Undifferentiated pleomorphic sarcoma (malignant fibrous histiocytoma) of the head in a dog

Pleomorphic sarcoma secondary to proximal femoral epiphysiolysis with bone infarction over 4 years after cementless total hip replacement in a dog

OBJECTIVE

To report a capital physeal fracture as the result of a bone infarction with subsequent neoplastic transformation 4 years following total hip replacement.

STUDY DESIGN

Case report.

ANIMALS

Five-year-old female spayed golden retriever.

METHODS

The dog was initially presented for evaluation of a 2 week history of spontaneous right hind-limb lameness. Pelvic radiographs demonstrated a displaced capital epiphysis and proximal femur changes consistent with a bone infarction. A cementless total hip replacement was performed, and limb function returned to normal until 51 months after surgery. A radiolucency adjacent to the femoral stem at the greater trochanter, partial calcar resorption, and stable implants were present on pelvic radiographs acquired 52 months after surgery. Surgical exploration of the surgical site for tissue collection for histopathology and bacteria culture was performed 58 months following surgery. No bacterial growth occurred and histologic findings were nonspecific. A right hind-limb amputation was performed 61 months after total hip replacement due to the dog's progression to a non-weight-bearing lameness, Additional tissue samples were taken from the femur for histopathologic examination.

RESULTS

Histopathologic examination was consistent with a pleomorphic sarcoma. No metallic or polyethylene particulate debris was present. Nine months after surgery there was evidence of regional and distant spread of the neoplasia.

CONCLUSION

In similar cases, submitting the femoral head for histopathologic examination should be considered at the time of the hip replacement surgery. If bone infarction is diagnosed as a causative agent, given the possibility of malignant transformation, long-term serial radiographic monitoring should be given serious consideration.

Case Series: Computed Tomography Features of Extraskeletal Osteosarcoma in Six Dogs

The objective of the present case series was to investigate the various computed tomography findings of six dogs diagnosed with extraskeletal osteosarcoma (exOSA) at several locations. Among the tumors evaluated, four were subcutaneous, one was mammary, and one involved the intestinal tract. Intralesional mineralization was observed in all six dogs. Most of the tumors were moderately calcified, exhibited amorphous mineralization, and were heterogeneous on post-contrast imaging. Three of the tumors were peripherally enhanced, and regional lymphadenopathy was identified in two of the dogs, which was presumed to be metastatic. No lymph node calcification was reported. Although the presence of intralesional mineralization is not a pathognomonic finding, it was consistently identified in the present case series. Therefore, exOSA should be considered in the differential diagnosis when mineralization occurs in a mass unrelated to osseous structures.

Multiple Undifferentiated Pleomorphic Sarcoma (Malignant Fibrous Histiocytoma) with Extradural Involvement in a 7-Year-Old Labrador Retriever

A 7-year-old castrated male Labrador retriever was referred for evaluation of progressive hind limb paresis of 4 weeks' duration. On computed tomography and magnetic resonance imaging examination, masses were found in several regions including the lung, right kidney, and peritoneum. Additionally, an extradural mass at the region of T13-L1 was identified, which is assumed to related to the chief complaint, progressive hind limb paresis. With the consent of the owner, a dorsal laminectomy was performed to remove the mass and surrounding tissues for the palliation of the hind limb paresis. Hematoxylin and eosin staining and immunohistochemical examination revealed the mass to be consistent with an undifferentiated (high-grade) pleomorphic sarcoma. The patient presented with recurrence of the hind limb paresis, respiratory discomfort, and urinary incontinence. The owner declined treatment and the dog was euthanized. Systemic metastasis was confirmed on postmortem microscopic examination. To the authors' knowledge, this is the first report describing multiple undifferentiated high-grade pleomorphic sarcoma with extradural involvement developing into the vertebral canal through the intervertebral space, resulting in spinal damage, in a dog.