8-year-old Cavalier King Charles Spaniel – Canine


Age: 8 year

Sex: Female – intact

Breed: Cavalier King Charles Spaniel

Species: Canine

SOURCE/HISTORY: Chronic GI bleeding, intestinal mass diagnosed, no signs of metastasis, cytology consistent with sarcoma, please evaluate margins.

Figure 1: 1X image of a transmural mass expanding and effacing the wall of the small intestine.
Figure 2: 20X image of the mass showing spindle cell proliferation surrounding an area of osteoid.
Click here for the IDEXX Pathology Report on this case.


Samples of the small intestine are evaluated. There is a transmural mass effacing a portion of the intestine. The mass is comprised of sheets of neoplastic streaming fascicles of spindloid cells with indistinct cytoplasmic margins, streaming, eosinophilic cytoplasm and oval, often eccentrically located nuclei with a lightly chromatin pattern. Cells exhibit moderate anisocytosis and anisokaryosis. One to 2 small nucleoli are present per cell. Multinucleated tumor giant cells are present throughout the tumor. Formation of tumor osteoid and bone are present throughout the tumor. In the oral and aboral margins there is edema and increased numbers of lymphocytes and plasma cells within the lamina propria.


Intestine: Intestinal osteosarcoma

Mitotic Count: 9

Excision: Completely removed, oral and aboral margins measure 40 and 59 mm but are not identified as to which is oral and which is aboral

Vascular Invasion: Not observed


Extraskeletal osteosarcoma is an extremely rare tumor in dogs. These are mesenchymal neoplasms of soft tissues and visceral organs that produce osteoid but do not involve bone or periosteal tissue. It has been established in humans that radiation therapy can cause osteosarcoma. Post radiation osteosarcoma has also been reported in dogs. These extraskeletal tumors in dogs developed in visceral organs in 86% of the cases in one study, with 14% of the tumors developing in the soft tissue of the extremities. The mean age of dogs reported was 11 years. These are considered highly malignant tumors. 64% of dogs had distant metastases in this study. The mean survival time of dogs with extraskeletal osteosarcoma in this study was 23 days.

REFERENCE: Patnaik AK. Canine extraskeletal osteosarcoma and chondrosarcoma: A clinicopathologic study of 14 cases. Vet Pathol. 27:46-55(1990)


Nicole Kraipowich, DVM, MS

Diplomate, American College of Veterinary Pathologists

Direct: 720-977-6154 1-888-433-9987, option 0, x76154

E-mail: nicole-kraipowich@idexx.com


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