Aberrant Pancreas in the Gastric Wall

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Abstract
Aberrant pancreatic tissue in the wall of the stomach is a most uncommon finding. For this reason the salient points of 3 cases in which the correct diagnosis was strongly suspected radiologically will be presented and the literature summarized. The pancreas is formed from several entodermal evaginations of the wall of the primitive duodenum (1). The dorsal diverticulum, which appears first, becomes the dorsal pancreas and afterward the body and tail. The right and left ventral evaginations unite to form the ventral pancreas, which, growing more slowly, becomes the head of the organ, fusing with the dorsal pancreas at about the sixth week. If one or more of the evaginations remain in the wall of the bowel, they may be carried from the rest of the gland by the longitudinal growth of the intestine; the aberrant tissue arising from the dorsal pancreas would be carried toward the stomach; that from the ventral pancreas, toward the jejunum (10). In some lower animals the pancreas is normally a divided organ which is found throughout the intestinal tract. Since the first description of heterotopic pancreatic tissue in 1727 (13), aberrant pancreatic nodules have been found in a wide variety of locations. In 300 cases collected (12) up to 1935 the distribution was about as follows: stomach, 31 per cent; duodenum, 31 per cent; jejunum, 21 per cent; ileum, 9 per cent; mesentery, etc., 3 per cent; biliary tract, 4 per cent; spleen, 0.7 per cent. Other sites mentioned were the umbilicus, appendix, and a mediastinal dermoid. In six series of consecutive autopsies, totaling 4,076 bodies, 62 examples were found, and the average incidence was 1.875 per cent. In a review of histologically proved cases, 68 per cent occurred in males. In contrast, 70 leiomyomas were found in 38,222 autopsies, an incidence of 0.21 per cent, and fibromas were found in 0.11 per cent of 32,268 autopsies. Schwannomas are variously described as “occurring more frequently than the common leiomyoma” (8) or “without doubt the rarest” (14). Palmer (11) discovered that almost three-quarters of the aberrant pancreatic nodules were submucosal. Nearly half were found in the stomach, slightly more in or near the pylorus than in the antrum. Martin (9) collected 125 cases of gastric diverticula, 15 of which contained pancreatic tissue. As seen from the mucosal surface, the lesions generally appeared as follows: (a) Hemispheric mass, often superficially creased as a result of deep lobulation (about half the cases). (b) Symmetrical cone, with ill-defined boundaries. (c) Short cylindrical nipple (about 10 per cent of cases). Only 2 lesions were pedunculated. The mucosa was intact in all but a few cases. In the majority of reported cases the aberrant nodule was composed of normal pancreatic cells and a definite functioning duct system. In about a third of the cases islets of Langerhans were present (6). All pathological changes that have occurred in the pancreas proper, such as acute pancreatitis, cystic changes, and chronic interstitial pancreatitis, have been seen in the heterotopic tissue. There is evidence in the literature that these nodules may at times be the site of origin of a carcinoma (3). The dimensions of the aberrant tissue vary, ranging from microscopic proportions to one specimen measuring 1 × 3.5 × 6 cm.

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