several observations of the coexistence of endometriosis 
 and cancer have been published [ 1 , 2 ] . we report a case of clear cell adenocarcinoma 
 derived from 
 pathologically confirmed endometriosis in the abdominal wall . we discuss the 
 epidemiological and clinicopathological features of malignancy arising in 
 abdominal wall endometriosis . a 49 year - old woman , 
 gravida 3 , para 0 , underwent a myomectomy , 20 years before , for uterus 
 leiomyoma through a midline incision . she is presented with a painful large abdominal wall 
 mass . on physical examination , a firm indurated mass was palpated in the lower 
 abdominal wall . abdominal and pelvic ultrasounds followed by computed tomography showed a 
 heterogeneous intramuscular mass of 8.5 cm diameter without local extension ( figure 
 1 ) . the clinical impression was of desmoid tumor and the patient taken to 
 surgery and the tumor was resected without rupture . the surgeon did not perform 
 any peritoneal washing or biopsies because of the absence of widespread tumor 
 in the peritoneal cavity . the surgical specimen consisted of 11 cm cutaneous and 
 muscular tissues , occupied by ill - defined white tumor , which contained cystic 
 cavities and abundant foci of necrosis . microscopically , the tumor showed a predominant papillary and tubulocystic 
 growth pattern ( figure 2 ) . the tumor cells were round or polygonal most with 
 hobnail configuration ( figure 3 ) . benign 
 endometriotic foci were observed in the proximity of the tumor ( figure 4 ) . immunohistochemically , 
 tumor cells showed diffuse and strong cytoplasmic positivity with vimentin , 
 epithelial membrane antigen , and cytokeratin 7 , but no staining for cytokeratin 
 20 progesterone and estrogen receptor . the diagnosis   of 
 clear cell adenocarcinoma arising from abdominal endometriosis foci was 
 retained . ultrasound and computed 
 tomography showed a recurrent mass at the abdominal wall with extension to the 
 bladder . three cycles of combination chemotherapy with cyclophosphamide and cisplatin 
 were given , but the tumor did not regress . she underwent surgery again with a 
 resection of 5 cm encapsulated nodule . at that time , three cycles of chemotherapy were also given but 
 failed to control the disease ; the chemotherapy she got is not precised . the 
 computed tomography showed again a recurrent mass with extension to the bladder 
 and pelvic bone , and adjuvant radiotherapy was indicated . endometriosis , 
 defined as the presence of endometrial - like tissue outside the uterine cavity , 
 is usually located in the ovaries and pelvic peritoneum [ 2 , 3 ] . parietal 
 endometriosis is very rare and constitutes 1 to 2% of endometriosis cases . it arises usually in a surgical scar of cesarean section or hysterectomy , and 
 less frequently in a surgical scar of hernia or of appendicectomy [ 1 , 4 ] . cases 
 of endometriosis without scar have been described . the incidence of 
 abdominal wall endometriomas is of 0.04% among 
 parturients undergoing cesarean section and it is more frequent than 
 endometriosis following conventional gynaecologic surgery [ 4 , 5 ] . in our case , the etiopathogenetic mechanism is more likely related to iatrogenic 
 transplantation of endometrium during gynecological surgery rather than hematogenous 
 dissemination or metaplasia [ 4 , 6 ] . women with pelvic endometriosis have a higher frequency of malignancy , but 
 malignant change in extrapelvic endometriosis is a rare event [ 1 , 2 , 4 , 7 ] . 
 twenty percent of malignancy in endometriosis occurs in extragonadal site [ 1 , 8 , 9 ] . there is extensive clinicopathological , molecular , and genetic evidence 
 supporting the hypothesis that endometriosis is a neoplastic process with a 
 potential for malignant transformation . the natural course of malignant 
 transformation of endometriosis is long and can be explained by estrogenic 
 stimulation [ 8 , 1012 ] . malignant 
 transformation 
  in endometriosis was first described by sympson in 1925 in  
  , who 
 proposed three criteria for diagnosis : demonstration of a clear example of the 
 endometriosis in proximity to the tumor , no other primary site for the tumor , 
 and histologic appearance consistent with an origin from endometriosis . scott 
 in [ 1 , 8 ] recommended the presence of transitional area between endometriosis and 
 cancer . atypical endometriosis , a term first coined by lagrenade and silvergerg 
 in 1988 in [ 8 , 13 ] , is rare and is characterized by endometriotic glands with cytological 
 and/or architectural atypia ( hyperchromatic or pale nuclei with moderate to marked 
 pleomorphism increased nuclear to cytoplasmic ratio , cellular crowding , stratification , 
 or tufting ) . fukunaga et al .   demonstrated that atypical endometriosis in ovary is 
 often associated with epithelial neoplasm and showed direct transition from 
 atypical epithelium to malignant tumor . in our case , the criteria of sympson 
 were fully satisfied . the demonstration of endometriosis might require the 
 examination of multiple levels and sections , that is why preoperative biopsy can not 
 make the diagnosis of malignancy arising in endometriosis . tumors that can 
 arise in endometriosis include in decreasing order : endometrio i d carcinoma 
 ( 75.969.1% ) , sarcoma 
 ( 2511.6% ) , clear 
 cell carcinoma ( 13.54.5% ) , and 
 mucinous or serous carcinoma ( 4.6%1% ) . in 
 extrapelvic localization , clear cell carcinoma is the most common histological 
 subtype , followed by endometrioid carcinoma . due to the rarity of malignant 
 transformation of endometriosis at extragonadal sites , it is difficult to 
 establish a treatment protocol . first - line treatment is surgery , removing as 
 much endometriosis as possible , staging at this point is also necessary . second - line treatment , with chemotherapy , radiotherapy , and even hormonotherapy 
 may be needed . prognosis is variable from 10 to 100% five - year survival , 
 depending on histological type and localization of the disease . cutaneous 
 localization of endometriosis is unusual and appears most frequently in 
 surgical scars from obstetric or gynecological interventions . it is important 
 to recognize the possibility of tumors arising from endometriosis when the 
 pathologist is confronted to an extraovarian tumor with endometrial appearance .