FNA of Meningioma with Rhabdoid Features Presenting as a Lateral Neck Mass.

Primary meningioma at extracranial head and neck sites is uncommon. Since fine needle aspiration (FNA) is often the first line diagnostic modality for the evaluation of masses in the head and neck, extracranial meningiomas can create a significant diagnostic pitfall for FNA. We report a case of meningioma with rhabdoid features and BAP1 loss in a 26-year-old woman, presenting as a large neck mass along the carotid sheath. FNA biopsy of the mass demonstrated a highly cellular specimen with clusters of uniform, epithelioid cells with round to ovoid nuclei and moderate nuclear to cytoplasmic ratio. An extensive immunohistochemical panel performed on cell block sections showed that the tumor cells were weakly EMA positive, progesterone receptor was focally positive, and SSTR2A was diffuse and strongly positive. BAP1 immunohistochemistry showed a diffuse loss of expression in the tumor cells. After the cytologic diagnosis of meningioma, a tissue biopsy was performed, and the diagnosis of meningioma with rhabdoid features and BAP1 loss was confirmed. We also perform a literature review of meningioma cases presenting as a neck mass and evaluated by FNA. Our case highlights the significant diagnostic challenges that can be caused by extracranial meningiomas on FNA and the importance of ancillary studies to avoid diagnostic pitfalls.

Grade group 4 prostate cancer without intraductal carcinoma on biopsy is more likely to be downgraded on prostatectomy than with intraductal carcinoma.

In this study, we investigated the association between intraductal carcinoma of the prostate (IDCP) along with several histopathological features on prostate biopsy and downgrading of grade group 4 (GG4) prostate cancer (PCa) in patients with the highest grade tumor of GG4 PCa in at least one core. A total of 29 cases had the highest grade tumor of GG4 PCa and radical prostatectomy performed between 2016 and 2021. IDCP was detected in 11 out of 29 cases on biopsy. The cases without IDCP were more likely to be downgraded on prostatectomy than with IDCP, with statistical significance (88.9% vs 36.4%, p = 0.003). The proportions of the highest-grade tumors by length and cores involved, average numbers of PCa-positive cores, and mean patient's age did not differ between cases that were downgraded and not downgraded at prostatectomy. Our results suggest that the absence of IDCP on biopsy could be a predictor of downgrading at prostatectomy for patients with the highest grade tumor of GG4 PCa.

Chromogenic detection of telomere lengths in situ aids the identification of precancerous lesions in the prostate.

BACKGROUND: Telomeres are terminal chromosomal elements that are essential for the maintenance of genomic integrity. The measurement of telomere content provides useful diagnostic and prognostic information, and fluorescent methods have been developed for this purpose. However, fluorescent-based tissue assays are cumbersome for investigators to undertake, both in research and clinical settings. METHODS: A robust chromogenic in situ hybridization (CISH) approach was developed to visualize and quantify telomere content at single cell resolution in human prostate tissues, both frozen and formalin-fixed, paraffin-embedded (FFPE). RESULTS: This new assay (telomere chromogenic in situ hybridization ["Telo-CISH"]) produces permanently stained slides that are viewable with a standard light microscope, thus avoiding the need for specialized equipment and storage. The assay is compatible with standard immunohistochemistry, thereby allowing simultaneous assessment of histomorphology, identification of specific cell types, and assessment of telomere status. In addition, Telo-CISH eliminates the problem of autofluorescent interference that frequently occurs with fluorescent-based methods. Using this new assay, we demonstrate successful application of Telo-CISH to help identify precancerous lesions in the prostate by the presence of markedly short telomeres specifically in the luminal epithelial cells. CONCLUSIONS: In summary, with fewer restrictions on the types of tissues that can be tested, and increased histologic information provided, the advantages presented by this novel chromogenic assay should extend the applicability of tissue-based telomere length assessment in research and clinical settings.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression.

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type-specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by 2 orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

Chromogenic detection of telomere lengths in situ aids the identification of precancerous lesions in the prostate.

Telomeres are terminal chromosomal elements that are essential for the maintenance of genomic integrity. The measurement of telomere content provides useful diagnostic and prognostic information, and fluorescent methods have been developed for this purpose. However, fluorescent-based tissue assays are cumbersome for investigators to undertake, both in research and clinical settings. Here, a robust chromogenic in situ hybridization (CISH) approach was developed to visualize and quantify telomere content at single cell resolution in human prostate tissues, both frozen and formalin-fixed, paraffin-embedded (FFPE). This new assay ("Telo-CISH") produces permanently stained slides that are viewable with a standard light microscope, thus avoiding the need for specialized equipment and storage. The assay is compatible with standard immunohistochemistry, thereby allowing simultaneous assessment of histomorphology, identification of specific cell types, and assessment of telomere status. In addition, Telo-CISH eliminates the problem of autofluorescent interference that frequently occurs with fluorescent-based methods. Using this new assay, we demonstrate successful application of Telo-CISH to help identify precancerous lesions in the prostate by the presence of markedly short telomeres specifically in the luminal epithelial cells. In summary, with fewer restrictions on the types of tissues that can be tested, and increased histologic information provided, the advantages presented by this novel chromogenic assay should extend the applicability of tissue-based telomere length assessment in research and clinical settings.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression.

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by two orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

Presence of cells in the polyaneuploid cancer cell (PACC) state predicts the risk of recurrence in prostate cancer.

BACKGROUND: The nonproliferating polyaneuploid cancer cell (PACC) state is associated with therapeutic resistance in cancer. A subset of cancer cells enters the PACC state by polyploidization and acts as cancer stem cells by undergoing depolyploidization and repopulating the tumor cell population after the therapeutic stress is relieved. Our aim was to systematically assess the presence and importance of this entity in men who underwent radical prostatectomy with curative intent to treat their presumed localized prostate cancer (PCa). MATERIALS AND METHODS: Men with National Comprehensive Cancer Network intermediate- or high-risk PCa who underwent radical prostatectomy l from 2007 to 2015 and who did not receive neoadjuvant treatment were included. From the cohort of 2159 patients, the analysis focused on a subcohort of 209 patients and 38 cases. Prostate tissue microarrays (TMAs) were prepared from formalin-fixed, paraffin-embedded blocks of the radical prostatectomy specimens. A total of 2807 tissue samples of matched normal/benign and cancer were arrayed in nine TMA blocks. The presence of PACCs and the number of PACCs on each core were noted. RESULTS: The total number of cells in the PACC state and the total number of cores with PACCs were significantly correlated with increasing Gleason score (p = 0.0004) and increasing Cancer of the Prostate Risk Assessment Postsurgical (CAPRA-S) (p = 0.004), but no other variables. In univariate proportional hazards models of metastasis-free survival, year of surgery, Gleason score (9-10 vs. 7-8), pathology stage, CAPRA-S, total PACCs, and cores positive for PACCs were all statistically significant. The multivariable models with PACCs that gave the best fit included CAPRA-S. Adding either total PACCs or cores positive for PACCs to CAPRA-S both significantly improved model fit compared to CAPRA-S alone. CONCLUSION: Our findings show that the number of PACCs and the number of cores positive for PACCs are statistically significant prognostic factors for metastasis-free survival, after adjusting for CAPRA-S, in a case-cohort of intermediate- or high-risk men who underwent radical prostatectomy. In addition, despite the small number of men with complete data to evaluate time to metastatic castration-resistant PCa (mCRPC), the total number of PACCs was a statistically significant predictor of mCRPC in univariate analysis and suggested a prognostic effect even after adjusting for CAPRA-S.

Splenogonadal Fusion: A Rare Mimicker of Malignancy.

Splenogonadal fusion is a rare congenital anomaly in which ectopic splenic tissue is found in the testis and can present as a testicular mass mimicking a testicular malignancy. We present a 27-year-old male who presented with a palpable left testis mass suspicious for malignancy and ultimately found to have discontinuous splenogonadal fusion after radical orchiectomy.

Telecytology validation: is there a recipe for everybody?

INTRODUCTION: Telecytology offers a suitable solution to the cost and time efficiency questions on rapid onsite evaluation (ROSE). An increasing number of institutions are adopting new telecytology systems to meet the increasing ROSE requests, although there is no agreement on the details of how a telecytology validation study needs to be conducted. We propose a standardized approach for telecytology validation studies that could be done in a variety of practices. MATERIALS AND METHODS: Consecutive cases from 6 months prior were chosen to reflect a case mix comparable to real life. A fellow assessed the slides at the ROSE site while 6 cytopathology faculty convened in a conference room with a television screen, and noted the adequacy, diagnostic category, and specific diagnoses. All participants were blinded to the original adequacy assessment and final diagnoses. For each case, evaluation time and the slides counts were noted. RESULTS: Fine-needle aspiration specimens from 52 patients were included in the study. Of these, 13 cases were used in the first "test" session. The adequacy concordance rates ranged between 92.3% and 100%, with an overall concordance rate of 94.8%. The diagnostic category concordance rates ranged between 90.3% and 95.5%, with an overall concordance rate of 91.9%. The specific diagnosis concordance rates ranged between 84.6% and 92.9%, with an overall concordance rate of 88.1%. CONCLUSIONS: Validation of telecytology requires a standardized approach just like any other new technology. In this study, we propose an efficient and accurate method for cytopathology departments of various case volumes to conduct telecytology validation studies.

Adrenal gland cytology reporting: a multi-institutional proposal for a standardized reporting system.

BACKGROUND: With the development of new technologies and the changing patient profiles, cytopathology departments receive increasing numbers of adrenal gland cytology specimens. In this study, the authors analyzed archival adrenal gland cytology cases and attempted to implement a diagnostic reporting system. DESIGN: Retrospective electronic medical record search was performed for adrenal gland cytology specimens in seven tertiary care centers. The cytology diagnoses were grouped in 7 categories: nondiagnostic, nonneoplastic, benign adrenal cortical elements (BACE), primary neoplasm of noncortical origin (NONC), atypia of undetermined significance (AUS), suspicious for malignancy (SM), and malignant (MAL). If available, histopathology results of concurrent and/or follow-up biopsies and/or resections were documented. RESULTS: A total of 473 adrenal gland cytology cases were included. BACE cases comprised 21.8%, whereas MAL cases were 57.5% of all cases. For BACE and MAL categories, there were 100% and 98.9% correlation, respectively, in the cases with histopathology follow-up. Six of 10 NONC cases had histopathology diagnoses and there were 3 pheochromocytomas and 3 schwannomas. Twenty-one AUS cases had histology follow-up and 10 (47.6%) of them were malignant. Six cases of SM had histopathology follow-up, and all of them were malignant on the follow-up. CONCLUSIONS: The authors propose a 7-tier diagnostic scheme for adrenal gland cytology. The risk of malignancy was 98.9% in MAL cases (87/88) in the cohort. The only case with discordance was reported as "adrenal cortical adenoma with marked atypia"' on resection. There was no difference between endoscopic ultrasound-guided and percutaneous methods. Further studies are needed to validate and make this approach universal.

Characterization of tumor-associated macrophages in prostate cancer transgenic mouse models.

BACKGROUND: Tumor-associated macrophages (TAMs) are critical components of the tumor microenvironment (TME) in prostate cancer. Commonly used orthotopic models do not accurately reflect the complete TME of a human patient or the natural initiation and progression of a tumor. Therefore, genetically engineered mouse models are essential for studying the TME as well as advancing TAM-targeted therapies. Two common transgenic (TG) models of prostate cancer are Hi-Myc and transgenic adenocarcinoma of the mouse prostate (TRAMP), but the TME and TAM characteristics of these models have not been well characterized. METHODS: To advance the Hi-Myc and TRAMP models as tools for TAM studies, macrophage infiltration and characteristics were assessed using histopathologic, flow cytometric, and expression analyses in these models at various timepoints during tumor development and progression. RESULTS: In both Hi-Myc and TRAMP models, macrophages adopt a more pro-tumor phenotype in higher histological grade tumors and in older prostate tissue. However, the Hi-Myc and TRAMP prostates differ in their macrophage density, with Hi-Myc tumors exhibiting increased macrophage density and TRAMP tumors exhibiting decreased macrophage density compared to age-matched wild type mice. CONCLUSIONS: The macrophage density and the adenocarcinoma cancer subtype of Hi-Myc appear to better mirror patient tumors, suggesting that the Hi-Myc model is the more appropriate in vivo TG model for studying TAMs and TME-targeted therapies.

#TwitterHomework During Pathology Electives: Transforming Pathology Pedagogy.

CONTEXT.­: Twitter has become a popular platform for pathologists, where they share cases and educational content, arrange journal club meetings, network, and collaborate. OBJECTIVE.­: To determine if composing original tweets or retweeting existing content can be used as an educational and networking tool for medical students during pathology electives. DESIGN.­: In this retrospective study, a survey was sent to assess if medical students who used Twitter during their pathology electives found the platform useful for the attainment of medical knowledge, and for networking and professional development. A similar survey was sent to rotating students who did not use Twitter, asking if they thought using the platform could be beneficial. Additionally, we used Twitter analytical software (Symplur Signals) to determine the potential for networking by analyzing the number of retweets and impressions. RESULTS.­: Most respondents who used Twitter described using the platform as helpful in increasing their medical knowledge and useful for networking and professional development. From August 1, 2017, to January 2, 2019, thirty-seven elective medical students composed a total of 527 original tweets. The tweets were retweeted a total of 3399 times by 810 nonstudent users, and this engagement resulted in 6 360 731 impressions. Most of the retweeting was done by pathologists and pathology residents. CONCLUSIONS.­: The responses from the survey suggest that Twitter can be an educational tool during pathology electives and be useful for networking purposes. The number of retweets and impressions, and the demographics of the users who retweeted the students confirm the networking potential of Twitter.

ACTH-Cell Pituitary Adenoma With Signet Ring Cells: A Rare Case Report and Review of The Literature.

Here, we present a case of pituitary adenoma producing adrenocorticotropic hormone (ACTH) in a 19-year-old woman. The patient was admitted to neurosurgery clinic because of a headache and decreased visual acuity. Transsphenoidal resection was performed. Microscopic examination of the tumor revealed signet-ring-like cell areas intermixed with conventional pituitary adenoma cells. Both populations of tumor cells showed immunoreactivity for chromogranin, synaptophysin, and ACTH. To date, there have been 3 reports of pituitary adenoma with signet-ring-like changes. To our knowledge, this is the first case of ACTH-secreting pituitary adenoma with signet-ring-like cell changes. The clinical reflection of signet cells in pituitary adenoma is unclear. Accumulation of the similar cases and investigation of molecular background of them may lighten the importance of this morphologic variance.

Consequences of interleukin 1ß-triggered chronic inflammation in the mouse prostate gland: Altered architecture associated with prolonged CD4+ infiltration mimics human proliferative inflammatory atrophy.

BACKGROUND: Elevated expression of the proinflammatory cytokine interleukin 1ß (IL-1ß) has been observed in expressed prostatic secretions of patients with chronic prostatitis/chronic pelvic pain syndrome, and genetic polymorphisms associated with the IL1B gene are linked to increased risk for aggressive prostate cancer. METHODS: To study the role of IL-1ß expression in prostate inflammation, we examined IL1B expression in human prostatic proliferative inflammatory atrophy (PIA) lesions and developed a tetracycline-regulated human IL1B transgene in the mouse prostate. RESULTS: Here, we demonstrate that IL1B expression is a common finding in human PIA lesions, which harbored focal IL1B expression in epithelial and stromal compartments. Human IL1B expression in the mouse prostate elicited acute and chronic inflammation. Penetrance and expressivity were variable and tunable by altering transgene dosage and the presence of an exogenous inducible marker antigen (green fluorescent protein). Inflammation was characterized by infiltration of CD4+ T cells, demonstrating an adaptive immune response. Chronic inflammation persisted after doxycycline (Dox) withdrawal. Reactive epithelia increased expression of downstream cytokines, and altered glandular architecture was observed upon sustained induction of IL1B. Immunohistochemical analyses revealed a higher proliferative index and decreased Nkx3.1 expression in inflamed mouse prostates. CONCLUSIONS: These data implicate IL-1ß in human prostate pathology and this model provides a versatile platform to interrogate molecular mechanisms of inflammation-associated prostate pathologies associated with episodic or sustained IL-1ß expression.

BCL-2 and PAX2 Expressions in EIN which Had Been Previously Diagnosed as Non-Atypical Hyperplasia.

The relationship between PAX2 and another anti-apoptotic gene, BCL-2, has been shown in a limited number of studies. The aims of this study are to investigate the value of PAX2 and BCL-2 expressions in lesions which have been defined as nonatypical hyperplasia in terms of detecting EIN and to evaluate the relations of these proteins in EIN. For this purpose, 108 cases of non-atypical endometrial hyperplasia diagnosed from 2006 to 2011 were re-evaluated. Immunohistochemical studies with PAX2 and BCL-2 were performed in 20 cases with EIN and 34 cases with benign hyperplasia. The mean BCL-2 immunohistochemistry scores of benign hyperplasia and EIN cases were 4.06 ± 1.04 and 4.63 ± 2.03, respectively. The mean BCL-2 score of EIN cases was significantly higher than benign hyperplasia (p = 0.021). The mean PAX2 scores of benign hyperplasia and EIN cases were 4.32 ± 1.07 and 2.19 ± 2.34, respectively. The mean PAX2 scores of EIN cases were significantly lower than benign hyperplasia (p = 0.001). BCL-2 expression was increased compared to normal endometrium in 66.7% of EIN cases, and PAX2 expression was decreased in 73.3%. Consistent with this, in 60% of cases, BCL-2 expression was increased compared to normal endometrium, while PAX2 expression was decreased. BCL-2 and PAX2 protein expression changes occur in early phases of endometrial tumorigenesis. These changes are often seen as a simultaneous increase in BCL-2 expression and decrease in PAX2 expression.

Molecular Pathology of High-Grade Prostatic Intraepithelial Neoplasia: Challenges and Opportunities.

A better understanding of the early stages of prostate cancer initiation, potentially arising from precursor lesions, may fuel development of powerful approaches for prostate cancer prevention or interception. The best-known candidate for such a precursor lesion has been referred to as high-grade prostatic intraepithelial neoplasia (HGPIN). Although there is significant evidence supporting the notion that such HGPIN lesions can give rise to invasive adenocarcinomas of the prostate, there are also numerous complicating considerations and evidence that cloud the picture in many instances. Notably, recent evidence has suggested that some fraction of such lesions that are morphologically consistent with HGPIN may actually be invasive carcinomas masquerading as HGPIN-a state that we term "postinvasive intraepithelial carcinoma" (PIC). Although the prevalence of such PIC lesions is not fully understood, this and other factors can confound the potential of identifying prostate precursors that can be targeted for disease prevention, interception, or treatment. Here, we review our current understanding of the morphological and molecular pathological features of prostate cancer precursor lesions.

Cytomorphological Analysis of Thyroid Nodules Diagnosed as Follicular Variant of Papillary Thyroid Carcinoma: a Fine Needle Aspiration Study of Diagnostic Clues in 42 Cases and the Impact of Using Bethesda System in Reporting-an Institutional Experience.

Follicular variant of papillary thyroid carcinoma (FVPTC) is the second most common subtype of papillary thyroid carcinoma (PTC) after classical PTC (cPTC). Follicular thyroid lesions such as follicular adenomas/carcinomas, FVPTC, and noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) pose some diagnostic challenges for FNAC. In this study, we aimed to explore whether FNAC can demonstrate diagnostic clues by re-evaluating cytology slides from histopathologically diagnosed FVPTC cases. A total of 42 patients were enrolled in this study: patients were diagnosed with FVPTC via surgical resection between 2006 and 2016, and all patients were subjected to preoperative FNAC, which was conducted at either a private center or at the teaching hospital of Kocaeli University and reported by the same cytopathologist (NP). Clinical and cytomorphological characteristics were reviewed by both authors .Most cases (76.2%) are diagnosed either Bethesda IV or V. The majority of cases had a high cellularity (38/42; 90.5%), and the most frequent observations were monolayer and large syncytial groups of cells (95.2%). While microfollicular structures were observed in 30 (71.4%) cases, nuclear crowding and large naked nuclei were observed in all cases. Nuclear grooves were sparsely detected in 23 (54.8%) cases, and nuclear pseudoinclusions were detected in only six (14.3%) cases. Because thyrocytes often have a mixed architecture in FVPTC, despite a distinct follicular morphology, we believe that nuclear overcrowding, enlargement, and hyperchromasia in cases presenting with increased cellularity are notable clues for the cytodiagnosis of FVPTC. We believe that the primary aim of FNAC in such cases is to give preoperative diagnosis as either category IV or V. Nuclear crowding, monolayered clusters with large syncytial formations, nuclear enlargement, and hyperchromasia are notable cytomorphologic clues for the diagnosis of FVPTC on FNAC.

Characteristics of Special Type Breast Tumors in Our Center.

OBJECTIVE: Breast cancer is a heterogeneous disease with different histological types. Ductal breast cancer constitutes the vast majority of the breast cancers. However limited data are present in the rest of breast cancers called special or rare type breast cancers. Here in this study, we tried to describe the clinical features of special type breast cancers in our center. MATERIALS AND METHODS: Retrospective descriptive study was performed in Kocaeli University School of Medicine, Department of General Surgery between January 2000 and January 2016. Women diagnosed with primary breast cancer other than ductal carcinoma were included to the study. In total, 101 patients were evaluated according to histologic types, molecular types, Tumor Node Metastasis (TNM) stages, and grades. Survival of the patients was also evaluated. RESULTS: Medullary and metaplastic types showed basal type; tubular, mucinous, micropapillary carcinoma, cribriform, lobular and apocrine tumors showed luminal type molecular pattern. Neither the existence of ductal carcinoma nor any histologic types had any effects on survival. Apocrine tumors were presented in younger ages. CONCLUSION: Histologic types of breast cancer are closely related with the molecular types of the breast cancer. Tumor size, grade, stage of the disease can show differences among histological types which might be due to the genetic background, late onset or limited number of patients. In order to achieve more significant results, multicenter national studies are needed.

Malignant tumors associated with ovarian mature teratoma: A single institution experience.

OBJECTIVE: The aims of this study are to present demographical features of cases diagnosed with malignant tumor associated with ovarian mature teratoma and to analyze histopathological features and clinical follow up of these tumors. STUDY DESIGN: Single-institution retrospective charts were reviewed to identify all cases of ovarian mature teratoma diagnosed from 1998 to 2015. Clinicopathological parameters that were analyzed include age, tumor size, tumor stage, histological type, laterality, IOC diagnosis and whether or not patient has received adjuvant chemotherapy. RESULTS: A total of 218 ovarian mature teratoma cases were identified during the study period. Of the 218 ovarian mature teratoma specimens, eight (3.7%) exhibited malignant tumors. The average age for cases of malignancy associated with ovarian mature teratoma was 44.6 years. The average size of tumors was 10.36cm. On final pathology, histological types of tumors were as follows: two cases each of squamous cell carcinoma and papillary thyroid carcinoma; one case each of mucinous adenocarcinoma, metastatic adenocarcinoma, sebaceous carcinoma and oligodendroglioma. Only one patient with Stage IIB tumor died of disease. One patient was alive with metastatic disease two months after initial diagnosis. Mean and median follow-up times were 64.1 and 49 months, respectively. CONCLUSION: An ovarian mass that has characteristics of a teratoma in a postmenopausal patient should alert for malignancy -regardless of tumor size. IOC is a valuable tool for the detection of malignancy and should be requested to determine the modality of surgical approach.