The cytopathology of bone marrow transplantation

Bone marrow transplantation (BMT) is an increasingly effective treatment for patients with hematologic disorders and malignant neoplasms. From 1975 to 1986, 1,457 specimens were obtained for cytologic evaluation from 328 of the 635 patients who received BMTs at Memorial Sloan-Kettering Cancer Center. These specimens consisted of 1,049 cerebrospinal fluids (CSFs) from 265 patients, 292 bronchoscopy specimens from 92 symptomatic patients and 116 other specimens (including brushings from the liver and gastrointestinal tract, sputa, urines and cervico-vaginal smears). CSF specimens examined before and after BMT from 80 (30%) patients showed an increased number of benign, nonepithelial cells, which were mainly lymphocytic or histiocytic in origin. Malignant cells were detected in CSF specimens from 44 (17%) patients. Bronchoscopy specimens from 3 patients had suspicious cells present; those from 27 patients contained opportunistic organisms. Atypical epithelial or lymphoreticular cells were seen in bronchial specimens from 49 patients. All cytologic findings were correlated with the pertinent clinical information as well as biopsy and autopsy material, including histopathologic evidence of graft-versus-host disease. Cytologic evaluation, especially of bronchial and CSF specimens, was useful in diagnosing the presence of malignant neoplasms, infectious organisms, inflammatory responses, reactive lesions and cellular atypia due to treatment.     

Preoperative cytologic diagnosis of primary gastrointestinal malignant lymphoma

This report is based on the review and study of primary gastrointestinal malignant lymphomas as seen in cytologic brushing and washing specimens. During a period of 12 years (1970 to 1981), a total of 2,675 patients with malignant lymphoma involving the gastrointestinal tract were seen at Memorial Sloan-Kettering Cancer Center. Of these patients, 73 were diagnosed as having primary malignant lymphoma of the gastrointestinal tract. A total of 49 preoperative cytologic specimens obtained from 29 patients with histologically confirmed primary gastrointestinal malignant lymphoma were examined and are the basis for this study. Twenty-four patients had gastric primaries; three tumors were in the colon and two were small intestinal lymphomas. Thirty-three cytologic specimens taken from 25 patients were considered diagnostic for malignant lymphoma. A positive cytologic brushing was the only diagnostic preoperative specimen for 9 of the 29 patients. Combined cytologic and biopsy specimens provided a diagnosis of malignant lymphoma for 16 patients. Cytologic washings did not add to the diagnostic accuracy. The 29 cases of malignant lymphoma reviewed here were histologically subclassified as 23 large-cell, poorly differentiated and six small-cell, well-differentiated lesions. The cytomorphologic features of malignant lymphoma as observed in gastrointestinal specimens are outlined, and differential diagnoses are discussed. Clinicopathologic implications of the cytologic findings are considered.     

Fine needle aspiration biopsy versus sputum and bronchial material in the diagnosis of lung cancer. A comparative study of 168 patients

A group of 168 consecutive lung cancer patients in whom a definitive diagnosis of primary lung cancer was established either in a conventional cytologic specimen of sputum or bronchial material or in a specimen obtained by fine needle aspiration (FNA) biopsy was reviewed to compare the relative accuracies between the modalities of sputum and bronchial material on one hand versus FNA cytology on the other in the diagnosis of lung cancer. The patients included in the study were selected from a total of 1,093 patients who had been diagnosed and treated for lung cancer at Duke University Medical Center over the five-year period of January 1, 1980, through December 31, 1984. In 325 (29.8%) of the 1,093 patients, a definitive cancer diagnosis was established from histopathologic study alone, without any cytologic diagnoses. In 420 patients (38.4%), both histologic and cytologic material had been interpreted as being conclusively diagnostic for lung cancer. In 348 patients (31.8%), a cytologic diagnosis of lung cancer was made without a histologic confirmation. Thus, in a total of 768 (70.3%) of the 1,093 cases, a definitive cytologic diagnosis of cancer had been made. Of these 768 patients, 168 had been evaluated by both conventional respiratory cytologic methods (examination of sputum and bronchial material) and with FNA biopsy cytology. In 9 patients (5.4%), only conventional respiratory cytologic specimens were conclusively diagnostic for cancer. In 122 patients (72.6%), only the FNA biopsy specimen was diagnostic. In 37 patients (22.0%), both conventional respiratory specimens and FNA specimens yielded a definitive lung cancer diagnosis. The FNA specimen was the only positive cytologic specimen in 90.2% of large cell undifferentiated carcinomas, 79.5% of adenocarcinomas, 66.7% of small cell undifferentiated carcinomas and 58.2% of squamous cell carcinomas. In 26.5% of the patients, a diagnosis of cancer could have been established on conventional cytologic specimens, without the necessity of proceeding to percutaneous FNA biopsy. From this study, it is concluded that the techniques of conventional respiratory cytology and FNA biopsy cytology are complementary in the diagnosis of lung cancer. While the percentage of lung cancers diagnosed by FNA biopsy cytology alone is much greater than that obtained by conventional respiratory cytology alone, more than one-fourth of these cancers could be detected by the less invasive techniques of sputum collection and bronchoscopy.     

Prognostic markers in histologic and cytologic specimens of breast cancer

OBJECTIVE: To correlate histologic and cytologic specimens of breast cancer by the expression of prognostic factors, such as estrogen receptor (ER), progesterone receptor (PR) and c-erbB-2, with immunochemical staining. STUDY DESIGN: Cytologic and histologic specimens from 83 patients were analyzed for expression of ER and PR, and 30 cases were analyzed for overexpression of c-erbB-2 using a standard immunochemical method. The material used for immunocytochemical staining was taken from the needle and syringe after each aspiration and smear preparation. The material was washed into a small container with preservative solution. Immunohistochemical staining was performed on paraffin-embedded specimens. RESULTS: A significant association was found between the histologic specimens and cytologic specimens by means of the expression of immunochemical markers. The best correlation between cytologic and histologic specimens was found when using c-erbB-2. CONCLUSION: A reliable and rapid evaluation of markers for breast cancer can be achieved by immunocytochemical staining on cytologic material. A good association was found between histologic and cytologic specimens using immunostaining.     

Overexpression of HER2/neu oncoprotein in cytologic specimens

OBJECTIVE: To assess the rate of HER2/neu overexpression in cytologic specimens by immunocytochemistry (ICC) and compare these results in matched surgical specimens by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), when available. STUDY DESIGN: All cytologic specimens processed for HER2/neu evaluation by ICC (72 cases) and available corresponding histologic specimens (16 cases) were retrieved from our files. ICC was applied to previously Papanicolaou stained, routine fine needle aspirations specimens (64 cases) and cytocentrifuged, alcohol-fixed, fluid specimens (8 cases). FISH was performed on 6 histologic specimens. RESULTS: Overexpression of HER2/neu was seen in 7/22 breast cancers (31.8%), 3/18 pulmonary adenocarcinomas (16.6%), 2/5 colorectal adenocarcinomas (40%), 1/2 adenocarcinomas of the biliary system (50%), 1/3 thyroid papillary carcinomas (33.3%) and 1/3 prostate adenocarcinomas (33.3%). Sixteen cases had IHC in matched histologic specimens: 14 (87.5%) cases were concordant (11 negative and 3 positive in both specimens), 1 case was negative in the cytologic specimen and positive in the histologic specimen (with no amplification by FISH), and 1 case was positive in the cytologic specimen and negative in the histologic specimen (not informative by FISH). CONCLUSION: Our data suggest that overexpression of HER2/neu oncoprotein can be successfully detected in routine cytologic specimens, providing a simple, fast and cost-effective method of selecting patients for specific treatment.     

Cytologic findings in vitreous fluids. Analysis of 74 specimens

OBJECTIVE: To review the cytologic findings of vitreous specimens and propose a simplified approach to them. STUDY DESIGN: Seventy-four vitreous specimens from 60 patients obtained either during a pars plana vitrectomy or by vitreous aspiration were reviewed. Clinical correlation was obtained on all patients. RESULTS: Findings suggestive of a specific disorder were present in 30 specimens (41%); cytologic examination of the remaining 44 showed nonspecific changes. A lymphoproliferative disorder, the intraocular malignancy suspected most often in this series, was identified in eight specimens (11%). Large cell lymphomas were evident in 5 specimens, 2 specimens were suspicious for lymphoma, and 1 specimen was consistent with plasmacytoma. Twelve specimens (16%) contained hemorrhage. In rare instances, specific infectious agents, such as parasites (5%), bacteria (1%) and fungi (3%), could be identified. The diagnosis of viral infections required ancillary studies. Lens fragments were identified in four cases (5%), and a diagnosis of lens-induced endophthalmitis could be rendered in one case (1%). Changes consistent with sarcoidosis were present in 3% of cases. CONCLUSION: Based on this experience with vitreous specimens submitted for clinical reasons, we found that they could be divided into three broad diagnostic categories: inflammation/infection (54 specimens/41 patients), hemorrhage (12 specimens/12 patients) and malignancy (8 specimens/7 patients).     

Diagnostic value of mitotic activity in endometrial stromal sarcoma: report of two cases

Two patients with endometrial stromal neoplasms, one low-grade and one high-grade malignant stromal sarcomas, were treated. The tumor cells of these two sarcomas had many common cytologic features and were similar to normal endometrial stromal cells. However, frequent mitoses were characteristic of the cytologic specimens of the high-grade stromal sarcoma but not of those of the low-grade sarcoma. Mitotic activity thus appears to offer a clear distinction in the cytologic differentiation between grades of endometrial stromal sarcoma and may serve as a guide to prognosis and treatment.     

Cytologic findings in posttransplant lymphoproliferative disease

Transplant patients are at an increased risk of developing lymphoproliferative disorders (LPDs). To examine the role of cytology in diagnosing LPDs, the cytologic reports on all transplant patients seen at the University of Iowa from January 1983 to July 1988 were reviewed. Thirteen of 649 transplant patients developed LPD; 10 of those 13 patients had a total of 25 cytologic specimens obtained within two months of the diagnosis of LPD available for review. Ten specimens (four cerebrospinal fluids [CSFs], four effusions, one respiratory specimen and one liver aspirate) from six patients were positive for LPD. Immunophenotypic or immunogenotypic studies on cytologic specimens from four patients showed a clonal B-cell process. The cytologic features ranged from those of a plasmacytoid LPD to those of an immunoblastic or large-cell lymphoma. An additional seven specimens (five CSFs, one effusion and one liver aspirate) from four patients were suspicious for LPD, exhibiting rare atypical cells or cells with plasmacytoid features. Ten patients died with LPD within 12 months; three are alive. Cytologic specimens, especially body fluids, are frequently positive in LPD and may be useful diagnostically. Since the differential diagnosis includes reactive lymphocytosis, confirmatory immunophenotypic or immunogenotypic studies are recommended.     

The cytologic features of chlamydial cervicitis

Chlamydial cervicitis is a common and important infection. Diagnostic cytologic criteria have been proposed, but not generally accepted. To better evaluate the cytologic changes, cervical cultures for Chlamydia trachomatis and duplicate cervical smears for Papanicolaou staining and immunofluorescence staining for chlamydial organisms were taken from 496 patients. A total of 61 (12.3%) of the patients had a positive culture for C. trachomatis. By immunofluorescence, the organisms were present as very small extracellular elementary bodies in mucus or as similar bodies in leukocytes; inclusions within epithelial cells were seen in only two cases. The organisms did not stain with the Papanicolaou stain. Chlamydial infection correlated with the degree of inflammation, with the presence of histiocytes and lymphocytes, especially large "transformed" lymphocytes, and with the presence of unidentified short bacteria, which stained red with the Papanicolaou stain. These features predict which patients should be tested more definitively for the presence of chlamydial organisms. However, we found no cytologic criteria that can reliably permit its diagnosis.     

Cytologic diagnosis of leishmaniasis in HIV infection. A report of eight cases

BACKGROUND: Leishmania organisms are among the intracellular microorganisms with a tendency to develop in patients with the acquired immunodeficiency syndrome (AIDS). With increasing travel to endemic areas by patients with human immunodeficiency virus (HIV) infection, it is becoming a more-frequent diagnosis in nonendemic areas. CASES: Ten cytologic specimens from eight patients with leishmaniasis and AIDS were reviewed. Eight samples were obtained from lymph nodes through fine needle aspiration (FNA). Another sample was obtained after scraping a tongue ulcer. The last one was an ascitic fluid specimen. Smears showed numerous parasitized histiocytes with abundant intracellular Leishmania organisms (amastigotes). Extracellular microorganisms were also abundant. Diff-Quik-stained smears allowed the clear recognition of the characteristic morphologic appearance with a deep-staining area (nuclei) and paranuclear zone (kinetoplast). Intracellular organisms were round, while single, extracellular forms were a more elongated. CONCLUSION: The polymorphous clinical manifestations usually seen in patients suffering from leishmaniasis and AIDS constitute a diagnostic challenge that can be facilitated by cytopathologic examination. Cytology permits easy and rapid identification of Leishmania amastigotes, allowing a specific diagnosis and treatment.     

Atypical epithelial cells, cannot exclude papillary carcinoma, in fine needle aspiration of the thyroid

OBJECTIVE: Atypical epithelial cells, cannot exclude papillary thyroid carcinoma (AEC-PTC), in fine needle aspiration (FNA) of the thyroid is a controversial diagnostic category that might cause a dilemma in patient management. STUDY DESIGN: Eighty-eight thyroid FNA specimens from 86 patients with a diagnosis of AEC-PTC were retrieved from our files in a 10-year period from December 1996 to December 2006. Of the 86 patients, 57 had follow-up histologic diagnoses and were included in this study. The cytologic and histologic materials were reviewed and correlated. RESULTS: Of the 57 patients, all had cytologic atypical features suggestive of PTC. Twenty-five cases of PTC were identified at surgery (44%). Review of the cytologic materials identified the following cytologic features, either alone or in combination strongly associated with PTC at resection: rare intranuclear cytoplasmic invagination (INCI), squamoid cytoplasm and psammoma bodies. CONCLUSION: The most common reasons for rendering the diagnosis of AEC-PTC in FNA of thyroid include rare atypical cells in a cystic thyroid nodule or a background of Hashimoto's thyroiditis. The cytologic features of LNCI, squamoid cytoplasm and psammoma bodies should alert the pathologist. Focal cytologic features of PTC in FNA samples are strongly associated with papillary carcinoma on resection.     

Cytology of bladder papilloma

Eighty-four urinary cytology specimens from 51 patients known to have bladder papilloma were reviewed and compared with 30 specimens from patients without neoplastic urologic disease, 12 specimens from patients later found to have papillomas that were unsuspected at the time of examination and 6 specimens from patients with a history of papilloma but no present evidence of the disease. No specific findings were identified that could be used to make a cytologic diagnosis of papilloma. However, the specimens from patients with papilloma were likely to contain an increased number of exfoliated epithelial cells, including atypically shaped cells that were small and round or, less frequently, elongated; they were also likely to contain a small number of red blood cells. This combination of cytologic findings yielded a pattern that can be described as consistent with or suggestive of papilloma in the appropriate clinical setting. It is not diagnostic since the absence of this cytologic pattern does not rule out papilloma, and the same cytologic features can be found (less frequently) in patients with other urologic diseases.     

Cytologic diagnosis of the papillary variant of renal-cell carcinoma

The papillary variant of renal-cell carcinoma is characterized by distinctive histologic, clinical and angiographic features. A study was undertaken to delineate the cytologic features of this tumor as it is encountered in cellular samples. Cytologic specimens containing tumor cells from eight patients who underwent resection for papillary renal-cell carcinoma were examined and compared to corresponding cytologic samples obtained from ten other patients who had nonpapillary renal-cell carcinoma. The cytologic appearance of papillary renal-cell carcinoma, which is deceptively benign, is marked by distinctive papillary structures that often resemble branched chains. The cells are usually small and contain uniform nuclei; numerous macrophages with foamy cytoplasm are often found in the background. These cytologic features were not observed in the cellular specimens from the nonpapillary renal carcinomas. We conclude that papillary renal-cell carcinoma can be confidently recognized in cytologic specimens.     

Ten years of respiratory cytopathology at Duke University Medical Center. II. The cytopathologic diagnosis of lung cancer during the years 1970 to 1974, with a comparison between cytopathology and histopathology in the typing of lung cancer

In 1975 Duke University Medical Center, a retrospective and prospective survey of respiratory cytopathologic specimens was undertaken for the ten-year period 1970 to 1979. The purpose of this study was to document the role of cytopathology in the diagnosis of lung cancer at this institution. This paper presents the results of the cytopathologic and histopathologic typing of cases of lung cancer seen at Duke University Medical Center from 1970 to 1974. During this period, 9,892 cytologic specimens from the lower respiratory tract were processed. Cytopathologic diagnoses of cancer with tissue confirmation were made on 483 specimens from 232 patients. Because original cytologic diagnoses, but not histopathologic diagnoses, had been made in conformity with a modified WHO classification of lung neoplasms, all histopathologic material was reviewed and reclassified when necessary. This was carried out by one of the authors (E.H.B.) as a blind review without benefit of knowledge of either preexisting cytopathologic or histopathologic diagnoses. Twenty-six patients were excluded from the current study because of lack of satisfactory histologic material. In 94 patients classified by histopathology as having squamous cell carcinoma, 76.4% of the positive cytologic specimens were also called squamous cell carcinoma; 18.6% were interpreted as large cell undifferentiated carcinoma. In 39 patients classified by tissue as having large cell undifferentiated carcinoma, the cytology agreed in 42.4% of the positive specimens. For the 29 patients thought histologically to have small cell undifferentiated carcinoma, the same diagnosis was rendered in 95.5% of the cytologically positive specimens from these patients. For the adenocarcinoma group of 43 patients, a cytopathologic diagnosis of adenocarcinoma was made in 67.8% of the positive specimens.     

Cystoscopic biopsy supernate. A new cytologic approach for diagnosing urothelial carcinoma in situ

The examination of cystoscopic biopsy supernates is a new cytologic procedure that can aid the urologist in the differential diagnosis of urothelial carcinoma in situ (CIS) and cystitis. Within the past two years, the Cytodiagnostic Urinalysis Laboratory has received 79 cystoscopic biopsy supernate specimens from 29 patients; these were prepared using a membrane filtration technique and stained with a modified Papanicolaou method. Positive diagnoses were rendered on 17 (21.5%) specimens, including 7 (41%) CIS and 10 (59%) papillary neoplasms. An 87% cytohistologic correlation was seen. Of the 17 cases with biopsy specimens that were denuded and thus nondiagnostic, 11 had negative supernate cytologies and 6 had positive cytologic diagnoses. Half of these positive specimens were diagnosed as CIS. Because urothelial CIS is often a friable lesion that yields denuded bladder biopsies, the cytologic examination of cystoscopic biopsy supernates offers a valuable adjunctive method for diagnosing urothelial CIS on otherwise lost cellular material.     

Prospective comparative cytologic study of direct peritoneal smears and lavage fluids in patients with epithelial ovarian cancer and benign gynecologic disease

Direct peritoneal samples obtained by scraping or brushing (with a Cytobrush) were compared to peritoneal lavages (washings) for the cytologic evaluation of patients with gynecologic disease. The direct samples were obtained during laparotomy or laparoscopy, following saline lavage if that was performed, and were immediately smeared on glass slides and fixed in 95% alcohol. Only 9 of the direct peritoneal samples taken from 64 patients with benign gynecologic disease were unsatisfactory for cytologic interpretation while 19 of the 33 lavage specimens simultaneously collected from these patients were considered unsuitable for analysis (P less than .001). Two direct smears from cases with benign histology were reported as suspicious. Nineteen patients with epithelial ovarian cancer also had cytologic specimens collected by direct sampling and by washing. The direct smears were positive for malignancy in 12 cases, suspicious in 4 cases and negative in 3 cases while the lavage samples were positive in 9 cases, suspicious in 4 cases, negative in 4 cases and unsatisfactory in 2 cases. These results indicate that direct peritoneal sampling is a simple and reliable alternative to peritoneal lavage and produces a significantly lower incidence of unsatisfactory specimens.     

Potential sampling error in fine needle aspiration biopsy of dedifferentiated chondrosarcoma: a report of 4 cases

BACKGROUND: Dedifferentiated chondrosarcoma is a rare, poorly understood and often fatal sarcoma that usually manifests as a high grade, non-cartilage-producing sarcoma juxtaposed against a low grade chondrosarcoma. A correct diagnosis requires recognition of both components. In the absence of complete resection, rendering a specific diagnosis on small biopsy specimens, such as fine needle aspiration biopsy (FNAB), may be extraordinarily difficult. CASES: We retrospectively reviewed 4 cytology samples (3 primary, 1 metastatic) from 3 patients with dedifferentiated chondrosarcoma, initially analyzed by FNAB, emphasizing the potential for sampling error. Two women, aged 78 and 57 years, both of whom had prior histories of carcinoma, presented with lesions involving the right and left femur, respectively. One 27-year-old man with multiple osteochondromatosis developed a dedifferentiated chondrosarcoma of the left pelvis. Two primary cytologic specimens consisted of moderately cellular smears containing a spindled to polygonal, nonspecific, pleomorphic sarcoma unaccompanied by definite matrix material; 1 of these had a concomitant core needle biopsy (CNB), also demonstrating pleomorphic sarcoma. The third primary cytologic specimen revealed low grade chondrosarcoma, but a concomitant CNB showed only a high grade, non-matrix-producing sarcoma. The last patient developed a metastasis to the opposite femur; FNAB revealed a high grade spindle cell sarcoma. In none of the FNAB or CNB specimens were both low and high grade components of dedifferentiated chondrosarcoma recognized. However, the diagnosis was strongly suspected based on the clinical and radiographic findings. CONCLUSION: Due to sampling error, the diagnosis of dedifferentiated chondrosarcoma may be difficult to establish by cytologic examination alone. Clinical and radiographic correlation is essential for an accurate diagnosis.     

Role of biliary brush cytology in primary sclerosing cholangitis

OBJECTIVE: To assess the role of brush cytology in the routine evaluation of patients with primary sclerosing cholangitis (PSC). STUDY DESIGN: From January 1995 to June 2000, 64 brush cytology specimens were obtained from 21 patients who had at least one cytologic sample obtained during endoscopic retrograde cholangiography. All patients had a diagnosis of primary sclerosing cholangitis. Cases were classified as benign, atypical or malignant according to major cytologic criteria (nuclear contour and chromatin irregularities) and minor cytologic criteria (polarity, cellularity, nuclear enlargement, mitosis, increased nuclear/cytoplasmic ratio) used by us to diagnose biliary brush cytology. Follow-up was available in all cases. RESULTS: Diagnoses were benign (13), atypical (5) and malignant (3) on cytology. Follow-up of the 13 benign cases showed bile duct stones (2), gallbladder adenocarcinoma at cholecystectomy (1), ascending cholangitis (1) and clinically/cytologically by benign follow-up (9). Five of 13 benign cases had subsequent liver transplantation for liver failure, with explants showing changes of primary sclerosing cholangitis. Of the 3 malignant cases, 1 had carcinoma in situ on biopsy, with the explanted liver showing high grade dysplasia; the second patient had cholangiocarcinoma on explant; and the third had hepatocellular carcinoma on liver five needle aspiration. The 5 patients with atypical cytology were reclassified on review as reactive (3) and atypical not otherwise specified (2). Follow-up showed benign disease in 3 of 3 atypical cases reclassified as reactive; 2 of 2 reclassified as atypical not otherwise specified showed low grade dysplasia in the explant. CONCLUSION: The overall incidence of malignancy was low (3 of 21) in patients with PSC. Bile duct brushing is a sensitive method of detecting neoplasia in the setting of PSC when well-defined cytologic criteria are applied.     

Thyroid Cytology and Risk of Thyroid Cancer: Differences Among Indeterminate Specimens

ObjectiveTo assess the potential for stratification of indeterminate cytologic findings on fine-needle aspiration (FNA) of thyroid nodules in an effort to improve therapeutic strategies.MethodsWe attempted to determine the malignant risk associated with various indeterminate FNA cytologic patterns by correlation of specimens with the final histologic diagnosis. For this analysis, we identified 294 computerized medical records of surgically treated thyroid nodules during a 5-year period at our institution with the corresponding FNA cytology reports available.ResultsOf the 294 surgical cases, 162 with a positive or indeterminate cytologic report were selected, reviewed, and classified. Of 52 patients with positive cytologic findings on FNA, 51 (98%) had a final histologic report of a malignant thyroid nodule. Of 110 patients with indeterminate specimens, 30 (27%) had a final histologic diagnosis of thyroid carcinoma. The presence of nuclear atypia was predictive of thyroid carcinoma in 75% of patients, a Hürthle cell cytologic pattern was associated with a malignant thyroid nodule in 33%, and a hypercellular smear was suggestive of malignant involvement in 26% of cases. The lowest rate of malignant potential was associated with cytologic microfollicular and scant colloid alone subtype (6%).ConclusionThe results of this study show that indeterminate thyroid cytologic specimens can be subdivided into groups with different malignant risks. A microfollicular cytologic pattern in the absence of a hypercellular smear or nuclear atypia does not support a recommendation of surgical treatment. A malignant cytologic diagnosis has a high positive predictive value for detection of thyroid cancer. (Endocr Pract. 2004;10:330-334)