Evaluation of cell proliferation in breast carcinoma. Comparison of Ki-67 immunohistochemical study, DNA flow cytometric analysis, and mitotic count

Growth kinetics of 102 breast carcinomas were studied by immunohistochemical analysis with the monoclonal antibody Ki-67, which reacts with a nuclear antigen in proliferating cells. The results were correlated with ploidy and S-phase fraction (SPF) analyzed by DNA flow cytometric study and with mitotic count analyzed by light microscopic study. The proportion of Ki-67-positive cells (Ki-67 score) in breast carcinomas varied from 0.6% to 80% (median, 6.3%). Ki-67 scores were significantly higher in the DNA aneuploid than in the DNA diploid tumors. Ki-67 scores correlated significantly with tumor SPF in DNA aneuploid tumors. In DNA diploid tumors SPF showed no correlation with Ki-67 score. High Ki-67 scores were associated with high mitotic counts (P less than 0.0001) and histologic grade (P less than 0.0001). Nuclear pleomorphism, tubule formation, or lymph node status were not correlated with Ki-67 score. In conclusion, Ki-67 immunostaining correlates with other measures of cell proliferation (SPF, mitotic count) supporting its clinical significance.

Different opinions on classification of DNA histograms produced from paraffin-embedded tissue

Flow cytometric DNA ploidy determination has been regarded as an objective prognostic parameter in several types of human cancer. To test whether DNA histograms are similarly interpreted, a series of flow cytometric DNA histograms was posted to six investigators working in the field for independent classification. The histograms were produced from paraffin-embedded adrenal adenomas or non-neoplastic tissue and had several different patterns. Only 44% of the histograms were similarly classified by all investigators, and 85% by five of the six participants, when DNA ploidy was evaluated. Different criteria for tetraploidy existed, and also some uncertainty in classifying peridiploid and small aneuploid peaks. It is concluded that lack of consensus on histogram classification may result in widely varying percentages of DNA aneuploid tumors found even if the data are similar. Until general agreement is reached on the definition of DNA aneuploidy and its subclasses, classification of DNA histograms is variable and subjective.

Suppression of autologous mixed leukocyte reaction in type 1 diabetes mellitus by in vivo-activated T lymphocytes

In vivo-activated interleukin 2 receptor-positive T lymphocytes (Tac cells) are demonstrable and the autologous mixed leukocyte reaction (AMLR) is impaired in several autoimmune diseases, including type 1 insulin-dependent diabetes mellitus (IDDM). We investigated AMLR in greater detail, together with possible relationships between AMLR and Tac lymphocytes in IDDM. Coculture experiments with HLA identical patient-healthy sibling pairs revealed that both responder and stimulator cells of diabetic patients function abnormally in AMLR. Suppressive Tac lymphocytes among responder T cells seemed to impair their proliferation. The removal of Tac cells by immunomagnetic beads led to a striking enhancement of proliferation, while the restoration of AMLR cultures with enriched Tac cells was accompanied by a diminished response. The reasons for the poor stimulatory capacity of patient cells are at present unknown but may be due to altered function and/or structure of HLA-DR molecules.

Primary invasive and in situ vaginal carcinoma. Flow cytometric analysis of DNA aneuploidy and cell proliferation from archival paraffin-embedded tissue

Eleven invasive and five non-invasive primary vaginal carcinomas were studied by DNA flow cytometry using archival paraffin-embedded tissue as starting material. Overall frequency of DNA aneuploidy in the invasive carcinomas was 8/11 (73%). DNA aneuploidy occurred in all four advanced stage (III-IV) and in 4/7 (57%) of the early stage (I-II) carcinomas. Among the squamous cell carcinomas aneuploid DNA content was also associated with non-keratinizing tumor type. Invasive vaginal carcinomas showed a high median S-phase fraction (SPF) (18.4%, range 6.9-31.8%). High SPF values were associated with advanced stage and non-keratinizing tumors. Corrected 5-year survival rate in invasive vaginal cancer was 44%, with no significant relation to DNA ploidy or SPF. In situ carcinomas were almost as often DNA-aneuploid (3/5, 60%) as the invasive carcinomas and had comparable median SPF value (13.4%, range 5.5-24.6). One in situ carcinoma with a high DNA-index and SPF relapsed, but overall 5-year survival rate was 100%. In conclusion, both invasive and in situ vaginal carcinomas frequently contain DNA-aneuploid stemlines and show a high SPF. Although DNA aneuploidy and high SPF correlate with advanced stage and non-keratinizing tumor type, they do not have much prognostic relevance in vaginal neoplasia.

Analysis of DNA synthesis in herpes simplex virus infected cells by dual parameter flow cytometry

The DNA incorporation of a thymidine analogue bromodeoxyuridine (BrdUrd) in herpes simplex virus type 2 (HSV-2) infected cervical cancer cell lines (CaSki and C-33 A) was studied by dual parameter flow cytometry. HSV-2 infection resulted in an exponential increase in DNA synthesis in the CaSki cells. In the less permissive C-33 A cells the proportion of DNA-synthesizing cells cycled during HSV-2 infection. The inhibition of viral DNA synthesis by phosphonoformate (PFA) was able to inhibit the virus induced changes in the CaSki but not in the C-33 A cells. In the C-33 A cells a part of the virus induced cellular DNA synthesis represents repair replication of cellular DNA.

Immunohistochemical determination of estrogen and progesterone receptors in human breast carcinoma. Correlation with histopathology and DNA flow cytometry

Human breast carcinomas (n = 232) were evaluated for estrogen and progesterone receptors (ER, PR) by immunohistochemical study and by cytosol steroid-binding assay (n = 185). The staining was scored (histoscore) by estimates of relative nuclear staining intensity and the percentage of positively stained carcinoma cells. Of the invasive ductal carcinomas 72% were ER-positive and 55% were PR-positive. The invasive lobular, intraductal, tubular, and mucinous carcinomas were the most frequent ER-positive tumor types, whereas comedo and medullary carcinomas only rarely contained ER. Progesterone receptor was most frequently present in intraductal, tubular, and mucinous carcinomas. Better differentiated tumors with lower histologic grade were significantly associated with high prevalence of immunohistochemically determined ER and PR (P less than 0.0001). Proliferative cell fraction, determined by DNA flow cytometric study (n = 63), was inversely related to ER (P = 0.03) and PR (P = 0.05) status. Aneuploidy was independent of ER or PR content.

Serum CA 125 in acute pelvic inflammatory disease

Serum levels of CA 125 and other selected tumour markers were measured in 31 patients with proven pelvic inflammatory disease (PID). Ten (32%) of the patients had elevated CA 125, one (4%) had elevated CEA, and none had elevated CA 15-3, AFP or beta 2-microglobulin. Compared to patients with normal CA 125, patients with elevated CA 125 were older, more often users of intrauterine contraceptive devices, had longer duration of symptoms, higher erythrocyte sedimentation rates, and more often had an adnexal mass on pelvic examination. There was a correlation between CA 125 levels and the severity of adnexal inflammation as defined by laparoscopy. Isolation of specific micro-organisms from the upper genital tract was not associated with elevated CA 125. In most women serum levels of CA 125 decreased during treatment. PID should be considered as a major cause of positive CA 125 findings among young women.

Prognostic assessment in stage I ovarian cancer using a discriminant analysis with clinicopathological and DNA flow cytometric data

We have previously defined three types of tumor DNA histograms, which are associated with favourable, intermediate and poor prognosis of patients with ovarian cancer. In the present study we evaluated the value of DNA histogram type combined with clinicopathological data in predicting long-term clinical outcome in stage I ovarian cancer. A stepwise discriminant analysis was done to find out the best combination of prognostic parameters in the distinction of two groups of stage I ovarian cancer patients; those with less than 5-year overall survival (22 cases) and those with longer than 5-year recurrence-free survival (47 cases). DNA histogram and histological type as well as FIGO stage in that order proved to be the most discriminating parameters and their combination allowed the correct prediction of clinical outcome in 78% of stage I ovarian cancer patients. In stage Ia the proportion of correctly classified cases based on DNA histogram and histological type was 82%. If DNA histogram was omitted from the discriminant analysis, the combination stage and histological type correctly classified a significantly lower percentage (68%) of patients. DNA flow cytometry thus improved the prognostic evaluation in stage I ovarian cancer, but even when combined with conventional clinicopathological factors failed to give correct prognostic assessment in about 20% of patients with stage I ovarian cancer.

Flow cytometric DNA analysis of 199 histologically favourable or unfavourable non-Hodgkin lymphomas

We have studied the nuclear DNA content of histologically favourable (n = 82) or unfavourable (n = 117) non-Hodgkin lymphomas (NHLs) diagnosed between 1957 and 1978 in the Tampere University Central Hospital. The DNA analysis was done by applying a trypsin digestion method to archival tumour samples. DNA aneuploidy was seen in 40 per cent of the unfavourable cases and in 10 per cent of the favourable cases, but varied considerably between different histological subtypes. The unfavourable cases showed high proliferative activity (S-phase fraction, SPF), while considerable variation in the SPF among the favourable NHLs was noted. Among the unfavourable NHLs, cases with DNA-aneuploid tumours had significantly (P less than 0.01) worse prognosis than stage and treatment matched cases with DNA-diploid tumours. In general, survival of the patients who had high SPF tumours was significantly lower compared with patients with low SPF tumours (P less than 0.01). However, SPF was not related to the prognosis in the unfavourable NHLs. We conclude that the flow cytometric DNA analysis revealed characteristic features in the favourable and unfavourable NHLs and may be useful in predicting the clinical outcome of patients.

DNA flow cytometric analysis indicates that many breast cancers detected in the first round of mammographic screening have a low malignant potential

An organized mammographic screening program covered 8,690 women from selected birth cohorts (aged 50-59) in the Tampere University Central Hospital district. Forty-four breast cancer cases were detected in the first round of mammographic screening, which is 3.7 times the expected annual number of new cases in this population. To evaluate the proliferative kinetics and biological properties of these cancers, DNA flow cytometric analysis was carried out in 37 of the screen detected cancers (SDCs) using 60 clinically detected stage I-II cancers and 30 screen-detected benign lesions as reference. DNA aneuploidy was observed in 17/37 (46%) of the SDCs as compared to 41/60 (68%) in the clinical controls (p less than 0.05), while all the benign lesions were DNA-diploid. The median S-phase fraction (SPF) in the SDCs was significantly (p less than 0.001) lower (3.5%) than in the clinical controls (9.6%). Differences in SPF persisted in subgroups defined by DNA ploidy and histological type. In stage-I SDCs the median SPF value (2.5%) approached that of benign tumors (1.9%). Our epidemiological and biological data indicate that the first round of mammography predominantly detects prevalent preclinical lesions, some of which are of very low malignant potential. At present such patients may often receive too extensive treatment. DNA flow cytometry could help in the identification of cases which could be treated, for example, by breast-conserving methods.

Improving the prognostic value of DNA flow cytometry in breast cancer by combining DNA index and S-phase fraction. A proposed classification of DNA histograms in breast cancer

To optimize the prognostic value of DNA flow cytometry in breast cancer the authors calculated several parameters from the DNA histogram, including the DNA index, the size and number of aneuploid peaks as well as S-phase and G2/M-phase cell cycle fractions. Of these, DNA index and S-phase fraction (SPF) proved to be the most valuable prognostic indices. DNA aneuploidy was associated with a three-fold risk of death as compared to DNA diploidy (P less than 0.0001). The highest risk of death was associated with hypertetraploid (greater than 2.20) DNA index, whereas a tetraploid DNA index (1.80-2.20) was associated with a relatively low risk. The SPF had significant additional prognostic value in both DNA diploid (P = 0.0002) and DNA aneuploid (P = 0.02) tumors. By combining DNA index and SPF the authors defined three types of DNA histograms, which were associated with favorable, intermediate, and poor prognosis of the patients. DNA diploidy together with low (less than 7%) SPF (type I DNA histogram) was associated with very favorable prognosis, whereas DNA aneuploidy with high DNA index (greater than 2.20) or high (greater than 12%) SPF (type III DNA histogram) was related to the worst prognosis with approximately eight-fold relative risk of death. In a Cox multivariate regression analysis the type of DNA histogram was an independent and most powerful prognostic indicator in breast cancer. The other independent factors in the Cox analysis were primary tumor size, nodal status, and progesterone receptor status.

Serum CA 15-3 assay in the diagnosis and follow-up of breast cancer

Serum CA 15-3 values were determined in 177 patients with primary breast cancer and in 41 with non-malignant breast disease. Increased preoperative serum CA 15-3 values (greater than 38 U ml-1) were observed in 7%, 17%, 64% and 67% of patients with stage I, II, III and IV disease, respectively and in none of the patients with benign breast disease. Patients with elevated serum CA 15-3 values had poor 3-year cumulative survival (27%). In the postoperative follow-up 9% of patients with no clinical evidence of disease, 33% with a single metastasis and 67% with two or more metastases had elevated values. Increasing or decreasing serum CA 15-3 values correlated with the clinical outcome in 26 out of 27 cases (96%), whereas serum values remaining in the reference range had no predictive value. At the time of recurrence elevated serum CA 15-3 values were also observed in patients with normal preoperative values. Increased serum CA 15-3 values preceded the clinical detection of tumour recurrence by up to 13 months. In conclusion, serum CA 15-3 levels had prognostic value in breast cancer, reflected the extent of clinically detectable disease and the presence of occult metastatic disease. Further research is warranted on the benefits of CA 15-3 assays in relation to adjuvant chemotherapy as well as the earlier detection and treatment of metastatic disease.

Comparison of fresh and paraffin-embedded tissue as starting material for DNA flow cytometry and evaluation of intratumor heterogeneity

Flow cytometric analysis of DNA ploidy and S-phase fraction (SPF) from paraffin-embedded tumors has become an important diagnostic and prognostic tool in clinical pathology and investigative oncology. The present study aimed at elucidating the reliability of the method. About 90% of the 1,400 paraffin-embedded tumors analyzed were evaluable for DNA index and about 70% for SPF, although considerable differences between various tumor types were detected. The within-assay coefficients of variation for determination of tumor DNA index and SPF were 2% and 6%, respectively. Intratumor variation in DNA index was observed in 24% of breast and in 21% of ovarian carcinomas and variation in SPF in 36% and 29% of the respective tumors. Intratumor variation in SPF was greatest in DNA-diploid tumors, which may indicate that SPF values in these tumors may be less reliable owing to variations in the proportions of tumor and nontumor cells. If the methodological variation and the intratumor variation were taken into account, there was a good correlation between DNA indices (r = 0.980) and between SPF values (r = 0.794) obtained from fresh and paraffin-embedded tumors. It is concluded that accurate determination of DNA index and SPF from paraffin-embedded tumors is possible in the majority of cases. Regardless of the type of starting material used for DNA flow cytometry it is advantageous to study several samples from each tumor to account for the intratumor heterogeneity.

Defective autologous mixed leukocyte reaction in newly diagnosed type 1 diabetes mellitus

We studied autologous mixed leukocyte reaction (AMLR) in type 1 (insulin-dependent) diabetes mellitus (IDDM) patients, their healthy siblings and healthy schoolchildren, Blood samples from the patients were drawn within 1 week after hospitalization and 2 months later. AMLR was significantly depressed in the patients when compared to healthy siblings or other healthy controls. In addition, the mean AMLR responsiveness of the healthy control group exceeded that of healthy siblings. The production of IL-2 in AMLR was impaired in the patient group and the defective AMLR could be restored by addition of exogenous IL-2 in 7-10 patient cultures. However, in 3-10 patients addition of IL-2 induced no enhancement of proliferation. While the patients in general had raised levels of activated T lymphocytes these three patients had higher numbers of activated T cells than other patients. Defective AMLR and presence of activated T cells may be related and may play a role in the pathogenesis of IDDM.

DNA ploidy level and cell cycle distribution in ovarian cancer: relation to histopathological features of the tumor

We analyzed nuclear DNA content and S-phase fraction (SPF) from 157 paraffin-embedded ovarian tumors by flow cytometry and compared the results with the clinicopathological features of the tumors. DNA aneuploidy was more common and mean SPF was higher in advanced than in early-stage tumors (p less than 0.001). DNA aneuploidy was most often (75%) observed in undifferentiated tumors (World Health Organization classification) and most seldom (30%) in mucinous carcinomas. Mean SPF values ranged from 17.7% in undifferentiated carcinomas to 11.1% in mucinous carcinomas. DNA flow cytometric results correlated better with nuclear than with histological tumor grade. The proportion of DNA-aneuploid tumors increased from 30% in nuclear grade I to 93% in nuclear grade III, and mean SPF increased from 9.9 to 20.2% (p less than 0.001). DNA ploidy and SPF were independently associated with both stage and nuclear grade of the tumor, whereas the differences between the histopathological tumor types virtually disappeared when the groups were adjusted for nuclear grade. On the basis of these clinicopathological correlations, it appears that DNA ploidy and SPF reflect the malignant potential of ovarian tumors and thus complement the routine histopathological evaluation.

Lipoprotein uptake in primary cell cultures of rabbit atherosclerotic lesions. A fluorescence microscopic and flow cytometric study

To characterize the lipoprotein metabolism of lipid-filled cells of atherosclerotic lesions, uptake of 3,3'-dioctadecylindocarbocyanine (DiI)-labelled low density lipoprotein (LDL), acetylated LDL (Ac-LDL) and beta-very low density lipoprotein (beta-VLDL) was studied by fluorescence microscopy and flow cytometry in primary cultures of enzymatically dispersed aortic cells from cholesterol-fed rabbits. Most of the foam cells were identified as macrophages on the basis of Fc-receptors and high activities of nonspecific esterase and acid lipase, although cholesteryl ester (CE) inclusions were found by filipin staining also in smooth muscle cells (SMCs). During the culture only SMCs proliferated and were confluent in about 1 week. After incubation with DiI-Ac-LDL most macrophage foam cells were brightly fluorescent, but also many SMCs accumulated fluorescence. In SMCs, an excess of LDL inhibited the uptake of DiI-beta-VLDL and DiI-LDL, indicating that these lipoproteins were taken up by the apoB,E receptor; the activity of this receptor was low 2 days after cell isolation but increased considerably during SMC proliferation. DiI-beta-VLDL was not taken up by the macrophage foam cells until after 7 days' culture, when their CE content had decreased, reflecting a feed-back regulation of these receptors as well. Our results indicate that, in primary cultures of enzyme-dispersed cells from rabbit atherosclerotic lesions, most of the foam cells have lipoprotein receptors resembling those described in macrophages and that also many SMCs accumulate Ac-LDL.

Prognostic significance of DNA index, multiploidy, and S-phase fraction in ovarian cancer

Paraffin-embedded tumor samples from 157 ovarian cancer patients were analyzed by DNA flow cytometry. Tumor ploidy had prognostic significance in both early and advanced ovarian cancer. After adjusting for stage, residual tumor mass, histopathologic type, treatment, and age of patient in a Cox regression analysis, the relative risk of death was two-fold higher in single DNA-aneuploid and sixfold higher in DNA-multiploid tumors as compared to DNA-diploid tumors (P less than 0.0001). A tetraploid DNA index was associated with a relatively low risk ratio, whereas hypertetraploid tumors were highly malignant. S-phase fraction (SPF) had prognostic value especially in DNA-diploid tumors. The simultaneous evaluation of DNA index, the number of aneuploid cell clones, and SPF gave more prognostic information than the determination of tumor ploidy alone. On the basis of these parameters we have developed a classification of tumor DNA histograms for better prognostic assessment of ovarian cancer.

Correlation between serum tumor marker levels and tumor proliferation in small cell lung cancer

We analyzed serum lactate dehydrogenase (LDH), neuron-specific enolase (NSE) and thymidine kinase (TK) levels in 22 patients with small cell lung cancer. Tumor proliferation was expressed as the proportion of S-phase cells (SPF), determined by DNA flow cytometry, from concomitantly taken biopsy samples. A positive correlation between serum NSE (r = 0.41) or LDH (r = 0.65, p = 0.05) levels and tumor SPF was noted, but was not found between serum TK levels and the SPF. The correlation between NSE and SPF was even more pronounced if only patients with extensive disease were considered (r = 0.77). The serum NSE and LDH, but not TK levels, were significantly greater in the patients with extensive disease (NSE 50.4 ng/ml, LDH 621 U/ml) compared to the patients with limited disease (NSE 21.0 ng/ml, LDH 272 U/ml, p = 0.05). Our results suggest that the combined determination of serum LDH and NSE levels gives valuable data on the primary tumor mass and its proliferative activity in small cell lung cancer.

Elevated serum HMFG antigen levels in breast and ovarian cancer patients measured with a sandwich ELISA

HMFG antigen is a tumour associated glycoprotein that has been immunohistochemically shown to be expressed by malignant cells in breast and ovarian and to a lesser degree in gastro-intestinal carcinomas. We have developed a non-isotopic sandwich ELISA for secretory HMFG antigen utilizing a polyclonal catcher and a tracer monoclonal antibody (MAb). 52/52 of healthy medical students (controls) had a serum value under 400 U/ml whereas 15/30 patients (50%) with evident ovarian cancer and 13/37 (35%) with advanced breast cancer had a value exceeding 400 U/ml. From other patients with malignant tumours 2/14 (14%) with endometrial carcinoma, 0/5 with cervical carcinoma, 0/5 with vulvar carcinoma, 1/33 with gastro-intestinal carcinoma, 0/4 with oesophageal carcinoma and 2/45 of patients with leukemia or lymphoma had an elevated serum HMFG value. Four cases of Crohn disease, 3 cases of ulcerative colitis and 2 cases of pelvic inflammatory disease all showed a serum value below 400 U/ml. Progression of ovarian cancer was accompanied by increasing serum HMFG antigen levels. The antigen detected by our assay is different from CA 125 but may be related with the tumour associated antigen CA 15-3.

Tumour DNA ploidy as an independent prognostic factor in breast cancer

We determined nuclear DNA content from 308 archival paraffin-embedded malignant breast tumours and evaluated the survival of the patients by univariate and multivariate statistical analyses. The overall 8-year survival rate of stage I-III breast cancer patients was 74.3% in DNA-diploid and 51.2% in DNA-aneuploid tumours (P less than 0.0001). DNA ploidy had prognostic significance in both node-negative and node-positive breast cancer, primarily in cases with steroid receptor-positive tumours. In a Cox multivariate analysis DNA ploidy (P = 0.001), primary tumour size (P = 0.0007), nodal status (P = 0.04) and the content of progesterone receptors (P = 0.0008) emerged as significant independent prognostic factors, whereas oestrogen receptor status, age and menopausal status of the patients had no significant independent prognostic value. If the histological grade of ductal carcinomas was also included in the Cox model, both grade and DNA ploidy had independent prognostic effect. In conclusion, our results indicate that the analysis of DNA ploidy is a useful adjunct in the assessment of prognosis for breast cancer patients.

Nuclear DNA content of non-endemic Burkitt's lymphoma

The nuclear DNA content of 26 non-endemic Burkitt's lymphomas was studied by flow cytometry. Eighteen of the tumours showed a pattern characteristic for diploid chromosome distribution, while eight of the tumours were aneuploid. Six of the aneuploid tumours showed an almost diploid, aneuploid DNA index, while two were tetraploid tumours. Patients with aneuploid tumours had a significantly worse prognosis (p less than 0.005) than those with diploid tumours. One of the aneuploid tumours was positive for Epstein-Barr virus DNA.

Increased serum placental-like alkaline phosphatase activity in smokers originates from the lungs

To study the origin of increased serum placental-like alkaline phosphatase (PLAP-like) activity in smokers, heat stable alkaline phosphatase activity was assayed from serum and bronchoalveolar lavage (BAL) fluid in 83 smoking and non-smoking patients. PLAP-like activity was increased in about 80% of the smokers, independently of the underlying lung disease. Isoenzyme activities in BAL fluid correlated (r = 0.631, p less than 0.001) with serum values. When adjusted for the albumin concentration, mean PLAP-like activity in BAL fluid was almost 1000-fold higher than that in serum, suggesting local synthesis of PLAP-like isoenzymes in the lungs. Although a direct dose-response effect was not observed, the values in serum and in BAL fluid tended to be higher in patients smoking over 10 cigarettes daily as compared to patients smoking less. In ex-smokers the results indicated that PLAP-like activity decreased to the level observed in non-smokers within 5 years after cessation of smoking. PLAP activity was L-leucine sensitive compatible with the Nagao-variant type of PLAP in almost all cases. In three patients the activity was due to the L-leucine resistant (true placental) isoenzyme.

Aneuploid DNA content and high S-phase fraction of tumour cells are related to poor prognosis in patients with primary breast cancer

The prognostic impact of DNA content and S-phase fraction (SPF) of tumour cells was studied in 93 patients with primary breast cancer. Aneuploid DNA content and high SPF were clearly associated with poor differentiation state of tumours and absence of steroid, especially progesterone receptors. Aneuploidy and high SPF tended to become more common with increasing primary tumour size, with more extensive nodal involvement and with more advanced stage of the cancer. Patients with diploid tumours had a slightly longer disease-free interval and survival than those with aneuploid tumours, whereas below median SPF as compared to above median SPF was associated with significantly longer (P less than 0.01) relapse-free interval and survival in patients with stage II-III cancer. We conclude that the DNA analysis of tumour cells is a promising method for the estimation of prognosis in breast cancer patients.