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Pleural nodules or sheets of histiocytes, admixed with eosinophils, giant cells, and other inflammatory cells are observed frequently in patients with spontaneous pneumothorax. This reaction, designated reactive eosinophillic pleuritis (REP), can closely resemble eosinophilic granuloma. Reactive eosinophilic pleuritis was found in pleural tissue of 22 of 57 patients with spontaneous pneumothorax in whom tissue was available for study. None of these patients had clinical or radiographic evidence of interstitial lung disease. Follow-up of 20 patients with REP ranged from six months to five years. None developed evidence of eosinophilic granuloma. Electron microscopy of one case did not show the Langerhans granules characteristic of the histiocytoses, including eosinophilic granuloma. Reactive eosinophilic pleuritit appears to be a nonspecific reaction to pleural injury, and is not a prodromal feature of pulmonary eosinophilic granuloma.

Histologic study of the hypophyseal component of a benign cystic ovarian teratoma disclosed elements that resembled sellar adenohypophysis, pars intermedia, and neurohypophysis. Histochemical dye methods revealed secretory cells with cytologic and granule-staining characteristics of somatotrophs, mammotrophs, melanocorticotrophs, and thyrotrophs. Nongranulated follicular cells and salivary gland rest cells also were present. Indirect immunoperoxidase staining with monospecific antisera to anterior pituitary hormones revealed abundant prolactin-containing cells, which comprised more than 50% of all chromophilic cells, as well as numerous cells that contained growth hormone and thyroid-stimulating hormone. Gonadotrophic cells could not be demonstrated by either tinctorial stains or immunostaining.

Monoclonal antibodies (MoAb) that cross-react with the shared epitopes of S100 protein have been prepared from mouse hybridoma cell lines and partially characterized. Nine of these MoAb were applied to sections of formaldehyde-fixed paraffin-embedded human tissues that were stained by immunohistochemical techniques. Three of these MoAb give uniformly and reproducibly positive staining in appropriate cell types when stained by avidin-biotin methods. Three of the MoAb were judged to be negative, although some MoAb gave inappropriate staining patterns. The three remaining MoAb showed either great heterogeneity in their staining patterns or intensities, or gave a lesser degree of reproducibility in a given tissue or neoplasm. One of the MoAb designated 15E2E2 that belonged to the first group of reproducibly staining antibodies was used to stain a larger number of normal human tissues and neoplasms. The staining that was observed appeared to recapitulate that which was previously described for conventional S100 protein antibodies. Monoclonal antibodies may, therefore, have a role in selected cases where standard microscopy is equivocal for a specific tissue diagnosis, or where independent verification of the diagnosis would be beneficial.

Pseudocysts are the most common nonfunctioning cystic adrenal lesions associated with symptoms. We have studied tissue from two patients with large adrenal pseudocysts in whom no antecedent cause could be documented. Immunohistochemical examination of these formaldehyde-fixed paraffin-embedded tissues with antibodies directed against the major proteins of the basement membrane (laminin and type IV collagen) revealed intense linear staining surrounding the cystic spaces and at the compressed adrenal cortical/pseudocyst interface. These findings lead us to conclude that these lesions are vascular in nature and, therefore, closely related to the previously recognized adrenal cysts of endothelial origin.