Page 138 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Mesenchymal Tumours and Other Neoplasms

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clinical history and presentation (e.g. history of previous trauma/surgery, radiotherapy or evi-
dence of a discrete mass) might help. The presence of a concurrent significant inflammation
VetBooks.ir may also point in the direction of a reactive process; however, histopathology is often required
for a definitive diagnosis.
Soft tissue sarcomas (STSs)
This term refers to a specific group of mesenchymal tumours that arise from the soft tissues and
that share a similar clinical behavior. STSs are locally infiltrative but have a low to moderate
metastatic rate. The group of STSs includes:

• Fibrosarcoma.
• Myxosarcoma.
• Peripheral nerve sheath tumours.
• Perivascular wall tumours.
• Liposarcoma.
• Anaplastic sarcoma with giant cells/undifferentiated pleomorphic sarcoma.
Other sarcomas originating from soft tissues, such as histiocytic sarcoma and haemangiosarcoma,
are conventionally excluded from this category because of their distinctive morphological features
and more aggressive clinical behaviour.
Grading of soft tissue sarcomas
The histopathological grading system for canine soft tissue sarcomas has a clinical significance
and is able to predict local recurrence and development of metastasis. It is based on degree of cell
differentiation, mitotic count and evidence of necrosis. These aspects can also be identified on
cytology; however, a validated cytological grading system is not available at the present time.