RESUMEN
International differences in rates and types of cancer serve as clues to its etiology. To study such variations of childhood cancer, we compared the frequencies of malignancy in the 220 children, age 0-14 years, diagnosed at the Jinnah Postgraduate Medical Center [JPMC], Karachi, Pakistan, 1974 - 1978, to the 1, 938 pediatric cancers in the U.S. Third National Cancer Survey [TNCS], 1969-1971. Type: Rectinoblastoma [RB]. JPMC: Not Equal 36, 16%. TNCS: 3%. Type: Non-Hodgkin's Lymphoma. JPMC: Not Equal 27, 12%. TNCS: 6%. Type: Leukemia. JPMC: Not Equal 26, 12%. TNCS: 33%. Type: Hodgkin's Disease. JPMC: Not Equal 20, 9%. TNCS: 4%. Type: Brian. JPMC: Not Equal 19, 9%. TNCS: 20%. Type: Wilms' tumor. JPMC: Not Equal 18, 8%. TNCS: 6%. Type: Soft tissue sarcoma. JPMC: Not Equal 18, 8%. TNCS: 4%. Type: Bone. JPMC: Not Equal 18, 8%. TNCS: 5%. Type: Gonadel, germ cell. JPMC: Not Equal 8, 4%. TNCS: 4%. Type: Neuroblastoma [NB]. JPMC: Not Equal 8, 4%. TNCS: 6%. Type: Other. JPMC: Not Equal 22, 10%. TNCS: 9%. The relative frequencies of cancers at the JPMC are similar to those reported from India, yet quite different from the TNCS, especially for 2 tumors of neuroectodermal origin RB and NB. Although RB was commonly diagnosed, it was bilateral in only 3 cases [8% vs 20% in U.S]. Bilateral RB, an autosomal dominant, is thought to occur among all peoples at the same rate; thus there appears to be an excess of sporadic RB. NB rates, low also in Central Africa, may be affected by a transplancental anticarcinogen. Lymphoma rates have an opposite pattern, they are increased and more often of a therapy-resistant subtype than in highly developed countries [RB-Retinoblastoma - NB - Neuroblastoma]