Mesothelial cells are described in situ at the surface of the pleura. Their functions are discussed, in relation with the inflammatory response to different agents (infectious agents, mineral fibres...) and with the carcinogenic transformation, particularly in relation to asbestos exposure. The mechanisms of fibrogenesis, either symphysis or pleural plaques, are not clearly understood. The numerous studies now in progress on the different steps and mechanisms of mesothelial transformation and mesothelioma genesis are summarized focusing on the most recent cytogenetic and molecular biology findings.

The etiology of breast cancer is thought to involve a complex interplay of various factors, among them: genetic alterations. Multiple studies have been made to identify and characterize mutations that frequently occur during tumorigenesis. In human breast cancer, some of these alterations involve implication of proto-oncogenes (c-myc, c-erbB-2 and int-2) that have been shown to contribute to tumorigenesis by using the transgenic mouse model. Loss of heterozygoty represents the other important type of abnormalities that has been frequently observed in breast tumor DNAs; these specific genic deletions could inactivate or remove suppressor genes. In some studies, specific alterations have been associated with some clinical parameters, but have led to numerous controversies. Larger studies would be necessary to confirm some alterations as useful prognostic factors of the post-surgical course of the disease.

Chronic myeloid leukaemia (CML) is an excellent model for the study of molecular rearrangements caused by a cytogenetic anomaly associated with a disease. The formation of a Philadelphia chromosome by translocation between chromosomes 9 and 22 provokes the breaking and migration of a cellular oncogen (ABL), located in the 9q34 region, towards chromosome 22 and the 22q11 region where the PHL gene is situated. This gene is broken in the bcr area the rearrangements of which are specific to CML. The ABL and PHL genes fragments fuse together, creating a new hybrid gene which is transcribed into an 8.5 kilobase messenger RNA specific to CML. This RNA is translated into a 210 kilodalton protein whose abnormally high tyrosine kinase activity seems to contribute to the development of the disease. Genetic engineering techniques improve our understanding of CML molecular mechanisms and can be very useful to clinicians as they permit the diagnosis of CML in some cases devoid of chromosomal markers, and the detection of a possible relapse in marrow-grafted patients with a much greater sensitivity (one in 100,000 cells) than that of cytogenetics.

Two patients affected with Gardner's syndrome and desmoid tumour are presented: a 35-year-old man without polyposis coli who developed a clavicular posttraumatic desmoid tumour, and a 52-year-old woman with polyposis coli who died of an intra-abdominal desmoid tumour 3 years after prophylactic colectomy. A close follow-up of patients with Gardner's syndrome for early detection of desmoid tumours after surgery is recommended.

This review summarizes the discovery of oncogenes which are the activated versions of normal cellular protooncogenes which serve essential functions in the control of cell proliferation and differentiation. Their activation disrupts the normal control mechanism which rests on the subtle balance between their effects and those of anti-oncogenes or tumor suppressor genes. One may reasonably hope that defining a complete profile of alterations of both these types of essential genes in the tumor or in the clinically healthy individual will be invaluable to assess prognosis or genetic predisposition, respectively.

Eighteen cases of pediatric acute multi-phenotypic leukemia from 24 French centers investigated during 5 years are reported. The multi-phenotypic character of these cases was shown by the paradoxical presence of 2 or 3 associated membrane antigens which are normally lineage restricted. The following bi-phenotypic combinations were found: B/T lymphoid (n = 6), B/myeloid (n = 7) or T/myeloid (n = 2). Three cases of tri-phenotypic association were also observed [B/T/myeloid (n = 2), B/myeloid/megakaryoblastic (n = 1)]. Our findings suggest that combinations with a myeloid composant and the presence of cALLA (common acute lymphoid leukemia antigen) on less than 45% of cells seem to be related to a shorter survival.

A geneological study made it possible to establish a link between two medullary thyroid carcinoma families from Normandy totalling 9 sick subjects, and a probable link with a third family. The study contributed to the diagnosis of multiple endocrine neoplasia type IIa, whereas the condition had been diagnosed for 6 years as familial medullary thyroid carcinoma, without phaechromocytoma. Group in these two families together increased the number of subjects tested, thereby facilitating genetic link analysis and enabling the link with markers of the disease on chromosome 10 to be asserted. The genetic study can now be used to detect individuals at risk, and with regular laboratory tests the diagnosis will be made at the "precancerous" stage. A genealogical study going back to the family-founding couple will increase the population which will benefit from screening in this region north of Rouen.

From a retrospective study of 3,500 platelet kinetic studies, we isolated 51 cases with chronic thrombocytopenia, excessive platelet volume without Döhle bodies and no functional platelet anomalies, normal megakaryocyte count and normal autologous and homologous platelet life-span. These cases were either discovered during the first year of life (i.e. constitutional) or proved as familial (with autosomal dominant transmission). Previous therapies (corticosteroids, immune globulins, androgens, immuno-suppressive agents, splenectomy) were unefficient in all cases as in their relatives.

The authors describe a case of microcephalic dwarfism observed in a newborn until 10 months of age and discuss the diagnostic challenge. They show that the Taybi-Linder syndrome and the primordial dwarfism type I and type III of Majewski are an identical recessive autosomal entity. The radiological evolution explains the initial separation of type I and type III. Because of the skeletal lesions, lacking in the Seckel syndrome, the name of sublethal microcephalic chondrodysplasia is proposed for this disease.