Genetics and cytogenetics of pediatric cancers

The polymerase chain reaction (PCR) in the routine genetic characterization of retinoblastoma: a tool for the clinical laboratory

The Polymerase Chain Reaction (PCR) is a highly innovative technique which allows for the generation of large amounts of DNA starting from minute quantities obtained from the blood or tissue of a patient. With the increasing knowledge concerning the structure of the human genome and the potential to amplify specific segments of DNA by the PCR technique, the molecular genetic characterization of many ocular disorders has been greatly facilitated. This is particularly true of retinoblastoma (RB) where the causative gene, RB1, gene has been identified and characterized. Using PCR technique, specific sequences of the RB1 gene can be amplified and analyzed to precisely define the genetic mutation in an affected individual. In addition, this technique can also be applied in order to characterize the genetic defect within the tumor itself. In this report we illustrate the use of the PCR technique in the genetic characterization of the RB1 gene and its application to the study of RB. These techniques are applicable even in a small clinical laboratory and can be extended to a number of ophthalmic disorders.

Characterization of a cell line derived from rhabdoid tumor of kidney

Rhabdoid tumor of kidney (RTK) is a rare, highly malignant childhood neoplasm of uncertain histogenesis. Several recent studies have described considerable histochemical heterogeneity among cases of RTK, with confusing combinations of epithelial, mesenchymal, myogenous, and neuroepithelial markers in some tumors. The present study characterizes the histology, ultrastructure, histochemistry, cytogenetics, and oncogene expression in a cell line derived from RTK. The surgical specimen, nude mouse xenograft, and cell cultures demonstrated characteristic intermediate filament whorls by electron microscopy and expressed vimentin (diffusely) and cytokeratin (focally, in hyaline cytoplasmic inclusions) without detectable desmin, Thy-1, or epithelial membrane antigen. S-100 protein was absent in the surgical specimen and heterotransplant, and was seen very weakly and focally in the cell cultures. Light microscopic features of cultures were unchanged by several compounds (tissue plasminogen activator, nerve growth factor, cyclic adenosine monophosphate) which induce differentiation of some other pediatric neoplasms. The growth factor requirements of RTK cultures indicate a cell with mesenchymal features. Insulin-like growth factor-2 mRNA was detected in the RTK and in three Wilms' tumors also studied. Unlike most Wilms' tumors, RTK expresses the c-myc rather than the N-myc oncogene.

Simultaneous hepatoblastoma in identical male twins

Identical male twin infants who in 1987 presented with hepatoblastoma at the age of 7 months are reported. Twin B was admitted for investigation due to enlarged liver and spleen. He was found to have an inoperable hepatoblastoma of fetal type and was treated with chemotherapy and local irradiation. However, 7 months after the chemotherapy the tumor recurred. The asymptomatic twin A was examined because of the known familial cases, and he proved to have an identical tumor. He was successfully radically operated on and 2 years after the chemotherapy is still doing well with no evidence of tumor. As the mother and the maternal grandmother had polyps in the colon, quite probably the hepatoblastomas of the twins were associated with familial adenomatous polyposis.

Childhood brain tumor: presentation at younger age is associated with a family tumor history

In a registry-based sample of 361 children with a brain tumor, those whose grandparents and great-grandparents had a history of any kind of tumor were younger at the time of presentation than were those who lacked this family history (p = 0.1). In post hoc analyses, the age difference was most apparent among children with cerebral tumors, and when family history was limited to brain tumors and to great-grandparents. These findings are in keeping with the hypothesis that a familial tumor diathesis contributes to an early age at onset of a brain tumor in some children.

Balanced reciprocal translocation (X;20) limited to Wilms' tumor in a Wiedemann-Beckwith syndrome

A girl aged 4 years 3 months with sporadic unilateral Wilms' tumor associated with Wiedemann-Beckwith syndrome, but without aniridia, was found to have a t(X;20) in the tumor cells. Karyotypes of peripheral blood of the patient and her parents were normal. This translocation was confined to the tumor and not been previously reported either in nephroblastoma or any other neoplastic processes. Although there is no microscopic deletion on chromosome 11 and catalase activity was not decreased, we cannot rule out the possibility of a point mutation or a submicroscopic deletion.

Retinoblastoma. Analysis of 75 cases and proposal for a new model of oncogenesis and tumor growth kinetics

A series of 75 retinoblastoma patients were analyzed at the Institute of Ophthalmology, Siena, and a mathematical model for the 'nodule to cancer' transformation applied to it. The authors obtained data in disagreement with Knudson's 'two hit' hypothesis but fitting an alternative model of oncogenesis. This model is based on probabilistic arguments and a possible pattern of tumor growth and evolution is given in detail.

A contemporary view of neoplasms in children. The pathologist's perspective

The diagnosis of childhood malignancy is a complex endeavor that requires the cooperation of the clinician and pathologist. On occasion, potentially problematic situations arise when a biopsy cannot answer all of the questions or is nondiagnostic. Delays may occur before a final diagnosis is possible in an especially complicated case that requires several time-consuming studies. The pathologist should appreciate the pressure placed on the clinician to initiate treatment and, in turn, the clinician should realize that several steps are necessary before the pathologic examination can be completed.

A new translocation t(1;4;11) in congenital acute nonlymphocytic leukemia (acute myeloblastic leukemia)

A new translocation t(1;11;4)(1pter----1p32::11q23----11q13::4p16--- -4qter) was found in the peripheral blood of a patient with congenital acute myeloblastic leukemia (AML). It was concluded that this translocation may represent a new mutation, which caused the leukemia with very high leukocytosis, hepatosplenomegaly, leukemic infiltration of the majority of the organs, and a very poor prognosis.