Benign developmental cysts of the mediastinum.

The examination of 40 benign developmental cysts of the mediastinum from the surgical pathology files supports the previous conclusions in the literature about these lesions. In distinguishing bronchogenic from esophageal cysts, the lining epithelium is not helpful, but the presence of two muscle layers in esophageal cysts and bronchial glands or bronchial cartilage in bronchogenic cysts enables categorization in the majority of cases. Gastroenteric cysts are lined by intestinal epithelium and are further distinguished by their location in the posterior mediastinum and association with other developmental anomalies. Pericardial cysts are histologically characterized by their simple, thin-walled structure, and they are usually closely associated with the pericardium and the diaphragm. A small group of cysts, usually bronchogenic or esophageal in type, cannot be readily classified because they are detached and do not contain helpful identifiable structures. An awareness of the developmental anatomy of the tracheo-bronchial tree and esophagus clarifies the relationships in location and structure that are seen in cysts of this region. All the benign developmental cysts in this series were easily removed at surgery, and there were no known postoperative complications.

Renomedullary interstitial cell lesions and hypertension.

The notion that renomedullary nodules of the kidney arise as a response to hypertension was tested. Heart weight, ratio of heart weight to body weight, and blood pressure in 160 patients in whom such nodules were found at autopsy were compared with similar measurements in 160 patients without nodules. There were no significant differences between the two groups, and it was concluded that there was no evidence to support the idea that the renomedullary nodule represents a response to hypertension.

Carcinoid tumors of the thymus.

Three patients with carcinoid tumors of the anterior mediastinum are described. Study of these patients and an analysis of previously reported cases indicates that the thymus is the primary site of these tumors, which are probably related to the presence of Kulchitsky cells in normal thymus. These neoplasms differ clinically and anatomically from conventional thymomas. They occur predominantly in men, are not associated with myasthenia gravis or red-cell hypoplasia, and are more aggressive tumors than thymomas. Histologically, they are similar to carcinoid tumors of other organs and differ from the variable combination of epithelial cells and lymphocytes of thymomas. Although they are usually locally invasive and frequently metastasize, the clinical course is usually protracted. It is probable that the reported examples of Cushing's syndrome related to thymomas were actually associated with thymic carcinoid tumors.

Oat cell carcinoma of the bronchus and the carcinoid syndrome.

A man with high urinary levels of 5-hydroxyindole acetic acid had an oat cell carcinoma of the bronchus. The patient had symptoms of the carcinoid syndrome and at autopsy was found to have evidence of carcinoid heart disease. This report supports the hypothesis that bronchial carcinoids and oat cell carcinomas are derived from argentaffin (Kulchitsky)-type cells of the lung.

Bronchial carcinoid tumors.

Twenty-eight pulmonary carcinoid tumors were reviewed histologically and clinically. Hematoxylin-and-eosin-stained sections were utilized, as well as special stains, including the argyrophil and argentaffin reactions. The 22 tumors located centrally, at the level of primary or segmental bronchi, had a microscopic appearance distinct from those located more peripherally. One peripheral tumor that was large in size appeared much more aggressive histologically, and was designated an atypical carcinoid. The origin of carcinoid tumors from Kulchitsky cells in the lung, the distinction of peripheral tumors from chemodectomas, and the relationship of bronchial carcinoids to bronchial epithelial hyperplasias and oat cell carcinomas are discussed.

Intravascular angiomatosis: development and distinction from angiosarcoma.

Histologic features similar to those present in angiosarcomas were found in organizing thrombi. Within the thrombi, freely anastomosing small channels, often lined by one or more layers of prominent, occasionally atypical, endothelial cells were noted. Papillary-like projections of organizing thrombus material lined by similar cells heightened the similarity of the process to angiosarcomas. The papillary-like structures appeared to develop due to a combination of endothelialization of thrombus fragments and of ingrowth of interlacing vessels. The peculiar process of thrombus organization, which has been called "intravascular angiomatosis," may be mistaken for true angiosarcoma and thus lead to unnecessary irradiation or radical surgery. The pseudoangiosarcoma differed from angiosarcoma in its confinement entirely within large vascular lumens and in its lack of mitoses, necrosis, and true solid cellular areas devoid of vascular differentiation.

Myxoma-like features of organizing thrombi in arteries and veins.

Evidence for the development of the cardiac myxoma from organizing thrombi has been presented previously. In this study, many of the features of the myxoma were observed in organizing thrombi in arteries and veins. Individual undifferentiated mesenchymal cells, cords of similar cells, vascular bud-like cellular aggregates, fibroblasts, well-formed vessels, and multiwalled vessels set within a loose, mucoid ground substance were present in the thrombi. These areas resembled the basilar layer of the cardiac myxoma. Cartilage-like cells, like those in the superficial zone of myxomas, were noted in some thrombi, and ossification had occurred rarely. These observations support a thrombogenic origin of the myxoma. Local physical factors may provide the stimulus for varying differentiation of mesenchymal cells in both the peripheral thrombi and the myxoma.

Experimental hypertension. The effects of chemical ablation of the renal papilla on the blood pressure of rats with and without silver-clip hypertension.

Because of the ease with which ablation of the renal papilla of the rat can be effected by chemical means, a study was carried out to determine the effects of this ablation on the blood pressure. Significant elevation was found, lennding support to the idea of the antihypertensive role of the renal medulla. Constriction of one renal artery of rats with their papillae removed resulted in a more rapid and greater elevation of pressure than the same procedure in rats ith their papillae intact. The rise in pressure approximated the sum of the rises caused by removal of the papilla alone and by renal artery constriction alone, consistent with the idea of two mechanisms being at work in this model.

Thiamine deficiency and oxalosis.

Type I hyperoxaluria results from reduced activity of alpha-ketoglutarate: glyoxylate carboligase, which is necessary for the synergistic decarboxylation of glyoxylate and alpha-ketoglutarate to alpha-hydroxy-beta-keto-adipate. Since thiamine pyrophosphate is a cofactor in the reaction, thiamine deficiency might be expected to result in tissue oxalosis. However, there was no significant increase in the incidence of renal oxalosis in 15 patients with Wernicke's encephalopathy at necropsy compared with controls. It is possible that hyperoxaluria was present in these thiamine-deficient patients but at a urine concentration below that necessary for calcium oxalate deposition. It is also possible that the severity of the thiamine deficit required for hyperoxaluria exceeds that for the neuronal and cardiac manifestations.

Local arterial wall injury caused by thromboemboli.

The changes in the walls of pulmonary and systemic arteries caused by overlying thromboemboli were studied at autopsy. A spectrum of alterations was observed, from mural inflammation to arterial false and dissecting aneurysms and rupture. The arterial abnormalities were confined to the region immediately beneath the thrombus. Although the pathogenesis of the arterial lesions is uncertain, mural ischemia secondary to the overlying thromboemboli is the most probable explanation. The similarity of the lesions in many instances to those of atherosclerosis also suggests that arterial mural thrombosis may be involved in the pathogenesis of atherosclerosis.