All atypia diagnosed at stereotactic vacuum-assisted breast biopsy do not need surgical excision.

The necessity of excision is debatable when atypia are diagnosed at stereotactic vacuum-assisted breast biopsy (microbiopsy). Among the 287 surgical excisions performed at Institut Bergonié from 1999 to 2009, we selected a case-control study group of 151 excisions; 52 involving all the diagnosed cancers and 99 randomly selected among the 235 excisions without cancer, following atypical microbiopsy (24 flat epithelial atypia; 50 atypical ductal hyperplasia; 14 lobular neoplasia; 63 mixed lesions). Mammographical calcification (type, extension, complete removal) and histological criteria of epithelial atypia (type, number of foci, size/extension), topography and microcalcification extension at microbiopsy were compared according to the presence or absence of cancer at excision. Factors associated with cancer at excision were Breast Imaging Reporting and Data System (BI-RADS5) lesions, large and/or multiple foci of mammographical calcifications, histological type, number, size and extension of atypical foci. Flat epithelial atypia alone was never associated with cancer at excision. BI-RADS5, atypical ductal hyperplasia (alone or predominant) and >3 foci of atypia were identified as independent pejorative factors. There was never any cancer at excision when these pejorative factors were absent (n=31). Presence of one (n=59), two (n=23) or three (n=14) factors was associated with cancer in 24, 15 and 13 cases with an odds ratio=5.8 (95% CI: 3-11.2) for each additional factor. We recommend that mammographical data and histological characteristics be taken into account in the decision-making process after diagnosis of atypia on microbiopsy. With experienced senologists and strict histological criteria, some patients could be spared surgery resulting in significant patient, financial and time advantages.

Ductal carcinoma in situ of the breast: influence of age on diagnostic, therapeutic, and prognostic features. Retrospective study of 812 patients.

BACKGROUND: The objective of this retrospective study was to identify prognostic, diagnostic, and therapeutic disparities between younger (≤ 40 years) and older (> 40 years) women with ductal carcinoma in situ (DCIS) of the breast. METHODS: From 1971 to 2001, all patients treated for DCIS at Institut Bergonié were included in our analyses. Follow-up data was collected over 10 years. We used univariate and multivariate analyses to investigate patient-, disease-, and treatment-related factors predictive of diagnostic, histological, therapeutic, and prognostic DCIS criteria. RESULTS: A total of 812 patients were eligible including 731 women aged >40 years and 81 women ≤40 years. Younger women with DCIS were more likely to receive a mastectomy and less likely to receive radiotherapy. Young age and initial surgical treatment (lumpectomy and especially nonfree margins) were revealed as predictive of recurrence in multivariate analyses. CONCLUSIONS: Young age represents a recurrence risk independent of histological and clinical characteristics of the tumor. Initial treatment, especially for nonfree margins, is also a predictive factor. Appropriate initial surgery with particularly wide margins appears essential for the treatment of young women with DCIS.

Molecular apocrine differentiation is a common feature of breast cancer in patients with germline PTEN mutations.

INTRODUCTION: Breast carcinoma is the main malignant tumor occurring in patients with Cowden disease, a cancer-prone syndrome caused by germline mutation of the tumor suppressor gene PTEN characterized by the occurrence throughout life of hyperplastic, hamartomatous and malignant growths affecting various organs. The absence of known histological features for breast cancer arising in a PTEN-mutant background prompted us to explore them for potential new markers. METHODS: We first performed a microarray study of three tumors from patients with Cowden disease in the context of a transcriptomic study of 74 familial breast cancers. A subsequent histological and immunohistochemical study including 12 additional cases of Cowden disease breast carcinomas was performed to confirm the microarray data. RESULTS: Unsupervised clustering of the 74 familial tumors followed the intrinsic gene classification of breast cancer except for a group of five tumors that included the three Cowden tumors. The gene expression profile of the Cowden tumors shows considerable overlap with that of a breast cancer subgroup known as molecular apocrine breast carcinoma, which is suspected to have increased androgenic signaling and shows frequent ERBB2 amplification in sporadic tumors. The histological and immunohistochemical study showed that several cases had apocrine histological features and expressed GGT1, which is a potential new marker for apocrine breast carcinoma. CONCLUSIONS: These data suggest that activation of the ERBB2-PI3K-AKT pathway by loss of PTEN at early stages of tumorigenesis promotes the formation of breast tumors with apocrine features.

[Adenoid cystic carcinoma of the breast: clinical, histological and immunohistochemical characterization]. / Le carcinome adénoïde kystique du sein: étude clinique, histologique, immunohistochimique et revue de la littérature.

BACKGROUND: Adenoid cystic carcinoma (ACC) of the Breast is a rare tumour (less than 1 % of all breast carcinomas). The aim of this study was to determine the clinical, histological and immunohistochemical characteristics of these tumours. METHODS: From the database of the Bergonié Institute of Bordeaux, 30 cases of ACC were identified. The clinical and histological features of these carcinomas were characterized. An immunohistochemical study was performed with the following antibodies: ER, PR, HER-2-neu, Vimentin, EGFR, P63, SMA, CK5/6, CK8/18, CK14, cKIT, MIB1, CD44 and CD24. RESULTS: Thirty patients were included (median age 60.7 years). The 10 axillary lymph node dissections and two sentinel lymph procedures were negative. The architecture was frequently of a mixed type (26/30) and less often solid (4/30). Among the 23 patients for whom follow up was available (median follow-up: 84 months [2-288]), there were three local recurrences and three metastatic events. The tumors with recurrence and metastasis showed more necrosis, a mitotic count greater than 4/10hpf, and in one case perineural infiltration. All the tumours were ER, PR and Her-2-neu negative. Morphological and immunophenotypical analysis disclosed in each tumor, a basaloid and a luminal cell population with divergent immunophenotypical patterns. CONCLUSIONS: The mammary ACC is made of two cell types and is of good prognosis despite its triple negative phenotype, similar to the basal-like infiltrating carcinoma NOS. Axillary lymph node dissection is not recommended. Good local control by at least large lumpectomy with long-term follow-up is necessary.

D2-40 in breast cancer: should we detect more vascular emboli?

Peritumoral emboli assessed on hematoxylin-eosin-stained slides are taken into account for treatment of patients with operable breast cancer. We assessed whether immunostaining with D2-40 improves the prognostic significance of emboli in a group of tumors with a large immunohistochemical sampling and a long-term follow-up. Topography, number, and extension of hematoxylin-eosin and D2-40 emboli were compared in 94 node-negative breast cancers (median number of immunostained slides per tumor: 3). Metastasis-free survival of patients with or without hematoxylin-eosin and/or D2-40 emboli were evaluated (median follow-up of 178 months). Hematoxylin-eosin emboli were detected in 14 (15%) tumors and were located at distance from the tumor. D2-40 emboli were detected in 39 (41%) tumors and was often multiple (n=30), extensive (n=23), located within (n=13), close to (n=10) or at distance from the tumor (n=16). The 12 distant hematoxylin-eosin and D2-40 emboli were located in the same vessels (seven missed at the first hematoxylin-eosin examination and secondarily diagnosed by D2-40 staining). A difference in metastasis-free survival was found only between patients with no D2-40 emboli and those with distant D2-40 emboli (P=0.02). D2-40 emboli located within or close to the tumor had no prognostic value. Comparing the metastasis-free survival of patients with or without hematoxylin-eosin emboli, the prognostically unfavorable significance of hematoxylin-eosin emboli was improved when taking into account the seven patients with missed emboli at the first examination and secondarily diagnosed by D2-40 staining (P=0.006 vs 0.003). To conclude, D2-40 increases the diagnostic sensitivity of emboli in breast carcinoma and the high incidence of D2-40 emboli might be related to the number of immunostained slides per case. Nevertheless, only distant D2-40+ emboli had a prognostic impact. In practice, D2-40 might be useful to detect missed hematoxylin-eosin emboli especially in cases without any other prognostically unfavorable criterion.

Prediction of HER2 gene status in Her2 2+ invasive breast cancer: a study of 108 cases comparing ASCO/CAP and FDA recommendations.

Most Her2 testing guidelines recommend that all cases scoring Her2 2+ by immunohistochemistry should be analyzed by fluorescent in situ hybridization (FISH) to determine HER2 status to confirm eligibility for Trastuzumab therapy in breast cancer. The aim of our study was to determine HER2 gene and chromosome 17 (CEN17) status in a series of 108 Her2 2+ consecutive cases and study the correlation between pathological characteristics of the tumors and HER2 amplification. Invasive breast cancers were tested by FISH using the Dako HER2 FISH pharmDx kit. The Her2 immunohistochemistry protocol was performed using the polyclonal AO485 antibody (Dako) diluted to 1:1500. HER2 and CEN17 status were correlated to tumor SBR grade, mitotic count, estrogen receptor, progesterone receptor status and percentage of Her2 immunohistochemistry-positive cells. Following Food and Drug Administration guidelines, ie, HER2/CEN17 ratio >or=2 and an HER2 copy number >4, amplified cases were observed in 36 (33%) and 49 (45%) cases, respectively, and following American Society of Clinical Oncology/College of American Pathologists guidelines, ie, HER2/CEN17 ratio >2.2 and an HER2 copy number >6, amplified cases represented 30 and 24% of the study population, respectively. Chromosome 17 polysomy (CEN17 >2.25) was observed in 39 (36%) tumors. Significant positive correlations were found between FISH HER2 amplified cases and Her2 immunostaining >60% (P=1.1.10(-5)), SBR grade 3 (P=0.0001), nuclear atypia (P=0.03) and mitotic count (P=0.008). By multivariate analysis, Her2 immunostaining >60% (P<10(-3)) and SBR grade 3 (P<10(-3)) were independent factors predicting HER2 amplification status irrespective to cutoff guidelines. All SBR grade 3 cases with more than 60% Her2+ cells had an HER2/CEN17 ratio >or=2, only one had a ratio

Identification of typical medullary breast carcinoma as a genomic sub-group of basal-like carcinomas, a heterogeneous new molecular entity.

INTRODUCTION: Typical medullary breast carcinoma (MBC) has recently been recognized to be part of the basal-like carcinoma spectrum, a feature in agreement with the high rate of TP53 mutations previously reported in MBCs. The present study was therefore designed to identify phenotypic and genetic alterations that distinguish MBCs from basal-like carcinomas (BLC). METHODS: Expression levels of estrogen receptor (ER), progesterone receptor (PR), ERBB2, TP53, cytokeratins (KRTs) 5/6, 14, 8/18, epidermal growth factor receptor and KIT, as well as TP53 gene sequence and high-density array comparative genomic hybridization (CGH) profiles, were assessed and compared in a series of 33 MBCs and 26 BLCs. RESULTS: All tumors were negative for ER, PR and ERBB2. KRTs 5/6 were more frequently expressed in MBCs (94%) than in BLCs (56%) (p = 0.0004). TP53 mutations were disclosed in 20/26 MBCs (77%) and 20/24 BLCs (83%). Array CGH analysis showed that a higher number of gains (95 regions) and losses (34 regions) was observed in MBCs than in BLCs (36 regions of gain; 13 regions of losses). In addition, gains of 1q and 8q, and losses of X were found to be common to the two groups, whereas gains of 10p (53% of the cases), 9p (30.8% of the cases) and 16q (25.8% of the cases), and losses of 4p (34.8% of the cases), and amplicons of 1q, 8p, 10p and 12p were the genetic alterations found to characterize MBC. CONCLUSION: Our study has revealed that MBCs are part of the basal-like group and share common genomic alterations with BLCs, the most frequent being 1q and 8q gains and X losses; however, MBCs are a distinct entity within the basal-like spectrum, characterized by a higher rate of KRT 5/6 expression, a higher rate of gains and losses than BLCs, recurrent 10p, 9p and 16q gains, 4p losses, and 1q, 8p, 10p and 12p amplicons. Our results thus contribute to a better understanding of the heterogeneity in basal-like breast tumors and provide potential diagnostic tools.

Epithelial atypia in biopsies performed for microcalcifications. practical considerations about 2,833 serially sectioned surgical biopsies with a long follow-up.

This study analyzes the occurrence of epithelial atypia in 2,833 serially sectioned surgical breast biopsies (SB) performed for microcalcifications (median number of blocks per SB:26) and the occurrence of subsequent cancer after an initial diagnosis of epithelial atypia (median follow-up 160 months). Epithelial atypia (flat epithelial atypia, atypical ductal hyperplasia, and lobular neoplasia) were found in 971 SB, with and without a concomitant cancer in 301 (31%) and 670 (69%) SB, respectively. Thus, isolated epithelial atypia were found in 670 out of the 2,833 SB (23%). Concomitant cancers corresponded to ductal carcinomas in situ and micro-invasive (77%), invasive ductal carcinomas not otherwise specified (15%), invasive lobular carcinomas (4%), and tubular carcinomas (4%). Fifteen out of the 443 patients with isolated epithelial atypia developed a subsequent ipsilateral (n = 14) and contralateral (n = 1) invasive cancer. The high slide rating might explain the high percentages of epithelial atypia and concomitant cancers and the low percentage of subsequent cancer after a diagnosis of epithelial atypia as a single lesion. Epithelial atypia could be more a risk marker of concomitant than subsequent cancer.

[Management of breast epithelial atypia]. / Prise en charge des atypies épithéliales du sein.

While awaiting a molecular classification of breast epithelial atypia, the authors give some guidelines about their management, in reference to studies in literature and to their own experience at the Institut Bergonié. This experience is based on the analysis of 2,833 serially sectioned surgical breast biopsies performed for micro-calcifications without any palpable mass (median number of blocks per biopsy: 26) in patients with a long median follow-up (160 months). Some guidelines are given about the application of the WHO classification of atypical non invasive proliferative breast lesions, measurement of atypical ductal hyperplasia, management of patients with epithelial atypia on core needle biopsies and management of surgical biopsies corresponding to re excision to set out a small concomitant close cancer, present in nearly one third of the cases. Indeed, epithelial atypia could be more a risk marker of concomitant than subsequent cancer.

Mammography of ductal carcinoma in situ of the breast: review of 909 cases with radiographic-pathologic correlations.

We retrospectively analysed mammographies of 909 ductal carcinoma in situ (DCIS) (1980-1999) and compared our results to those of literature. Microcalcifications were present in 75% of the cases, and soft-tissue abnormalities in 27% cases with association with calcifications in 14% of cases. Palpable masses were found in 12% of the cases and nipple discharge was present in 12% of the cases. The radiographic-pathologic correlation allowed to suspect the DCIS "aggressiveness" on radiologic signs. Granular, linear, branching and/or galactophoric topography of the microcalcifications were correlated with necrosis, grade 3, comedocarcinoma type. A number of microcalcifications higher than 20 was correlated with necrosis and grade 3. Mammographic size was correlated to histologic size. Masses were correlated with grade 1. A diagnosis strategy can be proposed with a multidisciplinar approach.

[Digitalized imaging pathology: application to quality control in cancer diagnosis]. / La numérisation d'images en anatomie-pathologique: application a l'assurance qualité pour le diagnostic de cancer.

OBJECTIVES: To test a double histology reading system based on digitalized imaging for cancer diagnosis. MATERIAL AND METHODS: Pathology images of cancer diagnosis material were produced in real time by a digital imaging system integrated into the laboratory data processing system. Over a 30-day period, second readings were performed using the digitalized images. Cases with second readings were classified according to the aspect on the digitalized images as malignant tumor with histological type, malignant tumor with no other precision, and doubtful malignancy. RESULTS: During the study period, 204 cases of cancer were diagnosed, including 178 with digitalized imaging (87%). Among the digitalized cases, 119 (67%) were classified as malignant tumor with histological type, 53 (30%) as malignant tumor with no other precision, and 6 (3%) as doubtful malignancy. The histology material of these latter cases were reviewed and corresponded to malignant tumors. Approximately 2 hours per week were devoted to the second readings. CONCLUSION: A integrated digitalized imaging system can participate in quality control of cancer diagnosis by allowing rapid efficacious second readings.

Comprehensive prognostic analysis in breast cancer integrating clinical, tumoral, micro-environmental and immunohistochemical criteria.

Significant morphological, clinical and biological prognostic factors vary according to molecular subtypes of breast tumors, yet comprehensive analysis of such factors linked to survival in each group is lacking. Clinicopathological and micro-environmental criteria, estrogen (ER), progesterone (PR) receptors, HER2, Ki67, basal markers, CD24, CD44, ALDH1, BCL2, E-Cadherin and Trio were assessed in 1070 primary operable breast cancers from a single center according to five main molecular subtypes and associations with distant metastasis-free survival (DMFS) were examined. There were 682 (64 %) luminal A (LA), 166 (16 %) Luminal B HER2 negative (LBH-), 47 (4 %) Luminal B HER2 positive (LBH+), 108 (10 %) triple negative (TN) and 67 (6 %) HER2-enriched tumors (H2+). Median follow-up was 13.7 years. At 5 years, DMFS in LA (90 %) was better than in LBH- (80.9 %), hazard ratio (HR) = 2.22 [1.44-3.43] P < 0.001; LBH+ (74.5 %), HR = 3.14 [1.69-5.84] P < 0.001, TN (71.5 %) HR = 3.63 [2.34-5.63], P < 0.001; and H2+ (65.2 %), HR = 4.69 [2.90-7.59], P < 0.001. In multivariable analysis, factors associated with shorter DMFS varied according to molecular subtype, with tumor size being associated with shorter DMFS in the LBH-, LBH+ and TN groups and the Rho GEF Trio and BCL2 phenotypes in TN tumors only. These findings help to define new clinicophenotypic models and to identify new therapeutic strategies in the specific molecular subgroups.

[Strategies for management of axillary lymph nodes in breast cancer. Point of view of the Institut Bergonié. ]. / Les stratégies de prise en charge des ganglions axillaires dans les cancers du sein. Le point de vue de l'Institut Bergonié.

Sentinel lymph node biopsy in breast cancer has changed pathology management of axillary lymph nodes by pathologists, but there is still no consensus either for serial sectioning nor for immunohistochemistry. We analyze: 1) data in the literature about the prognostic significance of micrometastases (pNlmi) and immunohistochemically detected infiltrating tumor cells (pN0(i+) in axillary lymph nodes. 2) management strategies at the Bergonié Institute and by other teams for axillary lymph nodes and sentinel lymph nodes. 3) questions and controversies on sentinel lymph node management and recommendations of the five main reference groups.

[Diagnostic approach to breast papillary lesions]. / Approche diagnostique dans les lesions papillaires du sein.

Breast papillary lesions are difficult to interpret and include a large variety of benign, atypical and malignant lesions. We report the case of a 41-Year-old woman presenting with an intracystic papillary carcinoma, in order to illustrate our pragmatic diagnostic approach, which includes the use of a decision tree, useful for differentiating the different types of breast papillary lesions.

An array CGH based genomic instability index (G2I) is predictive of clinical outcome in breast cancer and reveals a subset of tumors without lymph node involvement but with poor prognosis.

BACKGROUND: Despite entering complete remission after primary treatment, a substantial proportion of patients with early stage breast cancer will develop metastases. Prediction of such an outcome remains challenging despite the clinical use of several prognostic parameters. Several reports indicate that genomic instability, as reflected in specific chromosomal aneuploidies and variations in DNA content, influences clinical outcome but no precise definition of this parameter has yet been clearly established. METHODS: To explore the prognostic value of genomic alterations present in primary tumors, we performed a comparative genomic hybridization study on BAC arrays with a panel of breast carcinomas from 45 patients with metastatic relapse and 95 others, matched for age and axillary node involvement, without any recurrence after at least 11 years of follow-up. Array-CGH data was used to establish a two-parameter index representative of the global level of aneusomy by chromosomal arm, and of the number of breakpoints throughout the genome. RESULTS: Application of appropriate thresholds allowed us to distinguish three classes of tumors highly associated with metastatic relapse. This index used with the same thresholds on a published set of tumors confirms its prognostic significance with a hazard ratio of 3.24 [95CI: 1.76-5.96] p = 6.7 x 10(-5) for the bad prognostic group with respect to the intermediate group. The high prognostic value of this genomic index is related to its ability to individualize a specific group of breast cancers, mainly luminal type and axillary node negative, showing very high genetic instability and poor outcome. Indirect transcriptomic validation was obtained on independent data sets. CONCLUSION: Accurate evaluation of genetic instability in breast cancers by a genomic instability index (G2I) helps individualizing specific tumors with previously unexpected very poor prognosis.

[Accuracy of intraoperative imprint cytology of sentinel lymph nodes in cT1 infiltrating breast cancer]. / L'examen cytologique a-t-il encore sa place dans l'analyse extemporanée du ganglion sentinelle dans le cancer du sein ?

Intraoperative examination of sentinel lymph nodes (SLN) in breast cancer can avoid a new surgical procedure in case of positive SLN, but its value, efficacy and the methods used are still controversial. The aim of our study was to evaluate the imprint cytology intraoperative method of SLN analysis performed at our institution. We did a retrospective study of the sentinel lymph node procedures performed during a period of 24  months on cT1N0 unifocal breast cancers. Intraoperative procedure was mainly by imprint cytology (touch prep). A SLN procedure was performed on 187 women with 360 SLN. Two hundred and seventy-seven SLN among 156 women were analyzed intraoperatively by touch prep. 19/48 positive SLN were detected by intraoperative touch prep (sensitivity 39.6%; specificity 100%; positive predictive value 100%; negative predictive value 88.7%, accuracy 89.5%). False negative rate of cytological intraoperative examination of SLN was 11,2% by SLN and 18,3% by patient. By univariate analysis, this rate significantly increased with lymphovascular invasion, tumor size cT1b and c and histological SBR grade 2 or 3. By multivariate analysis, only lymphovascular invasion was a predictive factor of intraoperative touch prep failure (OR = 3.3; IC 1.3-8.4). Intraoperative imprint cytology of SLN in breast cancer is associated with a high rate of false negativity that questions its use in this setting.

Nucleic acid quality preservation by an alcohol-based fixative: comparison with frozen tumors in a routine pathology setting.

Pathologic diagnosis requires tissue fixation for histologic and immunohistologic analysis, and formalin is routinely used for this. The disadvantage of this fixative is its inability to preserve nucleic acids. Pathologic tumor diagnosis requires extensive molecular analyses, for which formalin fixation may be not adequate. Recently, an alcohol-based fixative (molecular fixative, MF) was described that allows nucleic acid preservation as well as histologic and immunohistologic studies. Moreover, the MF fixation processing system (Xpress) is fast and is well adapted to a routine process. We evaluated RNA and DNA quality within 1 month and after 1 year for 10 breast carcinomas and 20 sarcomas fixed in MF in comparison with the corresponding frozen tumors. The quality of DNA extracted from the MF-fixed tissue was similar to that extracted from the frozen tumors. The quality of RNA extracted from the MF-fixed tissue was lower than that of frozen tumors; nevertheless, a majority of RNA integrity number (RIN) values were greater than 7. Gene expression quantification by real-time polymerase chain reaction gave comparable results between tumors fixed with MF and frozen tumors. Tissue fixation at 4°C with the MF improved the RNA quality measured by the RIN value. However, after storage for 1 year at room temperature, although DNA quality was preserved, RNA extracted from tissues fixed with the MF was degraded. Tissue fixation with the MF is an important improvement for molecular pathologic diagnosis, enabling a combination of routine pathologic diagnoses and current molecular diagnoses if they are carried out near the processing time.

Is it useful to detect lymphovascular invasion in lymph node-positive patients with primary operable breast cancer?

BACKGROUND: Lymphovascular invasion (LVI) is a widely recognized prognostic factor in lymph node-negative breast cancers. However, there are only limited and controversial data about its prognostic significance in lymph node-positive patients. METHODS: Among 931 patients operated on and monitored at the authors' institution for an invasive breast carcinoma between 1989 and 1992, all 374 lymph node-positive breast cancers entered the study (median follow-up, 126 months). RESULTS: LVI was present in 46% of tumors and was associated with age < or = 40 years (P = .02), high histological grade (P = .01), and negative estrogen receptor status (P = .032), but not with tumor size, number of involved lymph nodes, or HER-2/neu status. LVI was an independent prognostic factor for distant metastases (P = .002). Furthermore, in HER-2/neu-negative/hormone receptor-positive (n = 287) tumors, the number of independent prognostic factors (LVI, age, histological grade, number of involved lymph nodes, and tumor size) was associated with a 5-years metastasis-free survival ranging from 100% if no factors (n = 25) to 89% +/- 2% if 1 or 2 factors (n = 186) and 67% +/- 6 if 3, 4, or 5 factors (n = 76) were present (P < .001). CONCLUSIONS: LVI is an independent prognostic factor in lymph node-positive breast cancer and merits further prospective investigations as a decision tool in the adjuvant chemotherapy setting.

Distinction between isolated tumor cells and micrometastases in breast cancer: is it reliable and useful?

BACKGROUND: In routine practice, the distinction between isolated tumor cells (ITC) and micrometastases (MIC) in patients with breast cancer is sometimes difficult to discern. The authors assessed differences in classifying patients according to the American Joint Commission on Cancer (AJCC) and the International Union Against Cancer (UICC) definitions and method of sizing. METHODS: We assessed the characteristics of metastatic deposits in only 1 involved lymph node in 337 patients with operable breast cancer (median follow-up, 15.3 years). When sizing multiple clusters, either the diameter of the area with close clusters (Method 1) or the size of the largest cluster (Method 2) was taken into account. Patients were classified and their survival was assessed according to the 2 sizing methods and the criteria used for definitions (size in AJCC; size and topography in UICC). RESULTS: With the AJCC definitions, 32 patients would be differently classified according to the method of sizing. With the UICC definitions, some patients with parenchymal ITC would be classified as pN1mi, 38 by Method 1 and 53 by Method 2. Some pathologists would classify the 66 patients who had isolated capsular vascular invasion as pN0. Classification was uncertain in 136 (40%) to 151 (45 %) patients. Survival was not significantly different between pN0(i+) and pN1(mi) patients. CONCLUSIONS: The distinction between ITC and MIC was often difficult and without any prognostic significance. Precise guidelines are more useful for staging than for therapy. Thus, complete axillary dissection is usually performed in pN0(i+) and pN1(mi) patients, whereas chemotherapy is not indicated or debatable when MIC is the only 1 pejorative criterion.