Gastric Adenomyosis vs. Aberrant Pancreas

The purpose of this paper is threefold: first, better to acquaint the radiologist with the concept of adenomyosis in the stomach (and elsewhere in the digestive tract); second, to discuss the relationship between this condition and aberrant pancreas; third, to present what we believe to be the first case in the literature diagnosed preoperatively as aberrant pancreas radiologically but proved histologically to be adenomyosis. Gastric adenomyosis, or adenomyoma, has received little attention in the surgical and pathologic literature (6, 7, 13, 14, 16). Grossly, this lesion consists of a nodule, usually within 5 or 6 cm. of the pyloric ring, the thickening being palpable from the exterior of the stomach, with bulging of the peritoneal surface and with intact overlying mucosa. On gross section, the small mass is found to protrude into the lumen of the stomach and the lesion is seen to be mainly submucosal, though the entire wall may be involved. Pin-point cystic cavities may be seen. The glandular structures may be differentiated from the muscular component by their lobulation and yellowish color. Microscopically, the condition is characterized by tubular or glandular formations with wide lumina, lined with tall columnar undifferentiated epithelium not unlike biliary or pancreatic duct epithelium and sometimes even suggesting neoplasia (13). These are embedded within a smooth-muscle stroma. Two other types of epithelial structures may be found, but these are differentiated: (a) acini with much smaller lumina than those of the undifferentiated epithelium, more or less like normal Brunner's glands, and (b) acini with practically non-existent lumina, somewhat resembling normal entopic pancreatic acini. At times, even pancreatic insular tissue may be present. As observed in individual cases, the condition runs the gamut from undifferentiated columnar epithelial structures exclusively, through stages with good amounts of both undifferentiated and differentiated acinar tissue, to a cellular pattern indistinguishable from normal pancreas, the so-called aberrant pancreas, or even normal entopic Brunner's glands (7). The naming of these microscopic stages has occasioned some confusion in the past. For example, the intermediate stages of differentiation have been called either adenomyosis or adenomyoma (depending on whether or not any neoplastic tendency was discernible), or incompletely differentiated aberrant pancreas; in the last case, the term adenomyosis was reserved for those cases in which no normal pancreatic acinar tissue was present. Examples consisting solely of tissue indistinguishable from normal entopic pancreas have been universally designated aberrant or heterotopic pancreas. As far as we have been able to determine, these have not been called adenomyosis.