Coping with breast cancer: a cluster analytic approach

The aim of this study was to generate distinct clusters of women with breast cancer, and to evaluate differences between clusters with respect to decisional control, psychological adjustment, and frustration expression. Thirtyseven Stage I and 33 Stage II newly diagnosed breast cancer patients from two medical oncology clinics participated. A cluster analysis of the coping data produced three distinct patient clusters. The primary finding was that women from the low avoidance coping cluster were significantly better adjusted than women from the remaining clusters. Women from the low avoidance coping cluster also preferred more active involvement in treatment decisionmaking. Further research is needed to prospectively detail the mechanisms by which cognitive avoidance hampers psychological adjustment to cancer.     

Unfavourable change in mammographic patterns and the breast cancer risk factors

The purpose of the study was to estimate the incidence of unfavourable mammographic pattern by risk factors of breast cancers. Data consisted of 1890 Finnish women with mammographic pattern of either N1 or P1 (Wolfe's classification) at the initial screening. The screening was repeated every second year from 1982 to 1990 and at each screening round the mammographic pattern was assessed. The incidence rate of P2,DY pattern was 1.9/100 woman years. The incidence of P2,DY pattern was significantly related to age. The ageadjusted odds ratio (OR) (based on logistic regression) was 2.0 (95 CI 1.0–3.9) among women with hormonal replacement therapy (HRT), 0.6 (95 CI 0.4–0.9) among postmenopausal women, 0.2 (95 CI 0.1–0.4) among women with large breasts and 0.2 (95 CI 0.1–0.3) among women with large body mass index (BMI). After multivariate adjustment by logistic regression only the effect of BMI remained statistically significant, odds ratio of P2,DY pattern for women with BMI 25 or more was 0.2 (95 CI 0.1–0.6) compared to women with BMI less than 20.     

Prognostic factors predicting survival from first recurrence in patients with metastatic breast cancer: analysis of 439 patients

We have analyzed retrospectively 439 women with recurrent breast cancer, followed at a single institution, in order to define potential prognostic factors for survival at the time of first recurrence. Median age at the time of first recurrence was 58 and the median disease free interval (DFI) from initial diagnoses to recurrence was 33 months. Thirteen percent of the patients did not receive any adjuvant therapy while 87% received different combinations of chemotherapy, radiotherapy and hormone therapy as adjuvant treatment. With a median followup of 44 months from the time of recurrence the median survival (MSR) was 24 months (SE 1.24) and fiveyear overall survival was 18% (SE 2.02). On the univariate analysis, pathological tumor size (pT) at diagnosis (p<0.0006), axillary lymph node status at diagnosis (p<0.00001), negative estrogen receptor (ER) status (p<0.0001), negative progesterone receptor (PgR) status (p<0.0001), adjuvant chemotherapy (p<0.001), disease free interval (p<0.00001), location of recurrence (p<0.0002) and number of metastatic sites (3: p, 0.0003), were significantly associated with shorter survival from first relapse. On the multivariate analysis, only the site of recurrence, axillary lymph node status at diagnosis, ER status and DFI remained independently associated with decreased MSR after first relapse.     

Adrenal androgens and human breast cancer: A new appraisal

A clearer picture of the role of adrenal androgens in the etiology of breast cancer is beginning to emerge. Women who develop breast cancer in premenopausal years tend to have subnormal serum levels of adrenal androgens, while subjects who develop the disease in postmenopausal years have supranormal levels of these hormones. Androgens, by acting via the androgen receptor, oppose estrogen-stimulated cell growth in premenopausal years. In postmenopausal women, elevated adrenal androgen levels stimulate cell growth by the action of the unique adrenal androgen 5-androstene-3,17-diol, also termed hermaphrodiol, via its combination with the estrogen receptor in a hormone milieu lacking, or having low concentrations of, the classical estrogen 17-estradiol.     

Tamoxifen and fenretinide in women with metastatic breast cancer

Background: Tamoxifen and fenretinide combination therapy has been shown to be an active treatment regimen in metastatic breast cancer patients. This pilot study sought to determine whether the addition of fenretinide to tamoxifen would be associated with antitumor activity in metastatic breast cancer patients who had been previously treated with tamoxifen or who had hormone receptor negative disease. The effect of this therapy on circulating plasma transforming growth factorbeta (TGF) levels and serum lipids was also examined.Patientsand Methods: Thirtyone patients were treated with tamoxifen (20mg po daily), and fenretinide (400mg po daily with a 3day drug holiday each month). Plasma TGF testing was performed using isoform specific sandwich ELISA.Results: Twenty four of the 31 patients were evaluable for an antitumor response including 14 estrogen receptor (ER) positive patients who had failed prior tamoxifen therapy, seven ERnegative patients, and three hormone therapy naive ERpositive patients. There were no objective antitumor responses; three patients had stable disease for 8, 8, and 24 months. Five patients (16%) discontinued therapy for toxicity (one for grade 3 skin rash and four for abnormal dark adaptation). There was a statistically significant decrease in total cholesterol (median change per patient of –13.5mg/dl; p=0.049, a 6.5% decrease), and an increase in HDL levels (median change per patient of +18mg/dl, p=0.0001, a 35% increase) with tamoxifen and fenretinide therapy.TGF-1 plasma levels were normal in 26 of 28 patients, and no changes in these levels post-treatment were demonstrated.Conclusions: Tamoxifen and fenretinide therapy is not an active combination in ER negative metastatic breast cancer or in patients whose disease has progressed on tamoxifen. This combination had a beneficial effect on total serum cholesterol and HDL levels with no associated rise in serum triglyceride levels. The 400mg dose of fenretinide was associated with symptomatic nyctalopia in one-third of patients making it an unsuitable dose for use in breast cancer prevention studies.     

Differential effects of chemotherapeutic agents on the Bcl‐2/Bax apoptosis pathway in human breast cancer cell line MCF‐7

The present study explored the effects of three commonly used chemotherapeutic agents on the Bcl2/Bax apoptosis pathway and the interaction of these chemotherapeutic drugs with the estradiolmediated regulation of this pathway. Our results showed that: (1) Treatment of MCF7 cells with Adriamycin resulted in time and concentrationdependent decreases in Bcl2 and increases in Bax mRNA and protein levels. (2) Camptothecin elicited similar trends on Bcl2 and Bax as Adriamycin, while etoposide, at 50–100 fold (1–5M) the effective concentration of Adriamycin and camptothecin, only resulted in an increase in Bax mRNA levels. (3) Adriamycin and camptothecin, but not etoposide, were effective in suppressing estradiolstimulated increases in Bcl2 mRNA levels. Our study provides evidence that the Bcl2/Bax apoptosis pathway may be differentially regulated by chemotherapeutic agents. In addition, interaction between these agents and estradiol on the Bcl2/Bax apoptosis pathway may also exist.     

Assessment of quality of life in women undergoing hormonal therapy for breast cancer: validation of an endocrine symptom subscale for the FACT‐B

Existing quality of life instruments do not include adequate items to measure the side effects and putative benefits of hormonal treatments given in breast cancer. We report the development and validation of an 18 item endocrine subscale (ES) to accompany a standardised breast cancer quality of life measure, the Functional Assessment of Cancer Therapy (FACTB) [1]. The FACTES (FACTB plus ES) was tested initially on 268 women with breast cancer receiving endocrine treatments. Alpha coefficients for all subscales demonstrated good internal consistency (range = 0.65–0.87). Testretest reliability of the ES indicated good stability (r = 0.93, p < 0.001). Advanced breast cancer patients' quality of life was high, showing the efficacy of endocrine therapy, but women with primary disease reported better physical, social, and functional wellbeing and fewer breast cancer concerns. Most frequently reported symptoms were loss of sexual interest (31%), weight gain (25%), and hot flushes (24%). Significant differences were found between treatment groups for hot flushes and vaginal dryness. Two assessments of the instrument's responsiveness to change were made; 32 women in a clinical trial of endocrine therapy and 18 women without breast cancer taking HRT completed the FACTES at baseline, 4, 8, and 12 weeks. Trial patients reported significantly more symptoms at 8 and 12 weeks than at baseline. Women taking HRT reported significantly fewer or less severe symptoms than at baseline. In conclusion the FACTES has acceptable validity and reliability and is sensitive to clinically significant change, making it suitable for clinical trials of endocrine therapy.     

Invasion marker PAI‐1 remains a strong prognostic factor after long‐term follow‐up both for primary breast cancer and following first relapse

In 1991, our group was the first to report the prognostic strength of plasminogen activator inhibitor type 1 (PAI1) in primary breast cancer. The prognostic impact of invasion markers PAI1 and urokinasetype plasminogen activator (uPA) on diseasefree survival (DFS) and overall survival (OS) in breast cancer has since been independently confirmed. We now report on the prognostic impact of PAI1 and uPA after longterm median followup of 77 months for our cohort (n=316).Levels of uPA, PAI1, and cathepsin D were determined in tumor tissue extracts by immunoenzymatic methods. Sphase fraction (SPF) was measured flowcytometrically in paraffin sections. Using logrank statistics, optimized cutoffs were found for PAI1 (14ng/mg), uPA (3ng/mg), cathepsin D (41pmol/mg), and SPF (6%). In all patients, various factors (PAI1, uPA, nodal status, SPF, cathepsin D, grading, tumor size, hormone receptor status) showed significant univariate impact on DFS. In Cox analysis, only nodal status (p < 0.001, RR: 3.1) and PAI1 (p < 0.001, RR: 2.7) remained significant. In nodenegative patients (n = 147), PAI1, uPA, and SPF had significant univariate impact on DFS, whereas in Cox analysis, only PAI1 was significant. PAI1 was also significant for DFS within subgroups defined by established factors. In CART analysis, uPA enhanced the prognostic value of PAI1 and nodal status for determination of a verylowrisk subgroup. For OS, only lymph node status and PAI1 were significant in multivariate analysis. PAI1 levels in the primary tumor were also a significant prognostic marker for survival after first relapse in both univariate and multivariate analysis.     

A case-control study of reproductive variables,alcohol, and smoking in premenopausal bilateral breast cancer

Summary The transforming growth factor-s are potent growth inhibitors of normal and transformed breast epithelial cells in culture. In vivo, these peptides modulate the development of the mouse mammary gland. Tissuespecific overexpression of mature TGF-1 in transgenic mice results in mammary gland atrophy and prevention of carcinogen-induced breast tumorigenesis. However, the inhibitory effect of endogenous or exogenous TGF-s on established tumor cells is less clear. Several published circumstantial and more direct data argue that, in some cases, the tumor cell TGF-s may contribute to the maintenance and/or progression of tumor cells in an intact host by modulating their interaction with host factors. This differential role of the TGF-s on mammary cells as determined by their normal or transformed phenotype as well as the biological and clinical implications of these data are discussed.Presented at the symposium "New Approaches in the Therapy of Breast Cancer", Georgetown University Medical Center, Washington DC, October 1994, generously supported by an education grant from Bristol-Myers Squibb.     

Synergistic action of apoptosis induced by eicosapentaenoic acid and TNP‐470 on human breast cancer cells

The effects of eicosapentaenoic acid (EPA) and an angiogenesis inhibitor (TNP470) on the suppression of breast cancer cell growth were examined in five human breast cancer cell lines (MDAMB231, T47D, MCF7, KPL1, and MKLF). In all five cell lines, EPA and TNP470 alone both showed tumor growth inhibition in a time and dosedependent manner, and in combination, a synergistic effect was seen at high concentrations. EPA plus TNP470 treatment evoked apoptosis as confirmed by the appearance of sub G1 populations, by DNA fragmentation, and by cell morphology. With the combination, the expression of Bax and Bc1x_S, the apoptosisenhancing proteins, was more upregulated and that of Bcl2 and Bclx_L, the apoptosissuppressing proteins, was more downregulated compared to the use of EPA or TNP470 alone, suggesting that their synergistic effect was due to an acceleration of apoptosis.     

Estrone sulfate: A potential source of estradiol in human breast cancer tissues

Summary Local formation of estradiol in human breast tumors could provide a more important source of estrogen than is delivered from plasma. Prior studies have suggested that estrone is primarily synthesized from estrone sulfate. The enzyme 17-hydroxysteroid dehydrogenase (HSD) would be required to convert estrone to estradiol.This study characterized HSD in 1000 × g supernatants from human breast tumors. Estradiol synthesis was linearly related to tissue concentration or time over the range studied. Cofactor requirements varied with estrone concentration. High and low affinity sites were found in 50% of tissues studied, while the remainder contained only low affinity sites. Screen assays showed measurable activity in all 42 samples tested. This activity ranged from 0.73–>100 nmol estrone synthesized/g protein/hr, with a median activity of 5.9 nmol/g/hr.We evaluated the biological relevance of the sulfatase-HSD pathway by testing the ability of estrone sulfate to stimulate colony formation in soft agar cultures of nitrosomethylurea-induced rat mammary tumors. The maximally effective concentration ranged from 10^–7 to 10^–4 M. Significant stimulation of colony formation was observed in 7 of 8 experiments. The estrone sulfate stimulation pattern was similar to that previously observed with estradiol. Of the³H-estrone sulfate added to the dishes, 20–98% was recovered as estrone and 0.2–6% as estradiol. These studies suggest that the requisite enzymes are present in human breast tumors for conversion of estrone sulfate to estradiol, and that this pathway may be biologically significant.This work presented in part at the International Congress on Endocrinology of the Breast, September 19–22, 1984, Torino, Italy.     

Coexpression of c-kit and stem cell factor in breast cancer results in enhanced sensitivity to members of the EGF family of growth factors

Insulinlike growth factor (IGF)I protects many cell types from apoptosis. As a result, it is possible that IGFIresponsive cancer cells may be resistant to apoptosisinducing chemotherapies. Therefore, we examined the effects of IGFI on paclitaxel and doxorubicininduced apoptosis in the IGFIresponsive breast cancer cell line MCF7. Both drugs caused DNA laddering in a dosedependent fashion, and IGFI reduced the formation of ladders. We next examined the effects of IGFI and estradiol on cell survival following drug treatment in monolayer culture. IGFI, but not estradiol, increased survival of MCF7 cells in the presence of either drug. Cell cycle progression and counting of trypanblue stained cells showed that IGFI was inducing proliferation in paclitaxeltreated but not doxorubicintreated cells. However, IGFI decreased the fraction of apoptotic cells in doxorubicin but not paclitaxeltreated cells. Recent work has shown that mitogenactivated protein kinase (MAPK) and phosphotidylinositol3 (PI3) kinase are activated by IGFI in these cells. PI3 kinase activation has been linked to antiapoptotic functions while MAPK activation is associated with proliferation. We found that IGFI rescue of doxorubicininduced apoptosis required PI3 kinase but not MAPK function, suggesting that IGFI inhibited apoptosis. In contrast, IGFI rescue of paclitaxelinduced apoptosis required both PI3 kinase and MAPK, suggesting that IGFImediated protection was due to enhancement of proliferation. Therefore, IGFI attenuated the response of breast cancer cells to doxorubicin and paclitaxel by at least two mechanisms: induction of proliferation and inhibition of apoptosis. Thus, inhibition of IGFI action could be a useful adjuvant to cytotoxic chemotherapy in breast cancer.     

Phase II of doxorubicin/taxol in metastatic breast cancer

Purpose. To assess the response rate, survival, and toxicity of Taxol®(paclitaxel) as 1h infusion plus doxorubicin as firstline treatment for patients with metastatic breast cancer (MBC).Patients and methods. Seventysix patients with untreated MBC were recruited. All of them had measurable disease and were evaluable for toxicity. Fiftyfive percent of the patients had visceral involvement. The dose of doxorubicin was fixed at 50mg/m² as a short intravenous infusion, followed by 200mg/m² of Taxol as a 1h intravenous infusion. Doxorubicin was administered during the first seven cycles, continuing with Taxol only up to a maximum of ten cycles.Results. Neutropenia was the most important toxicity: 30% grade 3 and 18% grade 4. Only 2 patients showed a decrease in the left ventricular ejection fraction (LVEF) which caused discontinuing the treatment. No clinical congestive heart failure (CHF) was observed. Seventyfour patients were eligible for response evaluation: 10 (14%) achieved complete response (CR) and 46 (62%) achieved partial response (PR). The mean duration of response was 13.47± 1.35 months (95% confidence interval (CI): 10.82; 16.12) and the mean survival was 21.50± 1.42 months (95% CI: 18.72; 24.29).Conclusion. The overall response (OR) rate was 76%. No CHF was assessed and 2 patients stopped treatment due to LVEF decrease. Although doxorubicin 50mg/m² followed by Taxol 200mg/m² in 1h intravenous infusion presents a toxicity profile which demands a close followup, it represents a convenient outpatient schedule with similar activity rate compared to longer Taxol infusions.     

Biophenotypes and survival of BRCA1 and TP53 deleted breast cancer in young women

The aim of this study was to examine the loss of heterozygosity (LOH) of BRCA1 (17q21) and TP53 (17p13.1) in early-onset breast cancer patients; to correlate biopathological characteristics with molecular alterations; and to investigate the survival of LOH-related cancers.BRCA1 and TP53 LOH were evaluated in 78 early-onset breast cancers (40 years, Group 1) and 80 patients with age <55 years (Group 2). Cases were characterized for multiple biological markers (ER, PR, proliferation index (PI), NEU and p53). LOH was carried out on microdissected paraffin embedded tissues; microsatellites D17S855 (BRCA1) and D17S786 (TP53) were amplified by fluorescent PCR and analyzed by an automated DNA sequencer. Early-onset breast cancers showed a higher frequency of ductal histotype (89,7% vs. 56,3% p<0.001), node-positive (53,8% vs. 38,7%), larger size (p=0.017), higher mitotic rate (p=0.025), higher nuclear and final grade (p=0.01 and p=0.001, respectively). D17S855 LOH was 32,8% in group 1 vs. 21% in group 2; D17S786 LOH was 50,7% vs. 31.3% (p=0.03), respectively. BRCA1 LOH was correlated with higher PI (p=0.032) and higher p53 expression (p<0.001) in group 1 and with higher NEU expression (p=0.028) in group 2. TP53 LOH was correlated with p53 overexpression (p=0.03) in group 1. A worse clinical outcome in early-onset LOH related cancers emerged from follow-up data: TP53 and BRCA1 LOH were associated with a shorter relapse free interval (RFI) (p=0.03) and a poorer overall survival (OS) (p=0.04), respectively. This study underlines different biological profiles in the two age groups investigated, probably reflecting different mechanisms of carcinogenesis. In accordance with adverse histopathological features in early-onset patients, LOH-related cancers have an unfavorable prognosis.     

Mdm2 sensitizes MCF7 breast cancer cells to cisplatin or carboplatin

Overexpression of Mdm2 in cancer cells with otherwise wildtype p53 is believed to be an alternative mechanism for p53 inactivation during carcinogenesis. Because a number of genetic alterations that inactivate p53, including mutation, homozygous deletion, or viral oncoprotein expression (e.g. HPV16E6), inhibit DNA repair, we tested the hypothesis that Mdm2 would likewise inhibit DNA repair. Repair of cisplatininduced DNA damage was reduced in MCF7 cells overexpressing Mdm2, compared to MCF7 cells in which wildtype p53 function was intact. MCF7Mdm2 cells exhibited preferential sensitivity to cisplatin and carboplatin. MCF7Mdm2 cells showed a pronounced Sphase arrest after cisplatin treatment, similar to that observed in mutantp53 cells in the present and prior studies. MCF7 cells with intact wildtype p53, on the other hand, arrested primarily in G2/M phase after cisplatin treatment. These findings indicate that Mdm2 overexpression can recapitulate the effect of p53 mutations on DNA repair of cisplatin lesions.     

Growth factor involvement in the multihormonal regulation of MCF-7 breast cancer cell growth in soft agar

Summary The hormone dependency of the MCF-7 breast cancer cell line, while extensively tested in liquid culture, has not been previously evaluated under conditions of anchorage-independent growth in serum-free media. Using the soft agar clonogenic assay, we demonstrate that physiologically relevant concentrations of estradiol (E₂), progesterone (Pg), and prolactin (PRL) similarly stimulated MCF-7 cell colony formation in the absence of serum. Addition of an anti-insulin-like growth factor-I (IGF-I) antibody inhibited E₂- and Pg-stimulated growth, while PRL action was not affected. Similar results were obtained with an anti-IGF-I receptor antibody, except that its inhibitory effect on Pg-induced colony formation was modest and not statistically significant. Administration of either an anti-transforming growth factor- (TGF-) antibody or an anti-epidermal growth factor (EGF) receptor antibody similarly inhibited E₂-stimulated MCF-7 cell growth in soft agar, while neither antibody influenced Pg or PRL effects. Addition of TGF-₁, -₂, -₃ similarly suppressed MCF-7 cell colony formation in a dose dependent manner to a degree comparable to that observed with 4-OH-tamoxifen (4-OH-T). Furthermore, the growth inhibitory effect of 4-OH-T was completely reversed by an anti-TGF- antibody. We conclude that IGFs and TGF- are important mediators of E₂-stimulated MCF-7 cell growth in soft agar. IGFs may also be playing a role in Pg action, while neither growth factor is involved in PRL-stimulated colony formation. Finally, TGF- appears to be an important mediator of antiestrogen-induced inhibition of tumor growth.Abbreviations IGF insulin-like growth factor - TGF transforming growth factor - E₂ estradiol-17 - Pg progesterone - PRL prolactin - 4-OH-T 4-hydroxy-tamoxifen - IMEM improved minimal essential medium     

Tissue inhibitor of metalloprotease (TIMP)‐1 and proliferative behaviour of clonal breast cancer cells

In the present paper, we have examined whether human tissue inhibitor of metalloprotease1 (hTIMP1) is able to exert a growth factorlike effect on two clonal cell lines (BC3A and BC61), isolated from a parental line of human breast carcinoma cells (8701BC), and endowed with different growth and invasive behaviour in vitro and in nude mouse. The data obtained indicate that only the more tumorigenic clonal cell line (BC61) is responsive to hTIMP1 treatment by increasing its proliferative rate in a dosedependent manner. It was also found that BC61 cells selectively express a transmembrane protein of about 80kDa able to bind hTIMP1 in vitro and in vivo with high affinity (K_d of 0.07 ± 0.004 nM), and that treatment of BC61 cells with a proliferationpromoting concentration of hTIMP1 is able to stimulate tyrosinetargeted phosphorylation. The cumulative results obtained strongly support the hypothesis that hTIMP1, classically regarded as a collagenase inhibitor, may be a crucial element of the extracellular signalling network during breast cancer development by controlling cell growth phenotype in autocrine and paracrine manner, and that intratumoural heterogeneity for the biological response to TIMP1 may exist within the composite cell population of the primary tumour site.     

Regulation of BAX and BCL‐2 expression in breast cancer cells by chemotherapy

Optimizing chemotherapeutic drug delivery strategies relies, in part, on identification of the most clinically effective sequence, dose, and duration of drug exposure. The combination of dose intensive etoposide (VP16) followed by cyclophosphamide has clinical efficacy in the treatment of advanced breast cancer. However, molecular mechanisms that underlie the effectiveness of this combination of chemotherapeutic agents have not been investigated. In this study we investigated regulation of BAX and BCL2 expression by VP16 and cyclophosphamide as a potential mechanism for the induction of breast cancer cell death induced by this regimen.There was a dose and time dependent increase in BAX expression in the breast cancer cell lines MCF7, MDAMB435S, and MDAMBA231 following in vitro treatment with 50–100M VP16. Elevation of BAX protein expression in the presence of VP16 alone did not correlate with reduced viability or induction of apoptosis in MCF7, MDAMB435S, or MDAMBA231. VP16 did effectively block the breast cancer cell lines evaluated (MCF7 and MDAMB435S) at G₂/M phase of the cell cycle, confirming activity of the drug in vitro. MCF7 and MDAMB435S cells that were pretreated with VP16 and subsequently exposed to 1.0–12.0g/m1 4hydroperoxycyclophosphamide (4HC), an active metabolite of cyclophosphamide, had markedly reduced viability when compared to matched controls treated with either VP16 or 4HC individually. Consistent with this loss of viability, exposure of all three cell lines to the combination of VP16 and 4HC resulted in higher BAX protein levels than those observed following treatment with either single agent. This combination of chemotherapeutic agents also resulted in reduced BCL2 expression.These observations suggest that combination chemotherapy may derive its efficacy, in part, through coordinated regulation of specific gene products associated with apoptosis. Characterization of molecular events that underlie susceptibility of specific tumor cells to combination chemotherapeutic regimens may lead to additional improvements in treatment strategies for this disease.     

Glycogen‐rich carcinomas of the breast display unique characteristics with respect to proliferation and the frequency of oligonucleosomal fragments

We determined the proliferation rate and apoptotic activity of glycogenrich carcinomas of the breast as opposed to nonclear cell tumors by means of MIB1 immunohistochemistry and in situ detection of oligonucleosomal fragments (TUNEL reaction). The retrospective biopsy series included six invasive clear cell carcinomas of the glycogenrich type as well as 15 randomly selected cases of invasive ductal carcinoma without evidence of glycogen storage. Three patients in the clear cell group and seven patients in the control cohort developed lymphnode metastasis. The MIB1 labeling index of glycogenrich carcinomas averaged 9.05%, while that of the controls was 30.03%. Apoptotic nuclei were present in a mean of 1.26% of glycogenrich carcinoma cells. The control tumors exhibited an average apoptotic frequency of 5.85%. Tumor size, hormone receptor status, and presence or absence of lymph node involvement were found not to correlate with either proliferation or apoptosis. We conclude that glycogenrich breast carcinomas are characterized by a peculiar low proliferationlow apoptosis cell kinetic profile. The aggressive clinical behavior of these neoplasms may possibly be accounted for by an ineffective apoptotic elimination of otherwise slowly proliferating tumor cells.