Fine needle aspiration cytology in the management of palpable benign and malignant breast disease. Correlation with clinical and mammographic findings

Two surgeons in a health maintenance organization group practice performed 280 fine needle aspirations (FNAs) on 257 palpable breast lesions in 200 patients. The cytology was interpreted by four pathologists at a community hospital. FNA cytology had a sensitivity of 96% and a specificity of 94% in these cases; there were no false-positive diagnoses of cancer. FNA cytology improved the identification of benign disease and decreased the risk of missing cancers. FNA cytology also improved the predictive value of mammographic information and was more helpful than mammography in demonstrating the need for biopsy of small palpable lesions that turned out to be "minimal" breast cancers.     

Papillary breast lesions diagnosed on cytology. Profile of 65 cases

OBJECTIVE: To analyze the cytologic features of nipple discharge and fine needle aspiration (FNA) cytologic smears from breast lesions reported as showing papillary features and to correlate them with histopathologic features. STUDY DESIGN: The study group consisted of FNA smears and/or nipple discharge smears from 65 breast lesions diagnosed on cytology as duct papilloma, papillary lesion, fibrocystic condition, fibroadenoma, papillary neoplasm or papillary carcinoma. Cytomorphologic features assessed included cellularity, cell pattern (clusters, papillary, 3-dimensionality, etc.) and cell characteristics (monomorphism, pleomorphism, apocrine change, plasmacytoid features). Histological material was available for review and cytohistologic correlation in all cases. RESULTS: Forty-six specimens were FNA smears, and 16 were nipple discharge smears; in 3 cases FNA and nipple discharge cytologic smears were available for review. Cytologic study could predict the presence of a papillary pattern in all neoplasms with pure or focal papillary differentiation. There was an overlap in cytomorphologic features between papillary and nonpapillary benign lesions as well as between benign and malignant papillary neoplasms. Frank blood in the aspirate, cell dissociation and atypia, however, were more frequent in the last. CONCLUSION: Overlap of cytologic features in nonneoplastic and neoplastic benign papillary lesions and between benign and malignant papillary neoplasms necessitates histologic evaluation in all cases diagnosed as papillary on cytology. Since 49.2% of lesions showing papillary features on cytology prove to be malignant, all cases reported as papillary on cytology should be excised urgently for histologic assessment.     

Stereotaxic fine needle aspiration cytology of clinically occult malignant and premalignant breast lesions

Stereotaxic fine needle aspiration (FNA) cytology was used to study clinically occult (nonpalpable) breast lesions in 114 consecutive patients with mammographically suspicious findings prior to excisional biopsy. The aspirate contained insufficient material for cytologic evaluation in 15 cases (13.2%), which were histologically diagnosed as benign (7 cases), atypical hyperplasia (7 cases) or carcinoma in situ (1 case). The cytologic findings indicated a benign lesion in 77 cases (67.5%), which were histologically diagnosed as benign (71 cases) or atypical ductal hyperplasia (6 cases). The cytologic sample showed atypia in eight cases (7.0%), which were histologically diagnosed as severe atypical ductal hyperplasia (three cases), carcinoma in situ (one case) or proliferative fibrocystic disease (four cases). In the eight cases (7.0%) cytologically interpreted as probably malignant, histology confirmed six invasive carcinomas, one carcinoma in situ and one fibrocystic disease. Of six cases (4.4%) cytologically reported as malignant, five were histologically diagnosed as invasive carcinoma and one as carcinoma in situ. Overall, stereotaxic FNA cytology reported as malignant or probably malignant 14 of the 15 cases with a histologic confirmation of malignancy, for a sensitivity of 93.3%. Cytology correctly identified 78 of the 83 histologically negative cases, for a specificity of 94.0%. The 16 cases histologically diagnosed as ductal hyperplasia, which carries a high risk for subsequent malignancy, were studied in detail in an effort to define histologic and cytologic criteria for this entity. Using selected histologic criteria, 11 of these cases were graded as showing mild-to-moderate atypical hyperplasia and 5 as showing severe atypical hyperplasia. Three of the latter cases were similarly identified by an analogous cytologic grading; the other two cases had insufficient cytologic samples. The total results in this series of 114 cases support the use of stereotaxic FNA cytology in the diagnosis of these nonpalpable breast lesions, examples of which are illustrated. In particular, it may help to raise the low specificity yielded by mammography alone, which would represent a significant advance for the patient in terms of the accuracy, expediency and reduced cost of diagnosing these lesions.     

Fine needle aspiration biopsy of the breast. Influence of the number of passes and the sample size on the diagnostic yield

The sensitivity of fine needle aspiration (FNA) biopsy of the breast as a function of the number of aspirations performed on any given lesion was investigated. Four separate aspirations each were performed on over 400 lesions of the breast, 93 of which yielded a cytologic diagnosis. The incremental diagnostic yields of each subsequent aspiration were tabulated. The first aspirate of the sequence gave the greatest yield, with smaller incremental yields on the second through the fourth aspirates. Benign and malignant lesions gave similar results, as did palpable and nonpalpable lesions (the latter being usually smaller in size). A mathematical extrapolation of the data indicates that three or four aspirations of any given lesion provide the optimal yield within the limits of practicality. This performance of multiple FNA biopsies is particularly important when the pathologist does not perform the biopsy, or is unable to assist in the immediate interpretation of the specimen to assess its adequacy.     

Cytology of nipple discharge in florid gynecomastia

OBJECTIVE: To determine the cytomorphologic spectrum of nipple discharge in florid gynecomastia. STUDY DESIGN: During a 22-year period (July 1979-June 2001), nipple discharge from nine males with breast lesions were examined. Smears from four of these cases with histologically documented gynecomastia were reviewed along with the tissue sections. RESULTS: In the three patients with florid gynecomastia the smears were cellular, with numerous benign ductal cells and papillary fragments along with foam cells and inflammatory cells. Epithelial atypia was mild in two cases and moderate in one. One of the three cases had an associated breast lump that showed features of florid gynecomastia on fine needle aspiration cytology. The biopsy from this case showed cystic hyperplasia of the breast similar to that in women with an intraductal papilloma. One case of simple gynecomastia on histology showed two fragments of benign ductal cells with occasional apocrine and foam cells. CONCLUSION: Nipple discharge in florid gynecomastia may pose problems in identification as the cellularity and atypia may lead to a misdiagnosis of carcinoma.     

Analysis of fine needle aspiration cytology of the breast: a review of 1,297 cases and correlation with histologic diagnoses

OBJECTIVE: To evaluate the accuracy of fine needle aspiration (FNA) cytology of the breast and to ascertain its usefulness. STUDY DESIGN: The authors reviewed 1,297 cases of FNA cytology of the breast which were performed at Chonnam National University Hospital from 1999 to 2002. Cytologic diagnoses were compared with histologic diagnoses in 457 cases that underwent both cytologic and histologic examination. RESULTS: Of 1,297 cases, 1,201 (92.6%) were satisfactory and 96 (7.4%) unsatisfactory. Subsequent histologic examination was performed on 291 cases (29.7%) out of 981 "benign" lesions, 28 (73.7%) of 38 "suspicious," 124 (68.1%) of 182 "malignant" and 14 (14.6%) of 96 "unsatisfactory." FNA cytology revealed 77.7% sensitivity, 99.2% specificity, 98.4% positive predictive value and 88.0% negative predictive value. Diagnostic accuracy was 91.1%. Of the 291 benign cases on cytology, 35 cases were malignancy on histology. Of the 124 cases reported as malignant, 2 were benign. Interpretive error was the leading cause of false positive diagnoses. CONCLUSION: Although FNA cytology is a useful diagnostic procedure for the evaluation of breast lesions, it should be combined with other diagnostic modalities, such as physical examination, ultrasonography and mammography.     

Audit of 6 years' experience of breast fine needle aspiration (FNA) cytology using the cytospin method; improvement through multidisciplinary clinical audit

Audit of 6 years' experience of breast fine needle aspiration (FNA) cytology using the cytospin method; improvement through multidisciplinary clinical audit
A breast FNA cytology service for palpable breast lumps was commenced in 1989 using the cytospin method. Over the following 6 years 2314 aspirates were received. The results were audited in detail in 1990, 1991/1992 and 1994. Multidisciplinary clinical audit meetings followed each audit cycle. Practice change was agreed after each audit. Each audit cycle was followed by demonstrable improvement in the complete sensitivity of the technique, being respectively 79%, 88% and 96%. The cytospin method is a viable alternative to the conventional smear method.     

Improved breast cytology results with near patient FNA diagnosis

OBJECTIVE: To examine the impact of a cytopathologist using near patient fine needle aspiration diagnosis (NPFD) for breast diagnosis. STUDY DESIGN: The cytology results of all palpable solid breast lesions undergoing fine needle aspiration (FNA) during a two-year period were prospectively audited and categorized as definitely benign or malignant (definite), probably benign, indeterminate or suspicious (indefinite) or unsatisfactory. The final diagnosis (benign or malignant) was determined from a review of patients' charts and a survey of patients' family physicians. Aspirates were performed by surgical staffand reported either later (non-NPFD) or by NPFD. RESULTS: Of 720 FNAs, 230 were by NPFD and 490 by non-NPFD. NPFD was associated with a significantly greater proportion of definite reports (91.9% versus 82.4%). NPFD of discrete breast lumps was associated with higher specificity (89.1% versus 67.5%) and a lower unsatisfactory rate (9.4% versus 19.6%) than non-NPFD. NPFD did not improve the unsatisfactory rate of FNAs from diffuse breast thickenings. CONCLUSION: FNA by a dedicated specialist and immediate reporting should be an integral part of a breast diagnostic service.     

High-throughput molecular analysis from leftover of fine needle aspiration cytology of mammographically detected breast cancer

We investigated whether residual material from diagnostic smears of fine needle aspirations (FNAs) of mammographically detected breast lesions can be successfully used to extract RNA for reliable gene expression analysis. Twenty-eight patients underwent FNA of breast lesions under ultrasonographic guidance. After smearing slides for cytology, residual cells were rinsed with TRIzol to recover RNA. RNA yield ranged from 0.78 to 88.40 μg per sample. FNA leftovers from 23 nonpalpable breast cancers were selected for gene expression profiling using oligonucleotide microarrays. Clusters generated by global expression profiles partitioned samples in well-distinguished subgroups that overlapped with clusters obtained using "biologic scores" (cytohistologic variables) and differed from clusters based on "technical scores" (RNA/complementary RNA/microarray quality). Microarray profiling used to measure the grade of differentiation and estrogen receptor and ERBB2/HER2 status reflected the results obtained by histology and immunohistochemistry. Given that proliferative status in the FNA material is not always assessable, we designed and performed on FNA leftover a multiprobe genomic signature for proliferation genes that strongly correlated with the Ki67 index examined on histologic material. These findings show that cells residual to cytologic smears of FNA are suitable for obtaining high-quality RNA for high-throughput analysis even when taken from small nonpalpable breast lesions.     

Fine Needle Aspiration of Palpable Breast Lumps: A 1-Year Audit Using the Cytospin Method

A fine-needle aspiration (FNA) service for the diagnosis of palpable breast lumps was started at the Royal Preston Hospital, Preston, UK, in November 1989. Over the subsequent year, 407 FNAs were taken from 393 women. A simple technique was used which involved the surgeon flushing the aspirate into 10 ml of Cytospin collection fluid; cytocentrifuge preparations were then safely and conveniently prepared in the laboratory. Slides were stained with Papanicolaou and H&E. The method detected 112 out of a total of 121 cancers (92.6%); of the nine that were undetected, five aspirates were inadequate and four were falsely reported as negative. There were no false positives. The overall inadequate rate was 11.0%. Excluding inadequate samples, the absolute sensitivity was 89.7% and complete sensitivity 96.6% with 94.4% specificity. This 1-year audit has shown the Cytospin method of FNA in palpable breast disease to have a favourable sensitivity and specificity, and therefore to be an alternative to conventional FNA using direct smears.     

A comparison of mammography and ultrasonography in the evaluation of breast masses

Aim: Aim of the study is to evaluate breast masses using mammography (MG) and ultrasonography (USG) independently and in combination. Materials and methods: Our study group consisted of 62 female patients, with breast symptoms such as palpable lumps, pain in the breast and nipple discharge who were examined prospectively over a period of 6 months. All 62 patients were examined by both MG and USG independently. Fine needle aspiration cytology (FNAC) or core cut biopsy was done according to the findings of MG and USG and then the results were correlated with each modality finding. Results: According to this study MG showed an efficiency of 81.8 % compared to 95.5 % for USG in detecting fibrocystic mastitis. However their combined approach resulted in 100 %. In the case of fibroadenomas, MG showed 75 % efficiency and USG only 35 % and the combination resulting in 93.7 %. For carcinomas, MG had an efficiency of 77.8 % and USG 55.6 %, but the combination had an efficiency of 98.1 %. Overall, the histopathological results when correlated with each modality finding showed that MG had an efficiency of only 77.4 % and USG only 69.8 % when used alone in detecting these lesions of the breast compared to an efficiency of 98.1 % obtained by their combined approach. In our study, we showed that there was no significant difference in sensitivity between MG and USG (p = 0.3768) but there was significant difference in MG alone and MG-USG combination (p = 0.0015) and USG alone and USG-MG combination (p = 0.0001). Conclusion: Our study confirmed that combined MG and USG had higher sensitivity rate than the sensitivity rate observed for either single modality. The diagnostic accuracy for carcinomas of the breast appear to improve when MG was combined with USG, even in cases which showed no evidence of microcalcification or other signs of abnormalities. Our study implies that, USG may be the only viable modality in pregnant and lactating women as it does not involve ionizing radiation and also in dense breast tissue, as density is a limiting factor for MG.     

Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA): experience of an academic centre in the USA

S. Zhang, D. V. S. DeFrias, R. Alasadi and R. Nayar
Endoscopic ultrasound‐guided fine needle aspiration (EUS‐FNA): experience of an academic centre in the USA Objectives: Endoscopic ultrasound‐guided fine needle aspiration (EUS‐FNA) has become widely accepted as an effective modality for obtaining tissue for primary diagnosis and staging. We have been using EUS‐FNA since July 2001 and herein we summarize our experience over a 5‐year period. Methods: A computer‐based search for in‐house EUS‐FNA was performed in the pathology database from July 2001 to October 2006. To calculate the sensitivity, specificity and accuracy of EUS‐FNA, the cytology diagnosis was compared with the surgical follow‐up. Results: A total of 951 EUS‐FNAs were performed during the study period and included 279 pancreatic solid lesions, 186 pancreatic cyst lesions, 249 lymph node aspirations, 111 gastrointestinal (GI) tract submucosal lesions, and 126 miscellaneous lesions. EUS‐FNA had a very high sensitivity and accuracy for solid pancreatic lesions (94.7 and 97.7%, respectively), low sensitivity and accuracy but high specificity (47, 64.8 and 95%, respectively) for cystic lesions. Cyst fluid carcinoembryonic (CEA) levels were significantly higher in mucinous neoplasms than non‐neoplastic cysts. EUS‐FNA also had very high sensitivity and specificity for detecting metastatic carcinoma in lymph nodes (95 and 100%, respectively). GI submucosal spindle cell tumours were further classified with immunohistochemical stains performed either on a cell block or a core biopsy obtained via EUS guidance. Conclusions: EUS‐FNA has a very high sensitivity and accuracy for pancreatic solid lesions, but the sensitivity for cystic lesions is generally low. Cyst fluid chemical analysis for CEA is helpful, but the overlap between mucinous neoplasm and non‐neoplastic cysts is significant. Recognizing GI contamination is important and immunohistochemical stains are useful for GI submucosal spindle cell lesions.     

Triple test approach to inadequate fine needle aspiration biopsies of palpable breast lesions.

OBJECTIVE: To perform a retrospective study evaluating the triple test for inadequate fine needle aspiration (FNA) biopsies of palpable breast lesions with a two-year clinical follow-up. STUDY DESIGN: All aspirates were reviewed and assessed for cellular adequacy in a one-year period. Specimen adequacy was based on the most stringent criteria, the presence of six or more epithelial cell clusters composed of at least six cells each. In all cases, clinical and radiologic results were reviewed and compared with the histologic outcome. RESULTS: Aspirates from 61 of 263 (23%) patients with palpable breast lesions that yielded nondiagnostic results were examined. The study showed a misdirected FNA rate of 21% and a misinterpreted rate of 1.6%. The other 77% of cases had benign surgical biopsies and/or clinical follow-up. Three of 61 (4.9%) cases with nondiagnostic smears were found to have cancer; two were inadequate due to misdirected aspirates, and one was misinterpreted microscopically. All cancer cases underwent surgical removal of the mass as a result of clinical or radiologic suspicion. CONCLUSION: We recommend utilizing the three diagnostic parameters of cytology, clinical findings and radiology, the "triple test," to achieve the best diagnostic accuracy in breast FNAs and to enhance patient management.     

Accuracy of touch imprint cytology of image-directed breast core needle biopsies

OBJECTIVE: To evaluate the accuracy of touch imprint (TI) cytology of image-directed core needle biopsy (CNB) specimens of nonpalpable breast lesions. STUDY DESIGN: Fifty-two consecutive CNBs from 44 patients were performed under mammographic or ultrasound guidance. Air- dried TIs of CNBs were stained with Diff-Quik. TI cellularity was considered adequate if six or more ductal cell groups were identified. CNBs and TIs were interpreted in a blinded fashion. RESULTS: TI cellularity was adequate in 37/52 (71%) cases, including 17/20 carcinomas and 20/32 benign lesions. Among 17 carcinomas, TIs were positive in 12, suspicious in 4 and atypical in 1. One case of lactational change was suspicious on TI, and 5/8 fibroadenomas were atypical. No benign lesions were called "carcinoma" on cytology. When lesions categorized as "carcinoma" or "suspicious" were considered positive and those classified as "atypical" or "benign" were scored as negative, TI sensitivity and specificity were 94% and 95%, respectively. When the "atypical" cases were grouped with the positive cases, TI sensitivity was 100%, with 75% specificity. CONCLUSION: With satisfactory cellularity, TIs of CNBs are highly accurate. When immediate evaluation of CNB specimens is important, TIs can potentially decrease the number of biopsy passes required and provide preliminary diagnoses.     

Ultrasound-guided fine needle aspiration cytology of impalpable breast lesions in a rural setting. Comparison of cytology with imaging and final outcome

OBJECTIVE: To analyze the effectiveness of fine needle aspiration (FNA) cytology in a multidisciplinary setting in rural Australia and to compare the imaging (mammographic and ultrasound) appearances and cytomorphologic findings with the final outcome. STUDY DESIGN: Prospective analysis of ultrasound-guided FNA cytology results from 426 women, aged 40-86 years, with screening-detected mammographic abnormalities. Cases of microcalcification, assessed mainly by stereotactatic core biopsy, were not included in the study. The FNAs were performed at a rural breast screening and assessment program in New South Wales, Australia, over a three-year period between May 1993 and May 1996. RESULTS: Imaging, FNA and combined imaging and FNA results from 426 women were as follows. The imaging diagnoses included 176 (41%) benign, 34 (8%) probably benign, 17 (4%) equivocal, 104 (24%) suspicious and 95 (23%) malignant cases. The FNA findings showed 59 (14%) no epithelial cells seen (nondiagnostic), 175 (41%) benign, 36 (8%) atypical, 41 (10%) suspicious and 115 (27%) malignant. Combined imaging and cytologic results comprised 224 (52.6%) benign, 10 (2.3%) atypical/equivocal, 59 (13.9%) suspicious and 133 (31.2%) malignant cases. All the malignant cases, by combined assessment, had malignant histology, and all the benign cases behaved in a benign fashion. In 80% of the suspicious lesions, the histologic diagnosis was malignant, but only 10% of the atypical/equivocal lesions had malignant histology. The positive predictive value of diagnosis of malignancy by combined imaging and FNA was 100%, and the false negative rate was 0%. CONCLUSION: Despite the recent surge in the popularity of core biopsy, FNA cytology of impalpable, mammographically detected lesions, when practiced in a multidisciplinary setting, is an extremely accurate test with high sensitivity, specificity, predictive values and efficacy. FNA cytology of the breast is a well-tolerated, relatively noninvasive test with a very low risk of complications. The sensitivity and positive predictive values for malignant and suspicious mammographic categories are also very high.     

Value of EUS‐FNA cytological preparations compared with cell block sections in the diagnosis of pancreatic solid tumours

Y. Kopelman, S. Marmor, I. Ashkenazi and Z. Fireman
Value of EUS‐FNA cytological preparations compared with cell block sections in the diagnosis of pancreatic solid tumours Objective: Endoscopic ultrasound‐guided fine needle aspiration (EUS‐FNA) is performed in order to achieve a definite tissue diagnosis of pancreatic lesions. This in turn is a guide to the appropriate treatment for the patient. Tissue samples collected by the same needle for cytological preparations and cell block histological sections (often referred to as FNA‐cytology and FNA–biopsy, respectively) are handled differently. The specific contribution of each of these tests was evaluated. Methods: One hundred and two consecutive patients underwent EUS‐FNA while being investigated for pancreatic solid lesions. Diagnosis was made by cytology, cell block sections or both. The diagnosis was confirmed by clinical outcome. Results: Male/female ratio was 61/41. Mean age was 65 ± 12 years (range, 22–94). Mean lesion size was 3.1 ± 1.8 cm (range, 0.6–10 cm); 68% were >2 cm and 75% were located in the pancreatic head. The average number of needle passes was two (range, 1–4 passes). Final tissue diagnosis was malignant in 66 (65%) patients. Sensitivity, specificity and accuracy were 73%, 94% and 81%, respectively, for cytology alone, and 63%, 100% and 78%, for cell blocks alone. Eighty‐two patients (80%) had cytology and cell blocks, which matched in 64 (78%) patients. EUS‐FNA results that relied on both techniques had 84% sensitivity, 94% specificity and 88% accuracy. Cytology revealed 13 malignancies not diagnosed on cell blocks, while cell blocks revealed five malignancies not diagnosed by cytology. Malignant lesions were more common in men; they were larger in size and located in the pancreatic head. Conclusion: EUS‐FNA cytology was more sensitive than cell blocks but less specific for the diagnosis of solid pancreatic lesions. The two methods are complementary and implementing both improves the diagnostic value of EUS‐FNA.     

Fine needle aspiration cytology of "minimal" breast cancer

The value of fine needle aspiration (FNA) cytology in the diagnosis of "minimal" breast cancer was studied. Sixteen (76.2%) of 21 cases of invasive breast cancer less than 1.0 cm in diameter and 14 (73.3%) of 19 cases of noninvasive breast carcinoma were given a positive diagnosis by FNA cytology. One "suspicious" and the five false-negative diagnoses occurred in cases of invasive carcinoma; the reasons were considered to be either a faulty technique of needling the tumor or the presence of prominent fibrosis in the tumor. In noninvasive carcinoma, atypical cells were misdiagnosed in two of the five smears that had been originally reported as negative. The results of the retrospective analysis showed that FNA cytology had a higher accuracy in the diagnosis of small lesions than did radiologic and echographic criteria, and FNA cytology was thus used as the main criterion for deciding on the necessity for preoperative surgical biopsies.     

Fine needle aspiration of breast masses. An analysis of 276 aspirates

A study of 276 consecutive fine needle aspirations (FNAs) of the breast in 240 cases is presented. Of these cases, 108 underwent subsequent biopsy of the breast; correlations between the FNA cytology and the surgical pathology findings revealed that FNA had a sensitivity of 79.4%, a specificity of 100% and a predictive value of a positive diagnosis of 100%. The overall diagnostic accuracy was 92.4%. These results are compared with those in other published series, and the pitfalls in and methods of improvement of breast FNA are discussed.     

Audit of Diagnostic Accuracy of Fna Cytology Specimens Taken By the Histopathologist In A Symptomatic Breast Clinic

One thousand and two patients with palpable breast lumps have had fine needle aspiration at a surgical symptomatic breast clinic where the pathologist takes, stains and immediately reports the aspiration cytology smears. High levels of complete sensitivity (95.7%) and specificity (100%) have been maintained with a combined complete sensitivity for aspiration cytodiagnosis, mammography and clinical assessment of 99.7%. Significant reductions of unnecessary biopsies and out-patient revisits have allowed major resource savings to be made. In view of the high degree of accuracy obtained by this approach to the investigation of palpable breast lesions, combined clinics with their benefits for the patient, both physical and psychological, should be encouraged.     

Neuroendocrine ductal carcinoma in situ of the breast: cytological features in 32 cases

T. Kawasaki, S. Nakamura, G. Sakamoto, T. Kondo, H. Tsunoda‐Shimizu, Y. Ishii, T. Nakazawa, K. Mochizuki, T. Yamane, M. Inoue, S. Inoue and R. Katoh
Neuroendocrine ductal carcinoma in situ of the breast: cytological features in 32 cases Objective: The purpose of this study was to clarify the cytological features of neuroendocrine ductal carcinoma in situ (NE‐DCIS) of the breast. Methods: We analysed the cytopathological findings in 22 fine needle aspiration (FNA) smears and 17 nipple discharge smears obtained from 32 Japanese patients with NE‐DCIS. Results: The background of the FNA smears was clear (59%), mucoid (23%), haemorrhagic (14%) or necrotic (5%). Most of the FNA smears (95%) showed high cellularity. Characteristically, NE‐DCIS cells were loosely arranged in three‐dimensional solid clusters or singly dispersed. Well‐developed vascular cores with or without malignant cells were occasionally recognized. The tumour cells were polygonal or spindle‐shaped with a fine granular, abundant cytoplasm. Nuclei with finely granular chromatin were round or oval and often eccentrically located (plasmacytoid appearance). Mitotic figures were infrequent. Nuclear grade was estimated to be low in 86%. Most nipple discharge smears had fairly low cellularity with poorly preserved cell clusters in a markedly haemorrhagic background, although two (12%) were extremely cellular with cytological characteristics similar to those of the FNA smears. Pre‐operative cytological malignant diagnoses were made in 42% of FNA smears and 0% of nipple discharge smears. Immunohistochemistry for neuroendocrine markers (chromogranin A and synaptophysin) confirmed the neuroendocrine nature of this tumour in adequate cytological specimens. Conclusions: NE‐DCIS has distinctive cytological features and can therefore be diagnosed as a neuroendocrine tumour in most FNAs and some nipple discharge smears by cytological examination employing immunohistochemical techniques. We emphasize that a breast lesion with these features may be in situ and not invasive, and also that there is a risk of under‐diagnosis.