Hypoxia and vascular endothelial growth factor expression in human squamous cell carcinomas using pimonidazole as a hypoxia marker.

Hypoxia in human tumors is associated with poor prognosis, but the molecular mechanisms underlying this association are poorly understood. One possibility is that hypoxia is linked to malignant progression through vascular endothelial growth factor (VEGF) induction and the associated angiogenesis and metastasis. The present clinical study measures hypoxia and VEGF expression on a cell-by-cell basis in human squamous cell carcinomas to test the hypothesis that hypoxia and VEGF protein expression are coupled in human tumors. Eighteen patients with invasive squamous cell carcinoma of the uterine cervix and head and neck have been investigated by a quantitative image analysis of immunostained sections from their tumors. The hypoxia marker pimonidazole was used to measure tumor hypoxia, and a commercially available antibody was used to measure VEGF protein expression. A quantitative immunohistochemical comparison of hypoxia and VEGF protein expression revealed no correlation between the two factors.

A clinical study of hypoxia and metallothionein protein expression in squamous cell carcinomas.

The objective was to discover whether the oxygen-regulated protein, metallothionein, is expressed in the hypoxic cells of squamous cell carcinomas. Twenty patients with squamous cell carcinoma of the uterine cervix or head and neck were infused with a solution of the hypoxia marker, pimonidazole hydrochloride, at a dose of 0.5 g/m2. The following day, biopsies were collected, formalin fixed, paraffin embedded, and sectioned at 4 microm. Sections from each biopsy were immunostained for pimonidazole binding, metallothioneins I and II, involucrin, and proliferating cell nuclear antigen. A total of 84 biopsies were analyzed. Sixty-four of 84 biopsy sections contained hypoxia. Of the hypoxia-containing sections, 43 of 64 or 67% showed no microregional overlap between hypoxia and metallothionein; 7 of 64 showed overlap; and 14 of 64 showed a combination of overlap and no overlap. On a tumor-by-tumor basis, 5 of 7 head and neck and 7 of 13 cervix tumors showed no overlap between metallothionein and hypoxia at the microregional level. Ranges for the percentage of the area of hypoxia in head and neck (<0.9 to 17%) and cervix (<0.1 to 14%) tumors were similar. In the hypoxia-containing sections, immunostaining for involucrin, a molecular marker for differentiation, overlapped with that for hypoxia in 82% of the cases. The majority of hypoxic cells in squamous cell carcinomas do not express metallothionein protein, although metallothionein is induced by hypoxia in human tumor cells in vitro. Hypoxic cells in human tumors tend to be in regions immunostaining for involucrin, and it seems possible that differentiation of hypoxic cells in squamous cell carcinomas might affect metallothionein I and II expression.

Proliferation and hypoxia in human squamous cell carcinoma of the cervix: first report of combined immunohistochemical assays.

PURPOSE: To characterize the distribution of hypoxia and proliferation in human squamous cell carcinoma of the cervix via an immunohistochemical approach prior to initiation of therapy. METHODS AND MATERIALS: Patients with primary squamous cell carcinoma of the cervix uteri received a single infusion of the 2-nitroimidazole, pimonidazole (0.5 g/m2 i.v.), and 24 h later punch biopsies of the primary tumor were taken. Tissue was formalin fixed, paraffin embedded, and sectioned for immunohistochemistry. Hypoxia was detected by monoclonal antibody binding to adducts of reductively activated pimonidazole in malignant cells. Staining for endogenous MIB-1 and PCNA was detected in tumor cells via commercially available monoclonal antibodies. Point counting was used to quantitate the fraction of tumor cells immunostained for MIB-1, PCNA, and hypoxia marker binding. RESULTS: Immunostaining for pimonidazole binding was distant from blood vessels. There was no staining in necrotic regions, and only minimal nonspecific staining, mostly in keratin. In general, cells immunostaining for MIB-1 and PCNA did not immunostain for pimonidazole binding. Cells immunostaining for MIB-1 and PCNA showed no obvious geographic predilection such as proximity to vasculature. Quantitative comparison showed an inverse relationship between hypoxia marker binding and proliferation. CONCLUSIONS: Immunohistochemical staining for pimonidazole binding is consistent with the presence of hypoxic cells in human tumors and may be useful for estimating tumor hypoxia prior to radiation therapy. Immunostaining for pimonidazole binding is an ideal complement to immunohistochemical assays for endogenous proliferation markers allowing for comparisons of tumor hypoxia with other physiological parameters. These parameters might be used to select patients for radiation protocols specifically designed to offset the negative impact of hypoxia and/or proliferation on therapy. The inverse relationship between pimonidazole binding and proliferation markers is a preliminary result requiring verification.

Human alveolar macrophage-56 and carcinoembryonic antigen monoclonal antibodies in the differential diagnosis between primary ovarian and metastatic gastrointestinal carcinomas.

The immunohistochemical expression and localization of monoclonal antibodies to carcinoembryonic antigen (CEA) and human alveolar macrophage (HAM-56) were evaluated in primary ovarian and metastatic gastrointestinal (GI) carcinomas. Immunohistochemistry was performed using an avidin-biotin-peroxidase complex method with capillary gap technology on formalin-fixed, paraffin-embedded tissues from 41 primary ovarian epithelial neoplasms, 17 metastatic gastrointestinal malignancies, and 10 tumors of uncertain primary origin. Overall, immunostaining for HAM-56 was positive in 35 (85%) ovarian epithelial neoplasms compared with only two (12%) gastrointestinal cancers. Carcinoembryonic antigen was positive in 16 (39%) ovarian versus 13 (76%) GI tumors. Of the primary ovarian neoplasms, 22 were positive for HAM-56 only, 13 were positive for both HAM-56 and CEA, three were positive for CEA only (all mucinous neoplasms), and three were negative for both. Of the primary GI neoplasms, 12 were positive for CEA only (including all eight colon cancers), one was positive for both HAM-56 and CEA, one was positive for HAM-56 only, and three were negative for both. Of the 10 neoplasms of unknown origin at initial presentation, six were positive for HAM-56 only, three were positive for CEA only, none was positive for both HAM-56 and CEA, and one was negative for both. Only three of these 10 neoplasms remained of indeterminate origin after pathological review and clinical follow-up. When positive, CEA was usually strong and generalized in GI cancers but weak and focal in ovarian neoplasms. The HAM-56 positivity in ovarian neoplasms was typically focal and largely limited to areas with glandular or papillary differentiation with apical linear accentuation. We conclude that an immunohistochemical panel using both HAM-56 (Enzo Diagnostics, Syosset, NY) and CEA monoclonal antibodies is helpful in differentiating primary ovarian neoplasms from metastatic gastrointestinal malignancies, and in evaluating metastatic adenocarcinoma of unknown primary site.

Recurrent alveolar proteinosis following double lung transplantation.

We present a case of recurrent alveolar proteinosis following double lung transplantation.

MRI of Askin's tumor. Case report at 1.5 T.

This represents the first case of an Askin's tumor demonstrated on MRI. It showed a large pleural-based mass which trapped pleural fluid in large pseudotumors. The disease was unilateral and involved the mediastinum as well. Magnetic resonance imaging was helpful in demonstrating extrathoracic disease in the area of the right brachial plexus.

Primary adenocarcinoma of the gallbladder presenting as primary gynecologic malignancy: a report of two cases.

BACKGROUND: Carcinoma metastatic to the uterus from extragenital sites is rare. Such metastatic disease is typically diagnosed at autopsy or in patients with known primary malignancies. This report discusses two cases of primary carcinoma of the gallbladder presenting as abnormalities in gynecologic screening procedures. CASES: A 71-year-old woman presented with postmenopausal bleeding. Uterine curettage revealed poorly differentiated adenocarcinoma of presumed endometrial origin. Intraoperative frozen-section analysis of the uterus showed carcinoma involving the lymphatics, but no primary tumor. Further exploration revealed primary adenocarcinoma of the gallbladder, with widespread metastases. The second case was a 67-year-old asymptomatic woman. Routine cervical cytology showed adenocarcinoma, but tissue studies were negative. She developed jaundice 1 month later. Computed tomography of the upper abdomen revealed a mass in the gallbladder fossa, and needle biopsy of the lesion showed adenocarcinoma. CONCLUSIONS: Metastatic carcinoma of non-genital tract origin may present as primary gynecologic malignancy. The physician should be aware of the implications of both the common and unusual interpretations of screening and diagnostic procedures. When the clinicopathologic presentation is atypical, a thorough knowledge of the differential diagnoses of abnormal test results allows appropriate and expeditious patient management.

Pelvic granulomata mimicking endometriosis following the administration of oil-based contrast media for hysterosalpingography.

BACKGROUND: Hysterosalpingography is used commonly in the evaluation of infertility and in the diagnosis of anomalies of the uterus and fallopian tubes. There is continued debate over the safety and diagnostic or therapeutic efficacy of water-soluble versus oil-based contrast media. CASE: A 29-year-old woman with secondary infertility underwent hysterosalpingography with both water-soluble and oil-based contrast. The fallopian tubes appeared normal. Six months later, a plain abdominal radiograph obtained at the occasion of a minor motor vehicle accident revealed evidence of retained loculated pelvic contrast material. Subsequent laparoscopy identified adhesions and cul-de-sac implants strongly suspicious for endometriosis. Biopsy and pathologic study documented lipogranuloma. CONCLUSION: Oil-based contrast media instilled into the pelvis at hysterosalpingography can persist for prolonged periods and create granulomatous lesions mimicking endometriosis. In view of the controversy whether oil-based contrast materials are superior to water-soluble media, the routine use of oil-based contrast media should be considered carefully.

Endometrial cancer: histologic correlates of immunohistochemical localization of progesterone receptor and estrogen receptor.

Progesterone and estrogen receptor localization, using monoclonal anti-receptor antibodies JZB39 and H222, was studied in 105 endometrial adenocarcinomas. Immunohistochemical evaluation incorporated both intensity and distribution of staining. Both anti-progesterone receptor and anti-estrogen receptor localized in the nucleus of target cells. Significant levels of progesterone receptor and estrogen receptor were seen localized in stromal and myometrial elements that diverged from the malignant epithelial component. Analyses of endometrial adenocarcinomas with anti-progesterone receptor and anti-estrogen receptor antibodies correlated with histologic differentiation. The ability to define divergent receptor populations in stromal and myometrial elements versus malignant epithelial elements indicates that immunohistochemical assay of progesterone and estrogen receptor provides information complementary to that from conventional quantitative ligand binding assays.

Effect of exogenous gonadotropins on endometrial maturation in oocyte donors.

OBJECTIVE: To determine the effects of controlled ovarian hyperstimulation (COH) on endometrial maturation. DESIGN: Prospective, before and after evaluation of midluteal endometrial biopsies in oocyte donor's spontaneous and subsequent COH cycles. SETTING: Tertiary academic medical center assisted reproductive technologies clinic. PATIENT(S): Nineteen oocyte donors. INTERVENTION(S): Exogenous gonadotropins, endometrial biopsies. MAIN OUTCOME MEASURE(S): Endometrial histology and an immunohistochemical marker of uterine receptivity, the alphavbeta3 vitronectin. RESULT(S): Glandular and stromal dyssynchrony was more common after COH in 16 (80%) of 20 cycles than 6 (30%) of 20 spontaneous cycles (P <.05). Glandular lag was more frequent in COH cycles and unaffected by progesterone administration. The beta3 subunit of the alphavbeta3 vitronectin receptor was present in 9 (45%) of 20 spontaneous and 2 (10%) of 20 COH cycles (P <.05). CONCLUSION(S): Exogenous gonadotropin use in healthy reproductive age women did not result in endometrial evidence of a luteal phase defect. A greater incidence of glandular-stromal dyssynchrony resulted from the use of exogenous gonadotropins. The presence of alphavbeta3 was noted in most endometrial specimens demonstrating in phase glandular maturation. We conclude that endometrial dyssynchrony that results from delayed glandular development most likely represents a normal histologic variant.

Desmoid tumor of the vulva associated with pregnancy.

Extra-abdominal desmoid tumor is a locally aggressive neoplasm that occurs most commonly in the pelvic or shoulder region in the third or fourth decade. We have identified one previously reported case of primary desmoid tumor of the vulva. Herein, we describe another case and, to our knowledge, the first reported case of vulvar desmoid tumor associated with pregnancy.

Villoglandular adenocarcinoma of the cervix: cytologic presentation.

Villoglandular adenocarcinoma of the uterine cervix is a recently described neoplasm which occurs primarily in young women and has an excellent prognosis. In many instances, these lesions may be treated conservatively with cervical conization rather than hysterectomy, a therapeutic option of particular importance for young women who wish to preserve reproductive capability. This paper describes the cytologic findings on cervical smears from three women with villoglandular adenocarcinoma, two treated conservatively with cervical conization and one managed with hysterectomy. Characteristic cytologic features in these cases included the presence of long villous fronds and papillae lined by columnar cells with intact cytoplasmic borders and minimal to moderate cytologic atypia. Also noted were strips and three-dimensional ball-like clusters of cells with smooth, intact communal cytoplasmic rims. Apoptotic bodies and scattered mitoses were observed. Recognition of the above features warrants inclusion of this entity in the cytologic differential diagnosis, with conservative histologic follow-up prior to more radical therapeutic measures.

Hypersegmentation of neutrophils in the cerebrospinal fluid: report of a case with hematologic correlation and review of the literature.

Hypersegmented neutrophils can occasionally be seen in the cerebrospinal fluid (CSF) of patients with acute pyogenic meningitis, and rarely as an artifact of cytocentrifugation. We report a case of florid neutrophil hypersegmentation in cytocentrifuged CSF specimens from a patient presenting with anemia and mental status changes. Megaloblastic anemia was excluded by a thorough hematologic evaluation, and the patient was later found to have an epidural abscess. The striking hypersegmentation is attributed to the combined effects of meningeal infection and cytocentrifugation, and a review of the available limited literature on cytomorphologic alterations in CSF cells, specifically neutrophils, is presented.

Are epithelial cells in fat or connective tissue a reliable indicator of tumor invasion in fine-needle aspiration of the breast?

The diagnosis of breast carcinoma tumor invasion by fine-needle aspiration (FNA) cytology continues to be controversial. To assess the reliability of predicting tumor invasion by FNA, we examined the cytologic smears of 183 FNAs of benign and malignant solid epithelial lesions of the breast for which histologic follow-up was available. The study group consisted of 94 invasive carcinomas, eight pure ductal carcinomas in situ (DCIS), and 81 benign lesions (fibroadenoma, fibrocystic changes, papilloma, adenosis). Epithelial cellularity, presence of epithelial cells in dispersed fat droplets and presence of epithelium within intact fragments of fibrofatty connective tissue were tabulated. Epithelial cellularity in dispersed fat was semiquantitatively scored. The cytologic diagnosis of the epithelial cells in all cases was recorded as benign, malignant, or indeterminant for malignancy. Findings showed that 95.5% of invasive carcinomas, 100% of DCIS, and 68.1% of benign lesions contained epithelial cells in dispersed fat; 80.8% of invasive carcinomas, 66.7% of DCIS, and 60.7% of benign lesions contained epithelial cells in intact fibrofatty connective tissue. Corrected score of epithelium within fat was 0.781 for invasive carcinoma, 0.727 for DCIS, and 0.562 for benign lesions. The difference in values for all parameters was not statistically significant between invasive carcinoma and DCIS, but reached significance between invasive carcinoma and benign lesions. Eighteen cases (7/94 invasive carcinomas, 5/8 DCIS, 6/81 benign lesions) contained atypical epithelial cells indeterminant for malignancy, all of which had epithelial cells present in dispersed fat when dispersed fat was present on the slides, indicating that this criterion was not helpful in discriminating between a benign and malignant diagnosis. We conclude that the presence of epithelial cells either admixed within dispersed fatty droplets or seemingly within fragments of fibrofatty connective tissue is not a reliable indicator of tumor invasion in FNA of the breast, and is frequently found in both benign and malignant breast lesions. The presence of epithelial cells in intact or dispersed fat is most likely a mechanical artifact of aspiration and/or smear preparation.

Fine-needle aspiration cytology of suture granulomas of the breast: a potential pitfall in the cytologic diagnosis of recurrent breast cancer.

The fine-needle aspirates of three cases of suture granulomas of the breast area following mastectomy, lumpectomy, or axillary node dissection were reviewed. The original histologic diagnoses were mucinous (colloid) carcinoma, intraductal carcinoma, and low-grade phyllodes tumor. In two patients a new nodule developed in the surgical scar, and in the third a nodule developed in the axilla 2 cm away from the scar. The cellularity of the aspirates ranged from low to moderate, and all three cases contained variable numbers of spindled cells and fragments of cellular stroma. Multinucleated giant cells characteristic of suture granulomas were absent in all cases. Abundant metachromatic amorphous background material was present in one case, which was interpreted as recurrent mucinous carcinoma. The remaining cases were interpreted as suspicious for recurrent neoplasm. Upon excision, all were suture granulomas with fibroblastic proliferation. Suture granulomas can both clinically and cytologically mimic recurrent malignancy. The predominance of spindled cells and dissimilarity to the original tumor appear to be the most helpful features to cytologically distinguish suture granuloma from recurrent carcinoma in the absence of the characteristic multinucleated giant cells.

Pulmonary alveolar proteinosis: a spectrum of cytologic, histochemical, and ultrastructural findings in bronchoalveolar lavage fluid.

Pulmonary alveolar proteinosis (PAP) is defined as abundant extracellular proteinaceous periodic acid-Schiff (PAS)-positive material which represents surfactant distending alveolar spaces. While this lesion is defined by histologic findings, there are characteristic radiologic features and cytologic findings in bronchoalveolar lavage (BAL) specimens that together may provide a confident diagnosis. The BAL specimens from all patients for which a diagnosis of PAP was made or suggested on either cytologic or biopsy specimens at University of North Carolina Hospitals from 1990-1999 were reviewed. There were 23 cytologic specimens from 11 patients. Patient ages ranged from 6 wk to 76 yr. All 23 specimens had slides prepared for Papanicolaou stain, 22 specimens (all patients) had Diff-Quik stains, 10 specimens (6 patients) had PAS stains, and 8 specimens (5 patients) had lipid stains. Nine patients had lung biopsies in addition to cytologic specimens. The clinical charts of all patients were reviewed. Twenty-one cytologic specimens were described as cloudy or milky, and 2 were bloody. By chart review and/or biopsy results, 8 patients were felt to have definite PAP. The initial lavage specimens from 6 of these patients showed classic cytologic findings of PAP, consisting of paucicellular specimens dominated by adundant extracellular granular to globular material which was basophilic on Diff-Quik stain, pale to focally eosinophilic on Pap stain, and PAS-positive, diastase-resistant. Five of these patients had biopsies; 3 showed PAP, and 2 were insufficient. Later BAL specimens after therapeutic lavage from these patients were often less characteristic, with scant extracellular material present. The other 2 patients with PAP clinically and by biopsy had atypical cytologic findings, with one showing numerous macrophages with scant PAS-positive material and abundant lipid mimicking lipid pneumonia, and one showing moderate eosinophils in addition to the extracellular proteinacous material. The remaining 3 patients were felt not to have PAP clinically or by biopsy (1 lymphocytic interstitial pneumonitis, 1 rheumatoid lung, and 1 hemosiderosis), and their BAL specimens predominantly contained macrophages with rare proteinaceous extracellular globules. Electron microscopy was performed in 5 patients (4 considered to have PAP, and 1 with lymphocytic interstitial pneumonitis) and in all cases showed whorled myelin figures characteristic of surfactant. The PAP cases and the non-PAP case had identical ultrastructural findings. We conclude that BAL specimens with classic cytologic features and supporting clinical and radiographic evidence may be diagnosed as PAP. Atypical specimens should be approached with caution, and may represent either PAP or other pulmonary diseases with secondary accumulation of surfactant. Cytology specimens taken subsequent to therapeutic lavage from PAP patients may also not be diagnostic.

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.

Subclassification of benign breast disease by fine needle aspiration cytology. Comparison of cytologic and histologic findings in 265 palpable breast masses.

The cytologic and histologic features of 265 benign breast masses were analyzed in order to examine the ability of fine needle aspiration cytology to accurately subclassify benign breast lesions. Two hundred two of the masses were pure histologic examples of benign breast lesions (72 nonproliferative fibrocystic change, 27 proliferative fibrocystic change, 65 fibroadenoma, 12 abscess, 8 fat necrosis, 7 papilloma, 7 duct ectasia, 2 tubular adenoma, 1 sclerosing adenosis, 1 microglandular adenosis), and 63 masses were mixed lesions. Part I of the study consisted of retrospective comparison of the original cytologic diagnoses with the histologic diagnoses. A nonspecific descriptive diagnosis had been rendered in 135 of 265 (51%) cases, and these descriptive diagnoses corresponded to fibrocystic change in the majority of cases (70%). A specific benign cytologic diagnosis had been made in 130 of 265 (49%) cases, and overall the specific diagnosis was correct in 80% of cases. Part II of the study consisted of the semiquantitative scoring of the cytologic findings of the 202 pure examples of benign breast masses and statistical analysis of differences in the expression of cytologic features between the different types of lesions. Overall cellularity, amount of bipolar stripped nuclei, amount and architectural arrangement of epithelium, epithelial atypia/pleomorphism/nuclear overlapping and amount of apocrine metaplasia, foam cells and stroma were the cytologic parameters that were statistically significant (P < .05) in distinguishing between the cases of fibroadenoma, abscess, papilloma, fat necrosis, duct ectasia and fibrocystic change as a group. No cytologic parameter reached statistical significance in distinguishing between proliferative and nonproliferative fibrocystic change. We conclude that the majority of benign breast lesions yield characteristic cytologic findings that allow their subclassification when sufficiently sampled by fine needle aspiration. The distinction between proliferative and nonproliferative fibrocystic change is less reliable, and cytologic differences observed within this spectrum did not reach statistical significance.

Tubal metaplasia. A frequent potential pitfall in the cytologic diagnosis of endocervical glandular dysplasia on cervical smears.

The detection of endocervical glandular abnormalities has risen in recent years due to the increased clinical use of improved endocervical canal sampling instruments, such as Cytobrushes. From January 1987 through August 1989, a diagnosis of endocervical glandular dysplasia was initially suggested on cervical smears from 50 women for whom histologic follow-up information was available. Retrospective review of the cytologic smears and histologic slides from these patients revealed tubal metaplasia in 19 of 29 (66%) cases evaluated by cervical conization and/or hysterectomy and in 19 of 21 (90%) cases confirmed by cervical biopsy and/or endocervical curettage. Cytologic criteria for the diagnosis of tubal metaplasia on cervical smears are discussed. Inasmuch as adenocarcinoma in situ of the cervix and endocervical glandular dysplasia are not readily discernible by colposcopy, the responsibility for the diagnosis of these lesions lies with surgical pathologists and cytopathologists. Familiarity with the cytologic features of adenocarcinoma in situ and endocervical glandular dysplasia that distinguish these lesions from tubal metaplasia and other potential mimics is essential.

Teaching cytopathology in the undergraduate medical school curriculum: the experience at the University of North Carolina.

A formal instructional unit in cytopathology in the 2nd-year medical school pathology course at the University of North Carolina is described. This unit was added to the traditional mechanisms and organ systems instruction in the pathology course to increase the exposure of students to modern diagnostic techniques and informed use of laboratory testing. The unit is presented at the end of the pathology course as a summation of organ systems pathology and an introduction to the clinical practice of one branch of pathology. Two lectures cover the general principles of cytopathology, specimen procurement and adequacy, cytologic findings of common lesions in three organ systems (female genital tract, lung, and breast), specialized techniques, clinical advantages and disadvantages of cytologic techniques, and accuracy. Clinical correlation and appropriateness of testing are stressed. An accompanying laboratory session includes examination of glass slides predominantly prepared from surgical specimens and discussion of clinical cases with experienced cytologists using Kodachrome illustrations of cytologic slides and subsequent histologic and clinical follow-up. Our experience to date suggests that this unit informs students about the role of cytology in modern medical practice and helps to bridge the gap between the basic science of pathology and clinical medicine.