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Query: UMLS:C0043346 (xeroderma pigmentosum)
 2,924 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two aspects can be distinguished in multistage carcinogenesis: etiological one (every stage is induced by a specific for this stage agent) and morphobiological aspect (every stage is characterized by specific morphological, genetic and other properties). The schema of the multistage carcinogenesis is presented in which morphological stages (diffuse and focal hyperplasia, benign tumours, dysplasia, carcinoma in situ, various phases of malignant tumour progression) are placed against genetic alterations. L. Foulds concept of tumour progression is discussed with special emphasis on precancerous stages, possibilities of cancer development de novo, and independent progression of different tumour characters. The following types of carcinogenesis are listed on the basis of interrelationship between etiological and genetic factors: 1) carcinogenesis induced by genotoxic agents; a) one agent is acting at high dose and for a long time thus ensuring the activation of protooncogenes and all stages of tumour progression (initiation, promotion, various phases of malignant tumour); b) those acting during a very short time, however sufficient for developing the genetic program working automatically without further exposure to known carcinogens (irradiation in case of the atomic bomb explosion or effect of short-living alkylating agents): in this case there is no stage of promotion; 2) carcinogenesis by non-genotoxic carcinogens (their mode of action is still unclear, the only human example is carcinogenesis by hormones); 3) development of tumours in frane of the two (or three) stage carcinogenesis when every stage is provoked by its own etiological factor, no human examples are known as yet; 4) development of tumours due to the genetic mechanism making the organism highly susceptible to the minimal doses of carcinogens as is the case with skin cancer by ultraviolet light in patients with xeroderma pigmentosum, the genetic damage in itself has nothing to do with tumour formation; 5) genetic damage leading to the development of tumour without visible participation of any known carcinogens or promoters (gene Rb in retinoblastoma, gene Wt in Wilms tumour, etc.).
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PMID:[Progression of tumors: etiologic, morphologic and molecular-biological aspects]. 147 43

Xeroderma pigmentosum is a rare inherited dermatosis that provides insight into the basic mechanism of carcinogenesis. It is a model disorder linking defective DNA repair with clinical abnormalities and neoplasia. UV light-induced damage to the skin begins early and results in multiple benign and malignant skin tumors, especially in sun-exposed areas of the head and neck. Oral cancers, primarily squamous cell carcinomas of the anterior third of the tongue, occur with greatly increased frequency. A patient with multiple facial neoplasia and oral manifestations of xeroderma pigmentosum is presented. The role of the dentist in surveillance of oral and perioral structures is emphasized. The dentist is advised against the use of UV light-curing units in these patients because UV-induced epithelial damage may cause dysplasia when DNA repair mechanisms are dysfunctional.
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PMID:Xeroderma pigmentosum: review and report of a case. 201 52

A patient with xeroderma pigmentosum group C was extensively examined for mutations in the p53 gene in normal skin exposed to varying degrees of sunlight and in excisional biopsies of basal cell cancer, squamous cell cancer, and squamous cell dysplasia. Seventy-three samples were analyzed by microdissection of small cell clusters, followed by PCR and direct DNA sequencing. In skin taken from areas that most likely had never been exposed to the sun, no mutations were found. However, in skin exposed to the sun, we observed a multitude of mutations in the p53 gene. UV light-induced mutations were found in all types of lesions, as well as in clusters of morphologically normal epidermal cells. Twenty-nine distinct mutations were found in exons 5-8, all missense or nonsense, of which 27 (93%) were UV-specific C --> T or CC --> TT transitions at dipyrimidine sites of the nontranscribed strand. Two types of normal skin areas containing p53 mutations were observed: areas that stain strongly with p53 antibody (p53 patches) and those that do not stain. Because no silent or intron mutations were found in these cell clusters, the alterations in the p53 gene of morphologically normal cells are likely to have resulted in a selective growth advantage. The poor correlation between mutations and morphological phenotypes demonstrates that p53 mutations alone do not determine the phenotypes observed.
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PMID:Clones of normal keratinocytes and a variety of simultaneously present epidermal neoplastic lesions contain a multitude of p53 gene mutations in a xeroderma pigmentosum patient. 962 88