Malignant transformation of solitary spinal osteochondroma in two mature dogs

MRI Features of Solitary Vertebral Masses in Dogs: 20 Cases (2010-2019)

The objective of the study was to describe the MRI features of cytologically or histologically diagnosed solitary vertebral masses in dogs and identify potential MRI features enabling differentiation between malignant and benign lesions. Patients were divided into malignant and benign groups according to the final diagnosis. Medical records and MRI studies were retrospectively reviewed, and specific imaging features were compared. The malignant group comprised 15 dogs, with 5 dogs included in the benign group. MRI features of the different histopathologic/cytologic types of masses are described. Involvement of the vertebral body, a hyperintense signal on T2-weighted, short tau inversion recovery, T1-weighted, and T1-weighted gradient echo sequences and evidence of cortical destruction were signifi-cantly associated with malignancy (P < .05). Hypointensity on T1-weighted gradient echo sequence was significantly associated with benign masses (P < .05). The presence of bone sclerosis was significantly associated with osteosarcomas compared with other malignant masses (P < .05). Fractures (5 cases) were only seen in the group of malignant masses. This pilot study identifies some MRI features that may help differentiate between malignant and benign solitary vertebral masses. Greater case numbers are needed in future studies.

A Holistic Approach to Bone Tumors in Dogs and Cats: Radiographic and Histologic Correlation

The skeletal system is a common site for neoplasia in dogs and cats, and primary bone tumors may develop from any of the mesenchymal tissues present in bone. Imaging and histopathology are routinely used in the diagnosis of bone tumors, and the 2 techniques are highly complementary. While imaging may be highly suggestive of a specific diagnosis and treatment may be instituted based on this, definitive diagnosis requires histopathology of either incisional or excisional biopsies or an amputation specimen. However, there are a number of diagnostic dilemmas when the pathologist interprets bone biopsy samples, such as distinguishing reactive bone and tumor bone, fracture callus and tumor bone, different benign fibro-osseous lesions, and different types of bone sarcoma. This review outlines the characteristic radiographic and histologic changes associated with these diagnostic problems to aid in resolving them. When a holistic approach is taken to evaluation of the signalment, history, and clinical, radiologic, and microscopic features, a diagnosis may be possible. The pathologist is greatly assisted in the interpretation of bone samples by having access to imaging and should routinely request either the images or the imaging reports if they are not received from submitting veterinarians.

Lumbar Myelopathy Caused by Multiple Cartilaginous Exostoses in a Dog

A 6-months-old male mixed-breed dog was admitted to the veterinary hospital with lameness in the right pelvic limb, proprioceptive ataxia, and suspected spinal cord injury in the lumbosacral segment. Upon palpation, firm nodules were noted on the bony surface of the thoracic and pelvic limbs, ribs, vertebrae, and tail. The radiographic study showed nodules of low radiopacity with well-defined limits and smooth contours, one of which was overlapping the fifth lumbar vertebra. Given the clinical presentation indicative of spinal cord injury, the animal was subjected to hemilaminectomy for nodular resection. Histopathological examination of the biopsy enabled the diagnosis of osteochondroma. The clinical follow up after surgery showed improvement in walking, despite persistent monoparesis in the right pelvic limb. The radiographic study in association with clinical and histopathological exams allowed the diagnosis and monitoring of the lesions.

Magnetic Resonance Imaging Features of Extradural Spinal Neoplasia in 60 Dogs and Seven Cats

This retrospective study describes the MRI features of extradural spinal neoplasia in 60 dogs and seven cats to identify potential distinguishing features between tumor classes and individual tumor types within each class. In dogs, mesenchymal tumors were most common (48%), with undifferentiated sarcomas being the predominant tumor type. Round cell neoplasms were second most common (35%), with lymphoma and multiple myeloma/plasma cell tumor comprising the majority of cases. Only two benign tumors were identified. In cats, lymphoma was most common (5/7), with one case of mesenchymal neoplasia and one case of metastatic carcinoma. Despite some overlap, certain imaging features were able to help prioritize differential diagnoses. The combined features that predicted round cell neoplasia (84%) included the preservation of vertebral shape, homogeneous contrast enhancement, and lesion centering on bone. The combined features that predicted mesenchymal neoplasia (73%) included altered vertebral shape, heterogeneous contrast enhancement, and lesion centering on paraspinal soft tissues. Round cell neoplasms were more likely to have cortical sparing, preservation of overall shape, lesion centering on bone, small soft tissue tumor size, and homogeneous contrast enhancement. Both epithelial and mesenchymal neoplasms were more likely to have cortical lysis, a cavitary component to the soft tissue mass and medium to large soft tissue mass size. The findings of this study can aid in prioritizing differential diagnoses in cases of extradural spinal neoplasia in cats and dogs, which can impact case management, but tissue sampling remains the gold standard for definitive diagnosis.

A de novo mutation in the EXT2 gene associated with osteochondromatosis in a litter of American Staffordshire Terriers

Background

We aimed to identify mutations associated with osteochondromatosis in a litter of American Staffordshire Terrier puppies.

Hypothesis

We hypothesized that the associated mutation would be located in a gene that causes osteochondromatosis in humans.

Animals

A litter of 9 American Staffordshire puppies, their sire and dam, 3 of 4 grandparents, 26 healthy unrelated American Staffordshire Terriers, and 154 dogs of 27 different breeds.

Methods

Whole genome sequencing was performed on the proband, and variants were compared against polymorphisms derived from 154 additional dogs across 27 breeds, as well as single nucleotide polymorphism database 146. One variant was selected for follow‐up sequencing. Parentage and genetic mosaicism were evaluated across the litter.

Results

We found 56,301 genetic variants unique to the proband. Eleven variants were located in or near the gene exostosin 2 (EXT2), which is strongly associated with osteochondromatosis in humans. One heterozygous variant (c.969C > A) is predicted to result in a stop codon in exon 5 of the gene. Sanger sequencing identified the identical mutation in all affected offspring. The mutation was absent in the unaffected offspring, both parents, all available grandparents, and 26 healthy unrelated American Staffordshire Terriers.

Conclusions and Clinical Importance

These findings represent the first reported mutation associated with osteochondromatosis in dogs. Because this mutation arose de novo, the identical mutation is unlikely to be the cause of osteochondromatosis in other dogs. However, de novo mutations in EXT2 are common in humans with osteochondromatosis, and by extension, it is possible that dogs with osteochondromatosis could be identified by sequencing the entire EXT2 gene.

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.

Surgical management of myelopathy caused by a solitary spinal osteochondroma in a young cat

Case summary

A 10-month-old, male castrated, domestic shorthair cat was presented with fast-progressing ataxia of the pelvic limbs. MRI and CT were performed, revealing a bony proliferation at T11, with mass effect and laterodorsal compression of the spinal cord. After hemilaminectomy and the removal of the bony mass, the cat recovered uneventfully. At the 1 year follow-up, the cat did not show any neurological deficits or signs of recurrence.

Relevance and novel information

Solitary osteochondroma as a cause of neurological deficits in the pelvic limb has been described in dogs and humans, but, to the best of our knowledge, there are no reported feline cases described in the literature, in which CT and MRI were performed in combination with the successful removal of the lesion and an excellent outcome for the patient.

Occurrence of osteochondromatosis (multiple cartilaginous exostoses) in a domestic pig (Sus scrofa domesticus)

Osteochondromatosis is a condition in which multiple benign, cartilage-capped tumors arise from the surface of bones formed by endochondral ossification. The current report describes the presence of 4 prominent exophytic masses, measuring between 4 and 13 cm in diameter, arising from the surface of the ribs, and located within the thoracic cavity, in a 2-year-old female domestic pig ( Sus scrofa domesticus). Histological studies revealed that masses were well-differentiated, cartilage-capped proliferations with an orderly pattern of endochondral mineralization toward deeper areas. The observed gross and microscopic findings are characteristic of osteochondromatosis.

Use of latissimus dorsi and abdominal external oblique muscle for reconstruction of a thoracic wall defect in a cat with feline osteochondromatosis

A 4-year-old, male castrated European shorthair cat was presented with a firm mass palpable on the right caudal rib cage. Lateral and ventrodorsal radiographs of the thorax revealed a 4×3×2 cm large, expansile and radiodense mass originating from the distal part of the 13th rib. After removal of the tumour, which was histopathologically confirmed as feline osteochondromatosis, the diaphragm, omentum, external abdominal oblique and latissimus dorsi muscles were used to reconstruct the defect. Feline osteochondromatosis is induced by retroviruses, eg, feline leukaemia virus, for which the cat tested positive. The tumour was removed for palliative reasons, because such tumours have the tendency to transform into osteosarcomas. Six months after the surgical excision the cat showed no clinical signs of reoccurrence.

Radiographic diagnosis: cartilaginous exostoses in a dog

A 6 month-old dog was examined for progressive paraparesis. On physical examination bony malformations were palpated over the cranial lumbar vertebral bodies and on the left metatarsal bone. Neuroanatomic lesion localization for the paraparesis was a T3-L3 spinal cord lesion. Radiographs confirmed bony masses at L1-L2 and on the left 3rd metatarsal bone. Magnetic resonance imaging was performed from T3-L3. Severe spinal cord compression was identified at L1-L2. Surgical decompression and biopsy confirmed the mass to be cartilaginous exostoses. This paper is an example of cartilaginous exostoses imaged with MR.

Neurologic conditions causing lameness in companion animals

Animals presented with non-weight-bearing lameness are a diagnostic challenge for the veterinarian. It is extremely important to distinguish between orthopedic and neurologic causes of lameness, because the diagnostic and therapeutic plans can be quite different. Myopathies can be confused with orthopedic disease because of gait abnormalities and associated muscle pain. Common myopathies seen in companion animal medicine include polymyositis, muscular dystrophy, endocrine and infectious myopathies, and myasthenia gravis. Lameness caused by disease of the nerve root or nerve is confused with orthopedic disease because of the disturbances of a nerve's sensory distribution (nerve-root signature) or disruption of the motor innervation. The diseases of the nerve root or nerve discussed are lateralized intervertebral disk disease, spinal cord neoplasia, malignant peripheral nerve sheath tumors, and traumatic neuropathies. The diagnosis of these diseases requires careful attention to the signalment, a complete history, and a thorough physical examination focusing on the neurologic and orthopedic components. Ancillary testing should be selected based on these results and a minimum database. Electrodiagnostic testing, radiography, and advanced imaging may help to localize the lesion more precisely and sometimes to confirm the diagnosis. Surgical exploration and histopathology often provide the definitive diagnosis. These cases of non-weight-bearing lameness are a diagnostic challenge, but when successful resolution can be reached, it is gratifying to the clinician, client, and patient.