Study Of Sonographic Features Of Rectal Neuroendocrine Neoplasms And Correlation With Pathology

AIM:To investigate the sonographic features of rectal neuroendocrine neoplasms (NENs) and correlation with pathology.MATERIALS AND METHODS:The test group consist of28consecutive patients with rectal NENs histopathologically established by biopsy and/or resected specimen. The control group consist of10homochronous rectal non-NEN submucosal tumors (SMTs) confirmed by pathology. The size, original layer, echoic intensity and homogeneity of the lesions and the perifocal structures were investigated.The average value of grey level of tumor was determined by computer. Masson Staining was conducted in23cases of NENs for study of correlation with echo intensity and spread mode of tumor cell and collagen fiber.RESULTS:The tumors located in the second (2nd) and third (3rd) wall layer in25/28cases of NENs, and with involvement of the fourth and/or fifth layers in4cases. Only2/28NENs and1/28NEN merely located in the second (2nd) and third (3rd) wall layer respectively. All NENs located at rectum within the range of2-13cm from the anus and appeared as nodous, round or egg-shaped lesions with intermediate echo (n=18,64.3%), hyperechogenicity (n=8,28.6%) and hypoechoic echopattern (n=2,7.1%) and a distinct border. Tumors ranged from2.6to24.8mm in size, with an average size of7.4mm. Homogeneous echogenicity was seen in all except for7(25%). Pathology showed the tumors located both in the second (2nd) and third (3rd) wall layer in all cases of NENs, and with involvement of the fourth layers in2cases. There is significant difference between the grey level of rectal NENs (83.1±29.6) and GISTs (43.3±18.9)(P=0.007). There is no significant difference among the grey level of rectal NENs with different spread modes of tumor cells except that the tubiform mode exceeds to the bridge modes (P=0.008). Masson staining shows that collagen fiber is the main fibrous connective tissue within the tumor cells of rectal NENs. There is significant difference between the echo intensity of rectal NENs with different spread modes of collagen fiber(P=0.015).CONCLUSIONS:NENs is the most frequent rectal SMTs. EUS characteristics of rectal NENs are round or nodous homogeneous medium-echoic lesions located in both the2nd and3rd wall layer clearly demarcated from the surrounding tissue.abundant collagen fiber spread in the NENs generate the hyperechogenicity and its spread modes determine the echo intensity.