Melanoma in situ is an early, non-invasive form of skin cancer that arises from melanocytes, the cells that produce melanin. In healthy skin, melanocytes sit in a neat row at the bottom of the epidermis — the thin outer layer of the skin. In melanoma in situ, these cells have become cancerous and have grown in abnormal …
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Merkel cell carcinoma is a rare type of skin cancer. It is a kind of neuroendocrine tumor, meaning it develops from neuroendocrine cells in the skin. Neuroendocrine cells are specialized cells that send signals by releasing chemical messengers in response to nerve activity. Merkel cell carcinoma tends to grow quickly and is more likely to …
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Adenoid cystic carcinoma is a type of cancer that most often starts in the salivary glands — the glands that make saliva. It has two unusual features. First, it tends to grow slowly but can come back many years after surgery. Second, it rarely spreads to lymph nodes, but it often spreads along nerves and …
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An angiolipoma is a benign (noncancerous) soft tissue tumour that develops in the subcutis, the layer of fat just beneath the skin. It is composed of two main components: mature fat cells, which resemble normal body fat, and small, thin-walled blood vessels, some of which contain tiny clots called fibrin thrombi. These features help pathologists …
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Seborrheic keratosis is a very common, noncancerous (benign) skin growth. It develops from squamous cells, the flat cells that make up the epidermis (the outer layer of the skin). Seborrheic keratoses become more common with age, and many people develop several over time. This article explains what a seborrheic keratosis is, what the findings in …
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Sebaceous carcinoma is an uncommon type of skin cancer. It develops from sebocytes, the cells that make up the oil (sebaceous) glands of the skin. These cells normally produce a fatty substance called sebum, and because the tumor cells continue to make this oily material, the tumor often looks yellow. Sebaceous carcinoma is found most …
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A trichilemmal cyst, also called a pilar cyst, is a non-cancerous growth that develops from a hair follicle in the skin. These cysts are very common and most often appear on the scalp, where they look like smooth, round bumps under the skin. Trichilemmal cysts can range in size from a few millimeters to several …
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What is a pilar cyst? A pilar cyst is a non-cancerous growth that starts from a hair follicle in the skin. They are very common and most start on the scalp where they look like a smooth, round bump on the skin. Pilar cysts range in size from a few millimeters to several centimeters. Another …
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Extramammary Paget disease (EMPD) of the vulva is a rare and slow-growing type of skin cancer that develops from glandular cells within the surface skin of the vulva. It is classified as an “in situ” cancer when the tumor cells stay within the top layer of skin (the epidermis), meaning they have not yet spread …
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Actinic keratosis (AK) is a pre-cancerous skin condition caused by long-term damage from ultraviolet (UV) radiation, most often from the sun. It is made up of abnormal skin cells called keratinocytes, which are the flat cells that form most of the epidermis (the outer layer of the skin). In actinic keratosis, the abnormal cells are …
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