[ Introduction]

　　 External endometriosis is a protean disease characterized by the presence and proliferation of endometrial tissue outside the uterus. The location of lesions varied and may induce different kinds of symptom and sign according to where it implanted.

[ Case Report ]

　　 A 35 y/o female patient suffered from sub-umbilical area fullness ( sometimes with pain ) about the time of menstruation for a long time since her last C/S delivery operation (Pfannenstiel incision ). Subcutaneous nodule at sub-umbilical area was found and sonography ( figure 1 ) revealed a 1.5*1.2*0.8 cm homogenous subcutaneous nodule. Under local anesthesia, mass was excised and microscopically, the section show endometriosis with endometrial glands and stroma in the soft tissue. ( figure 2 )

[ Discussion ]

　　 The lesion may cause a bulging nodule which becomes bigger and more painful while menstruation. The mass is not encapsulated with indurated surrounding tissue. C/S operation most likely to be followed by this complication and offer the possibility of spill of mullerian epithelium into the incision wound to cause the symptom and sign.