colorectal adenocarcinoma ( crc ) is one of the most common cancers worldwide and the third leading cause of death in the united states . crc can be histologically subtyped into adenocarcinoma ( ac ) , which accounts for the large majority of cases ; mucinous ac ; signet - ring cell carcinoma ( srcc ) , and other even less frequent subtypes . primary srcc of the colon is a rare entity , accounting for less than 1% of all crc . srcc is associated with a higher - grade tumor associated with young age , female patients , and distinct molecular patterns , such as microsatellite instability ( msi ) and activating mutations of the braf gene compared to mucinous ac . however , since clinical symptoms tend to occur late in the course of srcc , most cases are usually detected at an advanced stage with a poor overall survival rate . primary srcc at an early stage is rare , and only 27 cases have been reported . we report a case of a 36-year - old female who presented with progressive right lower quadrant pain and was diagnosed with primary srcc of the cecum . the patient responded well without any adverse reactions to an adjuvant fluropyrimidine ( 5-fu)-based therapy with oral capecitabine . a 36-year - old female presented to her primary care physician with progressive right lower quadrant abdominal pain without any significant past medical and family history . computed tomography ( ct ) scan of the abdomen and pelvis with contrast showed a 4.9  3.5  3.1 cm , lobulated , septated cystic mass arising from the cecum . the mass demonstrated wall enhancement with multiple coarse calcifications and ascites inferior to the mass ( fig . the specimen revealed organ - confined disease with final pathological staging iia ( pt3 , pn0 , pmx ) . high - grade mucinous carcinoma with signet - ring cells invaded the muscularis propria into the subserosal adipose tissue ( fig . the cells clustered into various sizes of clusters and gland - like structures at 40 magnification . at 400 magnification , the moderately differentiated malignant cells formed classical columnar strips ( fig . 3 ) . at 600 magnification , the cells floated within the abundant extracellular mucin pools as either clusters or isolated single cells ( fig . 4 ) . molecular study specific for msi showed the preserved protein expression of mlh1 , pms2 , msh2 and msh6 . carcinoembryonic antigen was within the normal limit ( < 0.3 ng / ml ) . due to the patient 's young age , early - stage disease , and aggressive high - grade mucinous carcinoma with microsatellite stability , an adjuvant 5-fu - based therapy with oral capecitabine the patient has completed 4 of the planned 8 cycles and has tolerated and responded to the therapy without any significant hematological or nonhematological toxicities . based on several reports including a large population - based study of 197,757 crc patients , srcc is a distinct entity based both on clinical presentation and pathology . srcc occurs in the younger population with female predominance , usually less than 40 years of age . more than 96% of cases of srcc arise in the stomach with the rest occurring in the colon , rectum , gallbladder , pancreas , urinary bladder , and breast . srcc usually presents at an advanced stage with node - positive disease and metastatic spread , which results in poor prognosis . a unique feature of srcc is its fibrotic appearance and preference for peritoneal metastasis over the liver . pathologically , srcc demonstrates unique features that distinguish the cells from routine ac of the colon and confer aggressiveness to these cells . the signet - ring , malignant cells are seen floating in abundant extracellular mucin pools either as clusters or isolated cells . these cells have a slightly lower prevalence of kras mutation but a higher braf mutation rate as compared to classical ac , and the prognostic implication is unknown . loss of e - cadherin expression has been reported and contributes to the high - grade and invasive nature of srcc as the cells acquire stem cell - like characteristics . there is some evidence that srcc patients with stage ii disease do not benefit from adjuvant therapy , whereas stage iii patients with high msi benefited from single - agent 5-fu adjuvant therapy . the overall prognosis of srcc in general is similar to other cancers in that staging and grade are important determinants . the available literature suggests that the tumor staging is the best predictive factor for the prognosis of srcc of the colon where higher tumor staging means poorer prognosis . the 5-year survival rate in srcc of the colon ranges from 0 to 12% , and disease recurrence is more frequent in srcc of the colon compared to ac . absence of lymphovascular invasion , lack of lymph node metastasis , and lower tnm stage had a favorable effect on the survival of srcc patients . patients with srcc can definitely benefit from closer follow - up or even intensified adjuvant therapy due to their high rates of local and distant recurrence . in a study by hugen et al . , adjuvant chemotherapy for srcc stage iii of the colon was associated with improved survival . other than presenting with abdominal pain and being microsatellite stable , her srcc occurred in the cecum and had invaded the subserosal fat . instead of having a fibrotic appearance , her cancer is more cystic in appearance than the generally reported srcc . due to early disease of stage iia and microsatellite stability in our patient , an adjuvant 5-fu - based therapy with oral capecitabine primary srcc is considered a distinct entity based on the clinical and pathological features . in this case report , we have shown a rare case of primary srcc of the cecum . given the poor prognosis of these patients , early disease of stage ii in microsatellite - stable patients should be considered for adjuvant 5-fu - based therapy in an attempt to prevent recurrence .
backgroundcolorectal adenocarcinoma ( crc ) is the third leading cause of death in the united states . 
 one of the histologic subtypes of crc is signet - ring cell carcinoma ( srcc ) , which has a distinct molecular and tumor biology from that of adenocarcinoma . 
 primary srcc diagnosed at an early stage is very rare as most cases are detected at an advanced stage . 
 therefore , overall prognosis of srcc is poor.case presentationa 36-year - old female presented to her primary care physician with new - onset progressive right lower quadrant pain without any significant past medical or family history . 
 computed tomography scan of the abdomen and pelvis with contrast showed a 4.9  3.5  3.1 cm , lobulated , septated cystic mass arising from the cecum . 
 the mass demonstrated wall enhancement and contained focal areas of coarse calcification . 
 there was nodal involvement either locally or distally . 
 the patient underwent right hemicolectomy , and pathology revealed a high - grade mucinous carcinoma with signet - ring cell variant invading through the muscularis propria and into the subserosal adipose tissue . 
 the margins were negative for tumor , and no lymphovascular or perineural invasion was noted . 
 none of the 14 resected pericolonic lymph nodes was positive for malignancy . 
 hence , she was staged as pt3 , pn0 , pmx - stage iia . 
 the appendix was not involved . 
 microsatellite instability testing showed the preservation of mlh1 , pms2 , msh2 and msh6 proteins by ihc and pcr . 
 carcinoembryonic antigen level was within normal limits . due to the patient 's young age , aggressive histology and microsatellite - stable status , 
 adjuvant fluropyrimidine ( 5-fu)-based therapy with the single agent capecitabine was initiated . 
 the patient completed 6 months of adjuvant therapy and has been disease free for approximately 18 months.conclusionprimary srcc of the cecum is a rare disease . given the poor prognosis of these patients , early - stage disease with microsatellite - stable patients should be considered for adjuvant 5-fu - based therapy in an attempt to prevent recurrence .