Internal hemipelvectomy with ischiectomy, partial acetabulectomy, and femoral head and neck excision in a cat with a pelvic osteochondroma.

CASE DESCRIPTION: A 2-year-old 5.1-kg (11.2-lb) castrated male Siberian cat was examined because of a history of an abnormal right pelvic limb gait and a 4- to 5-month history of progressive constipation. Radiographs obtained by the referring veterinarian showed an osteoproductive and osteolytic bony lesion that involved the right ischium and filled the obturator foramen. CLINICAL FINDINGS: A hard mass was palpable in the right inguinal area, and rectal examination revealed a smooth bony mass on the ventral aspect of the right pelvic floor with marked reduction in the pelvic canal space. A 3.9 × 3 × 4.6-cm, mineralized mass bridging the right obturator foramen was present on CT images. The ventral component of the mass was slightly larger than its dorsal component, and lysis of the right pubic bone was present. There was no obvious soft tissue involvement. TREATMENT AND OUTCOME: A limb salvage procedure involving internal hemipelvectomy with ipsilateral ischiectomy, contralateral partial ischiectomy, ipsilateral partial acetabulectomy, and femoral head and neck excision was performed. Histologic examination revealed that the mass was an osteochondroma. The cat recovered well and had good functional limb use immediately after surgery. The cat was still alive 1 year after surgery with good limb use. CLINICAL RELEVANCE: Internal hemipelvectomy involving ischiectomy, partial acetabulectomy, and femoral head and neck excision can result in a good functional outcome in cats if the procedure is planned appropriately with a full understanding of the regional anatomy and adherence to surgical oncologic principles.

Arthroscopic removal of a solitary osteochondroma interfering with the podotrochlear apparatus in a foal.

OBJECTIVE: To report the diagnostics, surgical treatment, and outcome of a juvenile foal with solitary osteochondroma (SO) interfering with the podotrochlear apparatus. STUDY DESIGN: Case report ANIMAL: One 36-day-old Arabian colt. METHODS: Clinical, radiographic, ultrasonographic, computed tomographic, and histopathologic examinations were required to characterize and treat an SO located at the palmar aspect of the diaphysis of the second phalanx of the left forelimb. This SO caused severe distal interphalangeal joint (DIPJ) inflammation, marked interference with the podotrochlear apparatus, and associated lameness. RESULTS: Despite the small size of the foal's foot, complete resection of the SO was possible via palmar DIPJ arthroscopy by using motorized equipment. Full resolution of the lameness was achieved within 3 months of surgery. CONCLUSION: Atypical SO located on the palmar aspect of the second phalanx can cause marked nonseptic inflammation of the DIPJ and interference with the podotrochlear apparatus and should be considered among the differential diagnoses for severe lameness in juvenile foals. Arthroscopic resection of the SO led to an excellent outcome.

Radiographic Description of a Bone Exostosis Lesion on the Caudal Aspect of the Proximal Tibia in Three Thoroughbred Yearlings (2014-2019).

This manuscript describes exostosis lesions originating from the caudal aspect of the proximal tibia identified in three Thoroughbred yearlings as part of the routine review of presale radiographic images. These lesions are hypothesized to be osteochondromas. The identification of bony exostoses on the proximal tibia has not been reported before in current literature. As they have not been described, the future effect on performance or soundness is unknown. Although these cases were not lame at the time of detection, the future growth of the lesion and its impact on surrounding soft tissues is unknown.

Rare Osteochondroma Associated with Natural Mortality of a Wild White-Tailed Deer ( Odocoileus virginianus).

Within a 6-mo period, a radio-collared, white-tailed deer ( Odocoileus virginianus) doe from Delaware, US, developed a fatal head mass consistent with osteochondroma. We suspected a retroviral etiology, but test results were negative. Population implications were not suspected, but this case is concerning as these tumors are not thought to cause mortality.

Multiple osteochondromas of the antlers and cranium in a free-ranging white-tailed deer (Odocoileus virginianus).

This paper reports a case of multiple osteochondromas affecting the antlers and the left zygomatic bone of a free-ranging adult white-tailed buck (Odocoileus virginianus) from Georgia, USA. Along with a few postcranial bones, the antlered cranium of the individual was found in a severely weathered condition and devoid of any soft tissue. The antlers exhibited five pedunculated exostoses that were composed of cancellous bone and, in their peripheral portions, also mineralized cartilage. The largest of the exostoses, located on the right antler, had a maximum circumference of 55 cm. The exostosis arising from the zygomatic bone was broad-based and much smaller than the exophytic outgrowths on the antlers. Diagnosis of the exostoses as osteochondromas was based on their overall morphology, the normal bone structure in their stalk regions, and the continuity of their spongiosa and cortex with the respective components of the parent bones. Antleromas, i.e., pathological outgrowths developing on antlers as a result of insufficient androgen production, were excluded in the differential diagnosis, based on (1) the apparent maturity and, except for the tumors, normal shape of the antlers and (2) the fact that exostosis formation had also affected the zygomatic bone. Previously only a single case of solitary osteochondroma of an antler has been described in the scientific literature. The case presented here is the first report of multiple osteochondromas in a deer. As antlers are regularly collected as trophies, and huge numbers of them are critically inspected each year, the fact that thus far only two cases of antler osteochondromas have been reported suggests that these tumors are very rare.

Osteochondroma on the cranial aspect of the distal radial metaphysis causing tenosynovitis of the extensor carpi radialis tendon sheath in a horse.

CASE REPORT: A 3-year-old Thoroughbred gelding was presented with a grade 3/5 lameness of the right forelimb and effusion of the extensor carpi radialis tendon sheath (ECRTS). Radiographic and ultrasonographic examinations revealed an osteochondroma on the cranial aspect of the distal radius projecting into the fibrous lining of the ECRTS. An open surgical approach was used to remove the osteochondroma and some of the proliferative synovial tissue. CONCLUSION: Six months after surgery the clinical signs had resolved and the horse raced successfully.

Diode laser ablation of a tracheal osteochondroma in a dog.

A mass almost completely obstructing the tracheal lumen was detected during endoscopic investigation of dyspnoea in a four-month-old golden retriever. Histopathology was consistent with osteochondroma. The lesion was ablated using endoscopic diode laser ablation.

SOLITARY OSTEOCHONDROMA OF THE DISTAL THIRD METACARPAL BONE IN A TWO-YEAR-OLD WHITE RHINOCEROS (CERATOTHERIUM SIMUM).

A privately owned, 2-yr-old, 600-kg, intact male white rhinoceros presented with a progressive lameness of the left front limb of 8-mo duration with a focal swelling situated over the dorsoproximal aspect of third metacarpophalangeal joint. Radiographs of the affected limb showed a 28 mm × 26 mm exostosis at the dorsodistal third metacarpal bone. Surgical removal of the exostosis was performed and histopathologic examination confirmed a solitary osteochondroma. A follow-up examination 1 yr after surgical removal revealed total abolishment of the left front limb lameness. This report documents the first diagnosis and treatment of solitary osteochondroma in a white rhinoceros.

Endoscopic treatment of an intrathoracic tracheal osteochondroma in a dog.

CASE DESCRIPTION: A 1.5-year-old spayed female Bernese Mountain Dog was examined for a 6-month history of intermittent vomiting, regurgitation, wheezing, and coughing. Initially, a diagnosis of gastroesophageal reflux disease with secondary aspiration pneumonitis was made but clinical signs did not resolve with treatment. CLINICAL FINDINGS: Thoracic and cervical radiography and CT revealed a sessile, irregularly marginated soft tissue opacity at the level of the fourth rib. Results of a CBC, serum biochemical analysis, and urinalysis were within reference limits. Results of abdominal ultrasonography were normal. TREATMENT AND OUTCOME: Tracheoscopy revealed a firm, irregularly marginated mass apparently originating from the ventral aspect of the trachea, occluding approximately one-half of the tracheal lumen, and located 2 cm cranial to the carina. Cytologic and histopathologic examination of fine-needle aspirate and biopsy samples suggested a benign etiology; therefore, endoscopic minimally invasive laser and electrocautery resection of the mass was scheduled. A total IV anesthetic protocol was administered with an oxygen-air mixture used to decrease the risk of fire during tracheal surgery. The mass was successfully resected, and histopathologic examination confirmed a diagnosis of osteochondroma. Clinical signs resolved, and at follow-up 32 months later, no regrowth of the mass was evident. CLINICAL RELEVANCE: Tracheoscopy-guided electrocautery and surgical diode laser resection was successful in removing an obstructive tracheal mass that was not resectable by means of a conventional open surgical approach. Minimally invasive procedures may decrease morbidity and mortality and improve outcome in appropriately selected small animal patients.

Solitary Osteochondroma in a Ring-Tailed Lemur (Lemur catta).

A 20-y-old, male, ring-tailed lemur (Lemur catta) presented with a large, firm mass on the proximal caudolateral left femur. The animal displayed no clinical signs associated with the mass. Radiographs revealed a mineralized mass protruding from the femur, with an intact femoral cortex. Histopathology diagnosed osteochondroma in view of the presence of a peripheral layer of cartilage with progressive endochondral ossification and typical remodeling of bony trabeculae. The mass grew quickly after the initial biopsy, and a second surgery to debulk 95% of the tumor was performed. Histopathologic features of the larger samples were similar to those of the initial biopsies, with the cartilage layer being discontinuous and development of bone from some borders progressing directly from a periost-like layer. Nineteen months after the second surgery, the mass had regrown and extended further proximally on the femur toward the epiphysis, but the animal remained asymptomatic, and additional debulking was not attempted. This report is the first description of an osteochondroma in a prosimian and describes unique behavior of the tumor compared with osteochondromas found in humans, dogs, and cats.

Extraskeletal osteochondroma on a cat´s elbow.

A solitary extraskeletal osteochondroma was diagnosed in a 6-year-old, castrated male Burmese cat, positive for feline leukaemia virus (FeLV). The cat presented with a rapidly growing, solid, non-painful mass on the craniolateral aspect of the left elbow. Radiographs revealed an oval, well circumscribed 2.0 cm × 1.5 cm × 1.5 cm mineralised mass separated from the underlying bone. Surgical excisional biopsy confirmed the diagnosis. Feline extraskeletal osteochondromas are benign tumours frequently seen in FeLV-positive cats which can transform into osteosarcomas or chondrosarcomas. Radiographically, they cannot be distinguished from a parosteal or an extraskeletal osteosarcoma.

Synovial osteochondroma involving the elbow of a cat.

CLINICAL PRESENTATION: A 12-year-old spayed domestic crossbred cat presented because she would not walk down stairs. A firm swelling on the medial aspect of the elbow was detected during physical examination. The lesion was not hot or painful on palpation and the lameness was mild, but the elbow had a reduced range of motion compared with the contralateral limb. DIAGNOSIS AND TREATMENT: Plain radiographs, physical findings, the appearance of the lesion at surgery and histopathological examination of biopsy specimens suggested the mass was a synovial osteochondroma arising from synovial membrane near the medial portion of the elbow joint. Resection of the lesion improved the cat's mobility and overall clinical status. At the time of writing, the cat continued to do well 18 months following surgery and was receiving standard doses of meloxicam for the concurrent elbow osteoarthritis. PRACTICAL RELEVANCE: Practitioners should be alert to the possibility of this benign entity. Misdiagnosis as a chondrosarcoma, for example, might conceivably lead to radical and unnecessary amputation.