**4.2 Radiological studies**

The main role of radiological investigations is to determine the extent of the disease. Chest radiograph can detect obvious pulmonary metastases while abdominal ultrasound can detect liver metastasis [25]. Computed tomography (CT) is helpful in accurate staging of the disease (**Figure 2**). On CT, the liver lesions show late arterial enhancement and hypoattenuation of liver parenchyma in the portal venous phase [26]. The pulmonary metastases on CT chest appear as multiple end-arterial nodules with tree-in-bud appearance [25]. Magnetic resonance imaging (MRI) is a good imaging modality for accurate assessment of the local invasion of the tumor

#### **Figure 2.**

*Anorectal melanoma appeared as a heterogeneously enhancing polypoidal mass (arrow) on contrast enhanced CT (A) and MRI (B, C).*

as well as for the detection of metastatic lesions in the liver (**Figure 2**) [27]. PETCT is the recommended imaging for the staging and response assessment of metastatic melanoma [20]. Melanoma cells have higher FDG avidity compared to normal tissues due to high metabolic rate [20].
