Macroscopically, there was a 2.5x1x1 cm nodular, solid submucosal lesion in the small intestine. Ischemic changes were detected in the intestinal wall. Microscopically, the lesion was located within the mucosa and submucosa. It was composed of glandular structures of variable size and shape. There were irregular muscular bundles surrounding the glandular structures (Figure 1A,B). The glandular structures were lined by cuboidal or tall columnar epithelium with regular basally located nuclei and without atypia or mitotic activity (Figure 1C). There were no pancreatic acini or islets. We did not observe Paneth cells or goblet cells. Immunohistochemistry was performed using antibodies against CK7 (OV-TL12/30, Neomarkers, CA, USA 1:150), SMA (1A4, 1:300 Neomarkers, CA, USA) and CK20 (Ks20.8, 1:100 Neomarkers, CA, USA). Immunohistochemistry revealed that SMA was positive in the smooth muscle fibers surrounding the glandular structures (Figure 1D) while CK7 was diffusely positive in the epithelium lining the glands (Figure 1E) and CK20 was negative (Figure 1F).
Table I: Clinicopathological findings of adenomyoma of the jejunum
The pathogenesis of adenomyoma of the gastrointestinal tract is not fully understood. It is generally considered to be either a form of hamartoma or a pancreatic heterotopia, but we agree with Clarke's suggestion that the term “adenomyoma” should be used only for lesions with smooth muscle and exocrine-type ducts without ectopic pancreatic acini or islets[1]. As in our case, CK7 (+) and CK20 (-) expression profile of the glandular element coincides with that of the pancreatic duct epithelium, but not with that of intestinal epithelium. This finding supports the theory of heterotopic pancreas. The presence of smooth muscle tissue might be explained by secondary muscle proliferation caused by stimulus of misplaced epithelium[23]. The pathological differential diagnosis must include enteritis cystica profunda, heterotopic pancreas, pneumatosis cystoides intestinalis, metastatic adenocarcinoma and hamartomatous polyp in Peutz-jeghers syndrome. The cysts in enteritis cyctica profunda are not encircled by muscle fibers. They are often confused with metastatic adenocarcinoma. Adenomyoma shows an orderly arrangement or lobular pattern of benign ducts that shows no atypia in a background of proliferating smooth muscle rather than desmoplastic stroma. The orderly arrangement of the two muscle layers around the ducts distinguishes adenomyoma from heterotopic pancreas[25]. The cysts with no epithelial lining in pneumatosis cystoides intestinalis contain gas, whereas the glands and cysts of adenomyomas are lined by epithelial cells[23]. The important feature in Peutz-Jeghers syndrome is the presence of branching cores of muscular fibers derived from the muscularis mucosa, while adenomyoma is located in the submucosa and/or muscularis propria. The diagnosis can be difficult, especially if the small biopsies come from an adult patient with obstructive symptoms.
In conclusion, this case was important for its unusual clinical presentation and rare location.
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