Use of the uranaffin reaction in the identification of neuroendocrine granules

The diffuse endocrine system: from embryogenesis to carcinogenesis

In the present review we will summarise the current knowledge about the cells comprising the Diffuse Endocrine System (DES) in mammalian organs. We will describe the morphological, histochemical and functional traits of these cells in three major systems gastrointestinal, respiratory and prostatic. We will also focus on some aspects of their ontogeny and differentiation, as well as to their relevance in carcinogenesis, especially in neuroendocrine tumors. The first chapter describes the characteristics of DES cells and some of their specific biological and biochemical traits. The second chapter deals with DES in the gastrointestinal organs, with special reference to the new data on the differentiation mechanisms that leads to the appearance of endocrine cells from an undifferentiated stem cell. The third chapter is devoted to DES of the respiratory system and some aspects of its biological role, both, during development and adulthood. Neuroendocrine hyperplasia and neuroendocrine lung tumors are also addressed. Finally, the last chapter deals with the prostatic DES, discussing its probable functional role and its relevance in hormone-resistant prostatic carcinomas.

Neuroendocrine differentiation in thymic epithelial tumors with special reference to thymic carcinoma and atypical thymoma

To determine the neuroendocrine (NE) features of thymic epithelial tumor, immunohistochemistry and electron microscopy studies were performed on eight NE tumors (thymic carcinoids) and 26 non-NE tumors (nine thymic carcinomas, five atypical thymomas, and 12 thymomas other than lymphocytic thymoma). Immunohistochemical studies were performed with antibodies against general markers for NE cells (synaptophysin, alpha subunit of a guanine nucleotide-binding protein, Go, and small-cell lung carcinoma cluster 1 antigen), and a broad panel of antibodies for hormonal substances. Thymic carcinoid showed synchronous diffuse immunoreactivity for the three NE markers and contained cells that were positive for a variety of hormonal products: human chorionic gonadotropin (hCG) alpha-subunit (eight of eight), hCG beta-subunit (three of eight), adrenocorticotropic hormone (ACTH) (three of eight), calcitonin (two of eight), calcitonin gene-related peptide (two of eight), and serotonin (one of eight). Conversely, although positivity for NE markers was neither synchronous nor diffuse in non-NE tumors, seven of nine thymic carcinomas, three of five atypical thymomas (focal or dispersed distribution), and none of the five thymomas were positive for at least two of these NE markers. A small number of neoplastic cells were positive for hCGalpha-subunit or ACTH in three thymic carcinomas and one atypical thymoma. Ultrastructurally, dense core granules (DCG) were much more frequent in thymic carcinoid, but several DCG-like granules were identified in 12 of 13 non-NE tumors with or without immunoexpression of NE markers. The presence of focal or dispersed NE cells in thymic carcinoma and atypical thymoma may reflect multidirectional differentiation within the tumor, which, like cytological atypia, epithelial CD5 expression, and lack of immature T cell infiltration, may be another feature of this group at thymic tumors.

Immunoelectron microscopy for chromogranin A in small cell neuroendocrine carcinoma of lung

To see if immunoelectron microscopy can improve localization of neurosecretory granules, postembedding immunolabelling for chromogranin A was performed on 15 examples of small cell anaplastic (neuroendocrine) carcinomas primary in lung, five cases of bronchopulmonary carcinoids, and two cases of pheochromcytoma; both the carcinoids and pheochromocytomas had neurosecretory granule-rich cytoplasm by routine electron microscopy and some neurosecretory granules were identified in each of the small cell carcinomas. Immunolabeling for chromogranin A resulted in many colloidal gold particles over cytoplasmic secretory granules in both pheochromcytomas and four of the carcinoids. One carcinoid that was focally positive by immunoperoxidase staining was negative by immunoelectron microscopy. None of the 15 cases of small cell carcinoma stained for chromogranin A using immunoperoxidase techniques, but three had a small number of secretory granules weakly labeled by the anti-chromogranin A/colloidal gold complex. Immunoelectron microscopy, at least using standard glutaraldehyde fixation and epoxy resin embedding, does not increase the sensitivity of neurosecretory granule identification in small cell neuroendocrine carcinomas of the lung. Results of other studies of this neoplasm suggest that despite transcription of chromogranin genes, synthesis of the specific protein may occur to a limited extent or not at all.

Pathology of APUDomas

The pathology of APUDomas involves two main areas. The first is the biochemical aspects of these tumours and the use of biochemical tests to investigate a patient suspected of having an APUDoma, and the other is the histopathology of these tumours. This review is devoted to the histopathological considerations.