The utility of sentinel lymph node biopsy in head and neck melanoma in the pediatric population

Intraoperative lymph node mapping and sentinel lymph node biopsy have proven beneficial techniques in staging adult patients with melanoma of the head and neck, where there is great variability in lymphatic drainage. This technique has also been applied to pediatric patients with truncal cutaneous melanomas in an effort to determine nodal status without the morbidity associated with complete lymph node dissection. Nevertheless, the utility of sentinel lymph node biopsy in head and neck melanoma in the pediatric population has not been established. The objective of the authors' study was to determine the clinical utility of intraoperative lymph node mapping and sentinel lymph node biopsy of head and neck melanoma in the pediatric population. The authors reviewed the records of seven pediatric patients with head and neck melanoma or borderline melanocytic proliferations of unknown biologic potential who underwent intraoperative lymph node mapping and sentinel lymph node biopsy between 1998 and 2001. All sentinel lymph node specimens were examined by a melanoma dermatopathologist for the presence of metastatic melanoma. The mean operative time for each case was 3 hours, 8 minutes (range, 2 hours, 15 minutes to 3 hours, 50 minutes). All seven pediatric patients who underwent extirpation of a primary head and neck melanoma and preoperative lymphoscintigraphy had unique and identifiable basins of drainage to regional nodal groups. Four of seven patients had at least one positive sentinel lymph node. Overall, five of 19 sentinel nodes (26 percent) resected had evidence of metastatic melanoma. Of the patients with positive sentinel lymph nodes, two of the primary lesions were diagnosed as melanoma while two were initially considered atypical melanocytic proliferations of uncertain biologic potential with melanoma in the differential diagnosis. Sentinel lymph nodes in pediatric patients with melanoma of the head and neck can be successfully mapped and biopsied, as in adult patients. In addition, this procedure can provide critical diagnostic information for those pediatric patients with diagnostically challenging, controversial, or borderline melanocytic lesions.     

Further testing of morphometric grading in T(A,1) urothelial carcinomas of the urinary bladder and the additional value of p53 immunoquantitation

OBJECTIVE: To analyze the value for grading of a previously developed quantitative morphometric/cytometric multivariate grading model (consisting of the mean nuclear area of the 10 largest nuclei (MNA-10, mitotic activity index = MAI and Ki-67 area% = Ki-67) in two new independent test sets of urothelial carcinomas (UCs) of the urinary bladder and to evaluate the additional value of p53 area% (p53) in this model. STUDY DESIGN: Ki-67 immunoquantitation, morphometric MAI and MNA-10 assessments using a previously described, strict protocol and matching of the resulting morphometric grade with subjective grade in two test sets of 154 T(A,1) UCs of the bladder (consensus grade between two independent observers). Further testing of this morphometric grading model was performed in 57 cases that lacked initial interobserver agreement on grade. Single and multivariate analysis of all features (including p53) was performed. RESULTS: With the previously developed morphometric/cytometric grading model, 93% (grade 1 vs. 2) and 91% (grade 2 vs. 3) of the consensus cases were correctly classified. These percentages were very similar to previous results, suggesting that the model is robust. Of the 57 cases that lacked initial interobserver agreement on grade, 53/57 (93%) were classified unambiguously as grade 1, 2 or 3 with the quantitative morphometric/ cytometric grading model. In the exploratory analysis, p53 was significant but with more overlap than the other features had. In multivariate analysis p53 did not improve the overall classification result of the original morphometric/cytometric model. CONCLUSION: The value of MNA-10, MAI and Ki-67 for grading in T(A,1) urothelial carcinomas of the urinary bladder was confirmed. p53 Did not improve overall grading classification of this combination.     

Preliminary study on oncogene product immunohistochemistry (c-erbB-2, c-myc, ras p21, EGFR) in breast pathology.

The expression of oncogene products related to cell growth (c-erbB-2, c-myc, ras p21, EGFR) was investigated in benign (15 cases) and malignant breast lesions (20 cases) by means of immunohistochemistry using the avidin-biotin-peroxidase technique with polyclonal and monoclonal antibodies. The aim of this study was to evaluate the relationship between the staining positivity and various morphological and biological features, such as tumour type, grading, hormone receptor status and cell kinetic parameters. In benign breast lesions, as expected, the kinetic parameters were low, both for Ki-67 and LI. All the specimens showed a diploid condition (the DI being equal to 1) and we found a limited degree of immunoreactivity for all the growth factors and oncogene products. In breast cancer we studied the distribution of immunohistochemical positivity for EGFR, c-erbB-2, c-myc, ras p21 and Ki-67, which was related to age, nodal status, ER and PgR receptor status, LI, DI and histopathological grading. A significant positive correlation was found both between ras p21 expression and nodal status and ER-ICA positivity. We observed a strong correlation between LI and Ki-67 and an inverse relation between Ki-67 and ER expression. These findings suggest the importance of studying the relationship between prognostic factors which may provide preoperative prediction in the biological behaviour of breast cancer, not only on biopsy specimens, but also on fine needle aspirates.     

Androgen Receptor (AR), E-Cadherin,and Ki-67 as Emerging Targets and Novel Prognostic Markers in Triple-Negative Breast Cancer (TNBC) Patients

BackgroundTNBC is an aggressive subset of breast cancer (BC) without specific target therapy.MethodsThis observational, retrospective study included 45 cases of TNBC. The aim of this study was to evaluate the expression of the AR, E-cadherin and Ki-67 in relation to histological type, time to relapse and overall survival (OS). Immunohistochemistry (IHC) was carried out on formalin-fixed paraffin-embedded tumor samples obtained from patients defined TNBC.ResultsThe AR was positive (IHC >10%) in 26.6%. E-cadherin (CDH1) expression was considered positive if the score was ≥ 2. This expression was negative in 53.3% cases. The Ki-67 index was ≥ 20% in 37.7%. Univariate analyses showed that AR, CDH1 and Ki-67 are significantly associated with OS. Multivariate analysis showed that AR and Ki-67 expression are independent variables associated with OS. The statistical analysis showed that patients with AR negative and Ki-67 positive expression have a significant correlation with poor outcome.ConclusionsOur data suggest that the combination of AR and E-cadherin expression as well as Ki-67 status might be useful prognostic markers in TNBC. Hence, these molecular determinants could play an interesting role to classify subgroups of TNBC.     

Assessment of Ki-67 as a potential biomarker in patients with breast cancer

Breast cancer is the most common cancer in females, it accounts for one third of all malignancies affecting women. Appropriate biomarkers play significant role in predicting the prognosis and decide the specific therapy to each patient. In this study we aimed at evaluating the value of Ki-67 as a prognostic marker in breast cancer patients and to analyze the associations between Ki-67 and their clinicopathological parameters. This study included 92 patients with developed non metastatic breast cancer and 10 women had benign breast tumor served as controls. We measured the serum level by ELISA technique and tissue expression of Ki-67 by immunohistochemical technique. Our results showed that there were no statistically significant differences in serum Ki-67 levels between the two studied groups. As for Ki-67expression in breast cancer cells, the score increases with increase of tumor size, grade, premenopausal, Ki-67 expression in estrogen and progesterone receptor positive tumors showed lower values than estrogen and progesterone negative tumors, while higher Ki-67 expression was more frequently associated with HER2-positive. In conclusion; our study supports the finding that tissue Ki-67 expression may add prognostic information to that obtained from classical prognostic factors and can provide data of significant value to other important prognostic indicators such as pathological grading, and axillary lymph node involvement.     

胃癌组织中Tenascin、MVD、Ki-67的表达及其临床意义

目的：探讨胃癌组织中Tenascin蛋白、微血管密度（microvascular density,MVD）、Ki-67的表达及其与临床病理特征的关系。方法：采用免疫组化Elivision法检测70例胃癌组织和20例癌旁正常组织中Tenascin、CD34和Ki-67的表达。结果：①正常胃黏膜上皮Tenascin阴性,胃癌中的Tenascin主要表达于肿瘤相关纤维母细胞的胞质中,且与胃癌的Lauren分型、分化程度、临床分期、淋巴结转移显著相关（P〈0．05）;②胃癌中MVD和Ki-67-LI（标记指数）均高于正常胃黏膜（P〈0．001）,且均与胃癌的临床分期、浸润深度、淋巴结转移显著相关（P〈0．05）;结论：胃癌组织中Tenascin可抑制胃癌的演进,MVD及Ki-67可作为胃癌患者预后的预测指标,联合检测胃癌组织Tenascin、MVD、Ki-67的表达情况,对于进一步了解胃癌的生物学行为和判断预后具有一定的临床价值与意义。     

Evaluation of Tumor Cell Proliferation by Ki-67 Expression and Mitotic Count in Lymph Node Metastases from Breast Cancer

Few studies have addressed the risk of recurrence by assessing proliferation markers in lymph node metastasis from breast cancer. Here, we aimed to examine Ki-67 expression and mitotic count in lymph nodes in comparison with primary tumors. A cohort of node positive breast cancer (n = 168) was studied as a part of the prospective Norwegian Breast Cancer Screening Program (1996–2009). The percentage of Ki-67 positivity was counted per 500 tumor cells in hot-spot areas (x630). Mitotic count was conducted in the most cellular and mitotic active areas in 10 high power fields (x400). Our results showed that Ki-67 and mitotic count were significantly correlated between primary tumor and lymph nodes (Spearman`s correlation 0. 56 and 0.46, respectively) and were associated with most of the histologic features of the primary tumor. Univariate survival analysis (log-rank test) showed that high Ki-67 and mitotic count in the primary tumor and lymph node metastasis significantly predicted risk of recurrence. In multivariate analysis, mitotic count in the lymph node metastasis was an independent predictor of tumor recurrence. In conclusion, proliferation markers in lymph node metastases significantly predicted disease free survival in node positive breast cancer.     

Prognostic biomarkers in renal cell carcinoma: relevance of DNA ploidy in predicting disease-related survival

OBJECTIVE: To investigate the prognostic value of DNA ploidy, Ki-67 index and p53 expression in relation to disease-related survival in a consecutive series of patients with renal cell carcinoma (RCC). MATERIAL AND METHODS: The study group consisted of 64 RCC patients treated by radical nephrectomy. Histological type, pathological staging and nuclear anaplasia were assessed according to the WHO classification, TNM system and Fuhrman grading criteria, respectively. Ploidy was determined by DNA flow cytometry using two sampling methods (frozen vs paraffin-embedded tissue). Ki-67 and p53 were evaluated by immunohistochemistry techniques using two cutoff points (10% vs mean value) for staining interpretation. Kaplan-Meier and Cox regression analyses were used for prognostic evaluation. RESULTS: Thirty-one tumors (48.4%) showed DNA diploidy and 33 (51.6%) were DNA aneuploid. Concordance between both ploidy measurement methods was found in 85.5% of cases (p=0.0455). The mean values for Ki-67 and p53 immunostaining were 3.65% (0-23.5%) and 5.90% (0-55.9%), respectively. DNA ploidy significantly correlated with staging, tumor size (pT), nuclear grading, and Ki-67 (mean value cutoff). Ki-67 (10% cutoff) correlated with staging and pT, while p53 (mean value cutoff) was associated with Ki-67 (mean value cutoff). There were significant differences between survival curves for pathological stage, pT, nuclear grade, ploidy, Ki-67 (both cutoffs), and p53 (10% cutoff). By univariate regression analysis, stage III and stage IV, pT3, aneuploidy, high Ki-67 (both cutoffs), and p53 overexpression (10% cutoff) showed significant correlations with worse disease-related survival. In addition, DNA aneuploidy significantly correlated with poor prognosis within stages I/II (p=0.0355) and stages III/IV (p=0.0138) of the disease. CONCLUSION: The results indicate that DNA ploidy has relevant prognostic value in RCC, adding useful information to the classic histopathological indicators of clinical outcome.     

Combined smooth muscle and melanocytic differentiation in lymphangioleiomyomatosis.

Pulmonary lymphangioleiomyomatosis (LAM) is characterized by abnormal proliferation of immature-looking smooth muscle (SM)-like cells (LAM cells), leading to lung destruction and cyst formation. In addition to expressing some SM markers, scattered LAM cells express the melanocytic maker gp100, which is recognized by antibody HMB45, suggesting that at least a few LAM cells may have melanocytic differentiation. Here we immunostained 26 LAM samples for several melanocyte-related proteins. These studies showed that all LAM cells express tetraspanin CD63, a melanoma-associated protein that belongs to the transmembrane 4 superfamily. The majority of LAM cells also immunoreacted with PNL2, an antibody against a yet uncharacterized melanocytic antigen. Furthermore, we examined the co-expression of PNL2 and Ki-67, an indicator of cell proliferation, and found that PNL2-positive LAM cells showed a significantly lower proliferation rate compared with their negative counterparts. Our findings shed new light on the nature of the LAM cells by demonstrating their combined SM and melanocytic differentiation and the existence of subpopulations with different proliferative potential. Furthermore, these studies provided two new antibodies useful in the diagnosis of LAM.     

Ki-67 immunostaining and stereologic estimation of nuclear volume in melanocytic skin tumors

OBJECTIVE: To investigate the proliferative activity and mean nuclear volume (MNV) of melanocytic skin tumors. STUDY DESIGN: Proliferative activity, assessed by immunostaining for the Ki-67 monoclonal antibody (reactive with all actively cycling cells), and MNV, estimated by means of a stereologic method, were determined in 60 cutaneous melanocytic tumors, including 28 primary malignant melanomas (PMM), 13 compound nevi (CN), 11 dysplastic nevi and 8 metastatic malignant melanomas. RESULTS: Both MNV and Ki-67 expression differed significantly between CN and other melanocytic tumors and showed a good correlation with Clark's level (a well-established prognostic parameter in PMM). CONCLUSION: The association of proliferative activity and quantitative nuclear features may be helpful in the interpretation of the degree of malignancy in melanocytic skin tumors.     

Preoperative Prediction of Ki-67 Labeling Index By Three-dimensional CT Image Parameters for Differential Diagnosis Of Ground-Glass Opacity (GGO)

The aim of this study was to predict Ki-67 labeling index (LI) preoperatively by three-dimensional (3D) CT image parameters for pathologic assessment of GGO nodules. Diameter, total volume (TV), the maximum CT number (MAX), average CT number (AVG) and standard deviation of CT number within the whole GGO nodule (STD) were measured by 3D CT workstation. By detection of immunohistochemistry and Image Software Pro Plus 6.0, different Ki-67 LI were measured and statistically analyzed among preinvasive adenocarcinoma (PIA), minimally invasive adenocarcinoma (MIA) and invasive adenocarcinoma (IAC). Receiver operating characteristic (ROC) curve, Spearman correlation analysis and multiple linear regression analysis with cross-validation were performed to further research a quantitative correlation between Ki-67 labeling index and radiological parameters. Diameter, TV, MAX, AVG and STD increased along with PIA, MIA and IAC significantly and consecutively. In the multiple linear regression model by a stepwise way, we obtained an equation: prediction of Ki-67 LI=0.022*STD+0.001* TV+2.137 (R=0.595, R’s square=0.354, p<0.001), which can predict Ki-67 LI as a proliferative marker preoperatively. Diameter, TV, MAX, AVG and STD could discriminate pathologic categories of GGO nodules significantly. Ki-67 LI of early lung adenocarcinoma presenting GGO can be predicted by radiologic parameters based on 3D CT for differential diagnosis.     

Host Resistance in Relation to Survival in Breast Cancer

The degree of lymphocytic infiltration in and around breast tumours together with sinus histiocytosis and follicular hyperplasia in regional lymph nodes has been studied in 310 cases of breast cancer treated with standard radical mastectomy. The presence of these features was regarded as evidence of host resistance against the tumour and made possible the division of patients into three classes—no or poor reaction, good reaction, and strong reaction. The grading was shown to have a close correlation with prognosis. The relationship between host defensive factor grading and malignancy, nodal metastases, and survival was also examined. The results support the hypothesis that prognosis in breast cancer is closely related to a histological picture of cell-mediated immunity against the tumour.     

Activation of the flavoprotein domain of gp91phox upon interaction with N-terminal p67phox (1-210) and the Rac complex

A series of truncated forms of His(6)-tagged gp91phox were expressed, solubilized, and purified in the presence of 30 microM FAD. The truncated gp91phox with the longest sequence in the C-terminal region (221-570) (gp91C) showed the highest activity (turnover rate, 0.92) for NADPH diaphorase in the presence of either 0.3% Triton X-100 or 0.5% Genapol X-80. Activity was not inhibited by superoxide dismutase but was blocked by an inhibitor of the respiratory burst oxidase, diphenylene iodonium. The flavinated gp91C contained approximately 0.9 mol of FAD/mol of protein (MW 46 kDa) and 12% alpha-helix content. In the absence of p47phox, p67phox showed considerable activation of gp91C in the presence of Rac. Carboxyl-terminal truncated p67phox (1-210) (p67N), which is the minimal active fragment, was fused with Rac or Q61LRac. The fusion protein p67N-Rac (or p67N-Q61LRac) showed a 2-fold higher stimulatory effect on NBT reductase activity of gp91C than the combination of the individual cytosolic p67N and Rac proteins. In contrast, Rac-p67N, a fusion with the opposite orientation, showed a smaller significant effect on the enzyme activity. The EC(50) values for p67phox, p67N, p67N-Rac, and Rac-p67N were 8.00. 4.35, 2.56, and 15.2 microM, respectively, while the K(m) value for NADPH in the presence and absence of the cytosolic components was almost the same (40-55 microM). In the presence of Rac, p67N or p67phox bound to gp91C with a molar ratio of approximately 1:1 but neither p67N nor Rac alone showed significant binding.     

磁共振成像表观扩散系数与乳腺浸润性导管癌组织学分级及预后指标的相关性研究

目的:探讨磁共振成像(MRI)表观扩散系数(ADC)与乳腺浸润性导管癌组织学分级及其预后指标的相关性。方法:收集2016年5月至2017年5月于我院就诊的并经手术病理确诊为乳腺浸润性导管癌的患者112例作为研究对象,选取患者乳腺癌组织样本作为病例组,同时选取患者对侧正常乳腺组织样本作为对照组,所有患者均行常规MRI和磁共振扩散加权成像(DW-MRI)检查,分别测量两组样本的ADC值,比较不同乳腺浸润性导管癌组织学分级与正常乳腺组织的ADC值,分析乳腺浸润性导管癌组织的ADC值与肿瘤直径大小、淋巴结转移状态、有无远处转移及雌激素受体(ER)、孕激素受体(PR)和Ki-67表达的关系,并分析ADC值与组织学分级及预后指标的相关性。结果:乳腺浸润性导管癌病理分级I级的ADC值低于对照组,病理分级II级的ADC值低于病理分级I级及对照组,病理分级III级的ADC值低于病理分级II级、I级及对照组,差异均具有统计学意义(P0.05)。乳腺浸润性导管癌患者中,肿块直径2 cm、无淋巴结转移、ER阴性、PR阴性、Ki-67阴性患者的平均ADC值均高于肿块直径≥2 cm、有淋巴结转移、ER阳性、PR阳性、Ki-67阳性患者,差异均具有统计学意义(P0.05);而有无远处转移患者之间比较差异无统计学意义(P0.05)。经Spearman秩相关分析结果显示,乳腺浸润性导管癌患者的ADC值与病理组织学分级呈现负相关关系(rs=-0.716,P=0.000);与肿块直径大小、有无淋巴结转移及ER、PR、Ki-67的表达均呈负相关(rs=-0.316、-0.545、-0.667、-0.598、-0.443,P均0.05),与有无远处转移无相关性(rs=0.091,P=0.887)。结论:乳腺浸润性导管癌的ADC值与癌组织学分级和预后相关指标存在一定相关性,可作为一种临床诊断和判断预后的重要指标,具有重要临床价值。     

Immunohistochemical evaluation of proliferative activity (Ki-67 index) in different histological types of cutaneous basal cell carcinoma

Evaluation of tumor cell proliferation status belongs to the basic prognostic indicators in a routine biopsy report. In cutaneous basal cell carcinoma (BCC), however, there are discrepancies about a true prognostic significance of this histopathological parameter. The aim of this study was to assess a proliferative activity (Ki-67 index) in BCCs of the skin. Biopsy specimens from 80 cutaneous BCCs (63 primary, 17 recurrent) of different histological types from 75 subjects (34 men, 41 women) were enrolled into this study. All samples were immunohistochemically stained by antibody against Ki-67 antigen (DAKO, clone MIB-1, dilution 1:100). For the statistical analysis, χ ² test was employed. We found a striking percentage variability of nuclear Ki-67 expression in individual tumors (range 2–70%). Mean value of Ki-67 index was 27.4% (in primary tumors 28.1 %, in recurrent lesions 25.6%). The highest Ki-67 expression occurred in infiltrative BCCs (average 38.1%), morpheaform BCCs (average 37.0%), and superficial BCCs (average 35.7%), the lowest expression was recorded in nodular BCCs (average 21.7%) and BCCs with adnexal (trichoepithelial) differentiation (18.6%). There were not persuasive and statistically significant quantitative differences in proliferation activity of tumor cells between the individual histological BCC types, as well as between primary and recurrent lesions. A distribution of Ki-67 positive cells in tumor nests was mostly irregular and areas with a high number of Ki-67 labeled cells often occurred adjacent to areas with a lower number of cells expressing this marker. Because of a marked Ki-67 staining variability, we can conclude that the simple quantification of BCC proliferation activity alone may not be sufficient for the prediction of further biological behavior, evolution and clinical outcome of this malignancy.     

DNA ploidy, Ki-67 and p53 as indicators of lymph node metastasis in early gastric carcinoma

OBJECTIVE: To perform flow cytometric and immunohistochemical analysis of early gastric carcinoma in order to investigate the clinical value of DNA ploidy, Ki-67 and p53 as indicators of lymph node metastasis. STUDY DESIGN: We studied 108 cases of surgically resected early gastric carcinoma, which comprised 21 cases showing positive lymph node metastasis (group A) and 87 cases showing negative lymph node metastasis (group B). RESULTS: Aneuploidy was seen in 16 cases (76.2%) in group A in contrast to 10 cases (11.5%) in group B (P = .0029). The mean value of the Ki-67 labeling rate in all cases was 21.9%, and 15 cases (79.0%) showed a Ki-67 labeling rate of more than 21.9% in group A, while they numbered 31 (37.4%) in group B (P = .0016). Cases with cell positive for p53 protein numbered 15 (75%) in group A, while they numbered 38 (46%) in group B (P = .0460). CONCLUSION: DNA aneuploidy, a high labeling rate of Ki-67 and overexpression of p53 are all useful indicators of lymph node metastasis in patients with early gastric carcinoma.     

Measurement of cell proliferation in gastric carcinoma: comparative analysis of Ki-67 and proliferative cell nuclear antigen (PCNA)

Summary Immunostaining to identify nuclear antigens expressed throughout the cell cycle provides a convenient way of assessing proliferating kinetics in tumours. We studied proliferation activity of gastric carcinomas by Ki-67 and PCNA immunostaining and the two methods were compared. The mode of tissue preparation differed, fresh frozen for Ki-67 and formalin-fixed paraffin-embedded for PCNA. Immunostaining with avidin-biotin was used in both. The labelling index (LI) and a semi-quantitative grading of cell proliferation were assessed in both markers. Significant correlation was shown between LI and grading with either Ki-67 and PCNA. However, no correlation was found between PCNA and Ki-67. This lack of relationship between the two markers may be attributed to a number of factors. 1. The most likely is the marked inter- and intra-tumour heterogeneity of gastric carcinomas reflected in high standard deviation values. 2. Preparation of tissue and small size sampling with Ki-67. 3. Long life of PCNA leading to detection of cells that have recently left the cell cycle. 4. One may be observing deregulated expression of DNA as seen in certain tumours. PCNA offers the advantage of being applicable to archival material.     

PCNA Ki-67 dissociation in childhood acute lymphoblastic leukaemia. An Immunofluorescent Laser Confocal Scanning Microscopical study.

Cell proliferation rates of diagnostic marrow aspirate cells of 21 children with Acute Lymphoblastic Leukaemia and 16 controls were compared using immunocytochemical labelling of PCNA and Ki-67 antigen as assessed by Confocal Laser Scanning Microscopy. The results showed an unexpected, highly significant degree of dissociation between PCNA and Ki-67 expression in ALL blasts. The PCNA labelling indices of ALL patients were significantly increased (mean 44, range 24-77) compared with normal reactive marrow cells (mean 13.8, range 4-26) (p<0.000001, Mann Whitney U two tailed test), suggesting an abnormal commitment to proliferation. Ki-67 expression was raised to a lesser extent in ALL cells (mean 14.8, range 1.2-35) when compared to non-malignant proliferations (mean 6.6, range 1.7-25) (p < 0.02). PCNA/Ki-67 LI ratios in ALL (mean 7, range 1.1-35) were higher than in controls (mean 2.7, range 1.04-6.5, p<0.09). As cell proliferation rates actually achieved in the bone marrow do not differ as strongly as suggested by the extreme difference in PCNA labelling, a pathological dissociation of PCNA / Ki-67 expression exists, suggesting immortalisation.