[Extracellular desoxyribonucleic acid in small cell bronchial carcinomas].

In more than half of 30 small cell anaplastic lung carcinomas the authors have observed deposits of hematoxylinophilic material, mainly in the wall of small blood vessels. This finding has been interpreted as the result of dystrophic calcification. Histochemical evaluation, however, reveals the presence of deoxyribonucleic acid (DNA) and basic proteins (histones) in this material. Such extracellular DNA-deposits are not specific for small cell anaplastic lung carcinomas. They may be detected in other tumors, particularly retinoblastomas. Occurrence of extracellular DNA appears to be independent of size and spread of the tumor, cytostatic treatment and/or radiotherapy. High cellularity, high nuclear/cytoplasmic ratio and propensity to necrosis are common denominators for tumors displaying extracellular DNA. The cause of the phenomenon is unknown; the role of immunologic factors has been evaluated in the literature. The authors advance in alternative hypothesis involving tumor-induced inhibition of deoxyribonuclease activity.