Abstract
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C. Squamous cell carcinoma
Ocular squamous cell carcinoma is common among cattle and is considered the most economically important neoplasm in this group of animals. In cattle, 70% of ocular squamous cell carcinomas arise at the bulbar conjunctiva of the limbus (Image 1). They often extend to the cornea, but intraocular invasion is uncommon. Ultraviolet radiation and lack of periocular pigment are primary risk factors. In cattle, prevalence is highest among the Hereford breed and those located in high-altitude regions. Grossly, the tumors appear variably sized, poorly demarcated, firm, and white to red. Microscopically, they range from well-differentiated carcinomas with keratin pearl formation to anaplastic carcinomas.
Reference: Tsujita H, Plummer CE. Bovine ocular squamous cell carcinoma. Vet Clin North Am Food Anim Pract. 2010;
Contributor: Rachel Hritz, Colorado State University
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B. Smooth muscle actin (SMA)
Piloleiomyosarcoma is a mesenchymal tumor derived from the arrector pili muscles (smooth muscle) supporting the hair follicles. It is a well-known entity in ferrets, where it typically develops in animals between 2 and 6 years of age, often in males, and on the dorsum of the head or trunk. They are considered low grade, poorly infiltrative malignancies with minimal metastatic potential. Prognosis is good following excision with adequate surgical margins. Neoplastic cells have cytoplasmic immunoreactivity for smooth muscle actin (Image 2) and desmin, which are markers of myogenic differentiation. Adjacent nonneoplastic arrector pili and blood vessels act as internal positive controls.
Reference: Fox JG, Muthupalani S, Kiupel M, Williams B. Neoplastic diseases. In: Fox JG, Marini RP, eds. Biology and Diseases of the Ferret. 3rd ed. Ames, IA: John Wiley & Sons; 2014:601–602.
Contributor: Rachel Neto, Auburn University
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D. Factor VIII-related antigen
Primary differential diagnoses for a destructive, intramedullary skeletal mass with prominent blood-filled spaces and intratumoral hemorrhage are hemangiosarcoma (primary or metastatic) and telangiectatic osteosarcoma. With small biopsies or osteoid-poor telangiectatic osteosarcomas, immunohistochemistry for endothelial immunomarkers such as factor VIII-related antigen may be necessary for differentiation, as malignant cells of osteosarcoma are negative for endothelial immunomarkers. In this case, pleomorphic spindle cells producing osteoid and lining blood-filled spaces (Image 3) are diagnostic for telangiectatic osteosarcoma. Telangiectatic osteosarcomas are often ascribed a worse prognosis, though this needs to be validated and studies repeated with larger sample sizes and immunohistochemistry.
Reference: Giuffrida M, Bacon N, Kamstock D. Use of routine histopathology and factor VIII-related antigen/von Willebrand factor immunohistochemistry to differentiate primary hemangiosarcoma of bone from telangiectatic osteosarcoma in 54 dogs. Vet Comp Oncol. 2016;
Contributor: Nathan Hoggard, University of Tennessee
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C. Cheetah (Acinonyx jubatus)
Splenic myelolipomas are common, frequently incidental nodules composed of well-differentiated adipose and varying amounts of hematopoietic tissue, including immature and mature cells of erythrocytic, granulocytic, and megakaryocytic lineages (Image 4A). Splenic myelolipomas occur in both wild and captive large felids, particularly in cheetahs, where they are often multifocal and throughout the splenic parenchyma (Image 4B). When small and multiple, they are considered metaplastic or hamartomatous rather than neoplastic. Myelolipomas also occur in other tissues including the liver and adrenal glands, and have been documented in domestic felines, canines, humans, cattle, and nonhuman primates.
Reference: Terio KA, McAloose D, Mitchell E. Felidae. In: Terio KA, McAloose D, St. Leger J, eds. Pathology of Wildlife and Zoo Animals. San Diego, CA: Elsevier; 2018:269–279.
Contributor: Ariel Carlson, University of Tennessee
Veterinary Pathology invites submission of exceptional gross or microscopic images for consideration as an Image Challenge, along with a multiple-choice question and answer. For details, see the Instructions to Authors on the journal Web site.