USMLE Guide: Pediatric Oncology

Introduction

Pediatric Oncology refers to the medical specialty that focuses on the diagnosis and treatment of cancer in children. This guide aims to provide an overview of important concepts and key points related to Pediatric Oncology, which may be useful for studying and preparing for the United States Medical Licensing Examination (USMLE).

1. Epidemiology and Risk Factors

• Childhood cancer is relatively rare compared to adult cancer, accounting for around 1% of all diagnosed cancers.
• The most common types of childhood cancer include leukemia, brain and central nervous system tumors, neuroblastoma, Wilms tumor, and lymphomas.
• Risk factors for pediatric cancer may include genetic predisposition, exposure to ionizing radiation, certain genetic disorders, and environmental factors.

2. Clinical Presentation and Diagnosis

• Children with cancer often present with non-specific symptoms such as prolonged fever, weight loss, fatigue, and unexplained pain.
• Diagnosis of pediatric cancer involves a combination of clinical evaluation, imaging studies (e.g., X-rays, ultrasound, MRI), laboratory tests (e.g., complete blood count, tumor markers), and tissue biopsy.
• It is vital to consider the possibility of cancer in any child with persistent or severe symptoms, as early diagnosis is crucial for better treatment outcomes.

3. Common Pediatric Cancers

3.1 Leukemia

• Leukemia is the most common childhood cancer, characterized by the abnormal proliferation of immature blood cells in the bone marrow.
• Acute lymphoblastic leukemia (ALL) is the most prevalent type of childhood leukemia, followed by acute myeloid leukemia (AML).
• Clinical features may include fatigue, pallor, easy bruising or bleeding, recurrent infections, and bone pain.
• Diagnosis is confirmed by bone marrow aspiration and biopsy, which reveal increased blast cells.
• Treatment typically involves chemotherapy, with the specific regimen based on risk stratification.

3.2 Brain Tumors

• Brain tumors are the second most common type of pediatric cancer.
• Medulloblastoma and gliomas are among the most frequently encountered brain tumors in children.
• Clinical presentation depends on the tumor's location and may include headaches, vomiting, visual disturbances, and neurological deficits.
• Imaging studies such as MRI are essential for diagnosis, followed by surgical biopsy for histopathological analysis.
• Treatment may involve a combination of surgery, radiation therapy, and chemotherapy, depending on the tumor type and stage.

3.3 Neuroblastoma

• Neuroblastoma is a tumor arising from neural crest cells, usually occurring in the adrenal glands or sympathetic ganglia.
• It commonly presents as an abdominal mass, along with symptoms such as weight loss, bone pain, and anemia.
• Diagnosis involves imaging studies like CT scan or MRI, as well as biopsy for histopathological confirmation.
• Treatment may include surgery, chemotherapy, radiation therapy, and immunotherapy, depending on the tumor stage and risk factors.

3.4 Wilms Tumor

• Wilms tumor, also known as nephroblastoma, is a malignant tumor of the kidney.
• It typically presents as a painless abdominal mass, along with symptoms like hematuria and hypertension.
• Imaging studies such as ultrasound and CT scan are used for diagnosis, followed by surgical resection and histopathological evaluation.
• Chemotherapy and radiation therapy may be required based on tumor staging and histology.

3.5 Lymphomas

• Lymphomas in children are predominantly Hodgkin lymphoma (HL) or non-Hodgkin lymphoma (NHL).
• HL commonly presents with painless lymphadenopathy, fatigue, and systemic symptoms such as night sweats and weight loss.
• NHL may present with lymphadenopathy, abdominal masses, bone pain, or symptoms related to extranodal involvement.
• Diagnosis involves lymph node biopsy and histopathological examination, followed by staging with imaging studies (e.g., CT scan).
• Treatment may include chemotherapy, radiation therapy, and stem cell transplantation, based on tumor type and stage.

4. Prognosis and Follow-up

• The prognosis of pediatric cancers has significantly improved over the years, with overall survival rates exceeding 80% in many types.
• Long-term follow-up care is essential for survivors, as they may experience late effects of treatment, including secondary malignancies, cardiac complications, and cognitive impairments.
• Regular surveillance, including imaging studies and laboratory tests, is crucial to detect and manage any potential late effects or recurrence.

This USMLE guide provides a concise overview of Pediatric Oncology, covering key aspects related to epidemiology, clinical presentation, diagnosis, and treatment of common pediatric cancers. It serves as a foundation for further studying and understanding the field, aiding medical students in their USMLE preparation.