Prolonged tamoxifen exposure selects a breast cancer cell clone that is stable in vitro and in vivo

The effects of long-term tamoxifen exposure on cell growth and cell cycle kinetics were compared between oestrogen receptor (ER)-positive (MCF-7) and ER-negative (MDA-MB-231) cell lines. In the MCF-7 cell line, prolonged tamoxifen exposure (0.5 mumol/l for > 100 days) blocked cells in G0-G1 of the cell cycle, and slowed the doubling time of cells from 30 to 59 h. These effects corresponded to an increase in the cellular accumulation of tamoxifen over time [mean area under concentration curve (AUC) = 77.92 mumoles/10(6)/cells/day]. In contrast, in the MDA-MB-231 cell line, long-term tamoxifen exposure had no obvious effect on the doubling time, and reduced cellular tamoxifen accumulation (mean AUC = 50.50 mumoles/10(6)/cells/day) compared to the MCF-7 cells. Flow cytometric analysis of MDA-MB-231 cells demonstrated that a new tetraploid clone emerged following 56 days of tamoxifen exposure. Inoculation of the MDA-MB-231 tetraploid clone and MDA-MB-231 wildtype cells into the opposite flanks of athymic nude mice resulted in the rapid growth of tetraploid tumours. The tetraploid tumours maintained their ploidy following tamoxifen treatment for nine consecutive serial transplantations. Histological examination of the fifth transplant generation xenografts revealed that the tetraploid tumour had a 25-30 times greater mass, area of haemorrhage and necrosis, a slightly higher mitotic index and was more anaplastic than the control neoplasm. The control wildtype MDA-MB-231 tumours maintained a stable ploidy following tamoxifen treatment until the eighth and ninth transplantation, when a tetraploid population appeared, suggesting that tamoxifen treatment may select for this clone in vivo. These studies suggest that prolonged tamoxifen exposure may select for new, stable, fast growing cell clones in vitro as well as in vivo.     

Quality of data regarding diagnoses of spinal disorders in administrative databases. A multicenter study

The purpose of the present study was to evaluate the accuracy of data regarding diagnoses of spinal disorders in administrative databases at eight different institutions. The records of 189 patients who had been managed for a disorder of the lumbar spine were independently reviewed by a physician who assigned the appropriate diagnostic codes according to the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM). The age range of the 189 patients was seventeen to eighty-four years. The six major diagnostic categories studied were herniation of a lumbar disc, a previous operation on the lumbar spine, spinal stenosis, cauda equina syndrome, acquired spondylolisthesis, and congenital spondylolisthesis. The diagnostic codes assigned by the physician were compared with the codes that had been assigned during the ordinary course of events by personnel in the medical records department of each of the eight hospitals. The accuracy of coding was also compared among the eight hospitals, and it was found to vary depending on the diagnosis. Although there were both false-negative and false-positive codes at each institution, most errors were related to the low sensitivity of coding for previous spinal operations: only seventeen (28 per cent) of sixty-one such diagnoses were coded correctly. Other errors in coding were less frequent, but their implications for conclusions drawn from the information in administrative databases depend on the frequency of a diagnosis and its importance in an analysis. This study demonstrated that the accuracy of a diagnosis of a spinal disorder recorded in an administrative database varies according to the specific condition being evaluated. It is necessary to document the relative accuracy of specific ICD-9-CM diagnostic codes in order to improve the ability to validate the conclusions derived from investigations based on administrative databases.     

Metaplastic carcinoma of the breast: mammographic appearance with pathologic correlation

OBJECTIVE: The objective of this study was to describe the mammographic appearance with pathologic correlation of metaplastic carcinoma of the breast. CONCLUSION: Metaplastic carcinomas of the breast are masses with mammographic characteristics of low suspicion because of their histologic appearance. Metaplastic carcinoma should be included in the differential assessment of predominately circumscribed, noncalcified masses revealed on mammography. One salient feature that may distinguish metaplastic carcinomas is the occurrence of a circumscribed portion with a spiculated portion, which is seen in carcinomas that have a significant mixture of metaplastic and invasive carcinoma growth patterns.