Section Editor: Allison Osmond MD FRCPC
May 26, 2026
The skin is the body’s largest organ. It protects the body, controls temperature, and senses touch. Skin samples are among the most common specimens a pathologist examines. They are usually taken as a small biopsy or removed completely with surgery. A pathologist examines the sample under a microscope and describes what they see in your pathology report.
This page brings together our guides to conditions found in the skin. The articles are grouped by type to help you find the one that matches your diagnosis. Select any article below to learn more.
Skin cancers
These diagnoses are cancers that develop in the skin, other than melanoma and lymphoma, which are covered in their own sections below. They include the most common skin cancers, such as basal cell carcinoma and squamous cell carcinoma. The articles explain how each type is diagnosed and what the details in your pathology report mean.
Basal cell carcinoma is the most common type of skin cancer. It grows slowly and very rarely spreads to other parts of the body. This article explains how it is diagnosed and what the details in your pathology report mean.
You may find this helpful if your report mentions basal cell carcinoma.
Basosquamous carcinoma is a type of skin cancer that has features of both basal cell carcinoma and squamous cell carcinoma. This article explains what this diagnosis means.
You may find this helpful if your report mentions basosquamous carcinoma.
Squamous cell carcinoma is the second most common type of skin cancer. It develops from the squamous cells that make up the surface of the skin. This article explains how it is diagnosed and what the details in your pathology report mean.
You may find this helpful if your report mentions squamous cell carcinoma of the skin.
Squamous cell carcinoma of the lip
Squamous cell carcinoma of the lip is a type of skin cancer that develops on the lip, often after years of sun exposure. This article explains what this diagnosis means.
You may find this helpful if your report mentions squamous cell carcinoma of the lip.
Merkel cell carcinoma is an uncommon skin cancer that tends to grow quickly. This article explains how it is diagnosed and what your pathology report describes.
You may find this helpful if your report mentions Merkel cell carcinoma.
Sebaceous carcinoma is an uncommon skin cancer that develops from the oil-producing glands of the skin, often near the eye. This article explains what this diagnosis means.
You may find this helpful if your report mentions sebaceous carcinoma.
Dermatofibrosarcoma protuberans
Dermatofibrosarcoma protuberans, or DFSP, is an uncommon skin cancer that grows slowly. It can grow into nearby tissue and come back after treatment but rarely spreads. This article explains what this diagnosis means.
You may find this helpful if your report mentions dermatofibrosarcoma protuberans or DFSP.
Atypical fibroxanthoma is an uncommon, low-grade skin cancer that usually develops on sun-damaged skin. It rarely spreads. This article explains what this diagnosis means.
You may find this helpful if your report mentions atypical fibroxanthoma.
Pleomorphic dermal sarcoma is an uncommon skin cancer that usually develops on sun-damaged skin. It is closely related to atypical fibroxanthoma but grows deeper. This article explains what this diagnosis means.
You may find this helpful if your report mentions pleomorphic dermal sarcoma.
Melanoma
Melanoma is a cancer that develops from melanocytes, the cells that give skin its color. The articles explain how invasive melanoma is diagnosed and what the details in your pathology report mean, including thickness and stage.
Invasive melanoma is a cancer that develops from melanocytes, the cells that give skin its color. This article explains how it is diagnosed and what the details in your pathology report mean, including thickness and stage.
You may find this helpful if your report mentions invasive melanoma or melanoma of the skin.
Lentigo maligna melanoma is a type of invasive melanoma that develops on chronically sun-damaged skin, usually in older adults. This article explains what this diagnosis means.
You may find this helpful if your report mentions lentigo maligna melanoma.
Precancerous changes
These diagnoses describe changes in the skin that are not invasive cancer. They range from sun-damage changes to non-invasive cancers that stay within the surface layer. They are treated to prevent an invasive cancer from developing. The articles explain what each diagnosis means.
Actinic keratosis is a common, precancerous change in the skin caused by long-term sun exposure. It is not cancer, but it can develop into squamous cell carcinoma over time. This article explains what this diagnosis means.
You may find this helpful if your report mentions actinic keratosis or solar keratosis.
Actinic cheilitis is a precancerous change on the lip caused by long-term sun exposure. It is the lip’s version of actinic keratosis. This article explains what this diagnosis means.
You may find this helpful if your report mentions actinic cheilitis.
Squamous cell carcinoma in situ
Squamous cell carcinoma in situ is an early skin cancer that is still contained within the surface layer of the skin. It has not grown into the deeper layers. This article explains what this diagnosis means.
You may find this helpful if your report mentions squamous cell carcinoma in situ of the skin.
Bowen’s disease is another name for squamous cell carcinoma in situ, an early skin cancer that is still contained within the surface layer of the skin. This article explains what this diagnosis means.
You may find this helpful if your report mentions Bowen’s disease.
Melanoma in situ is the earliest form of melanoma. The abnormal melanocytes are still contained within the surface layer of the skin and have not grown into the deeper layers. This article explains what this diagnosis means.
You may find this helpful if your report mentions melanoma in situ.
Lentigo maligna is a form of melanoma in situ that develops on chronically sun-damaged skin. The abnormal melanocytes are still contained within the surface layer of the skin. This article explains what this diagnosis means.
You may find this helpful if your report mentions lentigo maligna.
Moles and other melanocytic lesions
These diagnoses are growths made of melanocytes, the cells that give skin its color. Most are moles (also called nevi), which are very common and noncancerous. This group also includes atypical moles and a melanocytic lesion that cannot be clearly classified. The articles explain what each diagnosis means.
A nevus, commonly called a mole, is a very common, noncancerous growth made of melanocytes. This article gives an overview of moles and their types.
You may find this helpful if your report mentions a nevus or mole, or you want a general overview before reading about a specific type.
A junctional nevus is a common, noncancerous mole in which the melanocytes are found at the border between the upper and lower layers of the skin. This article explains what this diagnosis means.
You may find this helpful if your report mentions a junctional nevus.
A compound nevus is a common, noncancerous mole made of melanocytes found in both the upper and lower layers of the skin. This article explains what this diagnosis means.
You may find this helpful if your report mentions a compound nevus.
A dermal nevus is a common, noncancerous mole in which the melanocytes are found in the lower layer of the skin. This article explains what this diagnosis means.
You may find this helpful if your report mentions a dermal nevus or intradermal nevus.
A blue nevus is a noncancerous mole that looks blue or gray because the melanocytes sit deep in the skin. This article explains what this diagnosis means.
You may find this helpful if your report mentions a blue nevus.
A congenital nevus is a mole that is present at birth or appears in the first months of life. It is noncancerous. This article explains what this diagnosis means.
You may find this helpful if your report mentions a congenital nevus.
A Spitz nevus is a noncancerous mole that is most common in children and young adults. Under the microscope it can resemble melanoma, so it is examined carefully. This article explains what this diagnosis means.
You may find this helpful if your report mentions a Spitz nevus.
A dysplastic nevus is a mole that looks somewhat atypical under the microscope. It is noncancerous, but it is sometimes a sign that a person should have their skin checked regularly. This article explains what this diagnosis means.
You may find this helpful if your report mentions a dysplastic nevus or atypical nevus.
Atypical melanocytic proliferation
Atypical melanocytic proliferation is a term used when a melanocytic growth cannot be clearly classified as a noncancerous mole or as melanoma. This article explains what this finding means and what usually happens next.
You may find this helpful if your report mentions an atypical melanocytic proliferation.
Skin lymphomas
These diagnoses are lymphomas, a type of cancer of the immune system, that begin in the skin. The articles explain how each type is diagnosed and what the details in your pathology report mean.
Mycosis fungoides is the most common type of lymphoma that begins in the skin. It develops from T cells and usually grows slowly. This article explains what this diagnosis means.
You may find this helpful if your report mentions mycosis fungoides.
Primary cutaneous anaplastic large cell lymphoma
Primary cutaneous anaplastic large cell lymphoma is an uncommon, usually slow-growing lymphoma that begins in the skin. This article explains what this diagnosis means.
You may find this helpful if your report mentions primary cutaneous anaplastic large cell lymphoma.
CD30 positive T cell lymphoproliferative disorder
CD30 positive T cell lymphoproliferative disorder is a group of related skin conditions that develop from T cells. Most have a very good outlook. This article explains what this diagnosis means.
You may find this helpful if your report mentions a CD30 positive T cell lymphoproliferative disorder.
Primary cutaneous follicle centre lymphoma
Primary cutaneous follicle centre lymphoma is an uncommon, slow-growing lymphoma that begins in the skin and develops from B cells. This article explains what this diagnosis means.
You may find this helpful if your report mentions primary cutaneous follicle centre lymphoma.
Noncancerous tumors and growths
These diagnoses are noncancerous tumors, growths, and cysts of the skin. They do not spread to other parts of the body. Many are very common and are removed only if they cause symptoms or for cosmetic reasons. The articles explain what each diagnosis means.
A seborrheic keratosis is a very common, noncancerous skin growth. It often looks waxy or stuck-on. This article explains what this diagnosis means.
You may find this helpful if your report mentions a seborrheic keratosis.
A dermatofibroma is a common, noncancerous skin growth made of fibrous tissue. This article explains what this diagnosis means.
You may find this helpful if your report mentions a dermatofibroma.
A keratoacanthoma is a skin growth that develops quickly and often goes away on its own. It is closely related to squamous cell carcinoma and is usually removed to be sure. This article explains what this diagnosis means.
You may find this helpful if your report mentions a keratoacanthoma.
A cylindroma is a noncancerous skin tumor that develops from a sweat gland. This article explains what this diagnosis means.
You may find this helpful if your report mentions a cylindroma.
A hidradenoma is a noncancerous skin tumor that develops from a sweat gland. This article explains what this diagnosis means.
You may find this helpful if your report mentions a hidradenoma.
A poroma is a noncancerous skin tumor that develops from a sweat gland. This article explains what this diagnosis means.
You may find this helpful if your report mentions a poroma.
A spiradenoma is a noncancerous skin tumor that develops from a sweat gland. It often causes pain. This article explains what this diagnosis means.
You may find this helpful if your report mentions a spiradenoma.
A syringoma is a small, noncancerous skin tumor that develops from a sweat gland, often near the eyes. This article explains what this diagnosis means.
You may find this helpful if your report mentions a syringoma.
A hemangioma is a common, noncancerous growth made of blood vessels. This article explains what this diagnosis means.
You may find this helpful if your report mentions a hemangioma.
A pyogenic granuloma is a common, noncancerous growth made of small blood vessels. It often develops quickly and bleeds easily. This article explains what this diagnosis means.
You may find this helpful if your report mentions a pyogenic granuloma.
Verruca vulgaris is the medical name for a common wart. It is a noncancerous skin growth caused by the human papillomavirus (HPV). This article explains what this diagnosis means.
You may find this helpful if your report mentions verruca vulgaris or a common wart.
Condyloma acuminatum is the medical name for a genital wart. It is a noncancerous skin growth caused by the human papillomavirus (HPV). This article explains what this diagnosis means.
You may find this helpful if your report mentions condyloma acuminatum or a genital wart.
An epidermoid cyst is a very common, noncancerous cyst that forms under the skin. This article explains what this diagnosis means.
You may find this helpful if your report mentions an epidermoid cyst.
A pilar cyst is a common, noncancerous cyst that usually develops on the scalp. It is also called a trichilemmal cyst. This article explains what this diagnosis means.
You may find this helpful if your report mentions a pilar cyst.
A trichilemmal cyst is another name for a pilar cyst, a common, noncancerous cyst that usually develops on the scalp. This article explains what this diagnosis means.
You may find this helpful if your report mentions a trichilemmal cyst.
A keloid scar is a noncancerous, raised scar that grows larger than the original wound. This article explains what this diagnosis means.
You may find this helpful if your report mentions a keloid scar.
Xanthelasma is a noncancerous, yellowish deposit of fat-containing cells, usually on the eyelids. It is sometimes linked to high cholesterol. This article explains what this diagnosis means.
You may find this helpful if your report mentions xanthelasma.
Inflammatory skin conditions
These diagnoses describe inflammation of the skin. They are not cancer. Some describe a pattern of inflammation that a pathologist sees under the microscope, which can have several causes. The articles explain what each diagnosis means.
Spongiotic dermatitis is a pattern of skin inflammation that a pathologist sees under the microscope. It is often related to eczema or an allergic reaction. This article explains what this diagnosis means.
You may find this helpful if your report mentions spongiotic dermatitis.
Psoriasiform dermatitis is a pattern of skin inflammation that a pathologist sees under the microscope. As the name suggests, it can be caused by psoriasis, among other conditions. This article explains what this diagnosis means.
You may find this helpful if your report mentions psoriasiform dermatitis.
Interface dermatitis is a pattern of skin inflammation that a pathologist sees under the microscope. It can have several different causes. This article explains what this diagnosis means.
You may find this helpful if your report mentions interface dermatitis.
Cutaneous lupus erythematosus is a noncancerous condition in which the immune system causes inflammation of the skin. This article explains what a pathologist sees in this condition.
You may find this helpful if your report mentions cutaneous lupus erythematosus.
Pemphigus is a noncancerous condition in which the immune system attacks the skin, causing blisters. This article explains what a pathologist sees in pemphigus.
You may find this helpful if your report mentions pemphigus.
Pemphigoid is a noncancerous condition in which the immune system attacks the skin, causing blisters. This article explains what a pathologist sees in pemphigoid.
You may find this helpful if your report mentions pemphigoid.
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