BIRC5 (survivin): a pejorative prognostic marker in stage II/III breast cancer with no response to neoadjuvant chemotherapy.

PURPOSE: Neoadjuvant systemic therapy (NAC) is currently used in the treatment of stage II/III breast cancer. Pathological complete response as a surrogate endpoint for clinical outcomes is not completely validated for all subgroups of breast cancers. Therefore, there is a need for reliable predictive tests of the most effective treatment. METHODS: We used a combination of predictive clinical, pathological, and gene expression-based markers of response to NAC in a prospective phase II multicentre randomized clinical trial in breast cancer patients, with a long follow-up (8 years). This study concerned the subpopulation of 188 patients with similar levels of pathological response rates to sequential epirubicin/cyclophosphamide and docetaxel to determine predictive marker of pCR and DFS. We used a set of 45 genes selected from high throughput analysis and a standardized RT-qPCR. We analyzed the predictive markers of pathological complete response (pCR) and DFS in the overall population and DFS the subpopulation of 159 patients with no pCR. RESULTS: In the overall population, combining both clinical and genomic variables, large tumor size, low TFF1, and MYBL2 overexpression were significantly associated with pCR. T4 Stage, lymphovascular invasion, negative PR status, histological type, and high values of CCNB1 were associated with DFS. In the no pCR population, only lymphovascular invasion and high values of BIRC5 were associated with DFS. CONCLUSIONS: We confirm the importance of ER-related and proliferation genes in the prediction of pCR in NAC-treated breast cancer patients. Furthermore, we identified BIRC5 (survivin) as a main pejorative prognostic factor in patients with breast cancers with no pCR. These results also open perspective for predictive markers of new targeted therapies.

Prognostic impact of discrepant Ki67 and mitotic index on hormone receptor-positive, HER2-negative breast carcinoma.

BACKGROUND: Inconsistencies between mitotic index (MI) and Ki67 measures have been identified in many breast tumour samples. The aim of this study was to describe the prognosis of hormone receptor-positive (HR+) HER2- tumours having discrepant MI and Ki67. METHODS: We included a cohort of breast cancer patients initially treated by surgery between 2001 and 2005 in the Institut Curie. Breast cancer-specific survival (BCSS) and disease-free survival (DFS) were analysed according to three proliferation groups: high MI/high Ki67 (MI=3, Ki67>20%), low MI/low Ki67 (MI<3, Ki67⩽20%) and discrepant (high MI/low Ki67 or low MI/high Ki67). RESULTS: Among the 1430 patients, 19.6% had discrepant Ki67 and MI, 11.6% had high markers and 68.8% had low markers. The 5-year BCSS was 95.8%, 95% CI (0.93-0.98) in the discrepant group, 99.3%, 95% CI (0.993-0.999) in the low-proliferation group and 91.8%, 95% CI (0.88-0.96) in the high-proliferation group. In multivariate analysis, the survival of the discrepant group was lower than that of the low-proliferation group: BCSS hazard ratio (HR)=3.01 (1.32-6.84; P=0.008) and DFS HR=2.07, 95% CI (1.31-3.26; P=0.002). Among grade 2 tumours in multivariate analysis, DFS of the discrepant group was lower than that of the low MI/low Ki67 group: HR=1.98, 95% CI (1.14-3.46), P=0.02. Regarding BCSS, the obtained results were similar. CONCLUSION: The prognosis of patients with discrepant MI and Ki67 appears intermediate between that of low MI/low Ki67 and high MI/high Ki67 groups. These markers should be jointly analysed to clarify prognosis.

A short-term colorectal cancer sphere culture as a relevant tool for human cancer biology investigation.

BACKGROUND: Ex vivo colospheres have been previously characterised as a colorectal cancer (CRC) well-rounded multicellular model, exclusively formed by carcinoma cells, and derived from fresh CRC tissue after mechanical dissociation. The ability to form colospheres was correlated with tumour aggressiveness. Their three-dimensional conformation prompted us to further investigate their potential interest as a preclinical cancer tool. METHODS: Patient-derived CRC xenografts were used to produce numerous colospheres. Mechanism of formation was elucidated by confocal microscopy. Expression analysis of a panel of 64 selected cancer-related genes by real-time qRT-PCR and hierarchical clustering allowed comparison of colospheres with parent xenografts. In vitro and in vivo assays were performed for migration and chemosensitivity studies. RESULTS: Colospheres, formed by tissue remodelling and compaction, remained viable several weeks in floating conditions, escaping anoikis through their strong cell-cell interactions. Colospheres matched the gene expression profile of the parent xenograft tissue. Colosphere-forming cells migrated in collagen I matrix and metastasised when subrenally implanted in nude mice. Besides, the colosphere responses to 5-fluorouracil and irinotecan, two standard drugs in CRC, reproduced those of the in vivo original xenografts. CONCLUSION: Colospheres closely mimic biological characteristics of in vivo CRC tumours. Consequently, they would be relevant ex vivo CRC models.

Hemoglobin overexpression and splice signature as new features of inflammatory breast cancer?

INTRODUCTION: Inflammatory Breast Cancer (IBC) is the most aggressive form of breast carcinoma characterized by rapid onset of inflammatory signs and its molecular fingerprint has not yet been elucidated. OBJECTIVES: The objective of this study was to detect both gene expression levels and alternate RNA splice variants specific for IBC. METHODS: W e performed splice-sensitive array profiling using Affymetrix Exon Array and quantitative RT-PCR analyses in 177 IBC compared to 183 non-IBC. We also assessed the prognostic value of the identified candidate genes and splice variants. RESULTS: A 5-splice signature (HSPA8, RPL10, RPL4, DIDO1 and EVL) was able to distinguish IBC from non-IBC tumors (p<10-7). This splice signature was associated with poor metastasis-free survival in hormone receptor-negative non-IBC (p=0.02), but had no prognostic value in IBC. PAM analysis of dysregulated genes in IBC compared to non-IBC identified a 10-gene signature highly predictive of IBC phenotype and conferring a poor prognosis in non-IBC. The genes most commonly upregulated in IBC were 3 hemoglobin genes able to reliably discriminate IBC from non-IBC (p<10-4). Hb protein expression in epithelial breast tumor cells was confirmed by immunohistochemistry. CONCLUSION: IBC has a specific spliced transcript profile and is characterized by hemoglobin gene overexpression that should be investigated in further functional studies.

Detection of Epstein-Barr virus in invasive breast cancers.

BACKGROUND: Epstein-Barr virus (EBV) may be a cofactor in the development of different malignancies, including several types of carcinomas. In this study, we investigated the presence of EBV in human breast cancers. METHODS: We used tissues from 100 consecutive primary invasive breast carcinomas, as well as 30 healthy tissues adjacent to a subset of the tumors. DNA was amplified by use of the polymerase chain reaction (PCR), with the primers covering three different regions of the EBV genome. Southern blot analysis was performed by use of a labeled EBV BamHI W restriction fragment as the probe. Infected cells were identified by means of immunohistochemical staining, using monoclonal antibodies directed against the EBV nuclear protein EBNA-1. RESULTS: We were able to detect the EBV genome by PCR in 51% of the tumors, whereas, in 90% of the cases studied, the virus was not detected in healthy tissue adjacent to the tumor (P<.001). The presence of the EBV genome in breast tumors was confirmed by Southern blot analysis. The observed EBNA-1 expression was restricted to a fraction (5%-30%) of tumor epithelial cells. Moreover, no immunohistochemical staining was observed in tumors that were negative for EBV by PCR. EBV was detected more frequently in breast tumors that were hormone-receptor negative (P =.01) and those of high histologic grade (P =.03). EBV detection in primary tumors varied by nodal status (P =.01), largely because of the difference between subjects with more than three lymph nodes versus less than or equal to three lymph nodes involved (72% versus 44%). CONCLUSIONS: Our results demonstrated the presence of the EBV genome in a large subset of breast cancers. The virus was restricted to tumor cells and was more frequently associated with the most aggressive tumors. EBV may be a cofactor in the development of some breast cancers.

[Local recurrence of ductal carcinoma in situ after conservative breast surgery: mammographic appearance]. / Caractéristiques mammographiques des récidives locales des carcinomes canalaires in-situ après traitement conservateur.

OBJECTIVE: To review the mammographic features of local recurrences of DCIS treated conservatively. MATERIALS AND METHODS: Thirty-five patients treated conservatively for a DCIS have presented subsequently a local recurrence. Three patients had double metachronous and one a bi-focal recurrence. The mammographic appearances of these 39 recurrences were analyzed retrospectively and compared to initial mammograms. RESULTS: Median delay to recurrence was of 47 months (interval 8-240 months). Two-thirds of the recurrent lesions were similar to the initial presentation, of which 90% occurred at the lumpectomy site. In 18/ 35 cases (51%), an intra-ductal component was found at histological diagnosis and among these 11/18 (61%) were strictly intra-ductal. CONCLUSION: Local recurrences of DCIS are proteiform. However, the majority of which, occurring at the lumpectomy site were similar to the primary tumor, raising again the hypothesis of incomplete eradication even when the margins were considered free.

Truncation at conserved terminal regions of BRCA1 protein is associated with highly proliferating hereditary breast cancers.

The existence of two subgroups of BRCA1-associated breast cancer (BC) families has been recently posited: the first with highly proliferating tumors, and the second composed of cases with a low proliferation rate. Our aim was to test whether the proliferation rate of BRCA1-associated breast cancers was affected by the site of the germ line mutation in the BRCA1 gene. We analyzed the distribution of the mitotic index, a histoprognostic grade component shown to segregate in families, matching for germ line mutation location in a series of 28 breast cancers from 20 kindreds. We observed a prevalence of highly proliferating tumors when the mutation occurs in the two terminal conserved domains of the BRCA1 protein, ie., in the amino and carboxyl termini (P = 0.0024). Our data provide evidence for a genotype-phenotype correlation and along with their strong conservation during evolution argue for the importance of these two regions in the control of mammary cell growth.

Mutations at BRCA1: the medullary breast carcinoma revisited.

BRCA1-associated breast cancers (BRCA1-BCs) frequently harbor a high histoprognostic grade, p53 alterations, and estrogen receptor negativity. Although these parameters predict a poor outlook, the overall survival in BRCA1-BCs is equivalent to or even better than that in sporadic cases. These features are reminiscent of what is observed for breast carcinoma of the medullary type, a high-grade tumor with a particular favorable course. To explore a possible relationship between this phenotype and BRCA1 mutations, we first compared 32 BRCA1-BCs and 200 consecutive cases of breast cancer without familial history for the prevalence of typical medullary breast carcinoma (TMC) using the criteria given by Ridolfi et al. [R. Ridolfi et al, Cancer (Phila.), 40: 1365-1385, 1977]. Second, we searched for BRCA1 mutations in a set of 18 cases of TMC, using denaturing gradient gel electrophoresis and Cleavase fragment length polymorphism scanning. Six of 32 (19%) BRCA1-BCs were of the TMC type, compared to 0 of 200 controls (P < 0.0001). Among the 18 TMCs, 2 BRCA1 nonsense mutations were found. This corresponds to almost 7 times the contribution of BRCA1 mutations in the general population. Two additional missense mutations were identified. Together, these results suggest that, although TMC and BRCA1-BCs are not strictly coincidental, an important connection between the two populations does exist.

Prognostic factors in primary breast sarcomas: a series of patients with long-term follow-up.

PURPOSE: To describe the pathologic characteristics and prognostic factors of primary breast sarcomas (PBSs). PATIENTS AND METHODS: We reviewed the clinical records and pathologic slides of 83 women with PBS treated in our institution between 1954 and 1991, with a median follow-up of 7.8 years. The majority of patients had undergone surgical treatment. RESULTS: The main histologic type was malignant fibrohistiocytoma (n = 57). For the whole population, the 10-year overall survival (OS) and disease-free survival (DFS) rates were 62% and 50%, respectively. For Fédération Nationale des Centres de Lutte Contre le Cancer grade 1, 2, and 3 tumors, the 10-year OS and DFS rates were 82% and 61%, 62% and 51%, and 36% and 25%, respectively (P =.00007 and.004, respectively). For tumors measuring less than 5 cm, 5 to 10 cm, and more than 10 cm, the 10-year OS and DFS rates were 76% and 66%, 68% and 55%, and 28% and 15%, respectively (P =.002 and.009, respectively). In the multivariate analysis, the tumor size and histologic grade were correlated with the 10-year DFS rate (P =.04 and.01, respectively), but only the histologic grade was correlated with OS (P =.01). Angiosarcoma was the only histologic type significantly associated with a poorer outcome in the multivariate analysis. CONCLUSION: PBSs have the same clinical history and prognostic factors as sarcomas arising at other sites. Therefore, it is legitimate to use a similar treatment strategy for PBS as for other sarcomas.

Tissue expression and serum levels of the oncoprotein HER-2/neu in 157 primary breast tumours.

BACKGROUND: We studied HER-2 expression in paired serum and tissue samples, in 157 selected cases from 701 consecutive primary breast cancer patients with pre-treatment HER-2 extracellular domain (ECD) > or = 10 ng/ml, or < 10 ng/ml but showing a HER-2 ECD lead time before first metastasis. PATIENTS AND METHODS: HER-2 ECD was measured by the Immuno 1 automated ELISA (Bayer). Tumour tissue was analysed by immunohistochemistry (IHC) with Dako A 0485 and CB 11 antibodies and scored with the Dako scoring system. RESULTS: Mean HER-2 ECD was 12.48+/-7.08 ng/ml and 21/157 (13.4%) sera were > or = 15 ng/ml (cut-off). Forty tumours (25.48%) showed both invasive and intraductal components, 3 (1.91%) were pure in situ carcinomas and 114 (72.61%) were pure invasive tumours. Elevated HER-2 ECD concentration was related only to pT (p=0.0008), histological grade (p=0.0465), presence of comedonecrosis (p=0.0123) or comedo-type carcinoma (p=0.041) and was unrelated to the presence of an intraductal component. HER-2 ECD was > or = 15 ng/ml in 48% of Dako 3+ and 60% of CB 11 2+ and 3+ tumours. By logistic regression analysis, the significant parameters associated with HER-2 ECD concentration were pT (p=0.0038) and Dako 3+ scores (p=0.0005). In Dako 3+ or CB 11 2+3+ tumours, elevated mean HER-2 ECD concentrations were observed only when pT exceeded 28-30 mm (p=0.0062 and p=0.0036, respectively). CONCLUSION: In breast tumours, a threshold in size and HER-2 overexpression is necessary to observe elevated concentrations of HER-2 ECD at diagnosis. This information may be useful when the primary tumour is not available for IHC.

Normal and pathological breast, the histological basis.

Breast tissue is heterogeneous, associating connective and glandular structures, which grow and change cyclically under hormonal regulation. Hormones are also thought to be the main determinant of the major benign and malignant pathologies encountered in the breast. Benign lesions are more frequent and fibrocystic changes are by far the most common among them. They usually associate different entities, (adenosis, fibrosis, cysts and hyperplasia) but vary in intensity and extension. Thus, their clinical and radiographic presentation is extremely different from one patient to another. Adenofibroma is the most frequent tumour. It also undergoes modifications according to hormonal conditions. About 90% of malignant tumours are primary carcinoma. The incidence of intra-ductal carcinoma has risen dramatically since the development of screening because of its ability to induce calcification. Two mechanisms could be involved in the formation of calcification: one active (tumour cell secretion of vesicles), the other passive (necrotic cell fragments are released). Invasive carcinoma comprises numerous histological types. Stromal reactions essentially determines their shape: a fibrous reaction commonly found in ductal carcinoma creates a stellate lesion while other stroma, inflammatory (medullary carcinoma), vascular (papillary carcinoma) or mucinous determine nodular lesions whose borders push the surrounding tissue. The histological features which give rise to the radiographic pattern will be emphasised.

Use of radiology for the pathologist in the management of breast lesions.

Today radiology is an essential step in the pathological analysis of breast biopsies. It is determinant at each stage of the management of non palpable lesions, clusters of microcalcifications and opacities, whether this concerns the needle biopsy or the surgical excision. Firstly, an X-ray is necessary to ensure that the core needle biopsy specimen has been adequately sampled and when samples with microcalcifications are selected by the radiologist, management can be more specific and accurate. In the case of surgical specimens, the X-ray confirms the presence of the radiographic abnormality or the clip indicating the site of the surgical excision which guides sampling. Some radiographic features also provide information on underlying pathologies allowing management to be adapted accordingly. Radiographs are also important to ensure that microscopically detected microcalcifications or lesions exactly correspond to the radiographic abnormality in size and location. The paraffin block can also be X-rayed to select those containing microcalcifications for additional slicing. It is also important to identify the presence of modifications caused by the core needle biopsy (fibrosis, haemorrhage and inflammation) and to carefully recognize displacement of epithelial cells and pseudo-emboli resulting from the needle procedure. Such correlation between radiology and pathology is essential so that appropriate management of the specimen can be adapted and to avoid pitfalls arising from pre-operative procedures.

[Angiogenesis and breast neoplasms. The pathologist's point of view]. / Angiogenèse et tumeurs du sein. L'apport du pathologiste.

Angiogenesis is an essential step of the tumoral growth and of the metastatic dissemination. It provides the nutriments necessary to the tumor and by the direct contact of the lumen vessels, facilitates its metastatic extension. The activation implies a large number of different agents which closely interact with the extracellular matrix. The intra tumoral vessels constitute an irregular network with numerous shunts. Their wall is also abnormal, incompletely covered by pericytes, and their basal membrane is thin and fragmented, sometimes absent. These features are responsible for an increased permeability and despite the large number of vessels, deserve a less effective oxygenation. The hypoxia induced secondarily activates the synthesis of angiogenic factors. The pathologist receives today help from immunohistochemistry for the evaluation of angiogenesis. This means facilitates the detection of vessels by use of specific antibodies directed against the endothelial cells (CD31, CD34, fVIIIrag...). It also allows the quantification of vessels or "microvascular density". Its importance varies from one patient to another and for different areas of a same tumour, the "hot-spot" generally located at its periphery. Despite its heterogeneity and the complexity of mechanisms involved in the regulation, the microvascular density appears to be an independent prognostic factor for tumour of different histological types. Immunohistochemistry also permits the evaluation of different characteristics of vessels and the tumour such as the activators (VEGF, FGF...) or their specific receptors (VEGF-R). Such analysis is also important for the determination of the prognosis but appears more interesting for the selection of the antiangiogenic treatment. However, this step will require the standardization of the immunohistochemistry techniques and the implementation of an external quality control.

Correlation between contrast enhancement in dynamic magnetic resonance imaging of the breast and tumor angiogenesis.

RATIONALE AND OBJECTIVE: The authors determined the relation between tumor angiogenesis in small invasive breast carcinoma and contrast enhancement on magnetic resonance imaging (MRI) after gadolinium injection. MATERIALS AND METHODS: Magnetic resonance imaging was performed before surgery in a prospective study of 20 patients who had a small palpable lump. Spin-echo sequences after injection of gadolinium were studied by factor analysis of medical image sequences and were compared with a histologic quantification of tumor angiogenesis after immunocytochemical staining. RESULTS: In nine cases, there was good correlation between the MRI and the histologic plane. In four patients, an early factor was found on MRI. This factor was related to a high concentration of arterioles located in the stroma or, in one patient, to the intratumor repair process. CONCLUSION: Early enhancement correlated well with the number of vessels determined histologically.

New hemodynamic approach to angiogenesis: color and pulsed Doppler ultrasonography.

RATIONALE AND OBJECTIVES: To determine the capacity of color and spectral Doppler ultrasonography (US) to quantify angiogenesis in vivo and to characterize low-resistance intratumor blood flow. METHODS: Thirty-two tumors, xenografted into mice, were studied with Doppler US. The number of intratumor vessels visualized with color Doppler US was compared with the density of microvessels and the number of vessels >100 microm determined by histologic examination. The resistance index and the peak systolic velocities were evaluated. RESULTS: The number of intratumor vessels visualized by color Doppler US was correlated with the number of vessels >100 microm (P<0.001) determined histologically. When vessel density was >30, intratumor vessels were always detected by color Dopper US. The resistance index and peak systolic velocities were significantly lower in intratumor than in peritumor vessels. CONCLUSIONS: Color Doppler US evaluated tumor angiogenesis accurately. Spectral analysis confirmed the low resistance of intratumor blood flow.

Oral contraceptive use and risk of benign breast disease in a French case-control study of young women.

We report the results of a French hospital-based case-control study designed to analyse the relation between the use of oral contraceptives (OC) and the risk of benign breast disease (BBD). The cases were 286 women, each less than 46 years old, with BBD histologically verified between 1982 and 1985. Controls were 382 patients, matched to cases on year of birth and month of interview, and who were hospitalized for a non-malignant disease other than BBD. Odds ratios were estimated by multivariate regression, taking into account level of education, place of residence, family history of breast cancer, age at menarche, number of children, age at first full-term pregnancy and Quetelet index. The risk of BBD was found to decrease significantly with a longer use of OC before the first full-term pregnancy (FFTP), but there was no association between the risk of BBD and the duration of OC use after FFTP. OC use before FFTP reduced the risk of non-proliferative disease, but did not significantly affect the risk of proliferative disease. These results did not depend on the amount of oestrogen (0.05 mg or more vs < 0.05 mg) contained in OC.

PIP: This article reports the findings of a French-based case-control study examining the relationship between risk of benign breast disease (BBD) and oral contraceptive (OC) use. Special emphasis was given to duration of OC use before and after the first full-term pregnancy (FFTP). Conditional multivariate logistic regression was the statistical process used to analyze the findings. 286 women with verified BBD were studied. 382 women, who were hospitalized for a non-BBD disease, were used as controls. Each case was matched with at least one control. 7 confounders were adjusted for. Confounders included family history of breast cancer, level of education, place of residence, age at menarche, number of children, age at FFTP, and Quetelet index. The risk of BBD decreased with longer OC use before the FFTP. There was no association observed between risk of developing BBD and the duration of OC use after the FFTP. OC use before the FFTP reduced the risk of non-proliferative disease, but did not significantly affect the risk of proliferative disease.

Imaging and management of nonpalpable lesions of the breast.

Mammography remains the primary imaging modality for the evaluation of breast disease. Its performance level is clearly related to strict quality control measures and comprehensive diagnostic imaging. Ultrasonography remains an adjunct tool for analysing nonpalpable and palpable masses; diagnostic criteria for benign lesions must be strictly applied. Reliable histologic diagnosis is possible with percutaneous large needle core biopsies; benign findings should always be correlated with imaging data and follow-up is essential to detect delayed false negatives. MR imaging is still under evaluation for most indications. Its high sensitivity and negative predictive value are of particular interest for the detection or elimination of breast cancer in selected populations.

Histological findings in surgical specimens after core biopsy of the breast.

Pathological changes induced by needling procedures found in breast surgical specimens are rare but can induce misinterpretation or compromise the definitive histological analysis. These abnormal findings depend on the interval between the core biopsy and excision. Early findings are local haemorrhage, disrupted tissue and epithelial cell displacement, whereas, fibrosis, fat necrosis and inflammatory reaction are observed later in time. The radiologists must be aware of these histological pitfalls and must consider the benefits of their core biopsies (indications, surgeon's question, number of samples).

Mammographic patterns of inflammatory breast carcinoma: a retrospective study of 92 cases.

OBJECTIVE: To quantitate initial mammographic signs and to describe post-therapeutic patterns of inflammatory breast cancer. MATERIAL AND METHODS: Two radiologists retrospectively analyzed the initial clinical and mammographic findings of 92 patients with inflammatory breast carcinoma. The post-therapeutic mammogram (n = 75) was considered abnormal when focal opacity and or malignant-type microcalcifications were still visible. RESULTS: Redness of the skin, "peau d'orange' and increased temperature were the most common findings. A palpable mass was noted in 97% with axillary lymph node involvement in 83% of cases. All initial mammograms were abnormal. Isolated inflammatory signs were observed in 14% and malignant signs in 86% of patients (opacity = 77% and/or malignant-type microcalcifications = 47%). Skin thickening was seen in 93.5%, nipple inversion in 56.5%, increased breast density in 93.5%, stromal coarsening in 85% and hypervascularisation in 32.5% of mammograms. On post-therapeutic mammograms, 35 patients (46.5%) were suspected of having residual disease. During follow-up, 19 patients (25.3%) relapsed locally: 75% had abnormal post-therapeutic mammograms. CONCLUSION: The presence of isolated inflammatory signs on the mammogram is sufficient to suspect inflammatory breast carcinoma and biopsy must be performed in doubtful cases. Radical surgery is indicated when persistent malignant signs are still visible on mammogram after conservative treatment.

["Micrometastases": the pathologist's point of view]. / "Micrométastases": le point de vue de pathologiste.

The development of cancer screening has led to the discovery of smaller tumours and less frequent dissemination to lymph nodes and organs that requires special techniques for detection. Numerous papers on micrometastases reflect a considerable amount of work devoted to detection methods, technical problems and the prognostic value of these lesions. Apart from cytological techniques, the pathologist can rely on two methods for the detection of micrometastases: serial slicing of paraffin-embedded blocks and immunohistochemistry. When these methods are combined, the detection rate is similar to that of biological methods and can attain levels as high as 60% for the sentinel node with the added vantage of being able to visualise cells. Despite an impressive body of studies, major disparities are found in detection rates and the prognostic value of micrometastases is not firmly established. In order to facilitate comparisons and analyses, it is essential to adopt a common terminology with precise definitions. The UICC advocates the use of the term micrometastasis which denotes a metastasis smaller than or equal to 2 mm in size. The potential aggressiveness of micrometastases is dependent on other poorly explored parameters such as the number of cells detected in the bone marrow or lymph node and the location of micrometastases. The new pTNM classification takes into account this latter parameter and distinguishes two categories of micrometastases: "isolated tumor cells" located in the lumen of vessels or sinuses and "micrometastasis" which has already invaded an organ. This classification warrants further analysis to determine the prognostic value of these categories. The next challenging problem consists in determining the key biological properties that account for distant dissemination.