sarcoidosis is a common systemic disorder of unknown etiology which is characterized by the formation of noncaseating epithelioid cell granulomas .
in addition to their occurrence in systemic sarcoidosis , these granulomas have also been observed in various parenchymas and in the lymph nodes associated with other granulomatous diseases .
granulomatous reactions occurring within lymph nodes draining carcinomas are a well - known but uncommon occurrence .
these histologic changes have been termed sarcoid reactions , and such changes have been described in association with lymphoma and other solid tumors .
however , the presence of this response in colorectal cancer has been considered to be quite rare , and only a few reports have mentioned the presence of granulomatous reactions in colorectal cancer .
we herein report a rare case of adenocarcinoma of the ascending colon associated with sarcoid reaction in the regional lymph nodes .
a 56-year - old japanese man was assessed for anemia . computed tomography of the abdomen performed to investigate the cause of anemia showed a tumor mass in his ascending colon and many enlarged regional lymph nodes ( fig .
laboratory data showed no abnormality except for anemia , with 9.0 mg / dl hemoglobin .
the past clinical history mentioned hypertension , but neither inflammatory nor immunological disease . a typical ileocecal
gross examination of the operative specimen revealed a tumor measuring 70  55 mm at the ileocecal valve , and many enlarged regional lymph nodes were present , suggesting metastasis of the lymph nodes .
histopathological examination revealed moderately differentiated adenocarcinoma of the ascending colon which extended to the subserosa .
there was no metastasis to the dissected lymph nodes ; however , noncaseous epithelioid granulomas with multinucleated giant cells without necrosis were observed ( fig .
we here report a rare case of adenocarcinoma of the ascending colon associated with sarcoid reaction in the regional lymph nodes .
an association of sarcoid reaction with malignancy has been reported , and such reactions may occur in lymph nodes draining an area housing a malignant tumor , in the tumor itself , and even in nonregional tissues .
sarcoid reactions have been described in association with lymphoma , testicular cancer and other solid tumors .
however , this response in colorectal cancer has been considered to be quite rare , and there have been only a few publications that mention the presence of granulomatous reaction in colorectal cancer .
the mechanism of tumor - associated sarcoid reaction in the regional nodes has not yet been elucidated .
the possible mechanisms are summarized as follows : ( 1 ) a localized defense reaction to tumor cells themselves , ( 2 ) a simple tissue reaction to a tumor embolism in the lymphatic system or capillaries , and ( 3 ) an immunological reaction to substances released from the tumors transported along the lymphatic system [ 2 , 3 , 6 , 13 , 14 ] .
sarcoid reaction has also been reported after interferon therapy in patients with malignant melanoma and after interleukin-2 therapy for renal cell carcinoma .
thus , sarcoid reactions are most likely caused by antigenic factors derived from the tumor cells and could play an important role in the host 's defenses against metastatic extension .
sarcoid reactions may manifest as local t - cell - mediated reactions , and in hodgkin 's disease and gastric cancer there is evidence that patients with sarcoid reactions in the regional lymph nodes have a better prognosis .
it has been generally reported that patients with malignant tumors coexisting with sarcoid reactions have a good prognosis because this reaction commonly occurs in lymph nodes without metastasis .
in fact , in our case and a few case reports of colon cancer with sarcoid reactions in the lymph nodes , there was no metastatic carcinoma in the dissected lymph nodes despite the large size of the tumor .
in contrast , however , according to the few publications that mention lung - cancer - associated sarcoid reaction , such lesions do not influence the prognosis . to elucidate the relationship between this reaction and the prognosis of patients with cancer , especially colon cancer , an investigation based on a larger number of patients
fdg - pet is useful for preoperative diagnosis of distant lymph node metastases of colorectal cancers . in present case , 18f - fdg - pet
although 18f - fdg - pet is very sensitive for a variety of malignancies , it can lack specificity . in addition to malignant tissue , any active infectious or inflammatory process , including sarcoidosis , can demonstrate fdg avidity [ 6 , 24 , 25 ] .
thus , it is difficult to differentiate sarcoid reaction from lymph node metastases preoperatively , and there is no useful examination , except histopathological examination , for distinguishing lymphadenopathy caused by a sarcoid reaction from metastatic lymph nodes . in conclusion , we report a rare case of colon cancer with sarcoid reaction in the regional lymph nodes .
the effect of the response on the prognosis in cases with colon cancer has not been fully elucidated due to the small number of such cases , and further analyses from a large number of cases are warranted to evaluate the relationship between sarcoid reaction and colon cancer .
 lymph node swelling in the setting of malignancy generally suggests metastasis of the primary tumor . a granulomatous reaction , i.e. sarcoid reaction , occurring within the lymph nodes draining carcinomas is a well - known but uncommon occurrence . 
 the phenomenon is especially rarely seen in colon carcinoma . 
 we herein report a rare case of a 56-year - old japanese male with adenocarcinoma of the ascending colon associated with sarcoid reaction in the regional lymph nodes . a typical ileocecal 
 resection and lymph node dissection were performed . 
 histopathological examination revealed moderately differentiated adenocarcinoma of the ascending colon , and the dissected lymph nodes included epithelioid granulomas with multinucleated giant cells . 
 these findings suggest the existence of a sarcoid reaction associated with colon carcinoma ; there was no metastasis in the dissected lymph nodes . 
 the significance of this rare condition is discussed . 
Introduction
Case Report
Discussion