Types of Skin Lymphomas

There are many types of skin lymphomas. Classifying them can be confusing (even for many doctors) because many of them are not very common.

The main systems used to classify skin lymphoma are:

• World Health Organization (WHO) Classification of Hematolymphoid Tumors
• International Consensus Classification of Mature Lymphoid Neoplasms

The two systems are very similar and are based mainly on:

• Whether the lymphoma starts in T lymphocytes (T cells) or B lymphocytes (B cells)
• How the lymphoma looks under the microscope
• Whether certain proteins are on the lymphoma cells (based on lab tests)

T-cell skin lymphomas

Most skin lymphomas are T-cell lymphomas. These are sometimes called cutaneous T-cell lymphomas (CTCLs).

Mycosis fungoides (MF)

Nearly half of all skin lymphomas are mycosis fungoides (MF). MF can occur in people of any age, but most who get it are in their 50s or 60s. Men are almost twice as likely as women to develop this lymphoma.

The first sign of this disease is usually one or more dry, scaly, pink or red areas (called patches) on the skin that are often very itchy. Often these patches are the only symptom of MF.

In some people, MF might appear as thickened, raised areas on the skin with distinct borders (called plaques). Plaques most often start as patches, but in some people they might be the first sign of MF.

MF can also appear as tumors (nodules), which are typically larger and have a rounded, more distinct appearance. In some tumors, the skin might break open (ulcerate). Tumors might appear on their own, or they might develop from plaques over time.

Because MF can be confused with other skin problems, it can be hard to diagnose at first. Several biopsies of the areas might be needed before the diagnosis is confirmed.

Over time, MF can spread across the skin or invade lymph nodes and organs like the liver. In many people this disease grows slowly, but it can sometimes grow more quickly, especially in older people. Some people with MF may go on to develop Sezary syndrome (see below).

People with MF can also have weakened immune systems, which can increase their risk for infections.

Rare variants of MF include folliculotropic MF, pagetoid reticulosis, and granulomatous slack skin.

Sezary syndrome (SS)

This is often thought of as an advanced form of mycosis fungoides (MF), but these are somewhat different diseases.

• In Sezary syndrome (SS), most or all of the skin is affected. It tends to grow and spread faster and be harder to treat.
• In mycosis fungoides (MF), patches of skin are affected. It is usually slow growing.

People with SS typically have a very itchy, scaly red rash that can look like a severe sunburn. This is called generalized erythroderma. The skin is often thickened. Lymphoma cells, called Sezary cells, can be found in the blood and the lymph nodes.

People with SS often have weakened immune systems, which increases their risk of serious infections.

Adult T-cell leukemia-lymphoma (ATLL)

This rare type of T-cell lymphoma is more likely to start in other parts of the body, but it can sometimes be confined to the skin.

ATLL is linked to infection with the HTLV-1 virus (although most people infected with this virus do not get lymphoma). It is much more common in Japan and the Caribbean islands than in other parts of the world.

This lymphoma often grows quickly, but in some cases it advances slowly or even shrinks on its own for a time.

Primary cutaneous anaplastic large cell lymphoma (PC-ALCL)

This lymphoma usually starts as one or a few tumors on the skin. The tumors can vary in size, and some may break open (ulcerate).

Most people with this disease are in their 50s or 60s, but it can also happen in children. It is found at least twice as often in men as in women. In most cases, it doesn’t spread beyond the skin and the prognosis (outlook) is very good.

Lymphomatoid papulosis

Lymphomatoid papulosis is a benign, slow-growing disease that often comes and goes on its own, even without treatment. It often begins as several large pimple-like lesions that may break open in the middle.

This disorder is seen in younger people more than other T-cell skin lymphomas, with an average age of around 45. Men get this disease more often than women.

Lymphomatoid papulosis doesn’t spread to internal organs and is not fatal. Treatment often isn't needed right away, especially if it isn’t causing any bothersome symptoms.

Rarely, some people with this skin disorder develop another, more serious type of lymphoma.

Subcutaneous panniculitis-like T-cell lymphoma

This rare lymphoma invades the deepest layers of the skin, where it causes nodules (lumps) to form. Most often these are on the legs, but they can happen anywhere on the body.

This lymphoma affects all ages and is slightly more common in females. It usually grows slowly and tends to have a good outlook.

Extranodal NK/T-cell lymphoma, nasal type

This rare type of lymphoma can start in T cells or in other lymphocytes known as natural killer (NK) cells. It typically starts in the nose or sinuses, but sometimes it starts in the skin.

It has been linked to infection with the Epstein-Barr virus (EBV) and is more common in Asia and Central and South America. It tends to grow quickly.

Primary cutaneous peripheral T-cell lymphoma, rare subtypes

This is a group of rare skin lymphomas that don’t fit into any of the above categories. There are several types:

• Primary cutaneous gamma/delta T-cell lymphoma develops as thickened plaques (raised lesions) or actual tumors, mainly on the skin of the arms and legs, but sometimes in the intestines or lining of the nose. It tends to grow and spread quickly.
• Primary cutaneous CD8+ aggressive epidermotropic cytotoxic T-cell lymphoma develops as widespread patches, nodules, and tumors that often break open in the middle. It sometimes looks like MF, but a biopsy can tell them apart. It tends to grow and spread quickly.
• Primary cutaneous acral CD8+ T-cell lymphoproliferative disorder is very rare. It typically starts as a nodule on the ear, although it can also start on other parts of the body, such as the nose, hand, or foot. It tends to grow slowly and can often be cured with treatment.
• Primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder often starts as a single area of thickening of the skin or a tumor on the head, neck, or upper body. It tends to grow slowly and can often be cured with treatment.

B-cell skin lymphomas

These lymphomas are sometimes referred to as cutaneous B-cell lymphomas (CBCLs).

Primary cutaneous follicle center lymphoma

This is the most common B-cell lymphoma of the skin. It tends to grow slowly. The early lesions are groups of red pimples, nodules (lumps), or plaques (raised areas) that form on the scalp, forehead, or upper body. Less often, they are found on the legs. Sometimes the pimples grow into nodules.

This type of lymphoma is typically found in middle-aged adults. It tends to respond well to radiation therapy, and most people have an excellent outlook.

Primary cutaneous marginal zone B-cell lymphoma

This disease is also known as primary cutaneous marginal zone B-cell lymphoproliferative disorder. It tends to grow very slowly and is usually curable. In Europe (but not in the United States), it is sometimes linked to an infection with Borrelia, the germ that causes Lyme disease.

This disease can happen at any age, although it tends to happen more often in older adults. It appears as skin lesions that are red to purplish large pimples, plaques (raised or lowered, flat lesions), or nodules (lumps) on the arms or upper body. There may be only a single lesion, but there can sometimes be a few.

Primary cutaneous diffuse large B-cell lymphoma, leg type

This is a fast-growing lymphoma that begins as large nodules (lumps), mainly on the lower legs. It happens most often in older people and is more common in women than men. It sometimes spreads to lymph nodes and internal organs, causing serious problems.

This type of lymphoma often requires more intensive treatment. The outlook is better if there is only one lesion at the time of diagnosis.