The spectrum of breast lesions in children and adolescents varies markedly from that for adults, with the former lesions being overwhelmingly benign. A breast mass in a young boy or girl may arise from normal and abnormal breast development. Other causes of masses include infection, trauma, and cyst formation. After onset of puberty, most cases of breast enlargement arise from benign fibroadenoma in girls and gynecomastia in boys. These conditions have specific imaging appearances, although juvenile (often giant) fibroadenoma cannot be distinguished from phyllodes tumor, which can be benign or malignant. In children, both conditions usually appear as well-circumscribed, hypoechoic masses at sonography and show diffuse enhancement except for nonenhancing septations at magnetic resonance imaging. A diagnosis of juvenile papillomatosis (a benign lesion) portends later development of breast cancer, and patients with this condition should be closely monitored. Malignant lesions of the breast in children are rare. The most common malignant lesions are metastases and are usually associated with widespread disease. The most common primary breast malignancy is malignant phyllodes tumor. Primary breast carcinoma is exceedingly rare in the pediatric age group, but its imaging appearance in children is the same as seen in adults and is different from that of almost all benign lesions. In girls, diagnostic interventions may injure the developing breast and cause subsequent disfigurement. Given this risk and the low prevalence of malignant disease in this population, a prudent course should be followed in the diagnosis of breast lesions. Imaging findings are very helpful for selecting patients for further diagnostic procedures. Although malignancy is rare, lesions with suspicious imaging findings or progressive growth should be subjected to cytologic or histologic examination.

Malignant primary hepatic tumors in children include lesions unique to the pediatric age group and others that are more common in adults. Important considerations when evaluating a child with a liver tumor are the age of the patient, laboratory findings, and specific imaging features. The most common primary malignant hepatic tumor in the pediatric population, hepatoblastoma occurs almost exclusively in patients younger than 5 years with no history of liver disease. Hepatoblastoma is associated with elevated serum α-fetoprotein (AFP) level and appears predominantly solid. Hepatocellular carcinoma (HCC) is the most common malignant liver tumor in older children, often with a history of liver disease. HCC is associated with elevated serum AFP level and also appears as a solid mass. Fibrolamellar carcinoma occurs in adolescents without elevated AFP level and contains a T2-hypointense fibrous scar that usually does not enhance. Undifferentiated (embryonal) sarcoma occurs in young children, contains cystic and mucoid components, and mimics a cyst at magnetic resonance imaging and computed tomography but appears solid at ultrasonography. Epithelioid hemangioendothelioma is a multifocal vascular tumor in older children with a distinctive imaging appearance of confluent peripheral nodules with adjacent capsular retraction. Angiosarcoma rarely occurs in young children and frequently shows evidence of hemorrhage. Embryonal rhabdomyosarcoma of the biliary tree is unique to children, usually under 5 years of age, and frequently demonstrates an intraductal growth pattern. Knowledge of the pathologic features of these tumors and their imaging appearances can help radiologists offer an appropriate differential diagnosis and management plan.

Pancreatic neoplasms are rare in children and have a different histologic spectrum and prognosis than those in adults. In general, these tumors are well demarcated with expansile rather than infiltrating growth patterns. They may be quite large at diagnosis, and central cystic necrosis is common. They infrequently cause biliary duct obstruction. The imaging appearance of each neoplasm reflects its pathologic features. Pancreatoblastoma is the most common pancreatic neoplasm in young children. At imaging, pancreatoblastomas are heterogeneous and often multilocular with hyperechoic and enhancing septa. Solid-pseudopapillary tumor occurs in adolescent girls. It is heterogeneous in internal architecture, with a mixture of solid and cystic hemorrhagic and necrotic elements. This tumor is distinguished by its fibrous capsule and hemorrhagic nature, which are best shown at magnetic resonance imaging as a dark rim on T1- or T2-weighted images and hyper-intense foci on T1-weighted images, respectively. Islet cell tumors in children are insulinomas or gastrinomas. These tumors manifest early due to hormonal syndromes and are distinguished by their small size, homogeneous appearance, and intense enhancement with intravenous contrast material. All pancreatic neoplasms in children are capable of producing metastases, usually to the liver and lymph nodes; however, on the whole, these tumors have a better clinical outcome than most pancreatic tumors in adults. Knowledge of the differential diagnosis of pancreatic masses in children and their relatively good prognosis may promote correct preoperative diagnosis and appropriate treatment.

In a phase 2a study, the all-oral, interferon-free, and ribavirin-free regimen of daclatasvir, asunaprevir, and BMS-791325 was well tolerated and achieved high rates of SVR12 in patients with HCV genotype 1 infection. Further studies of this regimen are warranted. ClinicalTrials.gov, number NCT01455090.

The antiviral activity, resistance profile, pharmacokinetics (PK), safety, and tolerability of BMS‐790052, a nonstructural protein 5A (NS5A) replication complex inhibitor, were evaluated in a double‐blind, placebo‐controlled, sequential panel, multiple ascending dose study. Thirty patients with chronic hepatitis C virus (HCV) genotype 1 infection were randomized to receive a 14‐day course of BMS‐790052 (1, 10, 30, 60, or 100 mg once daily or 30 mg twice daily) or placebo in a ratio of 4:1. The mean maximum decline from baseline in HCV RNA ranged from 2.8 to 4.1 log10 IU/mL; the placebo group showed no evidence of antiviral activity. Most patients experienced viral rebound on or before day 7 of treatment with BMS‐790052 monotherapy; viral rebound was associated with viral variants that had been previously implicated in resistance development in the in vitro replicon system. The PK profile was supportive of once‐daily dosing with median peak plasma concentrations at 1‐2 hours postdose and mean terminal half‐life of 12‐15 hours. Steady state was achieved following 3‐4 days of daily dosing. BMS‐790052 was well tolerated in all dose groups, with adverse events occurring with a similar frequency in BMS‐790052‐ and placebo‐treated groups. There were no clinically relevant changes in vital signs, laboratory, or electrocardiogram parameters. Conclusion: BMS‐7590052 is the first NS5A replication complex inhibitor with multiple dose proof‐of‐concept in clinic. At doses of 1‐100 mg daily, BMS‐790052 was well tolerated, had a PK profile supportive of once‐daily dosing, and produced a rapid and substantial decrease in HCV‐RNA levels in patients chronically infected with HCV genotype 1. (HEPATOLOGY 2011