Fine needle aspiration cytology of sclerosing adenosis of the breast

OBJECTIVE: To analyze the cytologic findings of sclerosing adenosis of the breast. STUDY DESIGN: We reviewed the fine needle aspiration (FNA) cytologic slides of 7 cases of sclerosing adenosis of the breast and compared the cytologic findings with those of 10 cases of fibroadenoma and 7 cases of fibrocystic change. RESULTS: The smears of sclerosing adenosis were moderately to markedly cellular, consisting of small to large groups of benign epithelial cells arranged with variable architecture. Acinar sheets, scattered individual epithelial cells and small, dense, hyalinized stroma were found in all cases of sclerosing adenosis. Epithelial cells in sclerosing adenosis appeared more frequently as acinar sheets and discohesive individual cells than did those of fibroadenoma (P < .05). However, the branching pattern of epithelial sheets, large sheets and bipolar, naked nuclei were commonly found in fibroadenoma (P < .05). Fibroadenoma had large, hypocellular, fibromyxoid stroma, whereas sclerosing adenosis had small, dense, hyalinized stroma occasionally attached to the epithelial sheets. As compared with fibrocystic change, sclerosing adenosis had similar findings but showed more abundant cellularity, acinar sheets and individual epithelial cells, and the presence of stroma (P < .05). CONCLUSION: Findings of frequent acinar sheets and small, dense, hyalinized stroma attached to epithelial sheets can aid the FNA cytologic diagnosis of sclerosing adenosis. Awareness of the presence of scattered individual epithelial cells in cytologic smears of sclerosing adenosis can help prevent a misdiagnosis of malignancy.     

Fine needle aspiration of breast lesions in women aged 30 and under

Fine needle aspiration (FNA) biopsies of 1,598 breast masses were performed between 1983 and 1989, and of them, 48 were from women aged 30 and under for whom a cytologic diagnosis was made by FNA and histologic follow-up was available. In 37 (77%) of the cases, both the cytologic and histologic diagnoses were benign. Fibroadenoma (20/37) and fibrocystic changes (14/37) were the most common benign lesions aspirated. Eight (17%) FNAs showed cytologic atypia. Four of these atypical lesions proved to be benign (two fibroadenomas, two fibrocystic changes). Epithelial proliferation in fibroadenomas and fibrocystic changes and cellular stroma in a fibroadenoma mimicking phylloides tumor were the causes of atypia in these biopsies. Four of the eight atypical lesions were shown to be carcinoma at biopsy (three infiltrating duct, one atypical medullary). Low cellularity, epithelial cohesiveness mimicking a fibroadenoma and background lactational changes in a pregnant patient were the causes of the atypical, rather than unequivocally malignant, diagnoses in these cases. In three patients (6%), a diagnosis of carcinoma was made by FNA and confirmed histologically (all were infiltrating duct carcinoma). Although most breast masses in women aged 30 and under are benign, cytologic atypia in a breast fine needle aspirate in this age group warrants a surgical biopsy. Clinical follow-up alone may be appropriate for young women with clinically nonsuspicious breast masses without cytologic atypia.     

Criteria for the diagnosis of fibroepithelial lesions of the breast with liquid-based cytology

OBJECTIVE: To establish diagnostic criteria for diagnosing and differentiating fibroepithelial lesions of the breast on ThinPrep (Cytyc Corp., Boxborough, Massachusetts, U.S.A.). STUDY DESIGN: Eighty-four fibroepithelial lesions were sampled by ultrasound-guided aspiration biopsy. Based on smears and histologic correlates, there were 55 fibroadenomas, 26 papillary neoplasms and 3 phyllodes tumors. The ThinPrep slides for each sample were reviewed retrospectively and evaluated for specific morphologic and cytologic features. RESULTS: On ThinPrep slides, 95% of the fibroadenomas had a predominance of single myoepithelial nuclei, 89% had staghorn clusters, and 47% had myxoid stroma. Among the papillary neoplasms, 8% had a predominance of single columnar ductal cells, 31% had papillary groups, 23% had vessels, and 27% had collagenous spherulosis. The ThinPrep preparations of the phyllodes tumors showed that 67% had single myoepithelial nuclei, 33% had a predominance of single ductal cells, 67% had staghorn clusters, and 0% had myxoid stroma. A majority of the fibroadenomas and the papillary neoplasms showed mild to moderate ductal epithelial hyperplasia. A majority of the phyllodes tumors showed moderate ductal epithelial hyperplasia. CONCLUSION: Fibroepithelial lesions of the breast can be accurately differentiated using ThinPrep samples based on the evaluation of specific cytologic and morphologic features, including the presence of staghorn clusters, fibromyxoid stroma, vessels, collagenous spherulosis, papillary clusters and predominance of myoepithelial nuclei or columnar cells in the background. However, the degree of ductal epithelial hyperplasia does not aid in the diagnosis.     

Benign phyllodes tumour vs fibroadenoma: FNA cytological differentiation

The differential diagnosis of fibroadenomas vs phyllodes tumours by fine needle aspiration (FNA) cytology is not possible in the majority of cases. The present study aims to look at common and dissimilar features to allow differentiation, if possible. We reviewed the FNA findings of 18 histologically proven phyllodes tumours and 18 fibroadenomas, checking in each case the epithelial features, the stromal features, and any atypia. Using a semi-quantitative score assessed by two observers we were able in most cases to distinguish a phyllodes tumour from a fibroadenoma. The most important criteria were larger stromal fragments, numerous plump stromal bare nuclei, and the higher ratio of stromal bare nuclei to epithelial bare nuclei in phyllodes tumours. In the present study, an original diagnosis of phyllodes tumour was made in 7/18 (38.9%) cases but with our criteria this could be improved to 15/18 (83.3%) cases. Therefore, the presence of specific stromal features in a dimorphic cellular pattern should suggest the correct diagnosis and differentiate its appearance from a cellular fibroadenoma.     

Intraoperative cytologic crush preparation findings in craniopharyngioma: a study of 72 cases

OBJECTIVE: To describe the intraoperative crush preparation and the cytologic features of craniopharyngioma and the differential diagnosis. STUDY DESIGN: Twelve cases of craniopharyngioma were diagnosed by crush preparation cytology in the Department of Pathology, Shiraz Medical School, and formed the basis of this study. The patients' ages ranged from 7 to 43 years; 3 were female and 9 male. The cytologic findings together with the histologic findings were studied. RESULTS: All cases had a high yield of cells, consisting of honeycomb sheets of epithelial cells with and without palisading rows of cells, papillary clusters, squamous cell clusters, anucleated squames, calcification, multinucleated giant cells, cholesterol crystals, glandular or rosettelike structures, ciliated columnar cells and spindle cells. The smears were diagnosed as suggestive of craniopharyngioma. Histologic sections confirmed the cytologic diagnoses. CONCLUSION: Intraoperative cytologic crush preparation findings are helpful in the diagnosis of craniopharyngioma, when combined with clinical information. Crush preparation cytology is important in the diagnosis of central nervous system tumors.     

Fine needle aspiration of benign and malignant breast masses associated with pregnancy.

Of 1,612 fine needle aspirates (FNA) of breast lesions performed over a seven-year period, 25 cases (1.5%) were identified as breast masses associated with pregnancy. Patients ranged in age from 16 to 46 years, with a mean of 27. Gestational age at the time of FNA ranged from three months to three months postpartum or following breast-feeding. Cytologic diagnoses of these pregnancy-associated breast masses were: galactocele (5 cases, 20%), lactating adenoma (9 cases, 36%), fibroadenoma with lactational change (7 cases, 28%), juvenile fibroadenoma with lactational change (1 case, 4%), atypical reactive duct cells with lactational change (1 case, 4%) and infiltrating duct carcinoma (2 cases, 8%). The degree of lactational change varied proportionately with gestational age. None of the 22 patients with benign cytologic diagnoses of galactocele, lactating adenoma or fibroadenoma subsequently developed carcinoma. The mean clinical follow-up for these 22 patients was 27 months. Three cases of fibroadenoma and the case of juvenile fibroadenoma were confirmed by surgical excision. Biopsy of the lesion cytologically diagnosed as atypical reactive duct cells with lactational change revealed infiltrating duct carcinoma (IDC). All three patients with IDC had involvement of multiple axillary lymph nodes, and 1 patient had widely metastatic disease. In two cases of IDC the background lactational breast epithelium exhibited marked cytologic atypia that closely resembled the IDC. Pregnancy-related cellular atypia potentially results in a false-positive diagnosis of breast carcinoma on FNA. FNA is useful in distinguishing benign breast masses of pregnancy from those with marked cytologic atypia requiring surgical biopsy and may minimize the delayed diagnosis of carcinoma associated with pregnancy.     

Fine needle aspiration cytology of sclerosing lobular hyperplasia of the breast: a case report

BACKGROUND: Sclerosing lobular hyperplasia presenting as a palpable, circumscribed nodular mass in a young female's breast is characterized histologically by prominent hyperplasia of the lobules and sclerosis of the intralobular connective tissue. The cytomorphologic features and differential diagnosis of the lesion are presented. CASE: A 14-year-old female presented with a painless, progressively increasing, nodular, firm, mobile lump measuring 5 x 5 cm in the right breast. The clinical and radiologic diagnosis was fibroadenoma. Fine needle aspiration smears showed a clean background with uniform, round to oval epithelial cells in flat sheets, round clusters and rosettelike (acinar) arrangements. A few naked nuclei were present, while stromal fragments were not seen. CONCLUSION: When analyzed in the context of the clinical findings, the cytologic features of sclerosing lobular hyperplasia help to differentiate it from other benign palpable nodular lesions of the juvenile breast.     

Comparative immunohistochemical localization of fibronectin and actin in human breast tumor cells in vivo and in vitro

The presence and distribution of fibronectin and actin in breast fibroadenoma cells have been investigated in frozen sections and primocultures of the same samples, by means of indirect immunofluorescence techniques. In the tissue cells, epithelial cells were negative whereas myoepithelial cells were positive with the two antibodies. Moreover, fibronectin was mainly distributed in basal lamina of ducts and ductules whereas actin appeared to label stroma cells. In primocultures obtained from the same samples of fibroadenomas, the labelled patterns of fibronectin and actin were not really distinguishable between cells; the two protein distributions were quite usual. Our data on human breast fibroadenoma cells are in agreement with the concepts of cellular adaptation or selection in culture and emphasize the difficulty in correlating results of "in vitro" and "in vivo" studies.     

Fine needle aspiration cytology of fibroadenoma with multinucleated stromal giant cells. A review of cases in a six-year period

OBJECTIVE: To describe the fine needle aspiration cytology findings of fibroadenoma with multinucleated stromal giant cells, with histologic correlation. STUDY DESIGN: The author reviewed the cytologic findings of two cases of fibroadenoma with multinucleated stromal giant cells from the file of Pamela Youde Nethersole Eastern Hospital in a six-year period from 1995 to the end of 2000. The diagnosis was confirmed by histologic examination of the lumpectomy specimens. RESULTS: The two cases had similar cytologic findings. The direct smears contained cohesive clusters of bland-looking ductal cells arranged in a "staghorn" pattern. Numerous naked nuclei were also seen in the background. Also, there were occasional multinucleated giant cells in isolation. These giant cells contained 5-10 randomly arranged, round to oval nuclei, fine chromatin and sometimes distinct nucleoli. The cytoplasm was abundant and pale staining, and the cell border was ill defined. Associated epithelioid histiocytes and foamy macrophages were not seen. Histologic examination of the lumpectomy specimens showed architectural features of fibroadenoma with pericanalicular and intracanalicular patterns. In addition, scattered multinucleated giant cells with focal degenerative change were noted in the tumor stroma. Their stromal nature was confirmed by immunohistochemical study. CONCLUSION: Multinucleated stromal giant cells are rarely identified in fine needle aspiration biopsies of fibroadenoma. Recognition of this peculiar finding may help to avoid misdiagnosis of other, more sinister conditions, such as phyllodes tumor and metaplastic carcinoma.     

Mammary pseudoangiomatous stromal hyperplasia. A reappraisal of the fine needle aspiration cytology findings

OBJECTIVE: To describe and reevaluate the fine needle aspiration cytology findings of pseudoangiomatous stromal hyperplasia (PASH) of the breast, with histologic, immunohistochemical and ultrastructural correlation. STUDY DESIGN: The authors reviewed the clinical features, fine needle aspiration cytology, histology and immunohistochemical results in all cases of mammary PASH encountered at Pamela Youde Nethersole Eastern Hospital, Hong Kong, during the 4-year period from January 1998 to May 2002. Ultrastructural examination was carried out in a selected example. The findings were compared with those in the literature. RESULTS: Four cases of PASH of the breast were encountered during the study period. The ages of the patients ranged from 34 to 56 years. One of them was a male presenting with gynecomastia. Only 2 cases had fine needle aspiration biopsies with a satisfactory cellular yield available for review. The cytospin preparations were of moderate cellularity and showed cohesive clusters of bland-looking ductal cells in a background of single, naked nuclei and some spindle cells containing fine chromatin and a discernible amount of cytoplasm. Occasional ductal cell clusters assuming a "staghorn" pattern, a feature commonly seen in fibroadenoma, were noted. Besides, there were scantly, loose and hypocellular stromal tissue fragments that contained spindle cells and occasional paired, elongated nuclei embedded in a fibrillary matrix. Histologic examination of the excisional biopsies confirmed the presence of PASH. It was characterized by many slitlike spaces rimmed by CD34-positive myofibroblasts/fibroblasts in a focally hyalinized stroma. Sometimes, ill-formed, fusiform aggregates of fibroblasts were also observed. Their fibroblastic nature was confirmed by electron microscopy. CONCLUSION: Fine needle aspiration cytology of PASH closely resembles that of fibroadenoma. Though subtle differences do exist, a definitive diagnosis is unlikely on the basis of the cytologic examination alone. PASH needs to be distinguished from borderline lesions, such as phyllodes tumor, and more sinister conditions, which sometimes have a similar cytologic appearance.     

Criteria for the cytologic assessment of hyperplasias in endometrial samples obtained by the Endopap Endometrial Sampler

The Endopap Endometrial Sampler was used in 1,465 women, either just before endometrial biopsy or curettage (in 760 symptomatic patients) or as an office procedure (in 705 women). The samples were inadequate for interpretation in only 8.7% of the cases. Although all malignant lesions were identified by this screening technique, about one-fourth were initially classified cytologically as hyperplasia. Endometrial hyperplasias presented the greatest difficulties in interpretation, with only slightly over half of the proven cases correctly assessed on the endometrial sample. In an attempt to improve the accuracy of the cytologic diagnosis of hyperplasias, ten morphologic features were examined retrospectively in 207 cases. Five of the criteria were shown to provide an increased probability of correctly diagnosing endometrial hyperplasias on the cytologic sample: (1) the overlapping of cells in the glandular clusters or sheets, (2) the presence of nucleoli, (3) anisokaryosis, (4) granularity of chromatin and (5) the presence of sheets of stromal cells. The more of these criteria observed in a given case, the better was the chance of cytologically identifying a hyperplasia in the Endopap sample.     

Fine needle aspiration cytopathology of phyllodes tumor. Differential diagnosis with fibroadenoma

The differential diagnosis of benign or borderline phyllodes tumors of the breast in fine needle aspiration biopsy smears was studied. Smears from five histologically proven cases and 20 proven cases of fibroadenoma were evaluated with regard to their cytologic features. The findings indicate that the presence of a high cellularity of stromal fragments (including bipolar naked nuclei), clusters of hyperplastic ductal cells and giant cells and the absence of apocrine metaplasia may suggest a diagnosis of phyllodes tumor, as opposed to fibroadenoma. The borderline phyllodes tumor showed a sarcomatous atypia and/or small intranuclear cytoplasmic invaginations in some cells. The differential diagnosis of this tumor with malignant phyllodes tumor and plasma-cell mastitis is also discussed.     

Fine needle aspiration cytology of soft tissue tumors

OBJECTIVE: To review of the value of fine needle aspiration (FNA) cytology in the diagnosis of soft tissue tumors (STT). STUDY DESIGN: A review of the literature was coupled with the authors' experience with indications, diagnostic specificity and pitfalls; clinical information; and the final cytology report. RESULTS: Over the last few years, FNA has come to be considered a valuable tool in the management of STT in that it affords a specificity of > 90%. FNA is of particular value in any subcutaneous lesion > 5 cm, in all pediatric tumors and whenever direct incision biopsy is particularly contraindicated. Material from aspirates can be used to obtain cytologic smears for conventional staining, special pigment identification, histochemical techniques, cell blocks for paraffin embedding and ancillary techniques (immunocytochemistry, electron microscopy, and densitometric and cytogenetic analyses). The cytologic diagnosis, like its histologic counterpart, should be based on a correct evaluation of clinical data (age, localization, size, effect on bone, nerve and vessel involvement), radiologic information, cytologic findings (architectural pattern, cell and stroma characteristics) and results of special staining techniques. The final cytology report should place the tumor in one of three basic categories: benign, malignant, and inconclusive or undetermined. Wherever possible, a histopathologic diagnosis should also be provided, either based on purely cytologic criteria or aided by ancillary techniques. CONCLUSION: FNA does not present major complications and permits a swift, preliminary diagnosis in a large number of cases. The method is most effective when the aspiration is performed by an experienced pathologist.     

Fine needle aspiration cytology of breast fibroadenoma. A cytohistologic correlation study of 405 cases.

OBJECTIVE: To evaluate the cytohistologic correlation of breast fibroadenoma (FA) in order to assess the value of cytology in the conservative management of this lesion. STUDY DESIGN: A retrospective analysis of all aspirates diagnosed as FA or fibroadenomatous lesion (n = 1,549) for which a histologic follow-up study was available (n = 362). Forty-three aspirates, including 14 nonrepresentative smears, from histologically proven FAs with a different cytologic report were also included in the study. RESULTS: Cytohistologic agreement was present in 287 of the 362 cytodiagnoses. Lack of correlation was observed in 75 cases. Most diagnostic errors accumulated in the older patient group. The sensitivity of the cytologic diagnosis of FA was 86.9% (90.8% excluding nonrepresentative cases), with a positive predictive value of 79.3%. In 43 cases a histologic diagnosis of FA was given after previous erroneous (n = 29) or nonrepresentative cytodiagnoses (n = 14). The specificity of the cytologic diagnosis of FA reached 93.8%, with a negative predictive value of 96.3% (97.5% excluding nonrepresentative cases). Regarding malignancy, five tumors were diagnosed as FA and were malignant. No false positive diagnoses of malignancy were given, but nine aspirates were included in the category "suspicious for carcinoma." CONCLUSION: FA of the breast remains a diagnostic challenge for the cytopathologist. A considerable amount of benign breast lesions can mimic FA on cytology, and such diagnostic categories as "fibroadenomatous lesion" or "consistent with FA" are associated with low diagnostic accuracy. While the cytologic requisites for entering a program of conservative management of FA are established, it seems that strict diagnostic criteria should be applied even at the expense of diminishing sensitivity.     

Positive predictive value of fine needle aspiration cytology of breast lesions

The predictive value of fine needle aspiration (FNA) was assessed in 1,181 consecutive cases of breast lesions in which cytologic abnormalities were reported. The positive predictive value (PPV) of an FNA cytologic report of atypia, suspicious or positive was 0.49, 0.95 or 0.996, respectively. In the presence of a suspicious/positive report by both physical examination and mammography, the PPV of a cytologic report of suspicious was 0.99. The PPV was directly correlated with age, partly due to the incidence of fibroadenomas among younger patients; fibroadenomas were present in 53 of 146 cases with a false FNA report of atypia, in 10 of 19 cases with a false FNA report of suspicious and in 2 of 2 cases with a false FNA report of positive. Overall, 93 cases reported as benign by physical examination and mammography were biopsied on the basis of the FNA cytologic report; cancers were diagnosed in 33 of these 93 cases (6 cancers among 42 women less than 40 years old and 27 cancers among 51 women greater than 39 years old). The widespread use of FNA cytology to study breast lesions is thus recommended, without regard to patient age and even in the presence of clinically benign findings, since the increase in the rate of cancer detection is worth the excess of unnecessary biopsies. The predictive value of a positive report of FNA cytology, or even of a suspicious report in the presence of clinical suspicion, is so high that an intraoperative frozen section biopsy might be spared in such cases.     

Cystosarcoma phyllodes. Diagnosis by fine needle aspiration cytology.

The cytologic features of 10 benign, 2 borderline and 5 malignant phyllodes tumors were studied, and an attempt was made to correlate the cytologic findings with corresponding histologic categories. Seventy-five percent of the benign and borderline tumors were interpreted as benign cystosarcoma phyllodes on fine needle aspiration cytology. Eighty percent of the malignant phyllodes tumors were identified as malignant lesions cytologically. The cytologic features assessed were the epithelial:stromal ratio and morphology of the stromal component, including the degree of atypia, mitotic activity, capillary vessels traversing the stromal fragments, presence of foamy macrophages, histiocytic giant cells and bipolar naked nuclei. A diagnosis of phyllodes tumor was suggested cytologically by the presence of both epithelial and stromal elements; the stroma was present as cellular "phyllodes fragments" and isolated mesenchymal cells. The parameters suggesting malignancy were extreme paucity or absence of epithelial elements and stromal cells in diffuse sheets and clusters less cohesive than normal, with marked stromal atypia and mitotic activity.     

Analysis of the microvasculature and tissue type ratios in normal vs. benign and malignant breast tissue

OBJECTIVE: To analyze the microvasculature and tissue type ratios in normal vs. benign and malignant breast tissue to establish a baseline for expected values against which future imaging studies can be benchmarked. STUDY DESIGN: Using computer-assisted techniques on immunostained breast tissue (normal [n = 28], fibrocystic [n = 37], fibroadenomas [n = 19], invasive carcinomas [n = 19]), values were obtained for microvessel density (MVD), mean vessel area (MVA), vessel orientation (shape) and epithelial:stromal ratio (E:S). Measurement reproducibility and the effects of fibroadenoma stromal hyalinization and fibrocystic disease severity were also tested. RESULTS: Value ranges for the 4 diagnostic groups were significantly different (P < .001). For invasive breast carcinomas, E:S and MVD were significantly higher (P < .001) but MVA was smaller as compared to that in fibroadenomas. Peripherally vs. centrally there was no significant difference in MVD, MVA or vessel shape in the neoplasms. Decreases in E:S and MVD correlated with fibroadenoma stromal hyalinization. Increases in E:S and MVA correlated with more severe fibrocystic disease. Correlation coefficients for measurement reproducibility were high across the diagnostic categories. CONCLUSION: This study established a specific, reproducible, computer-assisted technique and baseline of expected values for morphologic criteria in normal, benign and malignant breast tissue that may be used in the future to correlate new breast imaging responses with these underlying biologic properties.     

Ultrasonic Elastography Features of Phyllodes Tumors of the Breast: A Clinical Research

The purpose of this study was to analyze the ultrasonic elastography features of phyllodes tumors of the breast comparing with fibroadenomas. A retrospective database was queried for the patients diagnosed as phyllodes tumors and fibroadenomas at Sun Yat-sen Memorial Hospital from January 2008 to August 2012. Three hundred and fifty lesions from 323 consecutive patients were included in the study. All the cases were examined by conventional ultrasonography and ultrasound elastography. Ultrasound elastography was used to calculate strain ratio of the lesions with bilateral breast tissue at the same depth as reference. There were 36 phyllodes tumors (27 benign, 8 borderline, 1 malignant) and 314 fibroadenomas (158 the pericanalicular type, 103 the intracanalicular type, 53 other special types). The strain ratio for phyllodes tumors (3.19±2.33) was significantly higher than for fibroadenomas (1.69±0.88) (p<0.05). The Spearman^.s correlation coefficient between strain ratio of ultrasound elastography and pathological groups was significant, with a value of 0.17 (p<0.05). Ultrasound elastography could provide additional information to differentiate phyllodes tumors from fibroadenoma in breast.     

Fine needle aspiration cytology of malignant mesothelioma

The results of fine needle aspiration (FNA) cytology in 19 cases of malignant mesothelioma are presented. Adequate material for a diagnosis of malignancy was obtained in 17 cases, and in 8 cases a specific diagnosis of mesothelioma could be made. In four other cases, the findings were either consistent with or suggestive of mesothelioma; in four, accurate distinction from other neoplasms was not possible, and in two cases, adenocarcinoma was suggested. The spectrum of cytologic findings ranged from neoplasms of purely epithelial appearance through more pleomorphic biphasic neoplasms to anaplastic tumors. A combination of epithelial-like cell clusters, pavement-like sheets of epithelial cells with well-defined cell borders and prominent cell separation, dispersed angular cells with dense cytoplasm and some spindle-cell forms was the most specific cytologic pattern for mesothelioma. In four neoplasms, ultrastructural examination of aspirated material provided the additional evidence for a definitive diagnosis. The identification of hyaluronic acid within intracytoplasmic vacuoles, either in smears or in cell blocks, confirmed the diagnosis in three tumors. Only in one case, with a strong clinical background suggesting mesothelioma, was the cytologic preparation sufficient for diagnosis without ancillary diagnostic methods. FNA is of particular value in the diagnosis of pleural mesothelioma in patients who do not present with a pleural effusion. Obtaining material for cell block preparations, cytochemistry or ultrastructural study is generally necessary for definitive tumor typing.