Fourteen cases of gastritis cystica polyposa, four gastric adenomas and 25 "mature" erosions removed by diathermy at endoscopy were studied by light microscopy. Twenty surgical resections from gastric cancer patients and 18 gastric resections from gastroenterostomy patients previously operated upon for benign lesions were also studied. The mucosa showed consistent changes which were grouped as "gastritis cystica superficialis". Most surgical specimens, three out of 25 "mature" erosions, the four adenomas, and eight cases of gastritis cystica polyposa showed cystic gastric glands within the submucosa closely resembling the changes seen in colitis cystica profunda. Thus the term "gastritis cystica profunda" is proposed. It is suggested that ischaemia and chronic inflammation as well as the effects of surgery and presence of suture material have a role in the pathogenesis of gastritis cystica profunda. A correlation seems to exist between gastritis cystica profunda and gastric ulcer.

Eight cases of mediastinal non-lymphoblastic large-cell lymphoma have been studied by histopathological and immunohistochemical methods. A common clinical, morphological and immunophenotypic pattern was identified. Six of eight cases proved to be of B-cell origin by the expression of B-associated antigens detected by specific monoclonal antibodies. Cells of large size with nuclei of varying morphology and a peculiar type of fine compartmentalizing fibrosis were observed in all specimens. Clinically the disease was characterized by the young age of the patients, primary mediastinal involvement, aggressive behaviour and spread to unusual sites (kidneys in four cases). This seems to be a hitherto unrecognized entity in the field of non-Hodgkin's lymphomas, often misdiagnosed because of location and a morphology uncommon for B-cell malignancies. Immunohistochemical analysis on frozen tissue sections appears to be mandatory for a correct diagnosis. Nevertheless, this type of lymphoma could be suspected also on the basis of its peculiar clinicopathological characteristics.

Non-polypoid hyperplastic mucosa similar to that adjacent to colorectal carcinomas and adenomas, the so-called "transitional mucosa" (TM), was found in 16 out of 27 cases of solitary ulcer syndrome of the rectum. In 18 cases fully developed hyperplastic (metaplastic) mucosa was also found. It is suggested that chronic ischaemia which takes place in the solitary ulcer syndrome leads to TM as an exaggerated regenerative phenomenon. Later maturation of TM could lead to hyperplastic (metaplastic) changes.

A case of adenocarcinoma occurring in a hyperplastic (metaplastic) polyp of the colon is presented. The polyp, two cm in diameter, was located in the transverse colon of a 45-year-old male patient, and was removed endoscopically. From the periphery to the centre, the polyp showed epithelial changes progressing from hyperplastic to severely dysplastic, terminating in a central focus of invasive adenocarcinoma. It is suggested that the considerable number of absorptive cells in large hyperplastic polyps may occasionally result in an excessive absorption of carcinogen thus leading to dysplastic changes.

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