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.
Male, 66 years, Basal cell carcinoma, nodular type
Skin cancer
Skin cancer can be divided into melanoma (see separate text and examples) and non-melanoma skin cancer. Non-melanoma skin cancer consists of two main subtypes, basal cell carcinoma and squamous cell carcinoma. Both these types of cancer are common and ultraviolet radiation from the sun is considered as the main etiological factor. The primary treatment is surgical removal of the tumor, which in most cases is sufficient for cure.
Basal cell carcinoma is the most common form of cancer in Caucasians and is rare in populations with more pigmented types of skin. The precise incidence of basal cell cancer is unclear, as this tumor type has not been included in the common cancer registries. It has been suggested that the incidence of basal cell cancer outnumbers all other forms of cancer taken together. Recreational sun exposure in young adulthood is considered as an important risk factor.
Basal cell cancers grow in hair bearing skin and the most common location is facial skin. Alike other epithelial malignancies, basal cell cancer exhibits invasive growth, but only in exceptional and rare cases does this type of tumor appear to develop metastases and thus prognosis is excellent.
Basal cell cancer develops without any known precursor stages and tumor progression is not a feature. The progenitor cell for basal cell cancer is believed to reside within the niche of hair follicle stem cells. Classification of basal cell cancer is descriptive and four major subtypes can be identified based on the microscopical growth pattern: (i) superficial, (ii) solid/nodular, (iii) intermediate and (iv) sclerosing type. The sclerosing type shows the most aggressive growth pattern with diffuse invasive growth of small strands of tumor cells surrounded by a specific fibroblastic tumor stroma. The common histopathological features of basal cell cancer include undifferentiated tumor cells (basal cell-like) with a pallisading arrangment of nuclei in the periphery of tumor nests. The tumor is often seen as connected to the epidermis and surrounding the tumor there is often a specialized loose connective tissue stroma rich in fibroblasts and collagen.
Squamous cell cancer of the skin is a common form of human cancer, mainly in Caucasian populations, and is most frequently located in facial skin and skin subjected to chronic sun exposure. The main risk factor for cutaneous squamous cell cancer is accumulated exposure to ultraviolet radiation from the sun. Squamous cell cancer in skin typically develops through precursor stages. A common precursor lesion is actinic keratosis, which is defined as epidermal dysplasia without invasive growth in combination with signs of ultraviolet damage in the dermis (solar elastosis). Squamous cell cancer in the skin can progress to poorly differentiated cancer and eventually develop metastases. Development of metastases is uncommon for squamous cell cancer of ordinary skin. However, squamous cell cancer that develops in skin adjacent to mucosal surfaces, e.g. lips and peri-genital/anal skin can often be more aggressive and metastasize to regional lymph nodes.
The histopathological features of cutaneous squamous cell cancer include growth of atypical cells with squamous differentiation into the dermis and deeper lying structures. The tumors can vary in degree of differentiation from well differentiated tumors with extensive keratinization to poorly differentiated tumors with severe cellular atypia and only hinted signs of squamous differentiation.
