Gastric inflammatory pseudotumors have radiographic, surgical, and histologic features that simulate malignant tumors. To avoid inappropriately aggressive therapy, it is important to know when to consider this diagnostic possibility preoperatively. The cases of two children with gastric inflammatory pseudotumors are presented to emphasize three findings in this entity: (a) An inflammatory pseudotumor should be considered if a gastric mass encompasses an ulcer or a confined gastric perforation. (b) Other unusual inflammatory responses associated with a gastric mass, such as sclerosing cholangitis and retroperitoneal fibrosis, should suggest the diagnosis. (c) Inflammatory pseudotumor is the most likely cause of a gastric mass in a child with Castleman syndrome.

Cystic lesions of the lung may be developmental or acquired. The authors describe two cases of developmental cystic lung lesions (mesenchymal cystic hamartomas) that harbored unsuspected mesenchymal sarcomas. Although in children the natural history of this lesion is incompletely characterized, there is a definite risk for malignant change. The initial appearance of these cystic lung lesions on the chest radiograph is generally benign. It is important to establish the nature of cystic lung lesions (developmental vs acquired) and recognize the potential risk of malignant change in mesenchymal cystic hamartoma. Cystic lung lesions of uncertain type should be resected.

Nephroblastomatosis is an abnormality of nephrogenesis characterized by incomplete maturation of primitive nephrogenic cells. The resultant individual lesions have variable histologic findings and distribution in the kidney. There is wide acceptance of nephroblastomatosis as a precursor lesion to Wilms tumor. Consequently, the role of imaging in assessing patients for neoplastic transformation of nephroblastomatosis should be emphasized. Computed tomography (CT) has been shown to be superior to ultrasound (US) in this regard. Nonetheless, the low cost and lack of radiation of US make it attractive for serial screening studies. Although magnetic resonance imaging shows promise in assessment of the kidney for nephrogenic rests, experience is limited in its use in evaluating patients for nephroblastomatosis. The authors present protocols for assessing patients identified as being at either high or low risk for the development of Wilms tumor due to nephroblastomatosis. These protocols take into account the advantages of CT and US. Scanning intervals are determined from epidemiologic data on the occurrence of Wilms tumor; the most intense screening occurs during the younger ages of life, when the likelihood of Wilms tumor development is highest.

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