On the welcome page of the dictionary, three major sections are shown: Normal tissues, Cancer and Cell structure. Below the image of each section are links to introductory texts for i) normal tissue histology, ii) hallmarks of cancer, and iii) cell structure overview. For the cancer-section there is also a link to current cancer statistics (incidence, survival, etc) for Sweden and the rest of the world. Within each section there are direct links to histology descriptions of different tissue types and tumor forms as well as descriptions of cell structures.
For the 'Tissue & cell types' and 'Tumor' sections, tissue-slides stained with hematoxylin and eosin (HE) are shown at three different levels of magnification. On the top level, an overview of the whole tissue-sample is shown with boxes in black indicating where zoomed-in representative parts of the tissue are available for viewing. Clicking on these boxes will zoom in on that part to show tissue structures, cells and features in greater detail. Throughout these sections, arrows indicate relevant tissue structures, cell-types and other features.
For the 'Cell structure' section, immunofluorescent images of formaldehyde-fixed cell lines are shown. The various cell structures that are demonstrated are always shown in the green channel using an antibody found in the Human Protein Atlas. The antibody name is linked to the subcellular location summary page of the target gene. The other channels: nucleus, microtubules and endoplasmic reticulum, are always shown in the blue, red and yellow channels, respectively. The channels can be toggled on and off by clicking on the respective coloured button above the image. When applicable, the immunofluorescent images are complemented by immunohistochemically stained cells where the location of the particular cell structure is shown in brown.
A common feature for all sections is that a general descriptive text about the tissue, tumor-type or cell structure is provided when browsing a particular topic.
Carcinoids comprise a group of neuroendocrine tumors derived from various tissues and organs. A common feature of these tumors is the existence of neuroendocrine secretory vesicles within the tumor cells. Neuroendocrine tumors form a spectrum ranging from well-differentiated neuroendocrine neoplasms, traditionally known as carcinoids, to poorly differentiated tumors with signs of neuroendocrine differentiation, such as small cell carcinomas. Carcinoids show variable expression of different endocrine markers and clinical symptoms vary dependent on the levels and composition of secreted proteins (hormones). Several carcinoids are endocrinologically silent. Furthermore, carcinoids differ with respect to malignancy grade, which determines the rate of growth and propensity to form metastases.
Carcinoids are common in the lung and approximately 5% of all primary lung tumors are carcinoids. The second most common location for carcinoids is the gastro-intestinal tract. Carcinoids growing in the gut are sub-classified according to anatomic location into fore-gut, mid-gut and hind-gut carcinoids, all displaying differences in secreted proteins, symptoms and aggressiveness.
Microscopically, classical carcinoids are well-differentiated neuroendocrine tumors that are characterized by the formation of well-defined nests of tumor cells separated by thin fibrovascular septa and populations of tumor cells with a homogeneous appearence. The tumor cells are relatively small and round with central nucleoli and abundant lightly eosinophilic and granular cytoplasm. Mitotic figures are often absent or rare. Necrosis and hemorrhage is not a feature of carcinoids. Within the spectra of carcinoids there are also moderately differentiated tumors, often named atypical carcinoids. These tumors have a higher degree of cellular atypia and mitoses. Clinically atypical carcinoids show a greater tendency for aggressive growth and metastatic spread.
Immunohistochemistry has played an important role to define carcinoids and commonly used antibodies include anti-chromogranin A (CHGA) to determine neuroendocrine differentiation and various antibodies towards the different hormones and peptides that are produced and secreted by the tumor cells.
