Perfil clínico, epidemiológico y terapéutico del tumor de Wilms pediátrico en Costa Rica / Clinical, epidemiological and therapeutic profile of pediatric Wilms tumor in Costa Rica

Resumen Justificación: El tumor de Wilms es el tumor renal maligno más frecuente en pediatría. El manejo terapéutico sigue el principio oncológico de curar la enfermedad mediante cirugía, quimioterapia y radioterapia. Se busca minimizar la toxicidad de los tratamientos. El objetivo del estudio fue describir las características clínicas, epidemiológicas y terapéuticas, con estimaciones sobre la supervivencia de los pacientes con diagnóstico de tumor de Wilms, atendidos en el Servicio de Oncología del Hospital Nacional de Niños "Dr. Carlos Sáenz Herrera", de la Caja Costarricense de Seguro Social, atendidos durante el periodo de enero de 2009 a diciembre de 2016. Métodos: Es un estudio observacional, descriptivo retrospectivo, de una serie de casos de pacientes pediátricos con tumor de Wilms atendidos durante un periodo de 8 años. Se revisó el expediente clínico para disponer de forma retrospectiva de los datos de todos los casos, según las variables de interés. Se aplicó análisis descriptivo de variables cualitativas y cuantitativas, así como para diseñar las curvas de supervivencia de Kaplan-Meier; se complementó con análisis inferencial. Resultados: Durante el periodo se atendió un total de 42 pacientes con este diagnóstico, de los cuales un 59,5 % fueron mujeres. La mayor prevalencia se registró en niños de 2 años o menos (66,7 %). Un 95,2 % de los pacientes presentó resultado de histología favorable; todos los casos con histología desfavorable fueron en mujeres. La intervención quirúrgica más común fue la nefrectomía. Todos los pacientes recibieron quimioterapia y solo el 38,1 % recibió radioterapia. Atribuido a la radioterapia, se reportó vómitos como el principal efecto adverso agudo. La supervivencia global estimada a 3 años fue del 85,6 %, y a 5 años fue del 79,9 %; la supervivencia libre de enfermedad fue del 78,8 % a los 3 y 5 años. Conclusiones: En pacientes pediátricos, el tumor de Wilms es una morbilidad oncológica que alcanza una baja frecuencia; aparece en ambos sexos, aunque con histología más desfavorable en mujeres. Ante este diagnóstico, los pacientes reciben tratamiento con cirugía, quimioterapia y radioterapia; la intervención múltiple ha sido exitosa y la gran mayoría de los pacientes alcanzan una supervivencia prolongada y libre de progresión de enfermedad, a los 5 años, los cuales están más cercanos a lo observado en países de ingresos medios.

Abstract Background: Wilms tumor is the most frequent malignant renal tumor in pediatrics. Therapeutic management follows the oncological principle of curing the disease through surgery, chemotherapy, radiotherapy. It seeks to minimize the toxicity of treatments. The objective of the study was todescribe the clinical, epidemiological and, therapeutic characteristics of patients diagnosed with Wilms tumor, treated at the Oncology Unit of the National Children's Hospital "Dr. Carlos Sáenz Herrera" CajaCostarricense de Seguro Social, during the period from January 2009 to December 2016. Methods: It is a descriptive, observational, retrospective study of one series of cases. The population analyzed were 42 pediatric patients with Wilms tumor for seven years. Medical records were revised retrospectively to collect data about all cases. The statistical analysis used qualitative variables and quantitative variables to descriptive and inferential techniques, and for survival analysis, Kaplan- Meier survival curves were used. Results: During a study period, a total of 42 patients diagnosed with Wilms tumor were studied. 59.5% were women. The prevalence is higher in children 2 years old or younger (66.7%). 95.2% of the patients presented favorable histology; and when discriminated by sex, 100.0% of unfavorable histology were women. The most common surgery was nephrectomy. All patients received chemotherapy and 38.1% radiotherapy. The main acute side effect of radiotherapy was vomiting. The estimated overall survival was 85.6% at 3 years, and 79.9% at 5 years and the disease-free survival was the same as 78.8% at 3 and 5 years. Conclusions: Wilms tumor exhibited low frequency in pediatric patients, in both sexes however bad histology most affected women. The patient received a combination of therapy with surgery, chemotherapy and, radiotherapy; his interventions have success and pediatric patients have longer overall survival and free disease progression survival at 5 years, like results of other average income countries.

Challenges on participation in a cooperative group of childhood renal tumors in Brasil

SUMMARY OBJECTIVE Children with renal tumors included in clinical trials have significantly better outcomes. In Brasil, the enrollment of patients in clinical trials remains challenging. Here we aimed to describe participation accrual in the Brazilian Wilms Tumor Study Group (BWTSG) and to identify barriers to trial registration of children with renal tumors. METHODS We determined the numbers of renal tumor diagnoses in 105 hospital-based cancer registries from 2001-2009. We then compared these totals with the numbers of renal tumor cases registered in the BWTSG from the same hospitals during the same time period. We also invited members of the Brazilian Pediatric Oncology Society to complete a 5-point Likert-type scale questionnaire regarding their opinions of the importance of participation in cooperative group trials. RESULTS The accrual rate of patient participation per hospital varied from 25% to 76%, and was highest in the South region. The accrual rate of hospital participation also varied according to the region (20-31%) and was highest in the Southeast region. For the questionnaire regarding the importance of participation in cooperative groups, the responses showed an agreement of >75% on 10 of the 13 statements. CONCLUSION Our results demonstrated low accrual of participation in a cooperative group trial in Brasil. We identified variations in registration rates according to geographic region and hospital, which may help targeted efforts to increase registration rates. The survey responses demonstrated that colleagues understand the importance of trial participation.

RESUMO OBJETIVO Crianças com tumores renais incluídas em ensaios clínicos apresentam melhora significativa na sobrevida. No entanto, o envolvimento desses pacientes em ensaios clínicos continua sendo um desafio no Brasil. Nosso objetivo neste estudo é descrever a taxa de aderência e adesão no Grupo Cooperativo Brasileiro para tratamento de Tumor de Wilms (GCBTTW) e identificar barreiras na participação ao protocolo. MÉTODOS Identificamos o número de casos de tumores renais diagnosticados em 105 registros hospitalares de câncer no período de 2001 a 2009. O número total desses casos foi então comparado ao número de casos de tumores renais registrados no GCBTTW provenientes das mesmas unidades hospitalares e durante o mesmo período. Os membros da Sociedade Brasileira de Oncologia Pediátrica foram convidados para completar um questionário com escala do tipo likert com o objetivo de conhecer suas opiniões sobre a importância e as dificuldades na participação em ensaios clínicos de grupos cooperativos. RESULTADOS A aderência de pacientes por hospital variou de 25% a 76% e foi maior na região Sul. A adesão da participação do hospital também variou de acordo com a região (20-31%) e foi maior na região Sudeste. Com relação ao questionário referente à importância da participação em grupos cooperativos, as respostas mostraram concordância de mais de 75% em 10 das 13 afirmações. CONCLUSÃO Nossos resultados demonstraram uma baixa participação em grupos cooperativos no Brasil. Houve variações nas taxas de adesão e aderência de acordo com a região geográfica e unidade hospitalar, o que pode auxiliar em futuros esforços para a melhora dessas taxas. As respostas ao questionário demonstraram que os profissionais entendem a importância da participação em grupos cooperativos.

Le néphroblastome au CHU de Brazzaville

Le néphroblastome est le deuxième cancer de l'enfant à Brazzaville. Nous avons mené cette étude afin d'en dégager les principales caractéristiques et les difficultés de leur prise en charge à Brazzaville au Congo.Il s'était agi d'une étude descriptive transversale sur une période de six ans (2008-2013). Nous avions ainsi colligé les patients atteints de néphroblastome dont nous avons décrits les aspects épidémiologiques, cliniques et thérapeutiques. Durant la période d'étude, 52 enfants, âgés de 0 à 14 ans avaient été colligés, dont 14 pour néphroblastome. Nous avions constaté une prédominance féminine et l'âge moyen au diagnostic était de 50,6 mois. La masse abdominale était la principale circonstance de découverte. Un cas de néphroblastome bilatéral avait été retrouvé. La survie globale à 6 mois, était de d'environ 65 %

Compromiso renal de los pacientes con tumor de Wilms bilateral / Kidney involvement in patients with bilateral Wilms tumor

El tumor de Wilms (TW) es el tumor renal maligno más frecuente en la infancia. Entre el 5-7% de los pacientes se presentan con enfermedad TW bilateral, de forma sincrónica o metacrónica. El TW bilateral generalmente ocurre en pacientes pequeños y más frecuentemente en niñas. La cirugía es un componente crítico en el tratamiento para lograr una alta tasa de curación preservando la mayor cantidad de masa renal. La quimioterapia preoperatoria a menudo reduce significativamente el tamaño del tumor, facilitando la cirugía posterior. Los pacientes con TW bilateral deben ser tratados en centros con experiencia en esta patología. El manejo de estos pacientes es aún un desafío (AU)

Wilms tumor (WT) is the most common malignant kidney tumor in childhood. Between 5-7% of the patients present with synchronous or metachronous bilateral WT. Bilateral WT typically occurs in young patients and most frequently in girls. Surgery is a critical component of the treatment as it has a high rate of cure while preserving the largest kidney mass. Preoperative chemotherapy often significantly reduces the size of the tumor, facilitating subsequent surgery. Patients with bilateral WT should be managed at centers with experience treating this disease. The management of these patients is still a challenge (AU)

Comparative study of quality of life of adult survivors of childhood acute lymphocytic leukemia and Wilms’ tumor / Estudo comparativo da qualidade de vida de adultos sobreviventes de leucemia linfocítica aguda e tumor de Wilms na infância

Abstract Objective To analyze and compare the health-related quality of life of adult survivors of acute lymphocytic leukemia and Wilms’ tumor amongst themselves and in relation to healthy participants. Methods Ninety participants aged above 18 years were selected and divided into three groups, each comprising 30 individuals. The Control Group was composed of physically healthy subjects, with no cancer history; and there were two experimental groups: those diagnosed as acute lymphocytic leukemia, and those as Wilms’ Tumor. Quality of life was assessed over the telephone, using the Medical Outcomes Study 36-Item Short Form Health Survey. Results Male survivors presented with better results as compared to female survivors and controls in the Vitality domain, for acute lymphocytic leukemia (p=0.042) and Wilms’ tumor (p=0.013). For acute lymphocytic leukemia survivors, in Social aspects (p=0.031), Mental health (p=0.041), and Emotional aspects (p=0.040), the latter also for survivors of Wilms’ tumor (p=0.040). The best results related to the Functional capacity domain were recorded for the experimental group that had a late diagnosis of acute lymphocytic leukemia. There were significant differences between groups except for the Social and Emotional domains for self-perceived health, with positive responses that characterized their health as good, very good, and excellent. Conclusion Survivors of acute lymphocytic leukemia showed no evidence of relevant impairment of health-related quality of life. The Medical Outcomes Study 36-Item Short Form Health Survey (via telephone) can be a resource to access and evaluate survivors.

Resumo Objetivo Analisar e comparar a qualidade de vida relacionada à saúde de sobreviventes adultos de leucemia linfocítica aguda e tumor de Wilms entre si, e em relação a participantes sadios. Métodos Foram selecionados noventa participantes, acima de 18 anos, os quais foram divididos em três grupos, sendo cada um com 30 sujeitos: Grupo Controle, que contou com indivíduos fisicamente saudáveis, sem histórico oncológico; grupo experimental formado por pacientes que tiveram diagnóstico de leucemia linfocítica aguda; e grupo experimental formado por pacientes que tiveram diagnóstico de Tumor de Wilms. A avaliação da qualidade de vida foi realizada por telefone e utilizou o Medical Outcomes Study 36-Item Short Form Health Survey. Resultados Os sobreviventes do sexo masculino apresentaram melhores resultados em relação aos do sexo feminino e controles no Aspecto vitalidade, para leucemia linfocítica aguda (p=0,042) e tumor de Wilms (p=0,013). Para os sobreviventes de leucemia linfocítica aguda nos Aspectos sociais (p=0,031), Saúde mental (p=0,041) e Aspectos emocionais (p=0,040), neste último também para as sobreviventes de Tumor de Wilms (p=0,040). Os melhores resultados relacionados ao domínio Capacidade funcional foram registrados para o grupo experimental de pacientes que tiveram diagnóstico tardio de leucemia linfocítica aguda. Observaram-se diferenças significativas entre os grupos, exceto para os domínios Aspectos sociais e emocionais para a percepção da própria saúde, que teve respostas de cunho positivo, que qualificavam a própria saúde como boa, muito boa e excelente. Conclusão O grupo experimental de pacientes que tiveram diagnóstico de leucemia linfocítica aguda não apresentou evidências de comprometimento relevante da qualidade de vida relacionada à saúde. O Medical Outcomes Study 36-Item Short Form Health Survey (via telefone) pode ser um recurso de acesso e avaliação de sobreviventes.

Incidence of childhood cancer in Kingston and St Andrew, Jamaica, 1983-2002 / Incidencia de cáncer infantil en Kingston y Saint Andrew, Jamaica, 1983-2002

OBJECTIVES: There have been several modifications to the classification of childhood cancers since the first report (1968-1981) specific to the Jamaican paediatric population was published in 1988. This paper reports on paediatric cancer incidence in Kingston and St Andrew, Jamaica, for the 20-year period 1983-2002 based on these modifications. METHODS: All cases of cancer diagnosed in children (0-14 years), between 1983 and 2002 were extracted from the Jamaica Cancer Registry archives and classified using the International Classification of Childhood Cancer, third edition. Incidence figures were calculated as per the International Agency for Research on Cancer (IARC) reporting format for childhood cancer. RESULTS: There were 272 cases (133 males, 139 females) of childhood cancer identified in the 20-year period. The overall age standardized rate (ASR) was 69.4 per million; that for males was 67.8 per million, and for females, 70.9 per million. The three most common malignancies overall were leukaemia (21.3%), lymphoma (15.8%) and brain and spinal neoplasms (14.0%). In males, the highest ASRs were seen for leukaemia (14.8 per million), lymphoma (12.7 per million), and brain and spinal neoplasms (8.2 per million), and in females, leukaemia (14.4 per million), nephroblastoma (11.3 per million), and brain and spinal neoplasms (10.6 per million). CONCLUSIONS: The rankings of the most common childhood malignancies in Jamaica (leukaemia, brain and spinal neoplasms and lymphomas) have shown few changes since the last review. However, there are differences in frequency and gender distribution of nephroblastoma and brain and spinal neoplasms.

OBJETIVOS: Ha habido varias modificaciones a la clasificación de los cánceres infantiles desde que el primer informe (1968-1981) específico para la población pediátrica jamaicana fue publicado en 1988. Este artículo reporta la incidencia de cáncer pediátrico en Kingston y Saint Andrew, Jamaica, en el período de 20 años de1983-2002, basado en estas modificaciones. MÉTODOS: Todos los casos de cáncer diagnosticados en niños (0-14 años) entre 1983 y 2002 fueron extraídos de los archivos del Registro de Cáncer en Jamaica, y clasificados utilizando la tercera edición de la Clasificación Internacional del Cáncer Infantil. Las cifras de incidencia fueron calculas siguiendo el formato de reporte de cáncer infantil de la Agencia Internacional para la Investigación del Cáncer (IARC, siglas en inglés). RESULTADOS: Hubo 272 casos de cáncer infantil (133 varones y 139 hembras) identificados en el período de 20 años. La tasa general de incidencia estandarizada por edad (ASR. siglas en inglés) fue 69.4 por millón; para los varones fue 67.8 por millón, y para las hembras, 70.9 por millón. En general, los tres tumores malignos más comunes fueron la leucemia (21.3%), el linfoma (15.8%) y las neoplasias del cerebro y la médula espinal (14.0%). En los varones, las tasas de ASR más altas fueron las observadas en relación con la leucemia (14.8 por millón), los linfomas (12.7 por millón), y las neoplasias del cerebro y la médula (8.2 por millón); en las hembras, la leucemia (14.4 por millón), los nefroblastomas (11.3por millón), y las neoplasias de cerebro y médula (10.6por millón). CONCLUSIÓN: Las clasificaciones por nivel de incidencia de los tumores malignos infantiles más comúnes en Jamaica (la leucemia, las neoplasias del cerebro y la médula espinal, y los linfomas) han mostrado pocos cambios desde la última revisión. Sin embargo, existen diferencias en la frecuencia así como en la distribución por sexo con respecto a los nefroblastomas y las neoplasias del cerebro y la médula.

Update on Wilms' tumor in children

Although rare, Wilms' tumor is the most common primary renal malignancy in children and is associated with a number of congenital anomalies and documented syndromes. Appropriate laboratory, radiologic and pathologic investigations are necessary components of the evaluation of children with suspected Wilms' tumor. This provides accurate diagnosis and subsequent staging; information which is essential to generate a multidisciplinary treatment plan utilizing surgery, chemotherapy and radiotherapy. Patients treated for Wilms' tumor as children must continue to be monitored for possible long-term sequelae as adults including secondary malignancies as well as treatment-related toxicity

Childhood malignancies at BS Medical College: a ten year study.

A retrospective study of malignant diseases of childhood was carried out at B. S. Medical College, Bankura, W.B. to know the prevalence. It includes cases detected in this institution during 1990-1999 in the age group of 0-14 years. Cases were identified from previous records. Histopathology slides, stained by hematoxylin and eosin, were recovered and reviewed. Diagnosis were made by morphology. Hematological diagnosis were made by morphology and cyto-chemistry. In total 120 cases were detected. Acute leukemia (39.2%) was the commonest, followed by retinoblastoma (19.2%), lymphoma (10.8%), Wilm's tumor (10%) and rhabdomyosarcoma (9.1%). Brain tumors were not found due to non-availability of Neurosurgical Unit in this institution. Frequency of neuroblastoma was very low, only 2 out of a total of 120. In comparison to studies in Southern India and Western countries retinoblastoma and soft tissue sarcoma are more prevalent here, while there is a much lower prevalence of neuroblastoma.

Malignancies in Down syndrome.

Down Syndrome (DS) is associated with an increased incidence of malignancies, especially leukaemias. We came across 8 DS children presenting with malignancies and having trisomy 21 as the sole cytogenetic abnormality. Of these 8 DS cases, 4 presented with acute lymphocytic leukaemia, 2 with acute myeloid leukaemia and one case each with Hodgkin's disease and Wilms' tumour. There are contradictory reports regarding the distribution of myeloid versus lymphoid malignancies in DS children and their response to therapy. The exact mechanism by which patients with DS are predisposed to develop malignancies is unclear. However, presence of the extra chromosome no. 21 is presumed to disrupt the genetic balance which increases generalized susceptibility to genetic and environmental trauma. Furthermore, an increased methotrexate toxicity observed in these patients should also be taken into consideration in designing treatment for DS children with malignancies.

Aspectos epidemiológicos del tumor de Wilms, en niños atendidos en hospitales de la ciudad de México / Epidemiology of Wilms tumor in children attended in hospitals of Mexico City

Introducción. El tumor de Wilms (TW) es una neoplasia maligna del riñón de tipo embriomnario, que se presenta comúnmente en los primeros años de la vida. Se presentan algunas características epidemiológicas en menores de 15 años, atendidos en hospitales de la ciudad de México. Material y métodos. Encuesta hospitalaria de base poblacional acerca de niños con TW en hospitales que atienden niños con neoplasias. Se estudiaron los atendidos entre 1981 y 1991l, en cuanto a variables de tiempo, persona y lugar, con análisis de frecuencias simples; se calcularon las tasas de incidencia anual y la razón estandarizada de la morbilidad y se evaluó la tendencia durante el periodo de estudio. Resultados. Se rvisaron 270 casos de TW de los que sólo 55 residían en el D.F. al momento del diagnóstico; se obtuvo una tasa de 3.74 x 106 para el año de 1991. Fueron 33 del sexo femenino y 22 del masculino, con una razón masculino-femenino de 0.66; 84 por ciento de los casos fueron menores de cinco años. El grado de escolaridad de los padres fue superior al promedio nacional; llama la atención que 56 por ciento de los padres fueron electricistas y 62 por ciento de las madres maestras de escuela. No hubo aumento en la incidencia en ningún grupo de edad en el tiempo que duró el estudio. El 82 por ciento (45 casos) sobreviven al momento de este informe. Conclusiones. Las características epidemiológicas de esta enfermedad en los niños atendidos en los hospitales del D.F., son similares a las que se informan en la literatura. Se comenta la necesidad de estudios epidemiológicos.

Tumor de Wilms en el hospital Dr. Robert Reid Cabral, 1988-1991 / Wilms tumor at Hospital Dr. Robert Reid Cabral, 1988-1991

Se realizó un estudio retrospectivo en el Hospital Dr. Robert Reid Cabral, en el periodo comprendido entre el 11 de enero de 1988 y el 15 de enero de 1991, con el objetivo de determinar la prevalencia del Tumor de Wilms. Encontramos 23 casos con este diagnostico, los cuales fueron mas frecuentes en niños de 3 años con un 56.5 por ciento , coincidiendo con otras investigaciones de este tipo. Los organos mas afectados por metástasis fuera del Riñon fueron los pulmones y el higado. La masa tumoral y la hematuria fueron los sintomas y signos clinicos mas frecuentes al momento de la presentación de los casos. La tasa de sobrevivencia en este estudio fue de 78.3 por ciento en tres años

Tumor de Wilms bilateral / Bilateral Wilms tumor

Se analizan los resultados de un protocolo propuesto y utilizado desde febrero de 1986 para el tratamiento del tumor de Wilms bilateral y la enucleación del tumor (tumerectomía) como cirugía conservadora inicial. El objetivo fue realizar una cirugía oncológica adecuada y preservar el máximo de parénquima renal funcionante para asegurar un desarrollo normal del niño. La punción con aguja fina previo al tratamiento se efectuó en 5 pacientes y fue diagnóstica en el 100%Se trataron 7 pacientes con 13 unidades renales, se efectuaron 12 tumorectomías, una nefroctomía radical inicial y posteriormente dos más por recidiva local luego de la tumorectomía. La enucleación del tumor o tumorectomía resultó una intervención de fácil ejecución,excepto en dos casos que involucraba el sistema colector. No presentó complicaciones postoperatorias. De los 7 casos tratados con el protocolo propuesto, 6 niños están vivos libres de enfermedad con un seguimiento medio de 31 meses (rango 12-53 meses). Un paciente se encuentra actualmente cumpliendo su quimioterapia. El protocolo propuesto le asegura al paciente la preservación de más parénquima renal funcionante con el mismo riesgo e iguales posibilidades de curación

Clinical Studies of Abdominal Tumors in Infants and Chi1dren: Ten Year Review

We have clinically observed 39 patients with abdominal tumors who were admitted in Severance Hospital during the past 10 years from April 1960 to March 1970. Unfortunately follow-up study couldn't be made. The following results were obtained. 1) Of the total number observed, 25 patients were male and 14 patients female. 2) The majority of the patients, 34 (87%) were under 6 years of age and 20 (51%) were between 1 to 3 years of age. The youngest patient was a 3-month-old female with Wilms' tumor. 3) In our series, Wilms' tumor (15 cases, 38.5%) was the most common and neuroblastoma (8 cases) was next most common tumor in the abdominal cavity. In addition we found another 4 cases of neuroblastoma in other sites. We observed hepatoma (8cases), ovarian tumor (3cases), lymphosarcoma (2cases), mesenteric cyst (one case) and adenoma of the left adrenal gland (one case) in that order of frequency. 4) In 15patients with Wilms' tumor, hypertension was observed in 8 patients and hematuria in 4 patients. Compared with Wilms' tumor, no hematuria was noted in the cases with neuroblastoma and hypertension occurred in 3 of these. 5) On abdominal X-ray, calcification was present in 4 cases with neuroblastoma (50%) and was present in only one of 15 patients with Wilms' tumor. 6) Comparing the sites of metastasis between Wilms' tumor and neuroblastoma, 4 of 15 patients with Wilms' tumor had lung metastasis and 4 of 8 patients of neuroblastoma had bony metastasis. Liver metastasis was found at autopsy in one case of neuroblastoma. 7) Three cases of hepatoblastoma were under 2 years of age and three cases of hepatocarcinoma were over 12 years of age. 8) Three cases of ovarian tumor were benign cystic teratoma. Tortion of the ovarian pedicle occurred in one of 3 patients with severe low abdominal pain. All patients were discharged in good condition after salphingo-oophorectomy. 9) One case of lymphosarcoma of the ileum was associated with intussusception. 10) A one year o1d female with adenoma of the left adrenal gland had typical Cushing's syndrome.

Wilms Tumor of the Kidney Among Koreans: A Clinicopathologic Study of 12 Proved Cases

Twelve cases of Wilms tumor proved by histological examination are recorded and the literature is reviewed because of the paucity of the reports on this neoplasm occurring in Koreans. The average age incidence was 4.2 years; the youngest patient was 9 months of age and the oldest one was 23 years of age. Three fourths of the patients were children under three years of age. Seven were males and five were females. The incidence of Wilms tumor among all renal cancers was 57 per cent and this is much higher than that reported in the foreign literature. This high incidence may be attributed to a much higher incidence of this neoplasm among Korean infants and children. The most prominent clinical finding was abdominal swelling and a palpable mass, but fever, hypertension, irritability, hematuria and cough were other common symptoms. Hypertension was encountered in 89 per cent of the cases. The common laboratory findings were anemia, leukocytosis, increased erythrocyte sedimentation rate and proteinuria. Gross and microscopic findings are described. All specimens were much 1arger than the normal kidney. The largest specimen, kidney plus tumor, weighed 1,800 gm. The tumors were composed of well formed tubules. solid islands of dark staining undifferentiated cells presumably of mesoblastic origin and various elements of stromal cells. The proportion of each element varied markedly from case to case and also in different parts of the same tumor. Nests of squamous cells, some of them forming pearls, and cystic structures identical with epidermal cysts were observed in three of our 12 cases, but unequivocal striated muscle cells as well as bone or cartilage were found in none of our cases. Some nests of squamous cells observed in tubules suggested that they were derived from metaplasia of the lining epithelium.