primary ovarian cancers tend to spread , at first , within the peritoneal cavity and the omentum , and are frequently associated with ascites , a fluid rich in growth factors and tumor cells disseminated from the primary cancer that fills the peritoneum .
tumor spread to more distant sites , including the contralateral ovary and bilateral ovarian cancers almost always represents a primary tumor and its metastasis rather than dual primary cancers .
the parallel evolution model suggests that cells with metastatic potential separate from the primary tumor at an early stage in development and evolve independently from the primary tumor .
the ovary is a site for a wide range of tumors , both primary and metastatic .
colorectal metastasis from primary ovarian carcinoma account for approximately 4.0% and an isolated rectal metastasis is very rare .
identification of the correct primary tumor is necessary for an optimal management , including , specific chemotherapy ( ct ) in advanced stages . whereas , ovarian adenocarcinomas respond to platinum based ct , cases of colonic adenocarcinomas are candidates for 5-fluorourocil based ct .
a 50-year - old female patient presented with bilateral adnexal lump and dysfunctional uterine bleeding with altered bowel habits . computed tomography of the abdomen and pelvis revealed a bilateral adnexal lump situated in the ovaries of sizes 108 cm and 43 cm , and a lobular mass of 8 cm at the rectum with peritoneal implants ( figure 1 ) .
she underwent a total hysterectomy , a bilateral adnexectomy , and a bilateral iliac lymphadenectomy for the bilateral ovarian lumps .
gross features of the ovaries showed capsular breach with presence of solid and cystic areas on cut sections .
the microscopic examination revealed a bilateral papillary serous adenocarcinoma with psammomatous calcification ( figure 2 ) .
the surgical findings revealed an 8.0 cm submucosal tumor in the rectum and invasion from the serosal side .
the tumor primarily involved the rectal muscularis propria and subserosa with only focal invasion of the rectal mucosa .
the pathological findings of the ovarian tumor specimen were consistent with those of the hemicolectomy specimen .
the patient was staged as t3cn1m1 and stage iv , according to tnm and figo classification respectively . 

figure 1computed tomography of the abdomen revealed a bilateral adnexal lump situated in both the ovaries with peritoneal implants . 
  computed tomography of the abdomen revealed a bilateral adnexal lump situated in both the ovaries with peritoneal implants . 

figure 2carcinoma ovary shows papillary serous adenocarcinoma with psammomatous calcification ( hematoxylin & eosin 40 ) . 
 
carcinoma ovary shows papillary serous adenocarcinoma with psammomatous calcification ( hematoxylin & eosin 40 ) . 

figure 3colorectal carcinoma shows moderately differentiated adenocarcinoma ( hematoxylin & eosin 40 ) . 
  colorectal carcinoma shows moderately differentiated adenocarcinoma ( hematoxylin & eosin 40 ) .
immunohistochemical staining was positive for cytokeratin 7 ( figure 4 ) and negative for cytokeratin 20 ( figure 5 ) .
this staining pattern was consistent with that of colorectal metastasis from the original ovarian lesion and immunohistochemistry supported the histological interpretation of a metastatic ovarian carcinoma .
post adjuvant 6 cycles of specific ct in the form of cisplatinum ( 50 mg ) and 5-fluorourocil ( 100 mg ) were administered to our patient and after 6 months of follow up period , she is doing well . 

figure 4positive immunohistochemical staining for cytokeratin 7 ( immunostain cytokeratin 7  40 ) . 
 
figure 5negative immunohistochemical staining for cytokeratin 20 ( immunostain cytokeratin 20  40 ) . 
 
haraoka et al . in an autopsy series , reported that colorectal metastases present with an ovarian origin in about 6.0% of cases and represent about 30.5% of all ovarian cancers .
their patients ranged in age from 34 to 77 years with an average age of 58.8 years .
the location was ascending colon in 4 patients , transverse in 2 , descending in 5 , sigmoid in 5 , and rectum in 5 .
the tumor appearance was protruding in 13 cases , ulcerative in 2 , and a submucosal tumor type in 1 of the 14 cases in which the macroscopic appearance was reported . in 9 of the 14 cases in which the tumor protruded
, distinguishing colorectal metastasis from ovarian carcinoma and primary colon cancer based on the macroscopic appearance is often difficult .
colorectal metastasis was observed to be synchronous with ovarian carcinoma in 7 patients in a study by loy et al . ,
, elevated levels of tumor markers such as ca-125 and cea may help to make a correct diagnosis .
however , up to 15% of the cases of ovarian carcinoma were present without any elevated levels of serum ca-125 .
reported a cytokeratin 7 positive / cytokeratin 20 negative immunophenotype to be nearly 100% specific for an ovarian origin .
conversely , a cytokeratin 7 negative/ cytokeratin 20 positive immunophenotype was seen in 94% of the tumors of colonic origin . in our case ,
the colonic tumor was positive for cytokeratin 7 and negative for cytokeratin 20 , a pattern consistent with an ovarian origin rather than a colonic one .
in addition , a comparison of the patient 's primary ovarian cancer with the colorectal mass revealed that the two tumors have similar histological features .
the spread of ovarian cancer to the colorectum can occur in four different ways , hematogenous spread , lymphatic spread , direct invasion and peritoneal dissemination .
the most plausible explanation of colorectal involvement in ovarian adenocarcinomas is through intra - peritoneal seedling .
hematogenous spread occurs in advanced peritoneal disease . in a substantial number of autopsy cases of advanced ovarian cancers , reed et al .
identified peritoneal involvement in 83100% cases , with large intestinal involvement in 5060% cases . in most cases of bowel metastases ,
the serosa is affected initially and then invasion extends from serosal and subserosal tissues into the muscularis propria and mucosa of the bowel wall . in the present case , the tumor mainly involved the rectal muscularis propria and subserosa with only focal invasion of the rectal mucosa and invasion of the retroperitoneum .
certain morphological features indicative of metastasis from colorectum include garland - like tumor necrosis , segmental destruction of glands and absence of squamous metaplasia , whereas cribriform growth patterns and intra - luminal dirty necrosis are indicators of ovarian adenocarcinomas .
however , the problem exists in sorting out these tumors , including in cases mucinous adenocarcinomas , when there is simultaneous involvement of the ovary and the colorectum at similar ( synchronous ) or at different ( metachronous ) times .
showed that morphologically , metastatic tumor deposits in the colorectum retained the morphology of ovarian papillary serous cystadeocarcinoma with foci of psammomatous calcification in 6 of their 11 cases .
absence of garland - like tumor and necrosis were pointers towards an ovarian primary , apart from the clinical context of a preceding ovarian tumor in 81.8% such cases .
it is thus important to identify whether or not a tumor has an ovarian origin using immunohistochemical markers , since the occurrence of gastrointestinal metastases from ovarian cancer is very rare .
as described lately , specific cytokeratin immunemarkers like cytokeratin 7 and cytokeratin 20 have been documented to be helpful in resolving these dilemmatic situations of ovarian involvement by colorectal carcinoma and vice versa .
zighelboim et al . described a single case of atypical sigmoid metastasis from a high - grade ovarian adenocarcinoma , using differential expression of ck7 and 20 .
o'hanlan et al . have reported that a longitudinal negative margin of 25 cm in the resected bowel along with a wedge resection of mesentery , including paracolic and intermediate - level nodes might be indicated to achieve optimal debulking of gastrointestinal metastases from ovarian carcinomas .
our patient underwent total hysterectomy , bilateral adnexectomy , and bilateral iliac lymphadenectomy with left hemicolectomy and postoperative chemotherapy .
in cases of colorectal involvement by ovarian adenocarcinomas and vice versa , it can be difficult to ascertain an exact primary .
in such cases , apart from complete clinical details , histomorphological features like garland - like necrosis , desmoplasia and psammomatous calcification are useful pointers towards exact primary and along with differential expression of cytokeratins 7 and 20 by immunohistochemistry can be helpful in solving these dilemmas .
 this report describes the case of a 50-year - old female patient who presented with bilateral adnexal lump and dysfunctional uterine bleeding with altered bowel habits . 
 computed tomography of the abdomen and pelvis revealed a bilateral adnexal lump situated in both the ovaries and a lobular mass of 8 cm in the rectum . 
 proctoscopy revealed an elevated irregular rectal lesion . 
 the microscopic examination of the ovarian lump revealed a bilateral serous adenocarcinoma with a papillary pattern with psammomatous calcification . 
 a left hemicolectomy with lymphadenectomy was also performed . 
 immunohistochemical staining was positive for cytokeratin 7 and negative for cytokeratin 20 . 
 the use of immunohistochemistry demonstrated the tumor to be of ovarian origin . 
 we report this case of synchronous involvement of the ovary and the colorectum because of its rarity and unusual presentation . 