Page 153 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

er 9
Chapt
140
Liposarcoma
VetBooks.ir Malignant tumour of the adipose tissue.

Clinical features
• Rare tumour observed in older dogs and cats.
• In some cases, an association with glass foreign bodies and implanted microchips has
been described in dogs.
• It belongs to the class of soft tissue sarcomas.
• Masses are usually solitary and firm. They occur more frequently on ventrum and
extremities. Another relatively common primary location is the tongue.
• Locally invasive neoplasm with a low metastatic potential.
• Over-represented canine breeds: Shetland Sheepdog and Beagle.

Cytological features
• Cellularity is often high.
• Background: clear, often containing numerous variably sized fat droplets.
• Cell morphology is variable. Cells vary from plump-oval to spindloid. They are either indi-
vidualized or in poorly cohesive aggregates, occasionally with a perivascular arrangement.
• Nuclei are round to oval, with coarse granular chromatin and often prominent nucleoli.
• The cytoplasm is pale basophilic and contains multiple, variably sized lipid vacuoles. Vacuo-
les are more numerous in well-differentiated forms, whilst they are less frequent in the
anaplastic and pleomorphic variants. Fine pink/eosinophilic cytoplasmic granulations are
also commonly seen.
• Cytological features of atypia are variable, often marked, especially in anaplastic and
pleomorphic forms. These include anisokaryosis, anisocytosis, atypical mitotic figures and
multinucleation.

Variants
Liposarcoma variants include well-differentiated, myxoid and pleomorphic forms. The pleo-
morphic variant carries a poor prognosis.

• Well-differentiated variant:
• This is the most common variant.
• It is characterized by abundant lipid in the background and neoplastic cells with large,
clear lipid displacing and flattening the nucleus to the periphery.
• Myxoid variant:
• Rare variant.
• Neoplastic cells vary in shape. They are loosely embedded in a myxoid eosinophilic
stroma that stains positive to Alcian blue.
• Pleomorphic variant:
• Rare variant.
• Cells are characterized by marked cellular atypia and bizarre binucleated or multinu-
cleated cells.