Heterogeneity of breast carcinomas determined by flow cytometric analysis

Intratumoral DNA content heterogeneity in breast carcinomas demonstrated by core punch tissue sampling and flow cytometry

Further to advancements in instrumentation and fluorescent dye technologies, there has been a resurgence of interest in the flow cytometric assay of formalin-fixed, paraffin-embedded specimens. Here we present a novel, simple and effective alternative to whole block sectioning that allows selective multisampling of tissues within a specimen block and the investigation of intratumoral heterogeneity. Formalin-fixed, paraffin-embedded breast carcinoma specimens were core-punched using 1.0 mm diameter needles and assayed by flow cytometry using a modified Hedley method. Intratumoral heterogeneity for DNA index and per cent S-phase fraction was detected in 10 of 23 (44%) and 11 of 23 (47%) specimens respectively. Macro-level genomic heterogeneity is common in breast cancer even within a single surgical specimen block. Studies investigating the relationship of DNA content heterogeneity to other markers of genomic instability such as mutations, deletions, insertions and translocations are warranted.

Allelotype analysis of flow-sorted breast cancer cells demonstrates genetically related diploid and aneuploid subpopulations in primary tumors and lymph node metastases

Flow cytometric DNA content measurements have demonstrated extensive DNA ploidy heterogeneity in primary breast carcinomas. However, little is known at the molecular level about the clonal relationship between these tumor cell subpopulations, or about the molecular genetic changes associated with aneuploidization. We have used flow cytometric cell sorting to dissect some of this complexity by isolating clonal subpopulations in breast carcinomas for comparative molecular genetic analysis. Clonal subpopulations were isolated from 12 primary breast carcinomas and 5 lymph node metastases from 4 cases based on DNA content and cytokeratin 8/18 labeling. DNA from these clones was screened for allelic imbalances with 92 polymorphic microsatellite markers mapped to 39 different chromosome arms. Diploid and aneuploid populations were concurrently present in 11 out of 12 primary tumors. The DNA ploidy status of primary tumors was identical to that of the related lymph node metastases. Allelic imbalance was present in 10 out of 11 diploid clones (mean, 3.4 +/- 4.2). All allelic imbalances observed in the diploid clones recurred in the cognate aneuploid clones, but were, in the latter, accompanied by additional allelic imbalances at other loci and/or chromosome arms (mean, 10.9 +/- 5.8). In only two of the four metastatic cases did the allelotypes of metastatic clones show small differences relative to their cognate primary tumors. The primary diploid tumor clone recurred in all lymph node metastases. This study indicates that the majority of allelic imbalances in breast carcinomas are established during generation of DNA ploidy diversity. Recurrence of the allelic imbalances in diploid clones in the aneuploid clones suggests linear tumor progression, whereas the simultaneous presence of early diploid and advanced aneuploid clones in both primary and metastatic tumor sites suggests that acquisition of metastatic propensity can be an early event in the genetic progression of breast cancer.

Quantitative changes in cytological molecular markers during primary medical treatment of breast cancer: a pilot study

AIM

To quantify the changes in biological molecular markers during primary medical treatment in patients with operable breast cancer and to assess their possible relationship with response to treatment.

METHODS

The treatment group consisted of 31 patients with operable breast carcinomas, median age 57 years (range 41-67), treated with four 3-weekly cycles of chemotherapy with Mitoxantrone, methotrexate (+/- mitomycin C), and tamoxifen before surgery. Fine needle aspiration (FNA) was used to obtain samples from patients prior to and at 10 or 21 days post-treatment. The following molecular markers were assessed: estrogen receptor (ER), progesterone receptor (PgR), p53, Bcl-2, and Ki67 measured by immunocytochemistry, and ploidy and S-phase fraction (SPF) by flow cytometry. To evaluate the reproducibility of the technique, repeat FNA was performed in a separate non-treatment control group of 20 patients and the same molecular markers assessed, two weeks after the first sample with no intervening treatment.

RESULTS

The non-treatment control group showed a high reproducibility for the measurement of molecular markers from repeat FNA. In the treatment group there was a non-significant reduction in SPF and a significant reduction (p = 0.005) in Ki67. Patients who responded to neoadjuvant therapy were more likely to have a reduction in these two markers than those who failed to respond. Similarly, a reduction in ER scores was observed between the first and second samples (p = 0.04). For PgR, the change between the first and second samples was not significant although there was a significant difference between responders and non-responders (p = 0.03). All nine patients with an increase in PgR were responders. No significant changes in p53 or Bcl-2 were observed during treatment.

CONCLUSION

Molecular markers can be adequately measured from FNA samples prior to and during neoadjuvant therapy. Changes in cellular proliferation and hormone receptors have been shown that may be related to tumour response. These relationships should be assessed in a larger cohort of patients.

Intratumoral heterogeneity in primary breast carcinoma: study of concurrent parameters

BACKGROUND AND OBJECTIVE

Intratumoral heterogeneity for prognostic factors (ploidy, proliferation, hormone receptor positivity) has been demonstrated in primary breast carcinoma by both flow cytometric and image analysis methods. Previously, heterogeneity in tumors had been demonstrated for only singular parameters. Our objective, using maps of tumors in which discrete regions can be analyzed simultaneously for DNA index (DI) and proliferative activity, was to demonstrate heterogeneity with respect to two parameters and to determine whether any interparametric relationships existed.

METHODS

We analyzed 25 cases of archived, paraffin-embedded breast carcinoma (ductal) for Feulgen stain DNA analysis and MIB-1 immunohistochemistry using the CAS 200 Image Cytometer. For each tumor, four discrete regions were analyzed including tumor-host tissue interface sectors.

RESULTS

Of 25 cases, 19 (76%) were homogeneously diploid or near-diploid aneuploid, and 6 (24%) were heterogeneous. Within the heterogeneous group, all cases had at least one diploid and one or more aneuploid populations from separate discrete regions. Five of six DI heterogeneous tumors displayed diploid values for the overall measurements of the respective tumors, based on analysis of 200 or more nuclei. Eight of 25 cases (32%) showed significant measurable variation for MIB-1 proliferative activity in various sectors of tumor. All the MIB-1 heterogeneous tumors, with one exception, were homogeneously diploid.

CONCLUSIONS

These findings demonstrate that (1) heterogeneity is present with respect to DI and proliferative activity in breast carcinoma and is relatively common, (2) tumors homogeneous for one parameter may be heterogeneous for another, and (3) heterogeneity for proliferative activity is more common in homogeneously diploid tumors than in heterogeneous/aneuploid tumors.

Tumour heterogeneity of DNA cell cycle variables in breast cancer measured by flow cytometry

AIM/BACKGROUND

Conflicting results have been reported concerning the prognostic value of DNA flow cytometric variables (DNA ploidy, DNA index, %S phase fraction) in breast cancer. Selection bias and differences in treatment may have contributed to these conflicting prognostic results. Differences in tissue processing, the number of nuclei measured, DNA histogram/cell cycle analysis, and intra-tumour heterogeneity may also have played a role. The aim of the present study was to assess intra-tumour heterogeneity of DNA flow cytometric variables in breast cancer.

METHODS

Fresh frozen specimens (n = 274) (0.3 x 0.3 x 0.3 cm) of 17 breast cancers and 167 slices, 50 microns thick, of 58 paraffin wax embedded blocks of 21 breast cancers were studied. All samples were prepared individually for DNA flow cytometry. DNA histograms were interpreted by semi-automated cell cycle analysis (MultiCycle) by two observers to avoid biased interpretation. An artificial averaged DNA histogram of each case was composed to simulate a sample prepared from whole tumour tissue.

RESULTS

With regard to DNA ploidy, classified as diploid or aneuploid, the fresh frozen and paraffin wax embedded breast cancers showed intra-tumour heterogeneity in 53% and 38% of cases, respectively. For fresh frozen and paraffin wax embedded material, respectively, six samples had to be measured to detect the highest DNA ploidy class in 71% and 86% of cases. Averaged DNA histograms showed a loss of DNA aneuploidy in 36% and 6% of fresh frozen and paraffin wax embedded samples, respectively. High intra-tumour heterogeneity (wide ranges) was found for the %S phase fraction. Average %S phase fraction and average aneuploid %S phase fraction had the widest ranges at 9.5-31.6% and 0.0-62.7%, respectively. There was no correlation between the number of stemlines and intra-tumour %S phase variability on the one hand and tumour size and grade on the other.

CONCLUSIONS

High intra-tumour heterogeneity for breast cancer was found for DNA ploidy, the DNA index and %S phase fraction as measured by flow cytometry, which may explain the conflicting prognostic results reported in the literature. To detect aneuploid cells, six samples may have to be prepared and measured separately. Measurement of these variables may be more reliable in paraffin wax sections because the thick slices provide a more representative sample. Prospective studies are required to determine whether the highest %S phase fraction value or the average value is more useful in the clinical context.

Intratumoral heterogeneity of DNA ploidy in breast carcinomas: a flow cytometric assessment of sampling techniques

Intratumoral heterogeneity of DNA ploidy has been identified in breast carcinomas; however, optimal sampling methods have not been determined. In this study of 28 invasive breast carcinomas measuring more than 1.4 cm in greatest dimension, two different techniques for obtaining cells for flow cytometric DNA ploidy analysis were compared. Two solid pieces of tissue were taken from opposite halves of the tumor. A third sample was obtained by scraping multiple cut surfaces of the tumor. Heterogeneity of DNA ploidy was detected in 43% of cases. Most cases demonstrating heterogeneity contained multiple aneuploid populations. However, in five cases classification of the tumors as either DNA euploid or DNA aneuploid differed among samples. A total of 39 non-diploid populations were detected in 23 of the cases. Thirty-three (85%) were detected by scraping and 35 (90%) were detected in either one or both tissue pieces. Intratumoral DNA heterogeneity emphasizes the need for adequate sampling. The scraping technique was as effective in identifying aneuploid cell populations as the combined results of the two pieces of tissue and better than sampling a single piece of tissue. Scraping also offers the advantage of tissue conservation which may be critical when various analytic studies are performed.

DNA analysis of in situ ductal carcinoma of the breast via flow cytometry

Flow cytometric (FCM) DNA analysis of 41 clinical cases of ductal carcinoma in situ (DCIS) of the breast was performed on fine-needle aspirates of unfixed, frozen tissue. Based on analysis of a single tissue sample, abnormal DNA content was found in 35 (85%) of the cases, and 15 (37%) disclosed heterogeneity. If five or more samples were analyzed, then heterogeneity was found in eight of ten cases. No conclusive correlation could be found between DNA index (DI) and histopathology. Our results on DCIS demonstrate a very high concordance with invasive breast cancer with respect to the frequency of DNA nondiploid cases, distribution of DI, occurrence of multiple clones, and S-phase fraction. This indicates that major genetic alterations and DNA heterogeneity are early events in carcinogenesis that are already established at the preinvasive stage.

Reproducibility in DNA flow cytometric analysis of breast cancer: comparison of 12 laboratories' results for 67 sample homogenates

Flow cytometric (FCM) DNA analysis yields information on ploidy status and the S-phase fraction (SPF), variables of prognostic importance in breast cancer. The clinical value of the SPF is currently being evaluated in prospective randomized trials. The widespread use of FCM DNA analysis emphasizes the importance of reproducibility (both intra- and interlaboratory). In this study, 67 nuclear suspensions of breast cancer samples were analyzed by 12 laboratories routinely performing FCM DNA analysis in breast cancer. No general guidelines were imposed; each laboratory used its own standard protocols. For DNA ploidy status (diploid vs. non-diploid), agreement was complete for 79% (53/67) of the samples, compared with 64% (43/67) of samples when tetraploidy was considered [i.e., euploid (diploid+tetraploid) vs. aneuploid (the remaining non-diploid)]. For the SPF, pairwise comparison of the results of all 12 laboratories yielded a mean Spearman's rank correlation of 0.78 (range: 0.54-0.93). For those 39 samples being categorized in low or high SPF by all laboratories, all agreed in 14 samples (36%). Similar patterns were obtained with kappa measures, agreement being good for ploidy status (diploid vs. non-diploid; overall kappa = 0.87 and 0.74 for euploid vs. aneuploid), but moderate for the SPF [overall kappa = 0.47 (for low SPF vs. high SPF vs. "no SPF reported")]. Discrepancies were chiefly attributable to differences in the categorization of the S-phase values, rather than in FCM procedures, other critical differences being in the detection and interpretation of near-diploid and small non-diploid cell populations, the definition of tetraploidy, and the choice and execution of the method used for S-phase estimation. Based on the observations of this study, detailed guidelines for FCM analysis and interpretation of data are proposed in the Appendix. Some issues remain, however, e.g., to standardize a method for S-phase calculation and tetraploid definition.

Measurement of S-phase fraction and ploidy in sequential fine-needle aspirates from primary human breast tumours treated with tamoxifen

Sequential fine-needle aspirates (FNAs) for cytodiagnosis and flow cytometry were taken from 21 patients with primary breast carcinoma at intervals ranging from 1 to 3 months after the commencement of first-line tamoxifen therapy. Nine patients achieved a sustained complete or near complete response over a 3-9 month period. The tumour cells from seven out of nine of these patients were initially aneuploid, while the remaining two patients had diploid tumours. An analysis of sequential FNAs showed that, in three out of the seven aneuploid tumours, only benign epithelial cells could be detected by cytology in the post-tamoxifen sample. In the remaining six cases, including the two diploid tumours, there was no change in ploidy but a reduction in S-phase fraction (SPF) to approximately 50% of the pretreatment level. In all cases, these changes in ploidy or SPF were seen with a mean lead time of 4 months before the tumour had reached clinical complete remission. None of these patients have relapsed after a mean follow-up period of 18 months. The tumours of 12 patients achieved no more than a temporary partial response to primary tamoxifen therapy. In seven out of eight of these cases, which were all initially aneuploid, sequential FNAs during tamoxifen therapy revealed either an increase or no change in the SPF with the tumour remaining aneuploid. In the remaining four cases the tumours were all recorded as being diploid in the pretreatment sample. However, although three of these cases had a temporary partial response to tamoxifen, an aneuploid component was picked up in repeat sequential FNAs with a mean lead time of 5 months before clinical confirmation of eventual disease progression. We conclude that changes in ploidy and SPF detected by flow cytometry may predict initial response and the likelihood of relapse of breast tumours to tamoxifen before clinical changes become evident. These data justify a larger study.

Nuclear DNA content of human breast carcinoma: a comparison of results obtained by microspectrophotometry and flow cytometry of paraffin embedded tissue

This study compares 2 techniques for estimating the nuclear DNA content of tumor cell lines: (i) static cytometry of smears taken from fresh tissue and (ii) flow cytometry of cells extracted from paraffin embedded tissue. Parallel determinations of DNA content, using both techniques, were made on samples of tissue taken from 130 female patients with breast carcinoma. Using a simple classification into diploid and non-diploid groups, the 2 techniques yielded discrepant results in 11% of cases. The most frequent causes of disagreement were (a) the inability of static cytometry to distinguish between a diploid and a near-diploid peak and (b) for flow cytometry, the difficulty of determining whether a minor peak in the tetraploid region represented the G2 peak of a diploid cell line or the G0/G1 peak of a tetraploid cell line. If it is deemed necessary to accurately assess ploidy status, flow cytometry on paraffin embedded tissue, using modern statistical programmes, would seem to be most practical for routine use, but some neoplasms, particularly those with an equivocal ploidy peak in the tetraploid range by this method, will require static cytometry to accurately assess nuclear DNA content. Using this approach, it appears that the disagreement between the 2 techniques would be less than 5%.

High levels of DNA index heterogeneity in advanced breast carcinomas. Evidence for DNA ploidy differences between lymphatic and hematogenous metastases

BACKGROUND

The aim of this study was to investigate DNA ploidy status and DNA index heterogeneity of lymphatic and hematogenous metastases of advanced breast carcinomas and the relations among the various tumor sites.

METHODS

DNA ploidy status was analyzed by flow cytometry on frozen and paraffin-embedded tissue blocks taken from primary and metastatic tumor sites in 18 patients with advanced breast cancer.

RESULTS

Presumably because of the extensive sampling, high percentages of DNA aneuploidy, DNA multiploidy, and DNA index heterogeneity were found in primary breast carcinomas as well as in lymph node and distant metastases. DNA aneuploid tumor stemlines were frequently accompanied by DNA diploid tumor stemlines. Most of the DNA tumor stemlines found in the primary tumors recurred in lymph node (55%) and distant (59%) metastases, even after 17 years of relapse-free survival. DNA tumor stemlines found in distant metastases, however, often differed from those in lymph node metastases (61%).

CONCLUSIONS

A marked DNA index heterogeneity can be found in primary and metastatic tumor sites when appropriate sampling is applied. There were no DNA ploidy subclasses, notably absent in either type of metastasis, indicating similar metastatic capacities of both DNA aneuploid and DNA diploid tumor stemlines in advanced breast carcinomas. The difference in DNA ploidy status between lymphatic and hematogenous metastases suggest that these metastases can be generated independently.

One or multiple samplings for flow cytometric DNA analyses in breast cancer-prognostic implications?

Flow cytometric assessments of DNA ploidy status and the S-phase fraction (SPF) have been shown to yield prognostic information in breast cancer. The aim of the present investigation was to elucidate the reproducibility of results with regard to tumor DNA heterogeneity, and to ascertain whether the prognostic value of DNA measurements might be enhanced by analyzing two pieces of a tumor instead of one. Agreement with regard to ploidy status (diploid versus non-diploid) was obtained in 90% of cases (71/79) when two adjacent sections of the tumor were investigated, and in 77% of cases (10/13) when four biopsies from different quadrants of the tumor specimen were investigated. The corresponding figures for agreement in SPF (divided into three categories, less than 7.0%, 7.0-11.9%, and greater than or equal to 12%) were 75% (59/79; 2-sample series) and 55% (7/13; 4-biopsy series). The main reason for variance in ploidy results was the difficulties in distinguishing near diploid cell populations. Discrepancies in SPF categories could be explained by minor fluctuations in SPF values near the cut-off levels, or by variance in ploidy status, the fraction of non-diploid nuclei, and background noise due to cell debris. There was a stepwise increase in recurrence rate (RR) among patients with increasing SPF category (RR: 20%, 41%, and 53%). Patients whose SPF categories varied, from low or intermediate in one part of the tumor to high in another, seemed to have a poor prognosis (RR = 57%).(ABSTRACT TRUNCATED AT 250 WORDS)

Regional heterogeneity in breast carcinoma: thymidine labelling index, steroid hormone receptors, DNA ploidy

We examined multiple samples of 65 primary breast carcinomas larger than 1 cm in diameter for thymidine labelling index (TLI), DNA index (DNAI, a measure of cellular DNA content by flow cytometry), and estrogen (ER) and progesterone (PgR) receptors by radioligand-binding. One or more axillary metastases were also assayed in 11 patients. Two to 15 samples were successfully assayed for TLI from 59 tumors, 2-31 samples for DNAI from 61 tumors, and 2-15 samples from 55 tumors for ER and PgR. Criteria for heterogeneity were excess inter-sample variance in comparison with intrasample variance at the p less than 0.05 level for TLI and DNAI, and variation of clinically significant magnitude in assay results for ER and PgR. Sixty-one percent of tumors were heterogeneous for TLI, 26% for DNAI, 24% for ER and 40% for PgR. High TLI disposed toward heterogeneity for TLI itself (p = 0.06), for ER (p = 0.04), and for PgR (p = 0.007). Young age favored heterogeneity for TLI (p = 0.12), ER (p = 0.002), and PgR (p = 0.04). Heterogeneity for DNAI was not related to age and TLI status but was more common in larger tumors (p = 0.08). After consideration of relationships between TLI, age, size, ER and PgR, TLI rather than age appears to be the more important determinant of heterogeneity for receptors. High TLI could lead to heterogeneity through increased numbers of cell divisions that favor emergence of variant stemlines, or by causing local vascular and humoral disparities through rapid growth. Regional heterogeneity can explain erroneous prognostic predictions in approximately 10% to 20% of breast carcinoma patients. We recommend multiple sampling of large breast carcinomas and analysis of axillary metastases for study of tumor markers.

Flow cytometric analysis of DNA stemline heterogeneity in primary and metastatic breast cancer

Flow cytometric DNA-ploidy analysis was used to investigate intratumor DNA stemline heterogeneity in primary breast carcinomas and lymph node metastases (LNM). The study was done in tumor specimens from 44 patients 35 of whom had LNM. In all, measurements were done in 214 different samples of primary tumors and 211 lymph nodes. Sixty-one percent (27/44) of the primary tumors were found to have multiple DNA aneuploid stemlines when the data of the separate samples per tumor (mean 4.9) were compared. Only five of 44 (11%) primary tumors were DNA diploid; two of these had DNA aneuploid metastases. Statistical analysis of these results indicated that, on average, four samples are needed for reliable determination of the DNA ploidy status of primary tumors by flow cytometry. In the majority of the cases (26/35), distinct tumor DNA stemlines found in LNM were also present in the primary tumor, which suggests that the generation of DNA ploidy diversity may have taken place prior to metastasis. Multiploidy was not related to tumor size but, particularly for LNM, was significantly correlated with age (r = 0.40, P = 0.02). The results of this study support the view that breast cancer is an extremely heterogeneous disease and that underestimation of this factor might account for the disagreement in literature about the prognostic value of DNA ploidy determinations.

Extended role for needle biopsy in the management of carcinoma of the breast

Treatment choice in primary breast cancer is wide and still controversial; it seems likely that the optimum treatment for individual patients could be dictated by biological indicators of tumour behaviour. If biopsy could provide prognostic information as well as detailed tissue diagnosis then definitive treatment, with or without adjuvant systemic therapy, could be planned from the outset. We studied 140 patients with a clinical diagnosis of primary breast cancer to determine how much information could be obtained from Tru-Cut needle biopsies performed at the first clinic visit. Ten patients were found to have benign disease. Of 130 carcinomas, 123 (95 per cent sensitivity) were diagnosed correctly from the needle biopsies, with seven false negative and no false positive results (100 per cent specificity). Precise histopathology was predicted in 121 (93 per cent). Grade was correctly assessed in 77 of 112 (69 per cent), but needle biopsy was not accurate for assessment of lymphatic invasion nor elastosis. Steroid hormone receptors were assayed in 59 needle biopsies, and the incidence of oestrogen receptor positivity (34, 58 per cent) was similar to the resected tumours (35, 59 per cent), but the incidence of progesterone receptor positivity (26, 44 per cent) was lower (33, 56 per cent, P less than 0.04). Immunostaining with monoclonal antibody human milk fat globule membrane was accurate in the needle biopsies. DNA analysis by flow cytometry was performed in 37 tumours and the concordance between needle biopsies and resected samples was high. Tru-Cut needle biopsy obviates open biopsy and gives reliable detailed information.

Intratumoral variations in DNA distribution patterns in mammary adenocarcinomas

Correlated flow-cytometric (FCM) and microspectrophotometric (MSP) techniques were applied to investigating whether intratumoral variations in the DNA distribution patterns of 21 primary mammary adenocarcinomas can occur. Although neoplastic cell populations with both diploid and tetraploid (i.e., euploid) distribution patterns could be found in varying proportions in some of the tumors, there was no evidence in any tumor nodule for the presence of euploid populations in one part and aneuploid populations in another. This statement was based on the results of the MSP technique, where the assessments were made on cytodiagnostically identified neoplastic cells. Also, when applying the FCM technique the statement was found to be essentially valid; only one of the tumor nodules showed a DNA distribution pattern that, by means of the criteria used in this procedure, was defined as being both euploid and aneuploid. Here, however, the technique consists of assessments made on a great number of microscopically non-identified cells. It was concluded that when conflicting reports are given from different laboratories on the prognostic value of the cytochemically assessed DNA distribution patterns in breast carcinomas, they are not likely to be attributed to intratumoral DNA heterogeneity but, rather, to differences in the methods used and in the criteria applied for the so-called ploidy assessments.

Effect of tamoxifen upon cell DNA analysis by flow cytometry in primary carcinoma of the breast

The effect of tamoxifen upon cellular DNA ploidy in carcinoma of the breast was assessed by flow cytometry (FCM), in a prospective group of 77 patients with primary operable disease. Each had a needle biopsy at the outpatient visit for diagnosis and FCM analysis, and definitive surgery was performed a median of 8 days later. Forty received tamoxifen during this period - 40 mg qds loading dose for 24 h, followed by 20 mg daily until the day of operation: 37 patients received no therapy. The DNA histogram from the needle biopsy was compared with that obtained from the resected tumour for each individual. There was little change between the pair of histograms from tumours from the untreated patients. In those who had received tamoxifen the most consistent effect was a marked reduction in the magnitude of the 'tetraploid' peak in tetraploid or near-tetraploid tumours with DNA indices 1.8-2.0. There was little change in diploid or 'other DNA-aneuploid' tumours. In tetraploid tumours (DNA index of 2.0) the percentage of nuclei in the diploid S phase was significantly related to the percentage of nuclei in the diploid G2 + M/tetraploid G1 peak (P less than 0.003, unpaired t test). These data suggest that an effect of tamoxifen can be demonstrated by FCM upon tumours exhibiting a tetraploid or near-tetraploid DNA content. It is possible that tetraploid or near-tetraploid human mammary tumours may be a distinct group of endocrine responsive tumours within the overall group of aneuploid tumours, and that the majority are probably derived from the diploid population rather than being a true aneuploid population.

Cell kinetics of histologic variants of in situ breast carcinoma

A thymidine labeling study of cell kinetics of 61 in situ breast carcinomas showed relationships between histological characteristics and kinetics. The thymidine labeling index (TLI) was significantly lower in cribriform-papillary intraductal carcinoma (median 1.30%, geometric mean 1.18%, mean 1.83 +/- 0.45%) and lobular carcinoma in situ (median 1.43%, geometric mean 1.12%, mean 1.63 +/- 0.46%) than in comedo intraductal carcinoma (median 4.40%, geometric mean 3.74%, mean 5.15 +/- 0.86%). The results for solid intraductal carcinoma, which is a less well defined and more heterogeneous entity, were intermediate (median 2.45%, geometric mean 2.40%, mean 3.32 +/- 0.80%). When invasive carcinoma was also available for kinetic study, the TLI of in situ and invasive components were usually similar (r = 0.66). The data indicate that the TLI usually does not change during the transition from in situ to invasive carcinoma. Cribriform-papillary intraductal carcinoma is a slowly proliferating entity that gives rise to slowly proliferating invasive carcinomas with relatively high levels of estrogen and progesterone receptors. Lobular carcinoma in situ similarly has low proliferative rates and gives rise to slowly proliferating invasive carcinomas. Intraductal comedocarcinoma has relatively high proliferative rates and gives rise to invasive carcinomas with high proliferative rates that often are receptor-negative. Nine of the 11 in situ carcinomas that were associated with invasive tumor and subsequent local recurrence or metastasis had TLIs above the median, and seven were comedo type with high TLIs. Our observations from thymidine labeling are consistent with a viewpoint regarding cribriform-papillary intraductal carcinoma as relatively bland, and comedo intraductal carcinoma as a distinctly more dangerous entity. Solid intraductal carcinoma seems to resemble cribriform-papillary more closely than comedo intraductal carcinoma.