Cytomorphology of a unique case of dedifferentiated chordoma involving a pleural effusion specimen.

Cytomorphology along with positive AE1/AE3 staining and Brachyury staining support the dignosis of metastatic dedifferentiated chordoma.

Low-grade squamous intraepithelial lesion, cannot rule out high-grade lesion: Diagnosis, histological outcomes and human papillomavirus results.

BACKGROUND: The 2014 Bethesda System for Reporting Cervical Cytology classifies squamous intraepithelial lesions (SILs) of cervix into two main categories: low-grade SIL (LSIL) and high-grade SIL (HSIL). In some clinical practices, the LSIL cannot rule out high-grade lesion (LROH) interpretive category is used in cases with LSIL and findings that may raise the possibility of HSIL. Our purpose is to assess follow-up histopathology and high-risk human papillomavirus (hrHPV) results in patients with LROH, in comparison with LSIL, atypical squamous cells, cannot rule out HSIL (ASC-H), and HSIL in our institution. DESIGN: Cervical Papanicolaou tests with LROH, LSIL, ASC-H and HSIL interpretation, surgical follow-up, and hrHPV status were retrieved from the computer database from May 2014 to December 2016. RESULTS: Of 109 963 total Papanicolaou tests, LROH comprised 0.3%, LSIL 3.1%, ASC-H 0.2% and HSIL 0.4%. Only 3272 cases with surgical diagnoses were included in the study. The most common histological outcome for ASC-H was cervical intraepithelial neoplasia (CIN)2/3 (32.6%); LSIL was CIN 1 (45.7%); LROH was CIN 1 (46.7%) and HSIL was CIN 2/3 (64.4%). For LROH and LSIL, 31.1% and 7.5% respectively, had CIN 2/3. Approximately 79% of cases were hrHPV positive. Of LROH cases with surgical follow-up, 86.9% tested hrHPV positive, accounting for the second most common positive group after HSIL (92.6%). CONCLUSION: In our study cohort, LROH interpretation is associated with a higher number of CIN 2 or higher lesions on follow-up compared to patients with LSIL (P < 0.0001), and is associated with a significant percentage of positive other hrHPV, supporting LROH as a useful diagnostic category that triggers appropriate follow-up in affected women.

Fine needle aspiration of a metastatic germ cell tumor to supraclavicular lymph node.

OBJECTIVE: Germ cell tumors are the most common tumors in men in their second decade. According to the National Comprehensive Cancer Network, the management of germ cell tumors depends on whether the tumor is diagnosed as a seminoma or a nonseminoma. Fine needle aspiration biopsy, compared to incisional biopsy, is relatively safe and facilitates rapid assessment of these tumors. METHODS: An ultrasound guided FNA biopsy was performed, and air-dried slides and alcohol-fixed slides were made for Diff-Quik staining and Papanicolaou staining, respectively. The syringes were rinsed and cell block was prepared. The resected specimen was fixed in 10% formalin and processed by routine histology techniques. RESULTS: We report a case of a 22-year-old male with an enlarged scrotal mass and a supraclavicular nodule. A superficial fine needle aspiration biopsy was performed on the nodule and the correct diagnosis was made via cytomorphology and immunohistochemistry. The cytologic diagnosis was correlated with the incisional biopsy results. CONCLUSION: Fine needle aspiration biopsy is very helpful in the initial triage of germ cell tumors. When the aspirate contains sufficient diagnostic material, a specific diagnosis may be reached. Likewise, as different germ cell tumors have characteristic immunohistochemical profiles, a cell block from an aspirate may be critical for correct diagnosis. However, because germ cell tumors often contain mixed elements, cytologic diagnosis may not be entirely representative due to incomplete sampling. Thus, it is important to correlate cytologic diagnosis with the excisional tissue biopsy results.

Fine needle aspiration of an unusual malignant mixed tumor in the parotid gland.

OBJECTIVE: The use of fine needle aspiration (FNA) biopsy in the triage of salivary gland tumors has been well established. The sensitivity and specificity of FNA biopsy for tumor diagnosis is generally very good. However, the diagnosis can be challenging due to the limited amount of tissue sampled, the occasional overlapping tumor morphology, and the presence of a malignant counterpart of a benign tumor. METHODS: FNA biopsy was performed with ultrasound guidance. Air-dried slides and alcohol-fixed slides were made for Diff-Quik staining and Papanicolaou staining, respectively. The syringes were rinsed and a cell block was prepared. The resected specimen was fixed in 10% formalin and processed by routine histology techniques. RESULTS: We report a rare case of a salivary gland neoplasm with 2 distinct components: adenoid cystic carcinoma and pleomorphic adenoma. These 2 components are clearly identifiable in both cytological materials from fine needle aspiration and histological analysis of surgical resection. CONCLUSION: Pleomorphic adenoma is the most common salivary gland tumor for patients in all age groups. The characteristic cytological feature is fibrillary extracellular matrix intermixed with epithelial cells. Malignant transformation occurs in 5% to 10% of cases. Rarely, pleomorphic adenoma exists as one component of a hybrid tumor. The surgical resection will be needed in those cases. The final diagnosis relies on the combination of the clinical information, histological findings and molecular study.

The diagnostic accuracy and prognostic implication of pelvic and peritoneal fluid cytology specimens in ovarian clear cell carcinoma.

INTRODUCTION: Ovarian clear cell carcinoma (OCCC) is a rare subtype of ovarian epithelial carcinoma. Patients with low-stage disease have an excellent prognosis, while the prognosis for those with high-stage disease is poor. Neoplastic cells in abdominopelvic washings upstages the patient to at least FIGO 1C3. Positive cytology confers a worse prognosis when compared to similar stage patients with negative cytology. This study aims to investigate the diagnostic performance of abdominopelvic fluid cytology specimens in cases with pure OCCC and reaffirm the importance of accurate cytologic detection and its impact on patient prognosis. MATERIALS AND METHODS: The laboratory information system was queried to identify all patients treated for ovarian clear cell carcinoma at our institution over a period of 20 years with a companion abdominopelvic fluid cytology specimen at the time of surgical resection. Cases were sorted by the FIGO stage of the corresponding oophorectomy specimen. Cytology results, patient demographics, fluid volume, immunohistochemical results, and follow-up data were recorded. RESULTS: A total of 143 cases were identified. The overall detection rate was 38%, with 54 of 143 cases positive for malignancy. Cytologic detection rates increased as FIGO stages increased. Fifty percent of stage 1C cases were upstaged on cytology alone. Ascites fluids performed better among stage 1 cases compared to pelvic wash specimens (77% detection rate versus 23%). Stage 1 patients with positive cytology trended towards a worse prognosis compared to those with negative cytology. CONCLUSIONS: Positive cytology in low stage cases of OCCC has significant prognostic and therapeutic implications. Our large cohort further underscores the importance of accurate cytologic detection and subsequent staging in this setting.

Reliably making the primary diagnosis of mesothelioma utilizing serous fluid cytology specimens: an institutional experience.

INTRODUCTION: The diagnosis of mesothelioma has historically been challenging, especially on serous fluid cytology (SFC). Distinguishing between reactive and neoplastic mesothelial cells can be difficult on cytomorphology alone. However, additional ancillary tests, such as BRCA1 associated protein-1 immunohistochemistry and fluorescence in situ hybridization for cyclin-dependent kinase inhibitor 2A deletion, can provide a sensitive and highly specific method of proving malignancy. MATERIALS AND METHODS: SFC specimens diagnosed as mesothelioma, suspicious for mesothelioma (SM), and atypical mesothelial cells (AMCs) since 2012 were identified by querying the laboratory information system. Clinical data and pathologic parameters were gathered. RESULTS: One hundred ten cases of mesothelioma, SM, and AMC were identified. Of these, 61 cases had a definitive diagnosis of mesothelioma on SFC. Average age at SFC diagnosis was 67 years (26-87 years), with most patients being male (67%). Out of the 61 cases, 11 cases (18%) had an initial diagnosis of mesothelioma made on SFC specimens, with 5 of these 11 cases being in patients that never received a histologic diagnosis of mesothelioma. Ancillary studies were utilized in all 11 cases. An initial diagnosis of metastatic mesothelioma was made on SFC in 9 cases (15%). For 6 of these 9 cases, the SFC diagnosis was the sole diagnosis of metastatic mesothelioma without a companion histologic diagnosis. In addition, 15 cases were diagnosed as SM, with 11 of these cases following a definitive mesothelioma diagnosis. Thirty-four cases were diagnosed as AMC, with 27 cases following a definitive mesothelioma diagnosis. CONCLUSIONS: The diagnosis of mesothelioma can be reliably made on SFC with the appropriate cytomorphology criteria and/or confirmatory ancillary testing.

Benchmarking cytology support for ROSE during endoscopic and bronchoscopic procedures.

INTRODUCTION: There has been an increase in endoscopic and bronchoscopic biopsies as minimally invasive methods to obtain specimens from gastrointestinal (GI) or pancreatobiliary lesions and thoracic or mediastinal lesions, respectively. As hospitals undertake more of these procedures, it is important to consider the staffing implications that this has on cytopathology laboratories with respect to support for rapid on-site evaluation (ROSE). MATERIALS AND METHODS: Volume and time data from endoscopic ultrasound and bronchoscopic procedures (including endobronchial ultrasound-guided transbronchial needle aspirations and small biopsies with touch preparation) in the GI suite, bronchoscopy suite, or operating room were reviewed for 2 months at 2 different medical centers with ROSE services provided by cytologists or fellows physically present at the procedure and cytopathologists located remotely using telecytology. Statistical analysis was performed to investigate significant trends based on the location of the biopsies and other factors. RESULTS: A total of 16 proceduralists performed 159 procedures and submitted 276 different specimens during 16 total weeks at 2 institutions. The total ROSE time for the on-site personnel to cover these procedures was 109.3 hours (bronchoscopy, 62.3 hours [57%]; GI, 29.8 hours [27%]; OR, 17.2 hours [16%]), which represents an average of 0.69 hour (41.4 minutes) per procedure or 0.40 hour (24.0 minutes) per part, with the shortest procedure times per sample recorded during bronchoscopy. When stratified by practice volume for individual proceduralists, the average time per specimen sample submitted was shorter for proceduralists with high volume practices and was most pronounced during bronchoscopy procedures. CONCLUSIONS: Endoscopic and bronchoscopic procedures account for an increasing amount of the ROSE time for the cytology team. On average, each ROSE procedure takes 0.69 hour (41.4 minutes) or approximately 0.40 hour (24.0 minutes) per specimen, with shorter time requirements for specimens obtained in bronchoscopy procedures and for operators with high volume practices for endobronchial ultrasound-guided transbronchial needle aspirations. This provides important benchmarking data to calculate staffing needs for cytology to provide ROSE support for different proceduralists.

Thoracic SMARCA4-deficient undifferentiated tumor with associated granulomatous reaction and response to pembrolizumab.

Thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) is a rare entity that was recently described in the current World Health Organization Classification of Tumors. These lesions are highly aggressive with dismal prognosis, and most patients present with metastasis at the time of diagnosis. While there are about 100 cases of SMARCA4-UT described in the literature, there are only few existing reports that describe the cytomorphology of these lesions. We present a patient with masses involving the mediastinum, right lung, right supraclavicular lymph node and right adrenal gland. Subsequent core-needle biopsy of the right supraclavicular lymph node showed epithelioid to pleomorphic tumor cells with prominent nucleoli and associated granulomatous inflammation. The tumor cells were positive for CD34 and synaptophysin, and were negative for cytokeratins. SMARCA4 and SMARCA2 both showed loss of expression, which led to the diagnosis of SMARCA4-UT. The patient underwent treatment with pembrolizumab (PD-1 blocker), carboplatin, etoposide, and radiotherapy, resulting in an almost 55% reduction in the size of the primary tumor. Our case illustrates that an associated granulomatous inflammation might be an uncommon presentation of an already rare malignancy, and awareness of this phenomenon would prevent from mistaking SMARCA4-UT for other more well-known entities that can present with granulomas.

Utility of cytopathologic diagnosis of adult solid renal lesions: An academic Institution's 10-year experience.

BACKGROUND: Fine needle aspiration (FNA) and/or needle core biopsy (NCB) are increasingly used for managing patients with renal lesions, especially small renal masses (SRMs). One of the treatment options for SMRs is active surveillance. Hence, accurate diagnosis of renal lesions is critical for treatment planning. The aim of this study is to investigate the utility of FNA and/or NCB in the diagnosis of adult renal lesions at our institute. MATERIALS AND METHODS: Laboratory information system was queried over a period of 10 years (2011-2020) to identify cases of FNA and/or NCB with touch preparation (TP) of adult renal masses. Patient demographics, cytopathologic diagnoses, ancillary tests and follow-up surgical resection data were reviewed and correlated. RESULTS: A total 138 cases from 138 patients (male = 80, female = 58) were identified. Sixty-one (44.20%) cases had FNA and NCB, 48 (34.78%) had NCB only and 29 (21.01%) had FNA only. 118 (85.50%) cases had definitive diagnoses and 13 (9.42%) had indeterminant diagnoses and seven cases were non-diagnostic (5.07%). Most common benign and malignant diagnoses were oncocytoma and clear cell renal cell carcinoma (CCRCC). 41/138 (29.71%) cases had follow-up resection. There were no false positive or false negative cases. Subtyping was feasible in majority cases with only 3/138 (2.17%) misclassified cases. CONCLUSIONS: Majority of renal masses (85.50%) had definitive cytology diagnoses. Only three had misclassification. FNA and/or NCB are useful methods in diagnosing and subclassifying adult renal masses and showed high accuracy (91.89%) when compared to surgical resections.

Cytopathologic diagnosis of extragonadal germ cell tumors: A 10-year institutional review.

BACKGROUND: The occurrence of extragonadal germ cell tumors (EGGCTs), either as primary tumors or metastatic disease, is rare. Forms of cytologic sampling, including fluid analysis, fine-needle aspiration, and/or small-core needle biopsy, have been shown to be reliable methods for the diagnosis of germ cell tumors. This study aims to investigate the utility of cytopathologic techniques in the diagnosis of EGGCTs at the authors' institution. METHODS: The laboratory information system was queried over a period of 10 years (2012-2022) to identify all cytology cases diagnosed on fluid cytology, FNA, and/or small-core biopsy as germ cell tumors in extragonadal locations. Patient demographics, tumor location, serum tumor marker levels, cytopathologic diagnosis, and follow-up surgical resection data were reviewed and correlated. RESULTS: A total of 35 cases from 32 patients (all males) were identified. Thirty specimens contained satisfactory material for diagnosis (86%) and five were less than optimal for evaluation (14%). Despite this, all cases had clinically useful cytopathologic diagnoses. A total of 19 cytology cases (16 patients) had follow-up resection specimens available. Of these, 11 patients underwent preoperative chemotherapy. Nine patients showed no evidence of residual tumor and two showed histologic concordance. Of the five patients who did not have preoperative chemotherapy, all showed concordant histologic diagnoses. CONCLUSIONS: Cytology can provide a reliable, accurate method for diagnosing EGGCTs. The practice of preoperative (neoadjuvant) chemotherapy places an extreme importance on the initial cytopathologic diagnosis because the majority of patients with follow-up resection in this series showed no residual tumor.

Fluorescent in-situ hybridization test performed on cell blocks is useful for establishing germ cell origin of metastatic tumors with unusual clinical presentation.

The majority of germ cell tumors (GCTs) are characterized by iso-chromosome 12p (i12p) abnormality. The aim of this study is to review the cytomorphologic features and analyze the utility of i12p fluorescent in-situ hybridization (FISH) test in diagnosing metastatic GCTs primarily evaluated by cytologic techniques in patients without prior history of GCTs. The laboratory information system was queried over a period of 10 years to search for cases where i12p FISH test was requested on cytology material. FISH test was performed using TelVysion 12p telomeric probe and CEP 12 centromere probe on cell-blocks. A ratio of 12ptel/CEP12 signal of 1.4 or greater was considered as positive. Patient demographics, clinical presentation, cytopathologic findings, and follow-up surgical resection data were reviewed and correlated. A total of three cases were identified, all men (age range 31-60 years). Cytologic diagnoses were favor metastatic embryonal carcinoma (Case 1, retroperitoneal fluid FNA), metastatic yolk sac tumor/YST (Case 2, lung mass FNA) and adenocarcinoma, likely representing a somatic-type malignancy (SM) arising from a preexisting GCT (Case 3, retroperitoneal mass FNA). This limited study demonstrated high sensitivity for detecting i12p abnormality by FISH test performed on cell blocks. The cytomorphology of extra-gonadal GCTs varies according to the histologic subtype. Sarcomatoid morphology of YST, SM or mixed GCTs further complicates cytology evaluation. FISH test for detection of i12p performed on cell-blocks is extremely useful in establishing germ cell origin of these metastatic GTCs with unusual cytomorphology and guides management in patients without prior history of GCTs.

Reassessing the optimal volume for malignancy detection in serous fluid cytology.

BACKGROUND: The international system for reporting serous fluid cytopathology (TIS) recommends submitting at least 50-75 mL of serous fluid to decrease false-negative results. However, prior studies did not agree on specific volume requirements or consensus adequacy criteria. Our study aims to assess whether fluid volume affects the adequacy rate and to assess the minimum volume necessary for optimal adequacy in pleural and peritoneal fluids. METHODS: A total of 8530 serous fluid cytology cases were identified in the laboratory information system. Differences in mean fluid volume received in the laboratory were compared using an ANOVA Games-Howell test based on TIS category. The percentage of malignant diagnoses across the volume ranges of 0 to 5 mL, 5 to 10 mL, 10 to 25 mL, 25 to 50 mL, 50 to 75 mL, 75 to 100 mL, 100 to 150 mL, 150 to 250 mL, 250 to 500 mL, 500 to 2000 mL was compared in pleural and peritoneal fluids using a chi-square test, and a SiZer analysis was performed. RESULTS: Mean fluid volume in inadequate, atypical, and negative cases was significantly lower compared to positive cases. A SiZer analysis showed a positive relationship between the malignancy fraction of pleural and peritoneal fluids and fluid volume. The percentage of malignant diagnoses in pleural and peritoneal fluid samples increased significantly up to a volume range of 75-100 mL. CONCLUSIONS: There is a significant relationship between fluid volume, adequacy and detection of malignancy in serous effusion cytopathology. The malignancy fraction increases with larger fluid volumes but at least 75-100 mL of fluid should be submitted for optimal diagnosis of malignancy in pleural and peritoneal fluids.

Cervicovaginal cytology, HPV testing and vaginal flora in transmasculine persons receiving testosterone.

BACKGROUND: Testosterone is one of the strategies that transmasculine persons can elect in order to align physical traits to their gender identity. Previous studies have shown morphologic changes in the genital tract associated with testosterone. Here, we aim to evaluate cervicovaginal cytology specimens (Pap tests) and high-risk HPV (HR-HPV) testing from transmasculine individuals receiving testosterone. METHODS: This is a retrospective cohort of 61 transmasculine individuals receiving testosterone from 2013 to 2021. Cytologic diagnoses from 65 Pap tests were correlated with HPV status and histologic follow-up and compared with the institutional data and a cohort of cisgender women with atrophic changes. RESULTS: The median age was 28 years and median time of testosterone use was 3 years. Transmasculine persons showed significantly higher rates of HSIL (2%) and unsatisfactory (16%) when compared with the institutional data and atrophic cohort of cisgender women. After reviewing slides of 46 cases, additional findings were noted: atrophy was present in 87%, glycogenated cells were seen in 30%, and Lactobacilli were substantially decreased in 89%. Among 32 available HPV tests, 19% were positive for HR-HPV and 81% were negative. On histologic follow-up, all HR-HPV-positive cases with abnormal cytology showed HSIL, while none of the HPV-negative cases revealed HSIL. CONCLUSION: Our study cohort demonstrated a high percentage of abnormal Pap tests in transmasculine persons receiving testosterone. Testosterone seems to induce changes in squamous cells and shifts in vaginal flora. HR-HPV testing can be a useful adjunct in the workup of abnormal Pap tests from transmasculine individuals.

Educational Case: Pancreatic Cystic Disease: A Multimodal Diagnostic Approach to Determine Clinical Management.

The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, see http://journals.sagepub.com/doi/10.1177/2374289517715040. 1.

A rare case of primary effusion lymphoma in HIV negative patient: Diagnostic challenges and literature review.

We present a rare case of primary effusion lymphoma (PEL) in a 75 year old, HIV-negative male patient with multiple comorbidities. Imaging studies revealed a massive right pleural effusion and a significant lung collapse with multiple plural soft tissue nodules. Immediate thoracentesis was performed. Cytologic evaluation of the pleural fluid showed abnormally large cell with increased nuclear to cytoplasmic ratio, irregular nuclear contours and prominent nucleoli, with phenotypic expression of HHV-8, CD138, CD30, and MUM1 markers and negative staining for epithelial and mesothelial markers. PEL is a rare and aggressive large B-cell lymphoma often affecting immunocompromised adults and is mostly associated with human herpes virus 8/Kaposi sarcoma-associated herpes virus (HHV-8/KSHV). However, cases in immunocompetent elderly patients have been reported. The cytomorphologic features of PEL overlaps with those of aggressive lymphomas such as diffuse large B-cell lymphoma, plasmablastic lymphoma, and anaplastic large-cell lymphoma. Also, mesothelioma, metastatic carcinoma or melanoma should be considered in the differential diagnosis. Hence, PEL should be kept in mind in the diagnostic algorithm of cytological evaluation of serosal fluid not only in HIV positive patients but also HIV-negative elderly patients. In this report, we aim to highlight the cytologic and immunohistochemical staining pattern of this rare entity to increase awareness of this entity among cytopathologists.

Adenomatous neuroendocrine tumors of the middle ear (MEANTs) with local invasion and lymph nodes metastasis: A brief report of a rare neoplasm.

Adenomatous neuroendocrine tumors of the middle ear (MEANTs) are very rare neoplasms which are composed of both epithelial and neuroendocrine components. They have mostly bland histology and indolent biological behavior, yet they may recur and metastasize. Here we present a case of MEANT with ipsilateral local brain, bone and nerve invasion and bilateral cervical lymphadenopathy in a 48 years old male with history of recurrent chronic otitis media and cholesteatoma. The patient underwent an initial fine-needle aspiration biopsy (FNAB) of an enlarged cervical lymph node followed by surgical excision of the tumor and immunohistochemistry which confirmed the diagnosis.

Follicular dendritic cell sarcoma: Cytomorphologic features and diagnostic challenges.

Follicular dendritic cell sarcoma (FDCS) is a rare malignant neoplasm, which primarily arises in lymph nodes with occasional cases occurring in extranodal locations. The diagnosis is often challenging particularly on cytology fine needle aspiration due to overlapping morphologic and immunohistochemical features. We present a case of FDCS diagnosed in an otherwise asymptomatic 33-year old male. The aim of our case report is to highlight the key cytomorphologic features and discuss various differential diagnoses of this unusual entity.

Educational Case: Diagnostic Approach to Salivary Gland Neoplasms.

The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, see http://journals.sagepub.com/doi/10.1177/2374289517715040. 1.

Educational Case: High-Grade Serous Carcinoma of the Ovary.

The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, seehttp://journals.sagepub.com/doi/10.1177/2374289517715040.1.

Comparison of quantitative internal and external measures of performance for trainees in cytopathology fellowships.

INTRODUCTION: Cytopathology fellowships need measures to assess performance of fellows. We sought to compare several internal quantitative assessment metrics in our fellowship with external metrics, such as performance on the American Society of Cytopathology (ASC) Progressive Evaluation of Competency (PEC) examination and United States Medical Licensing Examination (USMLE). METHODS: Quantitative parameters generated from our laboratory information system (LIS) on cytopathology fellows were evaluated over 6 years, including case volume and diagnostic discrepancies, in addition to ASC PEC and USMLE scores. For discrepancy reports, interpretations made by the fellow were compared with that of the cytopathologist, and classified as none (concordant), minor (<2-levels) or major (≥2-levels). RESULTS: We evaluated internal and external metrics on 13 fellows over 6 years. The program average diagnostic concordance rate was 89.9%, with an average major discrepancy rate of 1.5%, and an average monthly case volume of 260 cases. More fellows with above-average ASC PEC performance showed above-average concordant diagnoses and lower case volume, while below-average PEC scores were seen more often with higher major discrepancy rates. More fellows with above-average USMLE scores had higher case volumes, while low USMLE scores showed a trend towards higher major discrepancy rates. CONCLUSION: Our fellowship program has used a variety of internal and external measures of performance for cytopathology fellows. Although the findings show no statistically significant finding correlating performance, these quantitative parameters generated from our LIS were helpful to identify areas of improvement, facilitate comparison to peers, and provide case volume documentation.