Lymphoma is the most common blood cancer. The two main forms of lymphoma are Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL). Lymphoma occurs when cells of the immune system called lymphocytes, a type of white blood cell, grow and multiply uncontrollably. Cancerous lymphocytes can travel to many parts of the body, including the lymph nodes, spleen, bone marrow, blood, or other organs, and form a mass called a tumor. The body has two main types of lymphocytes that can develop into lymphomas: B lymphocytes (B cells) and T lymphocytes (T cells).
Anaplastic large cell lymphoma (ALCL) is a rare type of NHL, and one of the subtypes of T-cell lymphoma. ALCL comprises about one percent of all NHLs and approximately 16 percent of all T-cell lymphomas. Initial symptoms of ALCL can include fever, backache, painless swelling of lymph nodes, loss of appetite, and tiredness.
ALCL can initially appear either in the skin, in the lymph nodes, or in organs throughout the body. ALCL that appears in the skin is most often called primary cutaneous ALCL, and it typically has a less aggressive disease course than the systemic (throughout the body) types. The characteristic features of primary cutaneous ALCL include the appearance of solitary or multiple raised, red skin lesions that do not go away, have a tendency to ulcerate, and may itch. These ALCL lesions are tumors, and they can appear on any part of the body, often grow very slowly, and may be present for a long time before being diagnosed. Only about 10 percent of the time does primary cutaneous ALCL extend beyond the skin to lymph nodes or organs. If this occurs, it is usually treated like systemic ALCL.
Patients with systemic ALCL are divided into two groups, depending on whether or not their cells have an abnormal form of a protein on their surface called anaplastic lymphoma kinase (ALK). Although both systemic lymphomas are treated as aggressive (fast-growing) lymphomas, the disease course may be different in patients who have ALK-positive ALCL compared with those with ALK-negative ALCL. The ALK-positive form of ALCL responds well to standard chemotherapy treatments, putting most patients into long-term remission. In contrast, while most people with ALK-negative ALCL initially respond to treatment as well, the disease is more likely to relapse (disease returns after treatment) within five years in these people than in those with ALK-positive ALCL. Sometimes ALK- negative patients (and some ALK-positive patients with certain risk factors) are treated more aggressively, often with a stem cell transplant after remission. While ALK-positive ALCL usually affects children and young adults, ALK-negative ALCL is more common in patients over the age of 55 years. Primary cutaneous ALCL is always ALK-negative.
A diagnosis of ALCL requires taking a biopsy (small sample of tumor tissue or abnormal skin tissue) and looking at the cells under a microscope. Additional tests may be conducted to give physicians more information about the disease and how far it has spread in the body. These can include blood tests, a computed tomography (CT) scan, a positron emission tomography (PET) scan, a magnetic resonance imaging (MRI) scan, and a bone marrow biopsy.