Histopathology: skin pathology These presentations are to help you identify, and to test yourself on identifying, basic histopathological features. They do not contain the additional factual information that you need to learn about these topics, or necessarily all the images from resource sessions. This presentation contains images of basic histopathological features of common skin pathologies. Before viewing this presentation you are advised to review relevant histology, sections on inflammation, healing, neoplasia, psoriasis and dermatitis in a pathology textbook, relevant lecture notes, relevant sections of a histopathology atlas and the histopathology power point presentations on healing and neoplasia. Copyright University of Adelaide 2011 Med 3: skin cases semester 1
Skin, solar elastosis. Note the greypurple discolouration (it should be eosinophilic) of the dermal connective tissue (black star). This results from chronic sun damage. Age and sun related changes to the dermis, particularly to the elastic tissue component, lead to wrinkling.
Solar/actinic keratosis (epidermal dysplasia caused by sun damage) left side of black line, normal epidermis right side. Note that in the solar keratosis there is disorganization of keratinocytes and some keratinocytes have enlarged nuclei, the stratum granulosum is absent and nuclei are retained in the stratum corneum (parakeratosis). This results from more rapid proliferation of cells with insufficient time for normal differentiation as they ascend from the basal layer. The blue line denotes the approx. location of the epidermal basement membrane.
Squamous cell carcinoma (outlined by blue lines) invading through dermis into subcutaneous tissue (very low power view). Origin from the epidermis is not always readily seen. The tumour comprises invasive islands of cells that appear eosinophilic on low power due to their relatively low N:C ratios as many are similar to cells of the stratum spinosum. The dark discolouration (predominant staining with haematoxylin) in the dermis at the edges of the lesion is due to a chronic inflammatory cell infiltrate. Black stars: epidermis. (From Australian Cancer Society collection 1991)
Squamous cell carcinoma. High power view of tumour cells (tumour cells only, the invasive nature of the cells cannot be seen here). The cells show cytological features of malignancy: nuclear enlargement, pleomorphism, prominent nucleoli. These cells are mostly relatively well differentiated being similar to cells of the stratum spinosum with abundant eosinophilic cytoplasm and intercellular bridges (black arrows). However, some cells focally are differentiating further (black star), becoming flattened and keratinising and their nuclei are undergoing pyknosis, similar to more superficial squamous cells.
Squamous cell carcinoma. High power view of tumour cells. The cells show cytological features of malignancy: nuclear enlargement, pleomorphism, prominent nucleoli. These cells are mostly well differentiated being similar to cells of the stratum spinosum with abundant eosinophilic cytoplasm and intercellular bridges (black arrow). However, some cells focally are differentiating further, becoming flattened and fully keratinising, forming a keratin pearl (black star).
Squamous cell carcinoma, medium power view. The cells show cytological features of malignancy: nuclear enlargement, pleomorphism, prominent nucleoli. However, these cells are fairly poorly differentiated. It is difficult to tell that they are squamous. They still have some eosinophilic cytoplasm but there is no keratinisation. Intercellular bridges are difficult to distinguish at this power.
Basal cell carcinoma (outlined by blue lines) invading through dermis into subcutaneous tissue (very low power view). The tumour comprises invasive islands of cells that appear basophilic on low power due to their high N:C ratios as many are similar to cells of the stratum basale. Black stars: epidermis. (From Australian Cancer Society Collection, 1991)
Basal cell carcinoma (medium power). Islands of cells (black stars) originating from epidermis invading into dermis. Cells at the edges of the islands are arranged in a palisade pattern (peripheral palisading) and have high N:C ratios similar to cells of the stratum basale. Epidermis over the tumour is beginning to ulcerate (blue star) as is common in these lesions (which are sometimes referred to as rodent ulcers). A chronic inflammatory cell infiltrate is seen in the surrounding dermis. Red star: intact epidermis
Tumour Stroma Basal cell carcinoma (high power). The cells at the edge of the tumour are arranged in a palisade pattern (peripheral palisading - black arrows) and have high N:C ratios similar to cells of the stratum basale.
Normal epidermis and papillary dermis (high power). Scattered melanocytes (black arrows) are easily seen at the dermo-epidermal junction.
Normal epidermis and papillary dermis (high power). Melanin stains black in this Masson Fontana stain. Scattered melanocytes (black arrows) are easily seen. Note how most of the melanin has been transferred to keratinocytes.
Common types of benign melanocytic naevi generally contain bland naevus cells that are arranged as nests at the dermoepidermal junction and/or nests or sheets in the dermis. The image demonstrates a compound melanocytic naevus with both junctional (black arrows) and dermal (red stars) naevus cells. Note the prominent pigmentation which gives these lesions their brown colour macroscopically.
Invasive malignant melanomas contain melanocytes that are generally arranged as nests at the dermoepidermal junction and/or nests or sheets in the dermis. The cells however are atypical. In situ melanomas contain only a junctional component i.e. no invasive dermal component. The image demonstrates an invasive malignant melanoma. Black arrows: junctional nests of malignant melanocytes. Red stars: malignant melanocytes invading the dermis. In malignant melanoma, malignant cells also invade upwards into the epidermis (blue arrow), a feature known as pagetoid spread. Note the prominent pigmentation (mostly in macrophages here) which gives these lesions their brown colour macroscopically.
Invasive malignant melanoma. Black arrows: junctional nests of malignant melanocytes. Blue arrows: malignant melanocytes invading upwards into the epidermis Red star: malignant melanocytes invading the dermis
In the absence of metastases, the prognosis of melanoma is mainly dependent on the depth of invasion into dermis measured in mm from the overlying stratum granulosum (Breslow thickness). The grade and type are not significant in determining prognosis. (From Australian Cancer Society collection 1991)
Seborrhoeic keratoses may be pigmented. They often have a stuck on appearance macroscopically. Micrograph (low power): Benign epidermal proliferation. (From Australian Cancer Society collection 1991)
Depending on their likely nature and location, skin lesions may be removed in their entirety and sent to a pathology laboratory for assessment. Such excision biopsies are therapeutic as well as diagnostic. (From Australian Cancer Society collection 1991)
The specimen is placed in a container of formalin, labelled, and along with a request form, sent to a pathology laboratory.
In the pathology laboratory, the specimen with the lesion is transversely sectioned (black lines). The slices of tissue are embedded in paraffin, sectioned and stained and the resulting histopathology section demonstrates the excision margins as well as the lesion (inset). A diagnosis is made and the referring doctor can also be informed as to whether the lesion is completely excised. (From Australian Cancer Society collection 1991)
Psoriasis. Thickened (acanthotic) epidermis with elongated narrow rete pegs Black arrow: absence of stratum granulosum Red star: parakeratosis Blue star: Nuclear debris and inflammatory cells: microabscess
Acute eczematous dermatitis. Histologically, intercellular edema produces widened intercellular spaces within the epidermis (spongiosis), eventually resulting in small, fluid-filled intraepidermal vesicles. (From Robbins & Cotran Pathologic Basis of Disease 7E Copyright Elsevier).
Skin: full thickness burn (low power). Burned tissue undergoes coagulative necrosis - the architecture is still discernable (e.g. black stars indicate sweat glands in deep dermis) but no nuclei are seen.
Skin: partial thickness burn (low power). Cells in the deep dermis are still viable (nuclei are retained) but tissue in the superficial and mid dermis shows coagulative necrosis. The epidermis is no longer present. Black arrow: inflammatory cells Blue stars: necrotic sweat glands in mid dermis Black stars: viable sweat glands in deep dermis
Skin, burn: sweat glands (black star) and hair follicle (red star) showing coagulative necrosis. The architecture is still discernable but no nuclei are seen. The nuclei (black arrows) in the interstitial tissues are of inflammatory cells (probably neutrophils).
Skin, recent wound extending into subcutaneous adipose tissue. Blood clot fills the wound (blue star). Yellow star: surface scab Black star: adjacent dermis. Such a wound with closely opposed edges, especially if sutured, will undergo healing by primary intention.
Skin, recently healed wound extending into subcutaneous adipose tissue (very low power). Yellow star: epidermis has regenerated across the wound. Blue star: recently formed scar. Black star: adjacent dermis.
Skin, early fibrous scar (S) with normal dermis (D) on either side, low power. This represents the end result of healing by primary intention as healing followed a simple incision for removal of a skin lesion. The scar here still contains quite a few fibroblasts. (From Wheater s Basic Histopathology, a Colour Atlas and Text, 4th ed. by Stevens, Lowe and Young, Churchill Livingstone.)
Tissue taken from an ulcer of the skin showing granulation tissue. This larger area of damage will heal by secondary intention. Healing by secondary intention also occurs in chronic peptic ulcers and following infarction in organs (except in the brain)
In certain situations wound healing can be complicated by excessive formation of the components of repair. In keloids, thick bundles of collagen (black star) are formed that do not regress.