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Small intestinal stromal tumors with 'skeinoid fibers' are uncommon stromal tumors with an associated controversial histogenesis. Although their microscopic appearance is suggestive of a smooth muscle nature, they lack specific smooth muscle features, as evident by electron microscopy and immunohistochemistry. They also appear to lack features of neurogenic origin because they fall to react with neural/neuroendocrine markers such as S-100 protein, neuron-specific enolase and chromogranin. It is interesting, nonetheless, to note that the ultrastructural examination of these tumors may show structures reminiscent of neural differentiation, such as cytoplasmic projections, containing occasional membrane-bound, dense-core, neurosecretory-type granules, which mimick the long cytoplasmic processes seen in tumors of neural origin. Moreover, the association of these tumors with Von Recklinghausen's neurofibromatosis, as well as the presence of 'skeinoid fibers' in proven neurogenic spindle cell neoplasms such as gastrointestinal autonomic nerve tumors and schwannomas, suggests that these tumors might also be neurogenic in origin and enhances the diagnostic value of 'skeinoid fibers' as a possible ultrastructural marker of neural differentiation. Thus, light microscopic evaluation is clearly insufficient to accurately diagnose these tumors and to determine their histogenesis, electron microscopic and immunohistochemical studies being necessary. In this article the histogenesis of small intestinal stromal tumors with 'skeinoid fibers', regarding a jejunal neoplasm in a 63-year-old patient, is reviewed. The light microscopic, immunohistochemical and ultrastructural features are described and compared with findings usually seen in all those stromal tumors which may raise a differential diagnosis, such as smooth muscle stromal tumors, gastrointestinal autonomic nerve tumors, schwannomas, paragangliomas and fibrosarcomas.

A case of Goodpasture's syndrome with a negative immunofluorescence examination of the lung biopsy in a 32-year-old man is described. The patient was a 40 cigarettes per day smoker, who had been smoking cocaine (crack) up to 3 weeks before hospital admission. He developed a diffuse alveolar hemorrhage with extremely acute respiratory distress, followed by renal failure with anuria. Transjugular renal biopsy, immunofluorescence and serum antiglomerular basement membrane antibody titer studies confirmed the diagnosis of Goodpasture's syndrome without linear immunoglobulin G deposits as determined by immunofluorescence examination of the alveolar basement membranes. The case illustrates the potentially complex interrelations between an autoimmune disease and exposure to substances with possible antigenic properties, besides the imperative necessity for an early, accurate diagnosis and treatment for the potential for threatening life. Moreover, the association of Goodpasture's syndrome with crack has not been previously reported.

Aims: Very few cases of diffuse, malignant, peritoneal mesothelioma have been reported in young women. Distinction between peritoneal mesothelioma and serous epithelial tumours, including papillary serous carcinomas and borderline serous tumours, can be difficult. Differential diagnosis based on clinical appearance and imaging techniques is broad and inconclusive, thus the diagnosis must be confirmed by histological examination. Because the vast majority of tumours involving the peritoneal and serosal surfaces are due to primary or metastatic serous epithelial tumours, there is a tendency on part of pathologists to disregard the possibility of mesothelioma when examining a biopsy or excision specimen. This is especially likely to occur when mesothelioma is associated with highly elevated serum levels of CA-125, which is the typical tumoral marker of epithelial serous tumours from the ovary. The association between peritoneal mesothelioma and high serum levels of CA-125 has been reported in the literature only in two cases., Case Details: In order to avoid a misdiagnosis of this neoplasm we describe a new case of peritoneal mesothelioma in an 18-year-old woman with high serum levels of CA-125., Conclusions: Besides its clinicopathological characteristics and its histological, immunohistochemical and ultrastructural features, we describe its biological behaviour, which seems to be worst when CA-125 levels are high.