**4.3 Endoscopic studies**

For deeply located AM, especially rectal melanoma, endoscopy is very useful to visualize the lesions and take biopsies for histological examination. On endoscopy, the lesions appear as black or brownish plaques, ulcers or polyps due to the melanin pigment. The accuracy of endoscopic biopsy ranges from 50 to 100% [28]. The accuracy is low for lesions with atypical endoscopic characteristics. Endoscopic ultrasound is helpful in determining the depth of the lesions especially the extent of anal sphincter involvement and to look for perirectal lymphadenopathy. The lesions appear hypoechoic with uneven internal echoes [28].
