Page 76 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Cysts, Tumour-like Lesions and Response to Tissue Injury

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VetBooks.ir Pearls and Pitfalls
Cytological differentiation between haematoma and poorly exfoliative vascular neoplasms
•
is often not possible based on cytology alone. Final diagnosis requires histopathology.
• In cases of aspiration of fluid, erythrophagocytosis may occur in vitro, as a result of
delayed sample preparation.
• Haemosiderin can slightly vary in colour and, on certain occasions, may be difficult to
distinguish from other granules, including melanin. Haemosiderin can be confirmed by
using Prussian blue.
• Haematoidin is a haemoglobin product biochemically similar to bilirubin, which can be
extracellular and/or intracellular. It forms when haemorrhage occurs in a closed tissue com-
partment and is the result of haemoglobin metabolism under low oxygen tension conditions.
Following erythrocyte degeneration, haemoglobin is converted to porphyrin and then to bili-
verdin. The latter is reduced to crystalline haematoidin. As haematoidin can be converted
back to biliverdin, it is not always seen.

EXTRAVASATION ERYTHROPHAGOCYTOSIS HAEMOSIDERIN

HAEMORRHAGE Low oxygen tension

HAEMATOIDIN CRYSTALS

Fig. 7.5. Cytological changes expected in association with haemorrhage. Wright-Giemsa.