Accuracy of cytology vs. microbiopsy for the diagnosis of well-differentiated hepatocellular carcinoma and macroregenerative nodule. Definition of standardized criteria from a study of 100 cases

OBJECTIVE: To determine the accuracy of ultrasound (US)-guided fine needle aspiration (FNA) for the diagnosis of well-differentiated hepatocellular carcinoma (wd HCC) and macroregenerative nodule (MRN) and to identify the most useful cytologic and histologic criteria to distinguish between those two diagnoses. STUDY DESIGN: Cytologic and histologic specimens of 50 wd HCC and 50 MRN were reviewed blindly and the diagnosis compared to the final clinical diagnosis. Twenty-eight cytologic and 25 histologic criteria were examined and subjected to statistical analysis. RESULTS: Among 100 cases studied, the final diagnosis was available for 43. In those 43 cases, combining analysis of cytologic and histologic specimens, the sensitivity of US-guided FNA was of 75% and the specificity 100%. Cytologic analysis was better than isolated histologic analysis, with a sensitivity of 75% vs. 68%, respectively. Sensitivity of cytologic diagnosis was lower for smaller nodules and for those located in poorly accessible hepatic segments. With the use of stepwise logistic regression analysis, four cytologic features (increased nuclear/cytoplasmic ratio, cellular monomorphism, nuclear crowding, loss of bile duct cells) and four histologic features (increased nuclear/cytoplasmic ratio, decreased Kupffer cells, cellular monomorphism, increased trabeculae thickness) were identified as predictive of HCC.     

Fine needle aspiration cytology of lobular breast carcinoma. Comparison with other breast lesions

OBJECTIVE: To analyze the detailed cytomorphology of lobular breast carcinoma and to compare the cytologic smears of benign, borderline and infiltrating duct carcinoma. STUDY DESIGN: Fine needle aspiration cytology (FNAC) smears of histopathologically proven infiltrating lobular carcinoma (ILC), infiltrating ductal carcinoma (IDC), borderline lesions and benign breast lesions were selected for study. Detailed cytomorphologic analysis of the smears was carried out on hematoxylin and eosin- and May-Grünwald-Giemsa--stained slides, and a comparison of results was done. The various cytologic features were also graded semi-quantitatively with the numerical score; logistic regression analysis was done. RESULTS: There were 25 cases of ILC, 30 of IDC, and 10 borderline and 18 benign lesions. Cytologic diagnosis of malignancy on FNAC smears of ILC was offered in 19 cases; of them, 2 cases were diagnosed as ILC. The remaining six cases were diagnosed as borderline (four) and benign lesions (two). Overall sensitivity in detection of malignancy in ILC cases was 76%. FNAC smears of ILC showed moderate (52%) to abundant (32%) cellularity. The cells of ILC were arranged both in clusters and in dissociation (72%). Individual cells were monomorphic (40%) to mildly pleomorphic (60%), and the cells were smaller. The cells showed a smooth, regular nuclear margin; bland chromatin; and indistinct nucleoli. Indian file arrangement was frequently observed (28%). Nuclear molding (28%) and intranuclear inclusions (16%) were also noted. Intracytoplasmic lumina were seen in occasional cases. Logistic regression analysis was carried out, and a comparison between lobular carcinoma and ductal carcinoma, and borderline and benign lesions was done. Logistic regression analysis of cytomorphologic features showed that cellularity and nuclear margin irregularities were the two most important features to distinguish ILC from IDC. In comparison to borderline lesions, cell dissociation was more common in ILC. The salient cytologic features that helped to distinguish ILC from benign lesions was cell size, cellularity, cell uniformity and chromatin pattern. CONCLUSION: There are overlapping cytologic features between ILC, IDC and borderline breast lesions on FNAC smears. Logistic regression analysis may be helpful in this regard.     

Sarcomatoid renal cell carcinoma metastatic to the breast: report of a case with diagnosis on fine needle aspiration cytology

BACKGROUND: Tumors metastatic to the breast are a rare occurrence. The correct identification is essential as there are divergent management implications. Fine needle aspiration cytology (FNAC) is an effective method of diagnosis when coupled with the judicious use of immunocytochemistry. CASE: A 50-year-old Indian woman presented with a palpable right breast lump that was clinically suspicious for malignancy. There were no contralateral breast masses or palpable axillary lymphadenopathy. There was a history of nephrectomy carried out several years earlier for renal cell carcinoma (RCC). FNAC of the right breast lump yielded malignant epithelioid and occasionally spindled cells within an inflamed background, while immunocytochemistry showed positive reactivity of tumor cellsfor CD10, with negative staining for CK7. The cytologic diagnosis favored a tumor of renal origin. The patient underwent wide central excision of the right breast lump, whereby the diagnosis of metastatic RCC with sarcomatoid features was confirmed. On follow-up, she developed metastases to multiple organ sites and died. CONCLUSION: A high index of suspicion is required in the diagnosis of disease metastatic to the breast. FNAC is a reliable diagnostic tool in the distinction of metastasis from primary malignancy of the breast.     

Role of CD10 immunochemistry in differentiating hepatocellular carcinoma from metastatic carcinoma of the liver

Background:  Differentiation of hepatocellular carcinoma (HCC) from metastatic carcinoma in liver may be difficult on fine needle aspiration cytology (FNAC), especially when both appear as moderate to poorly differentiated tumours. A panel of immunocytochemical stains is frequently used in case of diagnostic difficulty. Recently, CD10 immunostain with a canalicular staining pattern has been shown to be a specific marker for hepatocytic differentiation.
Objective:  The present study was designed to assess the value of CD10 immunostain in distinguishing HCC from metastatic carcinoma in material obtained by FNAC of liver masses.
Materials and methods:  Formalin-fixed, paraffin-embedded cell blocks of 22 cases (7 cases of HCC and 15 cases of metastatic carcinoma), direct acetone-fixed smears and destained smears of 28 cases (18 cases of HCC and 10 cases of metastatic carcinoma) prepared from FNAC of the liver were immunostained using monoclonal antibody against CD10.
Results:  Seventeen (68%) of twenty-five cases of HCC were positive for CD10 with a canalicular staining pattern. Among them 7 (70%) of 10 cases were well-differentiated HCC and 10 (66%) of 15 cases were moderate to poorly differentiated HCC. Of 25 cases of metastatic carcinoma, four (16%) were positive for CD10 with a cytoplasmic (three cases) and membranous staining (one case) pattern.
Conclusion:  CD10 immunostaining is useful in discriminating HCC and metastatic carcinoma of the liver and is easily applied on cell blocks as well as FNAC smears.     

Fine needle aspiration cytology of metastatic skin nodules. A report of 2 cases

BACKGROUND: Skin is an uncommon site for metastatic deposits from internal malignancy. The scalp as a metastatic site is uncommon. Metastatic skin/scalp nodules can be diagnosed accurately by fine needle aspiration cytology (FNAC). However, few reports exist on the FNAC diagnosis of metastatic skin/scalp nodules. Metastatic skin nodules may mimic primary skin tumors, or vice versa, and some primary skin tumors may be mistaken for metastatic skin deposits. CASES: In case 1 a 60-year-old male presented with nodules on the scalp, back and upper extremity. The scalp nodule was noticed first, followed by the ones on the back and upper extremity. FNAC of nodules on the scalp and upper extremities showed deposits of carcinoma. The nodule on the back was excised. In case 2 a 66-year-old female presented with a nodule on the scalp. She also had enlarged bilateral cervical lymph nodes. FNAC of the scalp nodule and cervical lymph nodes revealed the cytologic features of non-Hodgkin's lymphoma. CONCLUSION: Metastatic cutaneous/staneous/subcutaneous deposits can pose diagnostic hurdles in the absence ofprevious or simultaneous malignancy. FNAC is a quick and cost-effective tool for the evaluation of such nodules.     

Fine needle aspiration cytology of Hodgkin's lymphoma: A cytohistologic correlation study from a cancer center in Kuwait

OBJECTIVE: To assess the diagnostic accuracy offine needle aspiration cytology (FNAC) in the diagnosis of Hodgkin's lymphoma (HL). STUDY DESIGN: We selected all the cases in which a cytologic diagnosis of HL, suggestive of or suspicious for HL, or HL as the prime differential diagnosis was offered on FNAC. These cases were correlated with histopathologic follow-up. Cases of primary HL diagnosed on cytology but without histopathology were excluded from the study. RESULTS: Histopathologic follow-up was available in 46 cases. Of these, 42 were correctly diagnosed as HL, and there was a discorrelation in 4 cases, comprising 3 cases of non-HL (T-cell-rich B-cell lymphoma [TCRBCL]-2, anaplastic large cell lymphoma-1) and 1 case of metastatic carcinoma. Overall accuracy was 91.3%. In 14 cases, the cytologic features were diagnostic ofrecurrence; hence, no histopathologic examination was done. No follow-up was available for the remaining 19 cases, which were excluded from the study. CONCLUSION: FNAC is very useful for rapid and accurate approach to the diagnosis of recurrent and most cases of primary HL. Because of morphologic similarities, it is difficult to differentiate HL from anaplastic large cell lymphoma and TCRBCL on FNAC. It is advisable to request a histopathologic examination in all cases of primary HL.     

Fine needle aspiration cytology of metastatic choriocarcinoma presenting as a breast lump. A case report

BACKGROUND: While choriocarcinoma is a rapidly invasive, widely metastasizing malignancy, it responds well to chemotherapy, so it is important to obtain an early diagnosis. We report the fine needle aspiration cytology (FNAC) of a case of choriocarcinoma metastatic to the breast. CASE: A 48-year-old female presented with a cough, hemoptysis and epistaxis. Chest computed tomography revealed multiple nodules in both lung fields. Also, a firm, slightly tender mass in the lower outer quadrant of the left breast was palpated. The breast mass was clinically suspected to be a metastatic lung cancer. FNAC of the breast showed a malignant tumor that had been misdiagnosed as a metastatic non-small cell carcinoma of the lung. Histologic examination of a nasal biopsy revealed metastatic choriocarcinoma. CONCLUSION: The cytologic features of choriocarcinoma are quite characteristic, with side-by-side, malignant, mononucleated cells and multinucleated giant cells corresponding to cytotrophoblasts and syncytiotrophoblasts, respectively. The disease is possible to diagnose by a careful examination of FNAC samples.     

Spleen metastasis from thyroid carcinoma. Report of a case with diagnosis by fine needle aspiration cytology

BACKGROUND: Lymphoreticular malignancies are the most common neoplasms involving the spleen. Metastasis can be caused by direct invasion from surrounding tumors or from hematogenous spread. Spleen metastases from thyroid carcinoma are unusual, and only 1 case has been reported; none have been diagnosed by fine needle aspiration cytology (FNAC). CASE: A 75-year-old female was diagnosed 6 months earlier with a poorly differentiated thyroid carcinoma with wide lymphatic and vascular invasion. Abdominal computed tomography (CT) and magnetic resonance imaging showed several spleen nodules. FNAC was performed under CT guidance. Cytologic examination showed atypical epithelial cells with thyroidal characteristics. CONCLUSION: This case had the cytologic findings of a poorly differentiated carcinoma of the thyroid metastatic to spleen. We confirmed the rarity of this pathology and the efficacy of splenic FNAC in the diagnosis.     

Carcinosarcoma of the palate: report of a case with a diagnosis of sarcomatoid metastasis by fine needle aspiration cytology

BACKGROUND: Carcinosarcoma (sarcomatoid carcinoma) is a rare tumor with a high predilection for the aerodigestive tract. Cytologic diagnosis of metastatic carcinosarcoma has been reported in very few cases. CASE: An 84-year-old woman presented with a 2-cm-diameter, right cervical lymph node that was referred for fine needle aspiration cytology (FNAC). She had received radiotherapy for a palatal squamous cell carcinoma 2 years earlier. The FNAC smears had a sarcomatoid appearance. Repeat fine needle aspiration was performed, with cytologic and immunocytochemical staining. Careful consideration of the cytologic and immunophenotypic features led to an impression of carcinosarcoma. Histologic sections of the palatal biopsy that had been previously diagnosed as squamous cell carcinoma were reviewed, and a final diagnosis of carcinosarcoma was established. CONCLUSION: Metastasis of rare lesions, such as carcinosarcoma may be confusing and difficult to diagnose on FNAC, especially when the cytologic sample shows a predominantly sarcomatoid component. The difficulty is compounded when the sarcomatoid component happens to have been overlooked on the initial histologic assessment. With representative cytologic sampling, immunocytochemical staining and review of the histologic material, the correct diagnosis was achieved in this case.     

Isolated carcinoid tumor metastatic to the thyroid gland: report of a case initially diagnosed by fine needle aspiration cytology

BACKGROUND: Neuroendocrine tumor metastatic to the thyroid gland is rare and may be difficult to differentiate from primary thyroid neuroendocrine tumors, such as medullary thyroid carcinoma (M/ITC). This report describes an unusual case of bronchial carcinoid metastatic to the thyroid diagnosed by fine needle aspiration cytology (FNAC). CASE: A 42-year-old woman with an undiagnosed bronchial carcinoid tumor presented to our clinic with a solitary nodule in the thyroid gland. FNAC of the nodule showed loosely cohesive groups of cuboidal tumor cells with scant, slightly granular cytoplasm; centrally located nuclei with a coarsely granular, salt-and-pepper chromatin pattern and inconspicuous nucleoli. Immunocytochemically the tumor cells were positive for neuron-specific enolase, chromogranin and synaptophysin and negative for thyroglobulin, calcitonin and carcinoembryonic antigen. The cytologic diagnosis of a metastatic neuroendocrine carcinoma was confirmed histologically. CONCLUSION: Metastasis to the thyroid gland may pose a diagnostic problem, particularly with tumors of neuroendocrine origin, as these have similar cytologic features in various organs. The correct preoperative cytologic diagnosis of metastatic carcinoid tumor in patients without a prior history of cancer and differential diagnosis with MTC are crucial because prognosis, workup and treatment are different in each.     

Frequency of cytologic features in fine needle aspirates from histologically and cytologically diagnosed fibroadenomas

Identification of key cytologic criteria for various lesions by means of stepwise logistic regression is common today and is often claimed to facilitate cytologic diagnosis. As can be expected, there usually is good agreement between the selected criteria and those given in the cytologic literature. In a study by Bottles et al based on 64 fibroadenomas, stroma, antler horn clusters and honeycomb sheets differentiated fibroadenoma from ductal carcinoma. We applied Bottles's criteria to our fibroadenoma material in order to test their value in clinical cytologic practice. In fine needle aspirates from histologically (cytologically) diagnosed fibroadenomas, stroma was found in 41 (57%), antler horn clusters in 59 (90%) and honeycomb sheets in 62 (81%), which reduced the clinical value of the criteria.     

Fine needle aspiration biopsy diagnosis of mucoepidermoid carcinoma. Statistical analysis

Fine needle aspiration (FNA) biopsy is an increasingly popular method for the evaluation of salivary gland tumors. Of the common salivary gland tumors, mucoepidermoid carcinoma is probably the most difficult to diagnose accurately by this means. A series of 96 FNA biopsy specimens of salivary gland masses, including 34 mucoepidermoid carcinomas, 51 other benign and malignant neoplasms, 7 nonneoplastic lesions and 4 normal salivary glands, were analyzed in order to identify the most useful criteria for diagnosing mucoepidermoid carcinoma. Thirteen cytologic criteria were evaluated in the FNA specimens, and a stepwise logistic regression analysis was performed. The three cytologic features selected as most predictive of mucoepidermoid carcinoma were intermediate cells, squamous cells and overlapping epithelial groups. Using these three features together, the sensitivity and specificity of accurately diagnosing mucoepidermoid carcinoma were 97% and 100%, respectively.     

Fine needle aspiration cytology of clear cell carcinoma of the gallbladder with hepatic infiltration: a case report

BACKGROUND: Clear cell carcinoma of the gallbladder (CCG) is an unusual histologic variant recognized in the World Health Organ ization classification of tumors of the gallbladder and extrahepatic bile ducts. Although the clinicopathologic features have been documented in a few reports, to our knowledge the cytologic findings have not been described before. We report the fine needle aspiration cytology (FNAC) findings in a case of CCG with hepatic infiltration. CASE: A 72-year-old woman presented with right upper quadrant pain and hepatomegaly. Serum levels of CA19-9 and alpha-fetoprotein were elevated. Computed tomography revealed several hepatic nodules, the larger of which was a mass in contact with the gallbladder, which had a thickened wall. FNAC showed loose sheets and disassociated cells with abundant, clear, finely vacuolated cytoplasm. Atypical bare nuclei, binucleated cells and some multinucleated cells were also found. A simultaneous trucut biopsy from the main hepatic mass confirmed the diagnosis. CONCLUSION: CCG is a clear cell neoplasm that should be considered when clear changes are observed on FNAC. Recognition of the cytologic features, together with adequate clinicoradiologic study, may be sufficient to establish the diagnosis.     

Fine needle aspiration cytology of mammary carcinoma with choriocarcinomatous features: a report of 2 cases

BACKGROUND: Neoplasms of the breast containing multinucleated giant cells (MGCs) include both benign and malignant entities, such as benign soft tissue giant cell tumors, atypical fibrous histiocytoma, sarcomas, metaplastic carcinomas and the uncommon carcinomas containing osteoclast-like giant cells (OGC). Breast carcinoma with choriocarcinomatous features (BCCF) is a distinct variant of breast cancer. CASES: We report the cytologic features, pathologic findings and immunohistochemical profile in 2 cases of this unusual variant of breast carcinoma. Two women aged 53 and 50 years women presented with a history of left and right breast lump but no local lymphadenopathy, respectively. Fine needle aspiration cytology (FNAC) of both cases revealed abundant MGC with highly pleomorphic tumor cells in the hemorrhagic necrotic background. Both of the cases were histopathologically diagnosed as BCCF. CONCLUSION: Choriocarcinomatous differentiation with multinucleated syncytiotrophoblast-like giant cells is extremely rare in breast tumors. Although rare, FNAC of breast cancer with pleomorphic MGC requires careful search for differential diagnosis; breast carcinoma with giant cell features (choriocarcinomatous features, OGC features) must be differentiated from metastatic tumors and other breast lesions containing giant cells.     

Diagnostic pitfalls in the evaluation of fine needle aspiration cytology of the thyroid: correlation with histopathology in 260 cases

Objectives:  Fine needle aspiration cytology (FNAC) of the thyroid is a non-invasive, cost-effective screening procedure that is valuable for distinguishing neoplastic lesions from non-neoplastic nodules. The aim of this study was to determine the diagnostic accuracy of FNACs performed at our institution by correlating FNAC results with histopathological diagnoses.
Methods:  Two hundred and seventy-one aspiration cytology specimens followed by thyroidectomy were included in the study, and the results of 260 adequate FNACs were compared with their histological diagnoses.
Results:  The sensitivity and specificity of thyroid FNAC for detecting neoplasia were 92.6% and 91.6%, respectively. There were 15 (5.7%) false positives and six (2.3%) false negatives.
Conclusions:  The results showed that follicular cells that exhibit some of the features of papillary carcinoma could be observed in a cytology slide of Hashimoto's thyroiditis, leading to a diagnostic pitfall. In addition, cellularity and overlapping cytological criteria in hyperplasia might lead to a false diagnosis.     

Fine needle aspiration cytology of the thyroid: a comparison of 5469 cytological and final histological diagnoses

OBJECTIVE: We evaluated the efficacy of fine needle aspiration cytology (FNAC) of the thyroid in a series of 5469 lesions with histological control and studied the causes of, and the possibility of reducing the limitations of the method. METHODS: FNAC was always performed by a pathologist under the guidance of a clinician, using a 22-gauge needle. Generally two aspirations were carried out, and usually four slides were obtained for each nodule; they were then stained with May-Grünwald-Giemsa and with Papanicolaou. The cytological diagnoses were classified in four groups: inadequate, benign, suspicious and malignant. RESULTS: We obtained a complete sensitivity of 93.4%, a positive predictive value of malignancy of 98.6%, and a specificity of 74.9%. At histological control, the cytological diagnosis of Hurthle cell neoplasm corresponded to a significantly higher incidence of malignant neoplasms than the diagnosis of non-Hurthle cell follicular neoplasm (32.1% versus 15.5%). There were 66 false-negative findings, the main cause of diagnostic error (24 cases) being failure to recognize the follicular variant of papillary carcinoma. The number of inadequate FNACs was low (4.2%). CONCLUSION: Our study confirmed the great efficacy of thyroid FNAC. A cytological diagnosis of Hurthle cell neoplasm should be considered an indicator of high risk. Awareness that failure to recognize the follicular variant of papillary carcinoma was the main problem in the interpretation of thyroid FNAC should lead to a decrease of false-negative diagnoses. The inadequate rate was very low, as it was the pathologist personally who performed the needle aspiration.     

Fine needle aspiration cytology of bone tumors

OBJECTIVE: To study the role of fine needle aspiration cytology (FNAC) in the diagnosis of bone tumors and its impact on therapeutic decisions. STUDY DESIGN: A group of 122 cases of bone tumor were evaluated by FNAC. Detailed diagnoses were compared with the available histology. RESULTS: Diagnostic accuracy of FNAC was 90.5% in this study. FNAC could differentiate between various round cell tumors such as Ewing's sarcoma and myeloma, among various giant cell-rich lesions of bone and between the benign and malignant chondroid bone tumors. Some uncommon variants were also correctly diagnosed. In metastatic bone tumors, the source of primary malignancy could not be indicated in the majority (52.9%) because of the poorly differentiated morphology. Osteoid or osteoid-like material was demonstrable in 63.6% cases of osteogenic sarcoma. A case of chondroblastic osteogenic sarcoma that was reported as chondrosarcoma was the only diagnostic error in the study. FNAC obviated the need of open biopsy in 63.8% patients, and therapeutic decisions were made according to the cytologic diagnoses. CONCLUSION: FNAC plays an important role in the early diagnosis of bone tumors by its accuracy, ease of use and rapidity and is helpful in making the therapeutic decisions.     

Fine needle aspiration cytology of thyroid nodules: how accurate is it and what are the causes of discrepant cases?

Fine-needle aspiration cytology (FNAC) is widely accepted as the most accurate, sensitive, specific and cost-effective diagnostic procedure in the assessment of thyroid nodules and helps to select people preoperatively for surgery. The purpose of this study was to evaluate the results of thyroid FNAC in our institution and to determine the reasons for discrepancies between the cytological and histological diagnosis. We evaluated the cytological and histological results of 254 FNACs obtained from 231 patients who underwent subsequent thyroid surgery. All of the material was blindly reviewed for quality control, by one experienced cytopathologist. All FNACs were carried out under ultrasound guidance. The cytological diagnosis was classified as benign, suspicious, malignant or unsatisfactory. The definitive histological study showed benign lesions in 195 of the 231 patients (84%). A benign diagnosis based on FNAC was correct in 105 of the 108 benign cases (97%). FNACs diagnosed as 'suspicious' resulted in a distribution of 49 benign (79%) and 13 malignant (21%) diagnoses. FNAC showed malignancy in 34 cases (13%) and in only one case did the final histology differ from cytology (correlation 97%). The percentage of FNACs that were inadequate for diagnosis was 20%. Review of cytological and histological slides did not lead to any change in the original diagnosis. Our study revealed a cytological-histological discrepancy (2%) in only 4 out of 231 cases over a period of 10 years, due to either a diagnostic or sampling error.     

Polyclonal carcinoembryonic antigen staining in the cytologic differential diagnosis of primary and metastatic hepatic malignancies.

In order to assess the utility of immunocytochemical staining of bile canaliculi with a polyclonal antiserum to carcinoembryonic antigen (pCEA) in the differentiation of primary hepatocellular carcinomas from metastatic malignancies, pCEA staining was performed on fine needle aspiration specimens from hepatic lesions in 60 patients. The original cytologic diagnoses were hepatocellular carcinoma in 22 patients, metastatic neoplasm or cholangiocarcinoma in 27 patients and benign hepatocytes in 11 cases. The cytologic diagnoses of malignancy were confirmed by surgical excision, autopsy or clinical investigations in 82% of the patients. Follow-up data, supported by pCEA staining, reversed the original cytologic diagnosis in three cases. Bile canalicular pCEA staining was identified in 18 of 22 cases of hepatocellular carcinoma and in all 11 benign hepatocellular aspirates. All 27 cases of metastatic malignancy or cholangiocarcinoma were negative for canalicular pCEA staining, although 11 cases exhibited cytoplasmic staining. Interpretation of pCEA staining was not affected by the intermingling of malignant cells and benign hepatocytes. Predictive values were 100% for a positive test and 87% for a negative test. These findings indicate that staining with pCEA antiserum is a useful adjunct in the differential cytologic diagnosis of malignant hepatic lesions.     

Fine needle aspiration cytology of invasive micropapillary carcinoma of the breast. A case report

BACKGROUND: Invasive micropapillary carcinoma of the breast is uncommon and was characterized only recently. Awareness of this entity and its cytologic appearance is important to allow early diagnosis by fine needle aspiration cytology (FNAC). To our knowledge, only two cases of FNAC of this lesion have been reported in the English-language literature. CASE: An 80-year-old female presented with a firm, nontender mass in the upper outer quadrant of the left breast. FNAC showed ductal carcinoma, and mastectomy showed invasive micropapillary carcinoma. The patient had axillary metastases and received tamoxifen. CONCLUSION: The cytologic features of invasive micropapillary carcinoma are distinctive, with clusters of cells showing hyperchromatic, irregular and crowded nuclei and peripherally located cytoplasm with a rare central lumen. Fibrovascular cores are absent. Although FNAC experience with this lesion is limited, the characteristic cytologic features, including "inside-out" cell clusters, should raise the suspicion of this variant of ductal carcinoma. Differentiation from other papillary lesions and malignancies may be possible, but more experience is needed as the number of reported cases remains limited.