Page 84 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Cysts, Tumour-like Lesions and Response to Tissue Injury

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7.7 Granulation Tissue
VetBooks.ir New connective tissue and blood vessels that form during the wound healing process.

Clinical features
• Variable clinical presentation, from thick plaque to distinct, solid nodules. It may be
ulcerated, inflamed and/or alopecic.
• It may be present anywhere in the body, at sites of previous trauma or surgery.

Cytological features
• Cellularity is often low, unless inflamed.
• Background: clear or pale basophilic with a variable degree of haemodilution.
• Variable numbers of spindle cells, either individual or forming loose aggregates with a
storiform arrangement. They are occasionally seen associated with small capillaries.
• Nuclei are generally small to medium sized, oval, occasionally folded. They have granular
chromatin and occasionally visible nucleoli.
• The cytoplasm is moderate in amount, moderately basophilic, elongated, occasionally vacuolated
or rarely containing small pink-purple granules.
• Cytological features of atypia are variable.
• Inflammatory cells of various types may be present.

Differential diagnosis
Soft tissue sarcoma

Pearls and Pitfalls
Differentiation between granulation tissue and mesenchymal neoplasia is easier on histopath-
ology than cytology. Regular granulation tissue shows a transition from large pleomorphic
cells centrally to more mature fibrocytes peripherally. Moreover, in granulation tissue, fibro-
blasts and capillaries are lined up perpendicularly to each other.