial fractures and was significantly lower for femoral (19/26) and treated humeral (4/6) fractures than for radial (23/24) or closed tibial (26/26) fractures. Micro-CT was used to assess fracture realignment during external skeletal fixator application and to evaluate fracture healing. CONCLUSIONS AND CLINICAL RELEVANCE The prognosis for rabbits with limb fractures was good, with fractures healing in most rabbits following fracture repair (109/123). Micro-CT was useful in assessing fracture realignment and evaluating fracture healing.

Multiple Histiocytic Foam Cell Nodules in the Tongue of Miniature Dachshund Dogs

Miniature dachshund dogs are a common breed in Japan and are known to be predisposed to granulomatous diseases. Here we report the pathologic features of multiple lingual nodules in 7 miniature dachshunds. Seven dogs had multiple nodules of variable sizes mainly on the ventral and lateral surface of the tongue. In addition, 1 dog also had masses on the left oral mucosa. Three cases had recurrence after surgical resection. Histologically, the lingual nodules were composed of aggregates of foam cells with clear vacuolated cytoplasm that were negative for oil red O, PAS, and alcian blue. They stained positively for CD204 (macrophage scavenger receptor) and MHC class II and negatively for Iba-1, E-cadherin, adipophilin, cytokeratins, S-100, and nestin. These findings indicate that the multiple lingual nodules in miniature dachshunds are an unusual, unique lesion consisting of macrophage-derived foam cells, which does not correspond to canine lingual diseases reported to date.

Combined hepatocellular-cholangiocarcinoma in a Yellow-headed Amazon (Amazona oratrix).

ABSTRACT A 9-year-old male Yellow-headed Amazon (Amazona oratrix) with a history of anorexia and vomiting died of a liver tumor. The tumor consisted of neoplastic cells with hepatocellular and cholangiocellular differentiations and their intermingled areas. Neoplastic hepatocytes showed islands or trabecular growth with vacuolated eosinophilic cytoplasm. Cells showing biliary differentiation formed ducts or tubules lined by cytokeratin AE1/AE3-positive epithelia, accompanied by desmoplasia consisting of myofibroblasts reacting to α-smooth muscle actin and desmin. The tumor was diagnosed as a combined hepatocellular-cholangiocarcinoma, which is very rare in the avian.

Cardiac hamartoma in a young squirrel monkey who died suddenly.

A case of cardiac hamartoma in a 2-month-old squirrel monkey is reported. The monkey showed a loss of appetite and died suddenly. Microscopically, an encapsulated nodular lesion was found at the right atrial wall. The lesion consisted of irregularly shaped, slender myocytes intermingled with a few fibroblasts and collagen fibers. Neither nuclear atypia nor inflammatory cell infiltrate was seen. The constituting cells had stratified striations in the cytoplasm and reacted immunohistochemically for desmin, indicating the nature of myocytes. Based on the above findings, a diagnosis of cardiac hamartoma was made. This is the first case of cardiac hamartoma in this species.