The relationship of anthropometric measures to radiological features of the breast in premenopausal women.

We studied 273 premenopausal women recruited from mammography units who had different degrees of density of the breast parenchyma on mammography, in whom we measured height, weight and skinfold thicknesses. Mammograms were digitized to high spatial resolution by a scanning densitometer and images analysed to measure the area of dense tissue and the total area of the breast. Per cent density and the area of non-dense tissue were calculated from these measurements. We found that the mammographic measures had different associations with body size. Weight and the Quetelet index of obesity were strongly and positively associated with the area of non-dense tissue and with the total area of the breast, but less strongly and negatively correlated with the area of dense tissue. We also found a strong inverse relationship between the areas of radiologically dense and non-dense breast tissue. Statistical models containing anthropometric variables explained up to 8% of the variance in dense area, but explained up to 49% of the variance in non-dense area and 43% of variance in total area. These results suggest that aetiological studies in breast cancer that use mammographic density should consider dense and non-dense tissues separately. In addition to per cent density, methods should be examined that combine information from these two tissues.

Breast cancer risk and measured mammographic density.

It has been well established that there is a positive correlation between the dense appearance of breast stroma and parenchyma on a mammogram and the risk of breast cancer. Subjective assessment by radiologists indicated relative risks on the order of 4 to 6 for the group of women whose mammograms showed a density of over 75% or more of the projected area compared to those with an absence of density. In order to obtain a more quantitative, continuous and reproducible means of estimating breast density, which is sensitive to small changes, we have developed quantitative methods for the analysis of mammographic density, which can be applied to digitized mammograms. These techniques have been validated in a nested case-control study on 708 women aged 40-59 years (on entry) who participated in a national mammographic screening study. An interactive image segmentation method and two completely automated techniques based on image texture and grey scale histogram measures have been developed and evaluated. While our methods all show statistically significant risk factors for dense breasts, the interactive method currently provides the highest risk values (relative risk 4.0, 95% confidence interval (CI) = 2.12-7.56) compared to a measure based on the shape of the image histogram (relative risk 3.35, 95% CI = 1.57-7.12) or the fractal dimension of the mammogram (relative risk 2.54, 95% CI = 1.14-5.68). All methods were highly consistent between images of the left and right breast and between the two standard views (cranio-caudal and medio-lateral oblique) of each breast, so that studies can be done by sampling only one of the four views per examination. There is a large number of factors in addition to breast density which affect the appearance of the mammogram. In particular, the assessment of density is made difficult where the breast is not uniformly compressed, e.g. at the periphery. We have designed and are currently evaluating an image processing algorithm that effectively corrects for this problem and have considered methods for controlling some of the variables of image acquisition in prospective studies. Measurements of breast density may be helpful in assigning risk groups to women. Such measurements might guide the frequency of mammographic screening, aid the study of breast cancer aetiology, and be useful in monitoring possible risk-modifying interventions. Using our techniques, we have been able to show that reduction of the proportion of fat in the diet can result in reductions of breast density, although the direct connection to risk has not yet been made. The relationship between breast density and hormone-related and genetic factors is also of great interest. It is often not possible or ethical to obtain mammograms on some groups of women for whom information on density would be very useful. This includes younger women as well as groups in which it would be desirable to obtain such information at frequent intervals. For this reason, we are exploring the use of imaging approaches such as ultrasound and magnetic resonance imaging, which do not require ionizing radiation, to make measurements analogous to those now being performed by using X-ray mammograms.

Automated analysis of mammographic densities and breast carcinoma risk.

BACKGROUND: There is considerable evidence that one of the strongest risk factors for breast carcinoma can be assessed from the mammographic appearance of the breast. However, the magnitude of the risk factor and the reliability of the prediction depend on the method of classification. Subjective classification requires specialized observer training and suffers from inter- and intraobserver variability. Furthermore, the categoric scales make it difficult to distinguish small differences in mammographic appearance. To address these limitations, automated analysis techniques that characterize mammographic density on a continuous scale have been considered, but as yet, these have been evaluated only for their ability to reproduce subjective classifications of mammographic parenchyma. METHODS: In this study, using a nested case-control design, the authors evaluated the direct association between breast carcinoma risk and quantitative image features derived from automated analysis of digitized film mammograms. Two parameters, one describing the distribution of breast tissue density as reflected by brightness of the mammogram (regional skewness) and the other characterizing texture (fractal dimension), were calculated for images from 708 subjects identified from the Canadian National Breast Screening Study. RESULTS: These parameters were evaluated for their ability to distinguish cases (those women who developed breast carcinoma) from controls. It was found that both the skewness and fractal parameters were significantly related to risk of developing breast carcinoma. CONCLUSIONS: Although the relative risk estimates were moderate (typically > 2.0) and less than those from subjective classification or for an interactive computer method the authors have previously described, they are comparable to other risk factors for the disease. The observer independence and reproducibility of the automated methods may facilitate their more widespread use.

Quantitative classification of mammographic densities and breast cancer risk: results from the Canadian National Breast Screening Study.

BACKGROUND: The radiographic appearance of the female breast varies from woman to woman depending on the relative amounts of fat and connective and epithelial tissues present. Variations in the mammographic density of breast tissue are referred to as the parenchymal pattern of the breast. Fat is radiologically translucent or clear (darker appearance), and both connective and epithelial tissues are radiologically dense (lighter appearance). Previous studies have generally supported an association between parenchymal patterns and breast cancer risk (greater risk with increasing densities), but there has been considerable heterogeneity in risk estimates reported. PURPOSE: Our objective was to determine the level of breast cancer risk associated with varying mammographic densities by quantitatively classifying breast density with conventional radiological methods and novel computer-assisted methods. METHODS: From the medical records of a cohort of 45,000 women assigned to mammography in the Canadian National Breast Cancer Screening Study (NBSS), a multicenter, randomized trial, mammograms from 354 case subjects and 354 control subjects were identified. Case subjects were selected from those women in whom histologically verified invasive breast cancer had developed 12 months or more after entering the trial. Control subjects were selected from those of similar age who, after a similar period of observation, had not developed breast cancer. The mammogram taken at the beginning of the NBSS was the image used for measurements. Mammograms were classified into six categories of density, either by radiologists or by computer-assisted measurements. All radiological classification and computer-assisted measurements were made using one craniocaudal view from the breast contralateral to the cancer site in case subjects and the corresponding breast of control subjects. All P values represent two-sided tests of statistical significance. RESULTS: For all subjects, there was a 43% increase in the relative risk (RR) between the lower and the next higher category of density, as determined by radiologists, and there was a 32% increase as determined by the computer-assisted method. For all subjects, the RR in the most extensive category relative to the least was 6.05 (95% confidence interval [CI] = 2.82-12.97) for radiologists and 4.04 (95% CI = 2.12-7.69) for computer-assisted methods. Statistically significant increases in breast cancer risk associated with increasing mammographic density were found by both radiologists and computer-assisted methods for women in the age category 40-49 years (P = .005 for radiologists and P = .003 for computer-assisted measurements) and the age category 50-59 years (P = .002 for radiologists and P = .001 for computer-assisted measurements). CONCLUSION: These results show that increases in the level of breast tissue density as assessed by mammography are associated with increases in risk for breast cancer.

Proteolytic processing of the alpha-chain of the lysosomal enzyme, beta-hexosaminidase, in normal human fibroblasts.

The two subunits of beta-hexosaminidase undergo many post-translational modifications characteristic of lysosomal proteins, including limited proteolysis. To identify proteolytic cleavage sites in the alpha-chain, we have biosynthetically radiolabeled the transient forms, isolated these by immunoprecipitation, gel electrophoresis, and electroelution, and subjected them to automated Edman degradation. The position of the NH2-terminal amino acid was inferred from the elution cycle of the radioactive amino acid and the primary sequence encoded in the alpha-chain cDNA. The amino terminus of the precursor obtained by in vitro translation of SP6 alpha-chain mRNA in the presence of microsomes was leucine 23. The same amino terminus was found in precursor alpha-chain synthesized by normal human fibroblasts (IMR90) in a 1- or 3-h pulse or secreted by these cells in the presence of NH4Cl. The alpha-chain isolated after a 3-h pulse followed by a 5-h chase (intermediate form) included a mixture of molecular species of which the amino terminus was arginine 87 (most abundant), histidine 88, or leucine 90. After a 20-h chase (mature form) the latter species predominated. This mature form of the alpha-chain remained fully reactive with antibody raised against the carboxyl-terminal 15 amino acids, indicating little if any proteolysis at the carboxyl terminus. Thus synthesis and maturation of the alpha-chain of beta-hexosaminidase includes two major proteolytic cleavages: the first, between alanine 22 and leucine 23, removes the signal peptide to generate the precursor form, whereas the second occurs between the dibasic amino acids, lysine 86 and arginine 87. The second cleavage is followed by trimming of 3 additional amino acids to give the mature form of the alpha-chain.

Heterogeneity of N-acetylglucosamine 1-phosphotransferase within mucolipidosis III.

The primary defect responsible for mucolipidosis III is a deficiency of UDP-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine 1-phosphotransferase activity (GlcNAc phosphotransferase). Genetic complementation analysis of cultured fibroblasts derived from 12 patients with mucolipidosis III identified complementation groups A, B, and C (Honey, N. K., Mueller, O. T., Little, L. E., Miller, A. L., and Shows, T. B. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 7420-7424). The GlcNAc phosphotransferase activity present in the cell lines comprising the complementation groups was characterized with respect to endogenous substrates and two exogenous acceptors, alpha-methyl-D-mannoside and high mannose glycopeptides. All group C cell lines and one group A cell line were found to have normal GlcNAc phosphotransferase activity levels at 37 degrees C when screened with these exogenous acceptors. The enzyme activity in group A cell lines was within normal range when assayed at 23 degrees C. Inhibition of the phosphorylation of alpha-methyl-D-mannoside in the presence of increasing amounts of endogenous substrate N-acetyl-beta-D-hexosaminidase B was demonstrated in normal cell lines at 23 and 37 degrees C and in group A cells at 23 degrees C. However, group C cell lines did not show any inhibition at either temperature. This suggests that the alteration of the GlcNAc phosphotransferase from individuals in group C affects the recognition site for the protein portion of lysosomal enzymes, whereas group A individuals have mutations which result in a temperature-sensitive enzyme.

I-cell disease and pseudo-Hurler polydystrophy: heterozygote detection and characteristics of the altered N-acetyl-glucosamine-phosphotransferase in genetic variants.

The human disorders I-cell disease and pseudo-Hurler polydystrophy (also known as mucolipidosis II and III, respectively) are caused by an inherited deficiency of UDP-GlcNAc: lysosomal enzyme precursor GlcNAc-P transferase activity. The most common genetic variants of these diseases (complementation group A) can be identified in homozygotes and heterozygotes using a GlcNAc-P transferase assay with artificial acceptors and commercially available radiochemicals. The kinetic characteristics of the residual GlcNAc-P transferase activity in complementation group A fibroblasts indicates that the low activity is due to a low Vmax. The measured Michaelis-Menten constants for the substrates UDP-GlcNAc and alpha-methyl mannoside are in the normal range. Homozygotes and heterozygotes of another less common variant of pseudo-Hurler polydystrophy (complementation group C) have normal activity and normal kinetic characteristics with this assay using alpha-methyl mannoside as the acceptor substrate. Several PHP variants with unusual characteristics are discussed.

Anterior segment complications and neovascular glaucoma following implantation of a posterior chamber intraocular lens.

Lens implantation is now a highly successful operation. Although follow-up over 5 to 10 years with posterior chamber lenses is incomplete, the complication rate appears to be as low or lower than other lens styles. We present an exception: a clinicopathologic analysis of a globe, enucleated 4 years postoperatively, which in spite of uneventful implantation of a posterior chamber lens, developed neovascular glaucoma. Microscopic studies suggest several mechanisms for this rare complication including deep erosion of a prolene loop into the ciliary body, anterior segment ischemia, and breakdown of the blood-aqueous barrier. Scanning microscopy showed cracking of this deeply embedded loop, a finding we interpret as possible stress cracking and/or oxidation. The more flexible loops now used in modern lenses may decrease the chance of deep erosion. Implantation of a loop in the capsular bag may minimize the danger of both erosion and loop degradation. Patients should be followed long-term in order to recognize and treat these rare, but potentially disastrous complications.

Mucolipidosis II and III. The genetic relationships between two disorders of lysosomal enzyme biosynthesis.

The genetic relationships between the multiple variants of mucolipidosis II (I-cell disease) and mucolipidosis III (pseudo-Hurler polydystrophy) were investigated with a sensitive genetic complementation analysis procedure. These clinically distinct disorders have defects in the synthesis of a recognition marker necessary for the intracellular transport of acid hydrolases into lysosomes. Both disorders are associated with an inherited deficiency of a uridine diphosphate-N-acetyl-glucosamine: lysosomal enzyme precursor N-acetyl-glucosamine-phosphate transferase activity. We had previously shown that both disorders are genetically heterogeneous. Complementation analysis between mucolipidosis II and III fibroblasts indicated an identity of mucolipidosis II with one of the three mucolipidosis III complementation groups (ML IIIA), suggesting a close genetic relationship between these groups. The presence of several instances of complementation within this group suggested an intragenic complementation mechanism. Genetic complementation in heterokaryons resulted in increases in N-acetyl-glucosamine-phosphate transferase activity, as well as in the correction of lysosomal enzyme transport. This resulted in increases in the intracellular levels of several lysosomal enzymes and in the correction of the abnormal electrophoretic mobility pattern of intracellular beta-hexosaminidase. The findings demonstrate that a high degree of genetic heterogeneity exists within these disorders. N-acetyl-glucosamine-phosphate transferase is apparently a multicomponent enzyme with a key role in the biosynthesis and targeting of lysosomal enzymes.

Mucolipidosis III is genetically heterogeneous.

Mucolipidosis III (ML III), or pseudo-Hurler polydystrophy, is an inherited childhood disorder characterized biochemically by low activities and abnormal electrophoretic patterns of multiple lysosomal enzymes in fibroblasts. The primary deficiency of ML III has been proposed to be in UDP-N-acetylglucosamine:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase. However, variation in this enzyme and in other biochemical properties of different ML III lines has been observed. Therefore, we investigated genetic heterogeneity within the disorder by complementation analysis. Heterokaryon cell fractions were generated by fusing together ML III fibroblast lines. When pairs of cells complemented, correction of lysosomal enzyme activities and electrophoretic patterns was observed. Twelve fibroblast lines from 10 sibships were analyzed and three distinct complementation groups were characterized. One complementation group represents the classical ML III disorder. A single cell line identifies a second complementation group. The cell lines comprising a third complementation group have a number of biochemical characteristics different from classical ML III and may represent a genetically distinct disorder.

Localization of intraorbital foreign bodies.

A study was performed utilizing 3 mock eyes of different sizes to determine the precision and accuracy of 3 radiographic methods of localization of intraorbital foreign bodies. The Comberg method was found to be the most precise and accurate, next, the Sweet method, and then the modified spectacle frame method. However, the modified spectacle frame field expedient method of localization yielded a surprisingly high degree of accuracy in 2 of the 3 planes of reference, that is, mediolaterally and superointeriorly. A more accurate field expedient type of device which will permit greater accuracy in localization of intraorbital foreign bodies in the anteroposterior axis is currently under development.

Aplasia of the optic nerve.

A case of unilateral true aplasia of the optic nerve in an otherwise normal and healthy child is presented. Twenty-eight previously reported cases of aplasia have been reviewed and classified according to criteria which we have presented. Only six of these cases, including the present case, represent true aplasia, manifested by total blindness and complete absence of the optic disc and retinal vessels.