Pyoderma gangrenosum (PG) is a pathergy positive, ulcerative neutrophilic dermatosis. Pathergy phenomenon is described as a sterile pustule and an ulcer development after minor skin traumas like a bump or bruise, or needlestick injury. In the literature, there are PG cases associated with the pathergy phenomenon on the post-surgical scar tissue. It presents as a necrotic and an ulcerative lesion clinically and, debridement is performed mostly with wrong pre-diagnoses. Debridement makes the lesion get wider and the morbidity increase. There are some PG case reports in the literature which were ended up with amputation due to debridement of a lesion which was an overlooked PG. Herein, we present a case with a giant abdominal pyoderma gangrenosum developed after a surgery in the abdominal drainage site and has reached to 30 cm size after debridement.