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Lipomas And Liposarcomas
Lipomas are benign, rapidly growing lumps of fatty tissue that appear as soft, pale yellow, encapsulated, and lobulated, subcutaneous masses. They most frequently occur over the sternum, and less commonly the abdomen, and thighs. Lipomas can cause ulceration of the overlying skin, and can become inflamed and necrotic if traumatized. Lipomas have been associated with abdominal thyroid gland function. Overweight hens often develop fat pads which can appear like lipomas. Liposarcomas are malignant tumors which develop as yellow to gray subcutaneous masses. They are more firm, more infiltrative, and more vascular than lipomas.
A surgical biopsy is required to differentiate between a liposarcoma and a lipoma. Surgical removal in combination with supplemental L-carnitine in the chicken’s diet can be successful at treating lipomas. However, if the lipoma is not completely removed, recurrence is common.
Case 1: Lipoma in a Conure. A 14-year-old blue-crowned conure of unknown sex was brought to the hospital with a 3-week history of straining and vocalizing during defecation. Physical examination revealed blood and urate staining on feathers around the cloaca. A 2.5-cm subcutaneous swelling was palpated along the midline of the caudoventral abdomen. During surgical exploratory, a subcutaneous soft-tissue mass was found, which extended through the body wall musculature and into the coelomic cavity. The abnormal tissue was adhered to the cloacal serosa, causing deviation of the cloaca caudally and ventrally. The mass was excised and submitted for histopathology, and the histopathologic diagnosis was infiltrative lipoma. The surgical incision healed uneventfully, and no evidence of tumor regrowth was apparent 7 months after surgery. Ref Primary tumor site: abdomenSites of Metastases: none
Case 2: Infiltrative spinal lipoma in a Goose. An adult Canada goose was presented unable to walk. On physical examination, conscious proprioception was absent in both legs, and motor function was decreased. The bird did not improve with supportive care and was euthanatized and submitted for postmortem examination. Sagittal sectioning of the spine revealed an intradural growth causing segmental deformity of the lumbosacral spinal cord. The growth was diagnosed as an infiltrative spinal lipoma. Infiltrative lipomas are locally invasive, benign tumors that can be found in any host tissue. Ref Primary tumor site: SpineSites of Metastases: none
Case 3: Intraosseous lipoma in a Cockatoo. A 9-year-old female rose-breasted cockatoo was presented for a humeral fracture. At presentation, the bird was severely lethargic and obese. On physical examination, an open right humeral fracture, healed left ulnar fracture, and intertarsal joint swelling were present. Results of hematologic testing and biochemical analysis revealed severe leukocytosis with heterophilia and increased creatine kinase and aspartate aminotransferase activities consistent with musculoskeletal lesions. Radiographs confirmed a right humeral fracture and showed severe polyostotic lytic and expansile lesions of the appendicular skeleton, as well as an enlarged hepatic silhouette. Surgical repair of the fracture was attempted, but the bird died during the procedure. Necropsy revealed severe bone deformities involving the fractured humerus, both ulnas, and the left tibiotarsus. Histologic findings were consistent with multiple intraosseous lipomas of the long bones and severe hepatic lipidosis. Ref Primary tumor site: wingSites of Metastases: none
Case 4: Liposarcoma in a Parrot. An adult African grey parrot was examined because of bilateral periorbital swelling of 1-year duration. Ultrasonographic imaging revealed bilateral periorbital and retrobulbar soft tissue swelling, most consistent with fat echogenicity. The bird was euthanatized, and computed tomography (CT) and magnetic resonance imaging (MRI) of the head were performed postmortem to delineate the extent of the lesions. At necropsy, the periorbital diverticuli of the infraorbital sinus were expanded bilaterally with soft, yellow tissue that elevated the overlying skin and extended into the retrobulbar spaces and the mandible. Histopathologic examination revealed that this mass was a well-differentiated liposarcoma Ref Primary tumor site: eyesSites of Metastases:
Case 5: Liposarcoma in a Silkie chicken. A dead 3-yr-old backyard silkie chicken, with a history of unknown skin lesions involving the entire body and severe weight loss, was submitted to California Animal Health and Food Safety Laboratory System–Turlock branch for necropsy. At necropsy, raised necrotic lesions involving the majority of the skin and multiple nodules in the liver, spleen, and bone marrow were noticed. Microscopically, stellate, spindle, and myxoid cells containing large vacuoles, which were confirmed as lipid droplets by Oil Red O, were observed infiltrating the dermis and underlying a necrotic epidermis, with metastasis to liver, spleen, bone marrow, and ovary being the most significant findings. PAS, Oil Red O, Ziehl-Neelsen, Congo red, Gram, and Von Kossa stains, along with immunohistochemistry for pan cytokeratin, vimentin, S100, CD3, pp38, and Meq were used to classify the lesions. Intensely positive vimentin immunohistochemistry, along with large quantities of Oil Red O–positive lipid droplets within the neoplastic cells, were supportive of our diagnosis of liposarcoma. Ref Primary tumor site: skinSites of Metastases: liver, spleen, bone marrow, and ovary
Case 6: Subcutaneous liposarcoma in a Bonnet macaque. A subcutaneous liposarcoma was diagnosed in a geriatric bonnet macaque. Clinical presentation was a rapidly growing, ulcerated, subcutaneous mass in the umbilical region of a 28-y-old female macaque. The mass was successfully removed through excisional biopsy, and histopathology provided a morphologic diagnosis of well-differentiated liposarcoma. The macaque recovered without complication and displayed no signs of recurrence for at least 18 mo after excision. Ref Primary tumor site: umbilical regionSites of Metastases: none