The diagnosis of neoplasia can be simple when a solid mass can be visualised or palpated, or when it can be identified on radiographic or ultrasound examination. But care is needed when considering the visual appearance of a tumour alone because appearances can be deceptive! An innocuous looking tumour of the skin could be a mast cell tumour, or a small black growth in the mouth could be a malignant melanoma, and fibrosarcomas along the gum margin of dogs often look benign (even under microscopic examination they can be misdiagnosed as fibromas) but they are in fact extremely invasive.

In all cases the diagnosis should be confirmed by the histopathological examination of a biopsy, or occasionally by the examination of fine needle aspirates or other techniques for obtaining neoplastic cells, e.g. impression smears.

In many cases the clinical signs associated with a neoplasm are non-specific and are due to systemic side-effects called paraneoplastic signs (Table 6.8). In geriatric patients it is important to evaluate the significance of such signs to rule out the possibility of the presence of a malignant or benign neoplasm.