Imaging Pathology: Leukemia
Leukemia is a form of cancer that affects the hematopoietic system. The hematopoietic system consists of blood forming organs such as the spleen, bone marrow, lymph nodes, and the thymus. Leukemia is characterized by an increase of white blood cells in the bone marrow or circulation. Leukemia is an umbrella term and there are many different forms of leukemia that exist. The type of leukemia is classified by what predominant white blood cells are involved and course of the disease (Britannica, 2018). Leukemias may be acute or chronic, and either myelogenic or lymphocytic. It is pertinent to mention the four types of leukemia which include: acute lymphocytic leukemia (ALL), acute myelogenous leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myelogenous leukemia (CML).
Acute leukemias develop quickly and involve immature cells. Immature leukemia cells tend to divide rapidly in the bone marrow. The main concern involving this, is that if left untreated, rapid cell death will occur. In chronic leukemias, more mature cells are involved. These cells are transported to tissues after they develop (Mayo Clinic, 2017). These cells do not function normally, and they can replicate or increase slowly in numbers. The main concern with some chronic leukemias are that the patient may be asymptomatic and go undiagnosed or untreated for years.
The form of leukemia depends on the rate of progression and where the cancer develops. Therefore, they all have different risk factors to take into account. Typically the risk for developing leukemia increases with age in all types except Acute Lymphocytic leukemia (ALL), which is most common in children. Gender also comes into play for three out of the four types of leukemia; where men are more likely to develop CML, CLL, and AML than women (reference). Although smoking may not be a direct cause of leukemia in patients, smoking can increase the risk of development of the disease. Exposure to high levels of radiation such as in atomic bomb explosions, and nuclear reactor accidents also increase the likelihood of developing all four types of leukemia.
In patients with leukemia a chest x-ray is most often ordered to check for signs of disease which include infections or tumors. Most commonly enlargement of mediastinal and hilar lymph nodes will be visualized in the chest cavity (Shahnazi, 2012). A skeletal survey may also be performed to check for signs of destruction of the cortex of long bones, and flat bones of the skull. A skeletal survey helps visualize the axial skeleton and large cortical bones (reference). Ultrasound can be used to detect cysts, tumors, and organ damage from leukemia. Another common image modality used is computed tomography (CT). A CT scan of the chest or abdomen can help detect enlarged lymph nodes or cancers in the liver, pancreas, lungs, bones, and spleen. This non-invasive test is also used to monitor a tumor’s response to therapy, or detect a return of cancer after treatment (Shahnazi, 2012). Magnetic resonance imaging (MRI) can also be used much like CT to view internal organs and enlargements of lymph nodes, MRI can also detect changes in bone earlier than conventional radiographic studies (Eisenberg, 2016).
Radiographic appearance varies on the stage of the disease and the age of the patient. In children leukemia which is most often acute lymphocytic leukemia, radiolucent bands at the metaphyseal ends of long bones are visible. These bands are most commonly seen at the knees, ankles, and wrists (Eisenberg, 2016). In acute forms of leukemia, as proliferation of neoplastic cells increases, destruction of the bone may cause patchy lytic lesions. These lesions will cause a moth-like appearance, and causes osteosclerosis (Pathology 2016). Due to bone destruction fractures are common on radiographs. On a chest radiograph in patients with acute forms of leukemia, it is common to see an enlargement of both hilar and mediastinal lymph node. Chronic leukemia is slow growing. Splenomegaly is a constant finding in these patients. The enlargement of the spleen can be demonstrated in radiograph of the abdomen (KUB). This will demonstrate a downward displacement of the splenic flexure of the colon, and elevation of the left diaphragm. (Eisenberg, 2016).
Prognosis for leukemia depends on several factors, the age of the patient, the patients’ health, and the type of leukemia the patient has. Many people do not realize that they have leukemia until the disease has progressed because early stages develop slowly. Patients with early symptoms often think they have a cold or the flu, symptoms include night sweats, fever, and fatigue. Other symptoms include unexpected weight loss, fever or chills, petechiae, frequent infections, and enlarged lymph nodes, liver, or spleen (Mayo Clinic, 2017). There are approximately 62,130 new cases of leukemia reported in 2017 with a five year survival of 60.6% in 2007-2013 (National Cancer Institution).
Clinical indications for treatment would include diagnostic exams that points towards the patient having leukemia. Diagnostic exams that may be performed are a physical exam, blood test, or bone marrow test in which a doctor will take a sample of bone marrow from your hip bone. There are many different treatment options for leukemia. Treatment depends on the type, and if it has spread to the central nervous system. Treatment options include multi-drug chemotherapy, radiotherapy, bone marrow transplant, or stem cell transplant. Chemotherapy is the most common treatment for leukemia (Mayo Clinic, 2017). Chemotherapy may be single drug, or a combination of drugs used to target the disease. Chemotherapy is administered by a pill or is injected into the vein. Interferon therapy is also used to help the body produce antiviral proteins that help reduce the production of leukemia cells (Eisenberg, 2016).
Britannica, T. E. (2018, March 08). Leukemia. Retrieved from https://www.britannica.com/science/leukemia
Eisenberg, R. L., & Johnson, N. M. (2016). Comprehensive radiographic pathology (Sixth ed.). St. Louis, MO: Elsevier
National Cancer Institute (2018). Leukemia. Retrieved from https://www.cancer.gov/types/leukemia
Leukemia and Lymphoma Society. (2015, February 26). Imaging Tests. Retrieved from https://www.lls.org/managing-your-cancer/lab-and-imaging-tests/imaging-tests
Mayo Clinic Staff. (2017, December 22). Leukemia. Retrieved from https://www.mayoclinic.org/diseases-conditions/leukemia/symptoms-causes/syc-20374373
Shahnazi, M., Khatami, A., Shamsian, B., Haerizadeh, B., & Mehrafarin, M. (2012, March). Bony Lesions in Pediatric Acute Leukemia: Pictorial Essay. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3522339/