Background Appendix’ anatomical variations are a rare occurrence which can mislead diagnosis and delay appropriate treatment. Case presentation We present a 9-year-old female patient that came with a clinical picture compatible with acute appendicitis. However, a cecal mass was identified instead of an inflamed appendix during surgery. Therapeutic decisions were extremely challenging due to clinical deterioration and an uncertain etiology. Only the histopathology report revealed the presence of a complete subserosal appendix which was responsible for the entire symptomatology. Here, we review all case reports regarding intramural, intracecal or subserosal appendixes. A discussion of the general approach to this specific case and the importance of consensual diagnostic criteria for these specimens are also presented. At last, an incidental finding is exposed and final treatment options are discussed given the overall presentation. Conclusions Considering these variants would guide physicians towards a more accurate approach to similar clinical pictures and hence an improved long-term prognosis.