About Anaplastic Large Cell Lymphoma
Lymphoma is the most common type of blood cancer. The two main forms of lymphoma are Hodgkin lymphoma and non-Hodgkin lymphoma. Lymphoma occurs when lymphocytes, a type of white blood cell, grow abnormally. The body has two main types of lymphocytes that can develop into lymphomas: B-lymphocytes (B-cells) and T-lymphocytes (T-cells). Cancerous lymphocytes can travel to many parts of the body, including the lymph nodes, spleen, bone marrow, blood or other organs, and can accumulate to form tumors.
Anaplastic large cell lymphoma (ALCL) is a rare type of NHL, but one of the more common subtypes of T-cell lymphoma. ALCL comprises about two percent of all NHLs and approximately 20 percent of all T-cell lymphomas. It can present either systemically (in lymph nodes or organs throughout the body) or in the skin.
When anaplastic large cell lymphoma (ALCL) presents in the skin it is called primary cutaneous ALCL and follows a less aggressive course. In almost all cases of primary cutaneous ALCL, the disease is confined to the skin. Despite a tendency to relapse, the relapses are usually in the skin only. As long as it is confined to the skin, it is usually managed as an indolent (slow-growing) lymphoma. Approximately 10 percent of the time, primary cutaneous ALCL extends beyond the skin to lymph nodes or organs. If this occurs, it is usually managed like the systemic forms of ALCL.
Occasionally, primary cutaneous ALCL is associated with another rare condition called lymphomatoid papulosis (LyP). LyP is a skin condition with similar features to primary cutaneous ALCL. While LyP is classifed as a lymphoma, the skin lesions always go away by themselves, usually over a four to eight week period, and, therefore, do not behave like a malignancy.
The characteristic features of primary cutaneous ALCL include the appearance of solitary or multiple raised red skin lesions, nodules or tumors, which do not go away, have a tendency to ulcerate and may itch. The lesions can appear on any part of the body, often grow very slowly and may be present for a long time before being diagnosed.
Patients with systemic ALCL are divided into two groups, depending on the expression of a protein called anaplastic lymphoma kinase (ALK). While both lymphomas are treated as aggressive lymphomas, the prognosis for ALCL depends on whether a patient is ALK positive (expresses the protein) or ALK negative (does not express the protein). ALK positive disease responds well to chemotherapy, putting most patients in long-term remission or cure. Most people with ALK negative ALCL respond to chemotherapy, but many will relapse within five years. Because of this, they are sometimes treated more aggressively, often with stem cell transplant. The ALK positive subtype usually affects children and young adults. ALK-negative ALCL is more common in patients over the age of 55 years.