In the normal appendix, myofibroblasts are found as normal cells in the mucosal pericryptal region. These cells play an important role in organogenesis and wound healing. We report the case of a 7 years old boy, who was admitted for an acute perforated appendicitis. An appendicectomy was performed with revelation of an appendiceal wall perforation. Histological examination of the appendicectomy specimen is performed. Samples taken from the area of perforation showed large number of moderately atypical spindle or stellate-shaped cells with large hyperchromatic nuclei with some observed multinucleations. Cytoplasm is often elongated and eosinophilic. Some rare mitotic figures were present. These cells express pancytokeratin and SMA, with no expression of H-caldesmon. In case of perforated acute appendicitis, cytokeratin- and SMA-positive myofibroblasts are observed in the subserosa. There are several theories trying to explain the origin of subserosal myofibroblastes. One theory postulates that these cells could originate from CD34 positive stromal cells, a second one links these cells to mesothelial cells and recently, it is believed that submesothelial cell could be the origin.