Ans a (Adrenal) Ref nelson 18th ed p 2137Neuroblastoma (NB) is an embryonal cancer of the peripheral sympathetic nervous system with heterogeneous clinical presentation and course. NB is the third most common pediatric cancer, NB is the most commonly diagnosed neoplasm in infants. Most cases of NB arise in the abdomen, either in the adrenal gland or in retroperitoneal sympathetic gan-glia.PATHOLOGY.NB includes a spectrum of tumors with variable degrees of neural differ-entiation, ranging from undifferenti- ated small round cells (neuroblastoma) to tumors containing mature ganglion cells (ganglioneuroblastoma or gan-glioneuroma).The tumors may resemble other small round cell tumors, such as rhabdomyosarcoma, Ewing sarcoma, and non-Hodgkin lymphoma. The prognosis varies with the histologic definition of tissue pattern (Shimada classification). Prognostic factors include the amount of stroma, degree of tumor cell differentiation, presence of enlarged and prominent nucleoli, and the mitosis-karyorrhexis index.Genetic characteristics of NB tumor tissue that are of prognostic importance and currently are used along with clinical factors to determine treatment include amplification of the MYCN (N-myc) proto-oncogene and hyperdiploidy of tumor cell DN A content. Amplification of MYCN has prognostic importance independent of stage and age and is strongly associated with advanced tumor stage and poor outcome. Hyperdiploidy confers better prognosis if the child is < 1 yr of age at diagnosis.NB may develop at any site of sympathetic nervous system tis-sue. The signs and symptoms of NB reflect the tumor site and extent of disease. Most cases of NB arise in the abdomen, either in the adrenal gland or in retroperitoneal sympathetic ganglia. Usually a firm, nodular mass that is palpable in the flank or midline is causing abdominal discomfort. On plain radiography or CT the mass often contains calcification and hemorrhage. Wilms tumor, another common flank mass in a young child, usually does not calcify.NB originates from cervical, thoracic, or pelvic ganglia in 30% of cases. Metastatic disease can be associated with myriad signs and symp-toms, including fever, irritability, failure to thrive, bone pain, bluish subcutaneous nodules, orbital proptosis, and periorbital ecchymoses. The most common sites of metastasis are the long bones and skull, bone marrow, liver, lymph nodes, and skin. Lung metastases are rare, occurring in <3% of cases. Prenatal diagnosis of NB sometimes is possible on maternal ultrasound scans.