Correlation between cytopathology and histopathology of the skin, lymph node and spleen in 500 dogs and cats

The results of 382 cytological examinations in dogs and 118 in cats were retrospectively compared with the correlating histological results. The histological diagnosis represented the gold standard. The investigation comprised skin, lymph node and spleen samples. The aim was to estimate the diagnostic value and the limits of cytological examinations in relation to the type of the changes. The cases were grouped in six categories: Corresponding diagnoses were formulated in 201 cases. In lymph node samples, they were reached almost twice as frequently than in skin and spleen samples. Round cell neoplasias (mast cell tumours, canine cutaneous histiocytomas and malignant lymphomas) were most often subclassified. Cytological diagnoses lacking subclassification were reached in 98 cases. The lesions were cytologically less precisely characterized than histologically. Provisional cytological diagnosis or differential diagnosis were formulated in 112 cases. Most commonly, the distinction between neoplastic and non-neoplastic character of a lesion was not possible (especially in mesenchymal spindle-cell proliferations). In 53 cases, the cytological diagnosis could not be established. In 22 cases, the relevant lesion was diagnosed only histologically whereas the cytological picture revealed another, usually secondary tissue reaction. Cytologically incorrect diagnoses were formulated in 14 cases.