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Changes in five spleens affected by hairy cell leukaemia were characterized using immunohistochemical staining for the basement membrane (BM) components laminin and type IV collagen. The ring fibres had not been totally destroyed, and were well preserved in places. The spaces filled by abnormal blood or hairy cells were assigned to the categories of altered sinus and two types of pseudosinus. In an altered sinus the staining pattern of the ring fibres had gained attenuations and the sinus was sometimes lined by a continuous BM of uneven thickness. The number of altered sinuses was related to the size of the spleen. The pseudosinuses were larger than normal sinuses and usually also larger than altered sinuses. One of the two types seemed to be derived from ruptured Billroth's cords and entailed spaces of irregular size and shape bounded by strips of fibres containing BM proteins. No ring fibres were seen in the wall. The other type of pseudosinus occurred in those spleens where no white pulp remained. These spaces were large, located around arteries and bounded by irregular strips of BM material. In three cases a number of hairy cells could be demonstrated which showed positive staining for laminin either in the surface or in the cytoplasm. Adhesive properties of hairy cells would be conceivable on the basis of the presence of laminin on the surface of the cells.

A case of pneumatosis cystoides intestinalis in the large bowel with complete resolution after eight weeks of metronidazole treatment is reported. This symptomatic case, with an acute onset classified as the primary (idiopathic) type, became asymptomatic after a few days and was followed until complete endoscopic and radiologic resolution. No recurrence was noticed during 15-month follow-up. This lends support to the assumption that anaerobic bacteria contribute to the etiopathogenesis of this condition. The choice of metronidazole as an easy ambulatory therapy is encouraged.

The distribution of basement membrane (BM) proteins, laminin and type IV collagen were studied immunohistochemically in a series of 12 normal thymuses representing different age groups (0-52 years) and in 10 cases of myasthenia gravis (age 7-53 years). The staining pattern was compared with that of conventional reticulin staining. BM proteins were present at the capsule-parenchyma interface and scantily distributed in the medullary stroma, where they were closely associated with reticulin fibres. The extrathymic perivascular space was effectively visualized by the staining of the BM's marginal to it. The fiber network present in this space stained with reticulin stain and, less continuously, in BM stainings. Lymph node like tissue with germinal centers was occasionally present in the perivascular spaces in normal thymuses and commonly in the myasthenia gravis cases, where the perivascular spaces were often dilated. The BM's of the perivascular space were mostly continuous in normal cases, but discontinuities were observed in cases of myasthenia gravis, especially in the spaces which were widely dilated. Immunohistochemical detection of BM proteins seems to be useful in the study of thymic structure, particularly in the demonstration of the characteristic changes of the perivascular space in myasthenia gravis. It is suggested that the reticulin fibres present in the medulla and in the perivascular space contain laminin and type IV collagen.

In a series of 44 patients with pernicious anemia examined by gastroscopy, three cases of gastric carcinoids were found. During the same ten-year period about 11,000 gastroscopies were performed on patients not suffering from pernicious anemia, and only one case of gastric carcinoid was detected. In two of the cases no endoscopic lesion was seen and the carcinoid was detectable only at histological examination, while in one case an unusual combination of carcinoid tumor and tubular adenoma in the same polyp was found. Most of the carcinoids arose in atrophic body mucosa, but in one case the mucosa around the carcinoid showed antral properties. One patient had slightly elevated values of pancreatic polypeptide, while no hormonal activity was found in others. No growth or spread of the carcinoid was observed during follow-up. It is suggested that the same pathogenetic factors may operate in the genesis of gastric carcinoid and gastric carcinoma in patients with pernicious anemia.

Seven human lymph nodes showing different types of reactive change, were examined for the presence of acid cysteine-proteinase inhibitor (ACPI) by the peroxidase-antiperoxidase method. A clear positive reaction was found in the germinal centres. The staining pattern indicated immunoreactivity of the dendritic reticulum cells, but the possibility that other cells, particularly histiocytic reticulum cells, may also react with antiserum raised against ACPI cannot be excluded.