Fig. 3

Diagnosis of a primary, anorectal small cell tumor. a-b Voluminous, hypermetabolic anorectal tumor lesion (PET-scan: axial and sagittal section; red arrows) diagnosed after 6 cycles of chemotherapy. c Tumor lesion of the right wall of the anorectal region (Colonoscopy; black arrows). d-f Voluminous tumor of the right rectal wall of 62 × 84 × 162 mm of diameter, infiltrating the prostate, the right seminal vesicle, the internal anal sphincter, the levator ani and the puborectalis muscle (pelvic MRI: coronal, sagittal and axial section; red arrows)