To the Editor
Adenomyoma of the gastrointestinal tract is a benign tumor-like lesion without malignant potential, which is histologically characterized by a mixture of glandular structures lined by tall columnar epithelium surrounded by smooth muscles. Adenomyoma rarely originates in the small intestine and accounts for only 6.8% of benign lesions of the small intestine. Here we report a rare case with adenocarcinoma that arose in adenomyoma of the small intestine.
A 47-year-old man with a renal dysfunction presented to our hospital with abdominal pain. Laboratory tests were normal. Abdominal computed tomography scan demonstrated a dilated small bowel which was consistent with small bowel obstruction. Emergent laparotomy was performed, and revealed two hard tumors (2.0 cm in diameter 150 cm and distal to the Treitz ligament (Tumor 1), 1.5 cm in diameter and 300 cm distal to the Treitz ligament (Tumor 2)). Segmental small bowel resections were performed. Recovery was uneventful and the patient was discharged 12 days after the operation. At the 14 months follow-up, no recurrence was evident.
Tumor 1 was completely circumferential resembling a submucosal tumor-like mass macroscopically (Fig. 1a). The intestinal wall was markedly thickened without ulcer formation. Microscopically, intestinal wall was thickened with hypertrophic smooth muscle bundles merged with muscularis mucosa, and glands (Fig. 1b). These glands scattered mainly from submucosal layer to subserosal layer, and only a few glands opened to the surface of intestinal mucosa. There were no pancreatic acinar glands or islets of Langerhans. Lobular structures similar to pyloric glands, and glands similar to gastric foveolar epithelia were found partially (Fig. 1c). Focally, most glands were lined by cuboidal or tall columnar epithelia without atypia (Fig. 1d). However, aside to this area, atypical glands such as biliary intraepithelial neoplasia (BilIN)1–3 and pancreatic intraepithelial neoplasia (PanIN)1–3 were found occasionally. Well to moderately differentiated tubular adenocarcinoma component was present in the focal area of the subserosal layer, and were exposed to serosal surface (Fig. 1e, f). Immunohistochemically, more than half of glandular cells were positive for MUC5AC and MUC6, and negative for MUC2, MIST-1, pepsinogen-1, H.K-ATPase, alfa-amylase. Carcinoma components were also focally positive for MUC5AC and MUC6.
Figure 1.
(a) The resected jejunum showed a tumor (2.0 cm in diameter) which was covered with normal mucosa. (b) The tumor showed surrounding growth with hypertrophic smooth muscle bundles and glands. (c) Lobular structures similar to pyloric glands, and glands similar to gastric foveolar epithelia were found partially. (hematoxylin-eosin, ×40). (d) Some dilated glands were composed of epithelia with and without atypia. (hematoxylin-eosin, ×100). (e) Several glands without atypia were scattered in the proper muscular layer (shown in upper half), and adenocarcinoma component was seen in the subserosal layer (shown in lower half). (hematoxylin-eosin, ×40). (f) Some glands showed focal progression to high grade dysplasia and to invasive adenocarcinoma. (hematoxylin-eosin, ×40).
Tumor 2 also showed submucosal tumor-like characteristics, and was composed of only cancer components. Many atypical glands with invasive growth from subserosal layer to submucosal layer were seen, and immunohistochemical findings showed almost the same result as Tumor 1. We therefore considered that Tumor 2 was metastatic foci of Tumor 1 which was considered the primary site.
To the best of our knowledge, this is the first case of adenocarcinoma arising from adenomyoma in the gastrointestinal tract. In addition to the primary tumor, the patient had a second lesion in the small bowel that was consistent with a metastatic lesion due to peritoneal dissemination.
The pathogenesis of adenomyoma is considered to take a form of myoepithelial hamartoma or a pancreatic heterotopia.1 In this case, more than half of the tumor cells were immunohistochemically positive for MUC5AC and MUC6, which are gastric marker mucins, and negative for MUC2, which is an intestinal marker mucin. In addition, they were negative for MIST-1, pepsinogen-1 and H.K-ATPase, gastric fundic gland markers. Therefore, we could say that the nodule consisted of various types of glands, from typical glands with gastric character to adenocarcinoma. Aberrant gastric mucosa and ectopic pancreas with gastric differentiation can be stated as a differential diagnosis. However adenomyoma is considered to be associated with ectopic pancreas, adenomyoma has no potential to differentiate into islets of Langerhan and pancreatic acinar glands. In fact, in this case, islets of Langerhans and pancreatic acinar glands were not found.
This case had a metastatic lesion at the other location of the small intestine by peritoneal dissemination, which confirmed malignant behavior of the primary lesion. Small intestinal adenocarcinoma is reported to have a poor prognosis with 5-year overall survival of 10%, with a high propensity to spread via peritoneal dissemination, which is found in 26% of cases.2 Chemotherapy is reported effective to improve survival.3 In this case, we considered that treatment for gastric cancer was efficient for the patient since the immunohistochemistry findings were consistent with gastric-type adenocarcinoma, and the patient received adjuvant chemotherapy regimen for gastric cancer. At the 14 months follow-up, no recurrence was evident.
Only a few cases of adenocarcinoma arising in adenomyoma in the other primary organs have been reported, such as the gallbladder.4 Some sporadic case reports and studies suggest that long-standing biliary stasis and resultant mucosal changes in the fundal compartment may explain the high prevalence of gallbladder cancer.5 In our case, the obstruction caused by the adenomyoma in the intestine leads to excessive intraintestinal pressure and changes in the epithelium of its mucosa, which ultimately transformed into malignancy. The question arises regarding prognosis of these malignant foci limited to the adenomyoma. However, no such case report has been described in the literature, the prognosis in such case where there is no invasion and the lesion is completely excised is expected to be favorable. The etiology and treatment of adenocarcinoma arising in adenomyoma is left to further studies.
Adenomyoma is a focal benign lesion composed of glandular structures and smooth muscle. Adenomyoma of the small bowel should be carefully evaluated and considered for surgical resection. Further reports are needed for a better understanding of the natural history of adenomyoma to guide optimal management.
ACKNOWLEDGMENTS
The authors would like to thank Prof. R. Kushima, Division of Diagnostic Pathology, Shiga University of Medical Science, for pathological diagnosis.
Footnotes
DISCLOSURE STATEMENT
None declared.
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