Canine extraskeletal osteosarcoma and chondrosarcoma: a clinicopathologic study of 14 cases

Canine extraskeletal osteosarcomas are extremely rare tumors. Over a period of 25 years at the Animal Medical Center, approximately 1,000 cases of skeletal osteosarcomas have been diagnosed. During the same period 11 cases of extraskeletal osteosarcomas and three extraskeletal chondrosarcomas were diagnosed. Tumors of the mammary gland were excluded. Extraskeletal osteosarcomas were found in the adrenal gland, eye, gastric ligament, ileum, kidney, liver, spleen, testicle, and vagina. The chondrosarcomas were found in the mitral valves, lungs, and omentum. The mean age of the dogs with extraskeletal osteosarcoma was 11 years, and the mean age of the dogs with extraskeletal chondrosarcoma was 14 years. The The sizes of the tumors ranged from 3 cubic centimeters to 8,315 cubic centimeters. Osteoblastic osteosarcomas were the most common histologic type (7/11, 63.6%); there was a single case of each of the following: fibroblastic, fibrous histiocytic, chondroblastic, and mixed osteo-chondroblastic osteosarcoma. Two of the dogs with chondrosarcomas had mesenchymal chondrosarcomas involving the lungs and omentum. The remaining dog had a regular chondrosarcoma involving the mitral valve. Distant metastases were present in seven of 11 dogs with extraskeletal osteosarcoma and in none of the dogs with chondrosarcoma. In contrast to human beings, in which most extraskeletal osteosarcomas occur in the soft tissues and the extremities, most canine extraskeletal osteosarcomas develop in the visceral organs.     

Spontaneous extraskeletal osteosarcoma with various histological growth patterns in the abdominal wall of an ICR mouse

Extraskeletal osteosarcoma is extremely rare in mice. This case report demonstrates a spontaneous murine extraskeletal osteosarcoma that exhibited various histological growth patterns in an ICR mouse. At necropsy, the tumor mass was located in the abdominal wall and was 45 × 30 × 25 mm in size. Histopathologically, the tumor showed the following four growth patterns: a solid pattern of polygonal cells embedded in an osteoid eosinophilic matrix with calcification, an irregular sheet pattern of short spindle cells accompanying some eosinophilic multinucleated cells, a fascicular pattern of spindle cells and a cystic pattern lined by short spindle cells. Immunohistochemically, most of the tumor cells were positive for vimentin, proliferating cell nuclear antigen and osterix. The multinucleated cells mentioned above were desmin positive and were regarded as regenerative striated muscles but not tumor cells. Since no clear continuity with normal bone tissues was observed, the tumor was diagnosed as an “extraskeletal osteosarcoma.”     

Spontaneous chondrosarcoma in Wistar rat: a case report

In rats, chondrosarcomas have been reported to occur both spontaneously and secondary to chemical induction. In a rare case, a spontaneous chondrosarcoma was identified in the deformed femur of a young male Wistar rat. After gross examination of the femur and knee joint, tissue was collected and preserved. The formalin-fixed tissue was decalcified, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Microscopic examinations revealed a large, highly proliferative, noncapsulated growth of chondrocytic or chondroblastic origin in the femoral bone, with proliferating chondrocytes invading the bone and surrounding tissues in an infiltrative growth pattern. Based on its histomorphological features, the lesion was diagnosed as a malignant cartilaginous neoplasm of spontaneous origin.     

Spontaneous extraskeletal osteosarcoma in the neck skeletal muscle of a Crlj:CD1 (ICR) mouse

Extraskeletal osteosarcoma is extremely rare in humans and animals, especially in rodents. This is the first case report on spontaneous extraskeletal osteosarcoma in the neck skeletal muscle of a Crlj:CD1 (ICR) mouse (36 weeks, dead). Necropsy revealed a solid white mass located in the neck skeletal muscle (scalenus muscle). Histological examination showed that the tumor consisted of atypical polygonal cells, a small osteoid clump, and bone tissue. Mitotic figures were observed. Serial sections showed that neoplastic cells lacked clear invasive proliferation to adjacent normal skeletal muscle and continuity with normal bone tissue. Immunohistochemical analysis showed that the neoplastic cells were positive for osteocalcin, osterix, vimentin, and S-100. Based on these results, the tumor was diagnosed as extraskeletal osteosarcoma in the neck skeletal muscle.     

Spontaneous extraskeletal osteosarcoma in the stomach of an aged f344 rat

Extraskeletal osteosarcoma is a very rare tumor in humans and animals including rats. This paper describes a case of extraskeletal osteosarcoma observed in the glandular stomach of an aged female Fischer 344 rat. Grossly, a whitish solid mass was observed at the greater curvature of the glandular stomach. Histologically, the tumor consisted of both atypical polygonal and pleomorphic spindle-shaped cells, with pleomorphic nuclei, and it contained variable amounts of osteoids and small clumps of mature bone tissue. In addition, mitotic figures were frequently observed. Neither invasion of the muscle layer or vessels in the stomach nor metastasis to distant organs was detected. There were no skeletal tumors in the body. Immunohistochemically, the tumor cells were positive for osteocalcin, osteonectin, vimentin and S-100 protein. Judging from these results, the present tumor was diagnosed as extraskeletal osteosarcoma. This is the first report of spontaneous extraskeletal osteosarcoma arising from the stomach in a rat.     

Immunohistochemical analysis of matrix metalloproteinase-1, -3, and -13 in naturally occurring cartilaginous tumors of dogs

OBJECTIVE: To determine immunoreactivity of matrix metalloproteinase (MMP)-1, -3, and -13 in cartilaginous tumors of dogs, correlate expression of MMP with histologic grade of tumors and clinical outcome of dogs, and compare MMP immunoreactivity between chondrosarcomas and chondromas. SAMPLE POPULATION: Formalin-fixed, paraffin-embedded tissues obtained from samples of naturally occurring chondrosarcomas (n = 31) and chondromas (8) of dogs that were submitted to our veterinary medical diagnostic laboratory. PROCEDURE: Histologic sections from each sample were stained with H&E and monoclonal antibody to MMP-1, -3, and -13 by use of an avidin-peroxidase immunohistochemical technique. For each section, histologic grade (I, II, or III) and immunohistochemical expression (0, 1, 2, or 3) were evaluated. Clinical outcome was obtained from medical records or interviews with referring veterinarians and scored as a good outcome, moderate outcome, or poor outcome. Correlations among variables and differences between chondrosarcomas and chondromas were analyzed. RESULTS: Samples from chondrosarcomas had significantly higher immunoreactivity of MMP-1 and -13, compared with immunoreactivity in samples from chondromas. In chondrosarcomas, a significant positive correlation (r, 0.386) was found between MMP-1 and -13 immunoreactivities, and a significant negative correlation (r, -0.390) was detected between MMP-3 and -13 immunoreactivities. CONCLUSIONS AND CLINICAL RELEVANCE: A significant increase in expression of collagenases (MMP-1 and -13) in chondrosarcomas, compared with expression in chondromas, suggests that collagenases may play an important role in tumor progression, and possibly metastasis, in chondrosarcomas of dogs.     

Musculoskeletal neoplasia: an important differential for lumps or lameness in the cat

PRACTICAL RELEVANCE: Musculoskeletal neoplasia is an uncommon but Important differential diagnosis for cats presenting with lameness, pain or swellings associated with bones and/or soft tissues. The most common tumours of soft tissue origin are the sarcomas (in particular feline injection site sarcomas [FISSs]); the most common bone tumour of the cat is osteosarcoma (OSA). CLINICAL CHALLENGES: FISSs present a clinical challenge in terms of their local invasiveness, difficulty in obtaining complete surgical excision and high risk of local recurrence. Axial and extraskeletal OSAs pose similar challenges, whereas appendicular OSA is usually easy to remove via limb amputation and can, therefore, carry a good prognosis in many cases. PATIENT GROUP: Cats of any age, gender or breed may be affected, although bone tumours predominantly affect middle- to old-aged cats. GLOBAL IMPORTANCE: Vaccination of cats is of global importance in preventing feline diseases; hence, any possible significant consequences of vaccination such as neoplasia, even of a low incidence, are of huge concern to cat owners and veterinarians alike. EVIDENCE BASE: This review is based on current literature relating to pathogenesis, pathology, presentation, diagnosis, staging, treatment and prognosis. It aims to summarise feline musculoskeletal neoplasia for clinicians in general practice.     

Use of alkaline phosphatase staining to differentiate canine osteosarcoma from other vimentin-positive tumors

Aspiration of lytic bone lesions is an excellent diagnostic test in the initial evaluation of primary bone neoplasia. However, cytologically, it can be difficult to differentiate osteosarcoma (OSA) from other bone neoplasms, including fibrosarcoma, chondrosarcoma, synovial cell sarcoma, and plasma cell myeloma. The purpose of this study is to determine the sensitivity and specificity of alkaline phosphatase (ALP) staining to differentiate OSA from other tumors that express vimentin by immunocytochemistry or immunohistochemistry. ALP is a hydrolytic enzyme present in multiple tissues including liver, kidney, intestine, placenta, and bone. Hypothetically, neoplasms actively producing bone should be specifically positive for ALP staining. Unstained, cytologic specimens were incubated for 8-10 minutes with nitroblue tetrazolium chloride/5-bromo-4-chloro-3-indolyl phosphate toluidine salt-phosphatase substrate. A positive reaction stains the membrane of the cells gray to black. Samples were counterstained with a Romanowsky's stain to determine whether the sample was of representative cellularity. A total of 61 vimentin-positive neoplasms have been evaluated and confirmed histopathologically. Tumors that expressed vimentin and were positive for ALP included 33 OSAs, one multi-lobular tumor of bone, one amelanotic melanoma, and one chondrosarcoma. Tumors that expressed vimentin and were negative for ALP included chondrosarcomas (three of four), multiple fibrosarcomas, and multiple synovial cell sarcomas. The sensitivity is 100%, and the specificity is 89%. In conclusion, ALP appears to be a highly sensitive and fairly specific marker in the diagnosis of OSA.     

A mixed mesenchymal sarcoma in the soft palate of a dog: light and electron microscopic findings

Soft tissue tumors containing a mixture of neoplastic fibrous tissue, cartilage, and bone have previously been classified as extraskeletal osteosarcomas in the dog. These tumors are often poorly differentiated, contain multiple neoplastic cell types, and might be more appropriately called mixed mesenchymal sarcomas. The present neoplasm caused clinical signs of stridorous respiration and dysphagia in a four and one-half year old dog. Four neoplastic cell types were demonstrated by light and electron microscopy.     

Canine sinonasal skeletal neoplasms: chondrosarcomas and osteosarcomas

We studied 34 chondrosarcomas and 17 osteosarcomas among 285 sinonasal neoplasms in the dog. Mesenchymal chondrosarcomas (24) were more common than ordinary chondrosarcomas. Ultrastructural studies done in one case confirmed mesenchymal chondrosarcoma. Of the osteosarcomas, fibroblastic osteosarcoma (7) was the most common. In contrast to non-sinonasal skeletal neoplasms which are composed mostly (80%) of osteosarcomas, chondrosarcomas (66%) and mesenchymal chondrosarcomas (47%) were predominant among the sinonasal skeletal neoplasms of this study. The average age (ten years) of the dogs with sinonasal osteosarcoma was higher than that of dogs with non-sinonasal skeletal osteosarcoma, and there was a distinct male predominance in the dogs with osteosarcoma and chondrosarcoma. Large breed dogs and boxers, frequently affected with skeletal neoplasms, were not affected commonly with sinonasal osteosarcoma. The frequency of metastasis in the dogs with chondrosarcoma and osteosarcoma was much lower than that seen in dogs with nonsinonasal skeletal neoplasms.     

Extraskeletal fibroblastic osteosarcoma in a rabbit (Oryctolagus cuniculus)

A seven-year-old rabbit was presented with a non-painful mass in the right upper lip. Tissue samples from the mass at three different stages of the disease process were diagnosed sequentially as an osteogenic sarcoma, a fibroblastic tumour with rudimentary osteoid formation and, lastly, a fibrosarcoma. No bone involvement or metastatic disease was found. The final diagnosis was of an extraskeletal fibroblastic osteosarcoma, which is, to the authors' knowledge, the first reported such case in a domestic rabbit. Without the first two tissue samples, an incorrect diagnosis would have been reached; therefore, this disease may be underrepresented in the literature.     

Spontaneous extraskeletal osteosarcomas of the subcutis in Djungarian hamsters (Phodopus sungorus): report of two cases

Spontaneous subcutaneous extraskeletal osteosarcoma was diagnosed in the subcutaneous tissue of two Djungarian hamsters. Histologically, the tumour was characterized by multiple nests of osseous and cartilaginous components within a proliferation of pleomorphic cells. No abnormality was observed in any skeletal bones and no change suggesting tumorous growth was observed in any other sites. This is the first report of extraskeletal osteosarcomas in Djungarian hamsters.     

Bone scintigraphy in the initial evaluation of dogs with primary bone tumors

Bone scintigraphy was performed as part of an initial diagnostic evaluation of 70 dogs admitted with primary bone tumors during a 2-year period. Tumors involved major long bones of the appendicular skeleton and included 62 osteosarcomas, 6 fibrosarcomas, and 2 chondrosarcomas. All dogs were free of radiographically detectable pulmonary metastases. Bone scintigraphy was not of value in distinguishing among various types of primary tumors. One dog with an ulnar chondrosarcoma had a scintigraphically detectable occult osseous metastasis or synchronous primary tumor, and 1 dog with osteosarcoma had a scintigraphically detectable lymph node metastasis. Pulmonary metastases were not detected scintigraphically. Of the 70 dogs, 44.3% had areas of increased isotope uptake associated with nonneoplastic disease processes.     

BONE SCINTIGRAPHY FOR METASTASIS DETECTION IN CANINE OSTEOSARCOMA

The purpose of this study was to assess the usefulness of serial bone scintigraphy in the detection of skeletal and extraskeletal metastases in dogs with appendicular osteosarcoma. Twenty-six dogs with primary, appendicular osteosarcoma were entered into a limb-sparing protocol. Bone scintigraphy was performed upon presentation, after neoadjuvant therapy but prior to surgery and at selective intervals after limb-sparing surgery to evaluate for the presence of metastasis. Thoracic radiographs, and radiographs of other sites, were also made at the time of each bone scan. All dogs had a complete necropsy. No dog had bone or lung metastases detected prior to treatment. The bone scans, medical records, and radiographs of each dog were reviewed retrospectively. All but one dog developed metastatic disease. Bone metastatic sites were confirmed at necropsy in 12 of the 26 dogs. Seven of these 12 dogs had bone metastatic sites which were not producing clinical signs, i.e. an occult metastasis. In five of the seven dogs, the occult site was the first metastatic site detected. Extraskeletal metastases were identified scintigraphically in six of the 26 dogs, but these were clinically apparent prior to bone scintigraphy in each dog. Suspected malignant scintigraphic lesions were proven benign in six dogs. In five dogs with malignant bone lesions at necropsy the last bone scan prior to euthanasia was normal. The time interval between scintigraphy and necropsy was variable in these five dogs. All dogs without bone metastases at necropsy had normal bone scans. This study validates the usefulness of bone scintigraphy for detection of occult bone metastasis and improved ability for tumor staging in dogs with appendicular osteosarcoma.     

Primary splenic mesenchymal chondrosarcoma in a dog

A large splenic mass was found during exploratory celiotomy in a 12-year-old Labrador retriever. Histologic examination of the mass revealed a mesenchymal chondrosarcoma. The dog was euthanatized 7 wk postoperatively, due to suspected tumor recurrence. Extraskeletal mesenchymal chondrosarcomas are rare in dogs and are associated with a guarded prognosis.     

Feline chondrosarcoma: a retrospective study of 67 cats (1987-2005)

The histories of 67 cats diagnosed with chondrosarcoma (CSA) from 1987 to 2005 were reviewed. The mean age was 9.6 years, and males were 1.9 times more likely to be affected than females. Chondrosarcomas were diagnosed in the following sites: appendicular and axial skeleton, nasal cavity, facial bones, and extraskeletal sites. Of the 46 (70%) CSA associated with bone, 63% arose in long bones and 37% arose in flat bones. The remaining (30%) CSA arose in the subcutis. In cases available for follow-up (n=24), no definitive evidence of metastases was found. Cats that underwent radical surgical therapies were more likely to achieve long-term control or cure.     

Primary pulmonary chondrosarcoma in a dog.

Extraosseous chondrosarcomas are uncommon in the dog, and those originating in the lung are rare. This report presents a 9-year-old Beagle dog with a pulmonary mass which caused depression, fever, tachypnea, cough, and laboratory abnormalities. The mass was composed predominantly of chondroid tissue, and was histologically diagnosed as chondrosarcoma.     

Radiography of orthopedic trauma and fracture repair.

Fracture of bone and bone healing are similar to healing of soft tissues; however, the crystalline structure of bone tissue and its slow but dynamic recovery give some mystique to the healing process. The problem is further complicated by the common misconception that radiology is the best way to assess the changes occurring in bone. It is becoming more apparent that radiology is best only to describe normal or disrupted anatomical conformation. Other established and emerging modalities are competing with radiology for evaluation of the skeletal tissues. It is most important to remember that a clinical examination with evaluation and assimilation of the clinical signs gives a better indication of the physiological and pathological status of bone healing that any of the sophisticated imaging modalities. Imaging should be reserved as an adjunct to the clinical examination.     

Malignant mesenchymoma with widespread metastasis including bone marrow involvement in a dog

A male castrated Golden Retriever was presented for evaluation of a large mass over the left shoulder extending to the lower part of the neck that had been present for an extended period of time, but had a recent history of rapid growth. Previous aspirates of the mass were consistent with a lipoma. The mass was surgically excised and was diagnosed as an extraskeletal osteosarcoma based on histopathology. After surgery, the dog was initiated on a chemotherapy protocol with carboplatin and metronomic cyclophosphamide. He became neutropenic, anemic, and thrombocytopenic 14 days after the carboplatin treatment was administered. The neutropenia resolved, but the anemia and thrombocytopenia progressed. A bone marrow aspirate revealed erythroid hypoplasia, myeloid hyperplasia with a predominance of early precursors, and a subset of cells that made up 20% of the total population that were reported as bizarre and unclassifiable. These cells were discrete in nature and were thought to be hematopoietic in origin. The dog was euthanized due to deterioration of the clinical condition. On postmortem examination, widespread metastasis involving the lungs, liver, kidney, heart, and bone marrow was found. Histopathology of the tumor lesions determined 2 distinct malignant populations of liposarcoma and osteosarcoma, consistent with malignant mesenchymoma. However, the possibility of 2 separate neoplastic processes cannot be definitively excluded. This is the first report of bone marrow metastasis of a malignant mesenchymoma in a dog.