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High-Grade Myxoid Liposarcoma (Round Cell Variant) in a Dog
Q D Plumlee1, A M Hernandez1, S D Clark1
1Department of Veterinary Pathobiology, USA.
Insights
A novel canine liposarcoma case presented with distinct cell populations and cytoplasmic vacuoles. This rare myxoid liposarcoma with round cells challenges current veterinary classifications.
Area of Science:
- Veterinary Pathology
- Oncology
- Comparative Pathology
Background:
- Liposarcomas are malignant tumors of adipose tissue.
- Accurate classification is crucial for prognosis and treatment in veterinary oncology.
- Canine liposarcoma classification currently follows the World Health Organization (WHO) system.
Observation:
- A 10-year-old Basset hound presented with a large abdominal wall mass.
- Cytology revealed neoplastic round cells with cytoplasmic vacuoles.
- Histology showed two distinct cell populations: spindle-shaped cells with myxoid matrix and round cells, with intracytoplasmic lipid vacuoles.
Findings:
- The canine neoplasm exhibited features of both myxoid and pleomorphic liposarcoma variants.
- Morphologically, it was analogous to human high-grade myxoid liposarcoma.
- This represents a previously undescribed variant: myxoid liposarcoma with round cells in dogs.
Implications:
- This case suggests the need for re-evaluation of the current WHO classification of liposarcomas in animals.
- Recognizing this distinct subtype may improve diagnostic accuracy and therapeutic strategies.
- Further research into canine liposarcoma subtypes is warranted.
Abstract:
A 10-year-old, neutered male, Basset hound had a 26 × 21 × 21 cm infiltrative mass on the left abdominal wall that did not extend into the peritoneal cavity based on radiographs and abdominal computed tomography. Cytological examination revealed moderate numbers of neoplastic round cells, which frequently contained numerous round, clear, cytoplasmic vacuoles. Histologically, the tumour was composed of two morphologically distinct cell populations forming a continuum of heterogeneously differentiated cells. The primary spindle-shaped population formed streams with abundant, lightly eosinophilic, alcian blue-positive, myxoid matrix. The second population was arranged in sheets and had a round cell appearance. Scattered within both populations were neoplastic cells containing variably sized, intracytoplasmic, osmium tetroxide-positive vacuoles (lipid). Multifocal large pools of mucin formed pseudocysts, and numerous small capillaries were present throughout the neoplasm. According to the current World Health Organization veterinary classification of liposarcomas, this neoplasm had morphological features of both the myxoid and pleomorphic variants of liposarcoma; however, it was analogous to the recently defined high-grade myxoid liposarcoma in man. Myxoid liposarcoma with round cells has not been described previously in dogs. This case highlights the need to potentially re-evaluate the current classification of liposarcomas in animals.
