原文
Pathology
The urachus is usually composed of three layers: an outer muscular layer, a middle layer of connective tissue and the innermost layer, which is usually lined with transitional epithelium. Although the lumens of urachal remnants passing through the bladder wall are most frequently covered with normal-appearing transitional cell epithelium, urachal cancers are nearly always adenocarcinomas. Only rarely have sarcomatoid, squamous or transitional cell elements been reported. These adenocarcinomas display an enteric-type histology more frequently associated with colorectal cancer. These tumors often have glandular structures and mucin production, and may also have colloid and/or signet-ring cell histology present.
Although the origin of these adenocarcinomas is not definitively known, two theories have been proposed regarding their development. Explaining their close resemblance to colorectal cancer is the theory that these tumors originate from
enteric rests left behind from the cloaca during embryological development. An alternative hypothesis is that these tumors result from a metaplastic pathway. Evidence supporting the latter includes the development of adenocarcinomas in the renal pelvis and ureter, which are not of cloacal origin, observations of adenocarcinoma arising from cystitis glandularis and the occurrence of adenocarcinomas in extrophic bladders despite transitional cell epithelium at birth.
译文
病理学
脐尿管通常是由三层组成：外层肌肉层，中间结缔组织层和最内层（通常是移行上皮）。
虽然脐尿管残余腔穿过膀胱壁，经常被看似正常的移行细胞上皮覆盖，但脐尿管癌几乎都是腺癌。据报道只有极少部分为肉瘤样、鳞状或移行细胞癌。这些腺癌显示肠型组织更常与结直肠癌有关。这些肿瘤常有腺体结构和粘蛋白的产生，还可能有胶状和/或印戒细胞组织存在。
虽然这些腺癌来源不是很确定，但是针对这些肿瘤的发展提出了两个理论。解释和结直肠癌症非常相似的理论是，这些肿瘤起源于胚胎发生期间泄殖腔的肠内皮静息细胞左后侧。另一种理论是，这些肿瘤来源于转化途径。支持后者的证据包括肾盂和输尿管处腺癌的形成（而不是源于泄殖腔），以及尽管出现移行细胞上皮但是观察到源于腺性膀胱炎的腺癌和出现外生膀胱腺癌。
