Evaluation of Artificial Intelligence-Based Gleason Grading Algorithms "in the Wild".

The biopsy Gleason score is an important prognostic marker for prostate cancer patients. It is, however, subject to substantial variability among pathologists. Artificial intelligence (AI)-based algorithms employing deep learning have shown their ability to match pathologists' performance in assigning Gleason scores, with the potential to enhance pathologists' grading accuracy. The performance of Gleason AI algorithms in research is mostly reported on common benchmark data sets or within public challenges. In contrast, many commercial algorithms are evaluated in clinical studies, for which data are not publicly released. As commercial AI vendors typically do not publish performance on public benchmarks, comparison between research and commercial AI is difficult. The aims of this study are to evaluate and compare the performance of top-ranked public and commercial algorithms using real-world data. We curated a diverse data set of whole-slide prostate biopsy images through crowdsourcing containing images with a range of Gleason scores and from diverse sources. Predictions were obtained from 5 top-ranked public algorithms from the Prostate cANcer graDe Assessment (PANDA) challenge and 2 commercial Gleason grading algorithms. Additionally, 10 pathologists (A.C., C.R., J.v.I., K.R.M.L., P.R., P.G.S., R.G., S.F.K.J., T.v.d.K., X.F.) evaluated the data set in a reader study. Overall, the pairwise quadratic weighted kappa among pathologists ranged from 0.777 to 0.916. Both public and commercial algorithms showed high agreement with pathologists, with quadratic kappa ranging from 0.617 to 0.900. Commercial algorithms performed on par or outperformed top public algorithms.

DNA methylome in pancreatic cancer identified novel promoter hyper-methylation in NPY and FAIM2 genes associated with poor prognosis in Indian patient cohort.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) is one of the leading cancers worldwide and has a poor survival, with a 5-year survival rate of only 8.5%. In this study we investigated altered DNA methylation associated with PDAC severity and prognosis. METHODS: Methylome data, generated using 450 K bead array, was compared between paired PDAC and normal samples in the TCGA cohort (n = 9) and our Indian cohort (n = 7). The total Indian Cohort (n = 75) was split into cohort 1 (n = 7), cohort 2 (n = 22), cohort 3 (n = 26) and cohort 4 (n = 20).Validation of differential methylation (6 selected CpG loci) and associated gene expression for differentially methylated genes (10 selected gDMs) were carried out in separate validation cohorts, using MSP, RT-PCR and IHC correlations between methylation and gene expression were observed in TCGA, GTEx cohorts and in validation cohorts. Kaplan-Meier survival analysis was done to study differential prognosis, during 2-5 years of follow-up. RESULTS: We identified 156 DMPs, mapped to 91 genes (gDMs), in PDAC; 68 (43.5%) DMPs were found to be differentially methylated both in TCGA cohort and our cohort, with significant concordance at hypo- and hyper-methylated loci. Enrichments of "regulation of ion transport", "Interferon alpha/beta signalling", "morphogenesis and development" and "transcriptional dysregulation" pathways were observed among 91 gDMs. Hyper-methylation of NPY and FAIM2 genes with down-regulated expression in PDAC, were significantly associated with poor prognosis in the Indian patient cohort. CONCLUSIONS: Ethnic variations among populations may determine the altered epigenetic landscape in the PDAC patients of the Indian cohort. Our study identified novel differentially methylated genes (mainly NPY and FAIM2) and also validated the previously identified differentially methylated CpG sites associated with PDAC cancer patient's survival. Comparative analysis of our data with TCGA and CPTAC cohorts showed that both NPY and FAIM2 hyper-methylation and down-regulations can be novel epigenetically regulated genes in the Indian patient population, statistically significantly associated with poor survival and advanced tumour stages.

Phenotypic similarities within the morphologic spectrum of DICER1-associated sarcomas and pleuropulmonary blastoma: Histopathologic features guide diagnosis in the LMIC setting.

Extrapulmonary DICER1-associated sarcomas (DS) can harbor morphological features overlapping with pleuropulmonary blastoma. We report three children with intracranial and genital tract sarcomas, suspected to have DS based on a heterogeneous yet defining combination of spindle-cell sarcomatous and blastemal morphology, with rhabdomyomatous differentiation. Foci of immature cartilage at diagnosis (n = 2/3) and increased neuroepithelial differentiation at recurrence (n = 1) were noted. Morphological suspicion prompted somatic testing at reference centers, confirming likely biallelic, loss-of-function, and "hotspot" missense DICER1 variants in all three tumors. This can serve as a model for this diagnosis in resource-limited settings and has implications for germline testing, surveillance, and tumor management.

Artificial intelligence assistance significantly improves Gleason grading of prostate biopsies by pathologists.

The Gleason score is the most important prognostic marker for prostate cancer patients, but it suffers from significant observer variability. Artificial intelligence (AI) systems based on deep learning can achieve pathologist-level performance at Gleason grading. However, the performance of such systems can degrade in the presence of artifacts, foreign tissue, or other anomalies. Pathologists integrating their expertise with feedback from an AI system could result in a synergy that outperforms both the individual pathologist and the system. Despite the hype around AI assistance, existing literature on this topic within the pathology domain is limited. We investigated the value of AI assistance for grading prostate biopsies. A panel of 14 observers graded 160 biopsies with and without AI assistance. Using AI, the agreement of the panel with an expert reference standard increased significantly (quadratically weighted Cohen's kappa, 0.799 vs. 0.872; p = 0.019). On an external validation set of 87 cases, the panel showed a significant increase in agreement with a panel of international experts in prostate pathology (quadratically weighted Cohen's kappa, 0.733 vs. 0.786; p = 0.003). In both experiments, on a group-level, AI-assisted pathologists outperformed the unassisted pathologists and the standalone AI system. Our results show the potential of AI systems for Gleason grading, but more importantly, show the benefits of pathologist-AI synergy.

Immunohistochemical screening for mismatch repair protein deficiency in paediatric high-grade gliomas - institutional experience and review of literature.

PURPOSE: Immunohistochemical (IHC) testing for mismatch repair (MMR) deficiency (MMRD) is used as a screening tool to identify microsatellite instability in various cancers (especially colon). This not only identifies hereditary cancer syndromes like Lynch and constitutional mismatch repair deficiency (CMMRD) but also aids in prognostication and prediction of sensitivity to checkpoint inhibitor drugs. There are very few reported studies on MMRD status of pediatric high-grade gliomas (pHGG) and none from the Indian subcontinent. The aim of this study is to evaluate the frequency of MMRD in pHGG and to assess if there is a need for universal screening with immunohistochemistry. METHODS: Paraffin blocks of consecutive cases of pHGG (< 18 years) were retrieved from 2 centres, and IHC with four MMR antibodies - MLH1, PMS2, MSH2 and MSH6 - was performed using tissue microarray-based technique. RESULTS: Three out of nine cases (33%) studied showed loss of staining. One case had loss of MSH2 and MSH6 confirmed by gene sequencing. Eight of the cases were glioblastoma. One case of IDH1-mutated anaplastic astrocytoma showed loss of MLH1 and PMS2 staining. Isolated PMS2 loss was noted in 1 case, where the non-tumour cells also showed loss of staining, indicative CMMRD syndrome. This patient had prior colon cancer with isolated PMS2 loss and responded to check-point inhibitor therapy with nivolumab. CONCLUSION: Our study shows that the frequency of MMRD to be about one-third of pHGG. Universal IHC screening for MMRD in all pHGGs may benefit early diagnosis and play a role in therapeutic decisions. A larger multi-institutional study will help better assess the prevalence and treatment implications in MMRD tumours.

Poorly differentiated chordoma showing loss of SMARCB1/INI1: Clinicopathological and radiological spectrum of nine cases, including uncommon features of a relatively under-recognized entity.

Poorly differentiated chordoma is a newly recognized entity in the recent World Health Organization (WHO) classification of tumors of soft tissue and bone. Slightly over 60 such cases have been documented. Herein, we present a clinicopathological profile, including radiological features, of nine cases, which occurred in five males and four females, with age varying from 1 to 29 years (median = 43), in the cervical spine (n = 2), skull base (n = 2), clivus (n = 2), thoracic spine (n = 1) lumbar spine (n = 1) and coccyx (n = 1) Average tumor size was 4.8 cm. None of the 6-referral cases was diagnosed as a poorly differentiated chordoma at the referring laboratory. Histopathologically, all cases displayed a cellular tumor comprising polygonal cells (n = 9) displaying moderate to marked nuclear pleomorphism with prominent nucleoli (n = 7), eosinophilic (n = 9) to vacuolated cytoplasm (n = 7), rhabdoid morphology (n = 4), interspersed mitotic figures (n = 5), focal necrosis (n = 6) and inflammatory cells (n = 9). A single tumor displayed areas resembling classic chordoma, transitioning into poorly differentiated areas. There were multinucleate giant cells and physaliphorous cells in two tumors, each, respectively. Immunohistochemically, tumor cells were positive for AE1/AE3 (7/7), EMA (7/7), cytokeratin (CK) MNF116 (1/1), OSCAR (1/1), brachyury (9/9, diffusely), S100P (4/7, mostly focally), and glypican 3(2/4). SMARCB1/INI1 was completely lost in all nine tumors. A single case tested by FISH showed homozygous deletion of the SMARCB1 gene. Therapeutically (n = 7), all patients were treated with surgical resection (invariably incomplete) (n = 5), followed by adjuvant radiation therapy (n = 4) and chemotherapy (n = 4). While a single patient partially responded to treatment and another patient is alive with no evidence of disease after 23 years, three patients died of disease, six, eight, and 11 months post-diagnosis, despite adjuvant treatments. A single patient presented with a metastatic lung nodule, while another developed widespread metastasis. Poorly differentiated chordomas display a spectrum of features, are associated with a lower index of suspicion for a diagnosis, and display aggressive outcomes. Critical analysis of radiological and histopathological features, including necessary immunostains (brachyury and SMARCB1/INI1), is necessary for their timely diagnosis. These tumors show loss of SMARCB1/INI1 immunostaining and homozygous deletion of INI1/SMARCB1 gene.

A novel hotspot and rare somatic mutation p.A138V, at TP53 is associated with poor survival of pancreatic ductal and periampullary adenocarcinoma patients.

BACKGROUND: Pancreatic Ductal Adenocarcinoma (PDAC) is a cancer of the exocrine pancreas and 5-year survival rates remain constant at 7%. Along with PDAC, Periampullary Adenocarcinoma (PAC) accounts for 0.5-2% of all gastrointestinal malignancies. Genomic observations were well concluded for PDAC and PACs in western countries but no reports are available from India till now. METHODS: Targeted Next Generation Sequencing were performed in 8 (5 PDAC and 3 PAC) tumour normal pairs, using a panel of 412 cancer related genes. Primary findings were replicated in 85 tumour samples (31 PDAC and 54 PAC) using the Sanger sequencing. Mutations were also validated by ASPCR, RFLP, and Ion Torrent sequencing. IHC along with molecular dynamics and docking studies were performed for the p.A138V mutant of TP53. Key polymorphisms at TP53 and its associated genes were genotyped by PCR-RFLP method and association with somatic mutations were evaluated. All survival analysis was done using the Kaplan-Meier survival method which revealed that the survival rates varied significantly depending on the somatic mutations the patients harboured. RESULTS: Among the total 114 detected somatic mutations, TP53 was the most frequently mutated (41%) gene, followed by KRAS, SMAD4, CTNNB1, and ERBB3. We identified a novel hotspot TP53 mutation (p.A138V, in 17% of all patients). Low frequency of KRAS mutation (33%) was detected in these samples compared to patients from Western counties. Molecular Dynamics (MD) simulation and DNA-protein docking analysis predicted p.A138V to have oncogenic characteristics. Patients with p.A138V mutation showed poorer overall survival (p = 0.01). So, our finding highlights elevated prevalence of the p53p.A138V somatic mutation in PDAC and pancreatobiliary PAC patients. CONCLUSION: Detection of p.A138V somatic variant in TP53 might serve as a prognostic marker to classify patients. It might also have a role in determining treatment regimes. In addition, low frequency of KRAS hotspot mutation mostly in Indian PDAC patient cohort indicates presence of other early drivers in malignant transformation.

A Nonchordomatous-looking Chordoma: When INI-1 and Radiology Came to the Rescue!!!

SMARCB1/integrase interactor (INI)-1 is one of the core subunit proteins of the ATP-dependent SWI/SNF chromatin remodeling complex and acts as a tumor suppressor. INI-1 loss can be easily assessed using immunohistochemistry and is an important diagnostic clue for a histopathologist. Chordoma is a malignant tumor commonly occurring in the sacrococcygeal spine of adults and is characterized by nuclear expression of brachyury. Poorly differentiated chordoma, a morphologically and molecularly distinct entity, also shows nuclear brachyury positivity along with INI-1 loss. It usually occurs in children and has a predilection to involve the base of the skull. We describe a case of a poorly differentiated chordoma in a 5-year-old girl and discuss its unusual histomorphologic and immunohistochemical features.

Redefining adequate margins in oral squamous cell carcinoma: outcomes from close and positive margins.

PURPOSE: Adequacy of surgical margins impacts outcomes in oral cancer. We sought to determine whether close and positive margins have different outcomes in patients with oral cancer. METHODS: Retrospective data from 612 patients with oral carcinoma were analyzed for the effect of margin status on locoregional recurrence-free survival (LRFS), disease-free survival (DFS) and overall survival (OS). RESULTS: A total of 90 cases (14.7%) had close margins and 26 patients (4.2%) had positive margins. Recurrences were documented in 173 patients (28%), of which 137 (22% of the study sample) were locoregional, and 164 patients (27%) had died. Among patients with close or positive margins, a cutoff of 1 mm optimally separated LRFS (adjusted p = 0.0190) and OS curves (adjusted p = 0.0168) whereas a cutoff of 2 mm was sufficient to significantly separate DFS curves (adjusted p = 0.0281). CONCLUSIONS: Patients with oral carcinoma with positive margins (< 1 mm) had poorer outcomes compared to those with close margins (1-5 mm) in terms of LRFS, DFS and OS. There is a suggestion that a cutoff of < 2 mm might provide slightly more separation for DFS.

Utility of PAS and ß-catenin staining in histological categorisation and prediction of prognosis of hepatoblastomas.

AIMS: The aim of this study was to assess the usefulness of PAS, ß-catenin and Ki-67 in categorising hepatoblastomas (HBs) and their significance in predicting prognosis. In addition, we have also documented the various chemotherapy induced histologic changes in HBs. METHOD: In this retrospective observational study of 29 cases of hepatoblastomas, 27 cases were considered for statistical analysis, excluding two cases of diagnostic core biopsies. All clinicopathological parameters and follow up data were collected. All HB cases including the mixed epithelial and mesenchymal HBs were classified into two groups: fetal predominant and embryonal predominant type according to the predominant epithelial component. PAS, ß-catenin and Ki-67 staining were done and their correlation with histologic subtypes was assessed. Kaplan-Meier survival analysis was performed in relation to histology, PAS, ß-catenin and Ki-67 staining characteristics. RESULT: Diffuse nuclear staining of ß-catenin was significantly more common in embryonal predominant type (p = 0.036), whereas strong PAS positivity was significantly associated with fetal predominant type (p = 0.002). But no significant correlation was seen between histologic type and Ki-67 staining (p = 0.42). Survival analysis showed cases with diffuse PAS positivity, focal nuclear ß-catenin staining and low Ki-67 LI had better survival. CONCLUSION: PAS is a simple stain and can be utilised in histological categorisation of HB and also predicting its outcome. Nuclear ß-catenin staining which is significantly common in embryonal elements in HB predicts shorter survival.

Primary Renal Rhabdomyosarcoma: An Unusual Bone Metastasizing Tumor of Kidney.

Rhabdomyosarcoma (RMS) is one of the common malignant tumors in the pediatric age group. There is only a single case report of primary renal alveolar RMS. Fine needle aspiration (FNA) findings of primary renal RMS has not been reported so far. Hence we present an unusual case of primary alveolar RMS of the kidney. An 11 year old boy presented with an abdominal mass. On FNA a diagnosis of undifferentiated sarcoma and anaplastic Wilms tumor were considered. The tumor was resected and showed histopathological features of alveolar rhabdomyosarcoma. He developed multiple bony metastases and succumbed to the illness despite aggressive chemotherapy. RMS of the kidney should be considered in the differential diagnosis of children with a renal mass, and may have an aggressive clinical course with bone metastases.

Usefulness of Wieneke criteria in assessing morphologic characteristics of adrenocortical tumors in children.

PURPOSE: Adrenocortical tumors (ACT) occur rarely in pediatric age group. Pediatric ACTs behave differently from their histologically similar adult counterparts and standard adult criteria often cannot accurately predict their clinical behavior. The aim of the present study was to document the clinicopathologic spectrum of pediatric ACTs and to assess the utility of Wieneke scoring system in predicting clinical behavior of these tumors. METHODS: This multi-institutional study comprised of 13 cases of pediatric ACTs from January 2005 to May 2014. Clinical features and gross pathologic characteristics were obtained from records. Comprehensive analyses of microscopic features were performed. Each tumor was assessed according to criteria proposed by Wieneke et al. and was assigned to benign, intermediate for malignancy or malignant group. The standard adult Weiss criteria were also applied for comparison. RESULTS: There were total 6 cases of adrenocortical adenomas and 7 cases of adrenocortical carcinomas. Most of the children (76.9%) presented with endocrine dysfunction. Lower age of presentation was significantly associated with better prognosis. Applying Wieneke criteria, there were 6 benign and 6 malignant cases and one case was assigned to intermediate for malignancy group. The clinical behavior of all the cases was consistent with Wieneke criteria categorization. Applying Weiss criteria, 3 cases with benign clinical behavior were assigned to malignant group. CONCLUSION: Our study validates the reliability of Wieneke scoring system in predicting malignancy in pediatric ACTs. It is simple and easy to use and therefore useful in day-to-day practice.

Challenges in the Assessment of Medullary Bone Invasion in Oral Cavity Cancers and Its Prognostic Significance.

BACKGROUND: As per AJCC 8th edition TNM staging system, bone invasion is a poor prognostic marker that upstages oral cavity squamous carcinoma (OSCC) to pT4a. Cortical erosion alone of bone or tooth socket by a gingival primary is not sufficient to upstage a tumour. The differentiation of cortical erosion from invasion through the cortical bone into the medulla is often challenging, limiting accurate staging. This review aims to assess the difficulties in differentiating cortical erosion from medullary invasion and evaluate the prognostic significance of different patterns of bone involvement. METHODS: A retrospective review of OSCC with primary curative surgery and bone resection treated at a single-center over 10 years, was performed to assess the prognostic significance of bone invasion. Hematoxylin-eosin stained slides of a subset of cases were re-reviewed in a planned manner to assess difficulties in precise categorization (no invasion/erosion/cortical invasion and medullary invasion), evaluate interobserver agreement, and correlate with clinical outcome. RESULTS: Five hundred and ninety patients were included, with a median follow-up of 28 months. On univariate analysis, the 3-year local, nodal and distant metastasis control were not significantly different in the 3 groups of no invasion, erosion, and invasion (p = 0.43, 0.47, and 0.47, respectively). Overall survival (OS) at 3 years was 78.1% and disease-free-survival(DFS) was 63.7% in the entire cohort. On univariate analysis, there was significant difference in OS and DFS based on these groups. This did not translate into independent prognostic benefit on multivariable analysis (p = 0.75 and 0.19, respectively). The independent prognostic factors were margin positivity, tumor differentiation, perineural invasion and pathological nodal involvement. Planned re-review of a subset of 202 cases resulted in a change in bone involvement category in 26/202 cases, which was mainly due to difficulty in assessing cortico-medullary junction near the tooth socket and bone fragmentation. The assessment showed moderate to near complete agreement (kappa 0.59-0.82) between 2 observers. CONCLUSION: Our study shows that bone involvement is not an independent prognostic marker and there is no specific correlation of medullary invasion with outcome over those that showed cortical erosion. Several factors contribute to difficulties and interobserver variability in assessing bone involvement.

Application of Classroom Assessment Techniques in Medical Education: Results From the Community Medicine Teaching and Learning Experience.

Introduction Efficient delivery of medical education (ME) is crucial to improving the standards of future physicians or clinicians. India has been experiencing an enormous increase in medical colleges and student admissions into medicine. This has resulted in overcrowding and compromised the student-to-teacher ratio. Conversely, students and teachers face difficulties with learning and teaching, respectively. Classroom assessment techniques (CATs) offer an egalitarian and productive approach to student learning and evaluation. This study was conducted to understand the role of CATs in improving student learning and motivation during community medicine lectures. Further, this study assessed the classroom teaching and learning (TL) process. Method This study included 100 third-year medical students pursuing a Bachelor of Medicine and Bachelor of Surgery (MBBS) and 12 faculty members working at Great Eastern Medical School and Hospital (GEMS&H), Srikakulam, India. To facilitate learning and boost motivation, this study applied three CATs including a one-minute paper (OMP), muddiest point (MP), and student-generated test questions (SGTQs). After two months of applying CATs, the teachers and students were asked for feedback on their experiences. The data generated from feedback forms were tabulated and analyzed. Results According to 76% (76/100) of students, these strategies have stimulated their interest in learning community medicine. Besides, 64% (64/100) of students believed utilizing these strategies would improve their exam outcomes. Further, 77% (77/100) of students believed these methods must be applied in subsequent lessons. About 68% (68/100) of students thought other subject teachers should also employ these strategies. Of the 12 faculty members included in the study, they mostly liked the OMP (5; 41.66%) and MP technique (5; 41.66%). Conclusions Teachers and students have highly welcomed the utility of CATs to improve learning in community medicine. Of the three CATs applied, the OMP was the most popular with students, and teachers agreed that using OMP in the classroom along with MP would be beneficial. Most students and teachers were enthusiastic about employing additional TL strategies like CATs.

A re-look at the modified Ryan regression scoring system in esophageal cancer-validation of prognostic significance and comparison with other less commonly used systems.

BACKGROUND: Neoadjuvant chemoradiotherapy (NACRT) using CROSS protocol is currently the treatment of choice for esophageal cancer (EC). Tumor response grade (TRG) is a mandatory reporting criterion in most guidelines. One of the most commonly used TRG systems is the modified Ryan system. We aim to assess the TRG using modified Ryan and seven other systems (Mandard, Chireac, Swisher, Japanese esophageal society guidelines, modified rectal cancer regression grading (mRCRG), CROSS, and Becker) to evaluate their reproducibility and role as a prognostic marker. MATERIALS AND METHODS: Two pathologists independently reviewed all cases of post-NACRT (CROSS) EC, to score TRGs and other histological parameters. Inter-rater agreement assessment for different TRG systems and correlation with disease-free survival (DFS) was performed. RESULTS: Our series includes 93 patients with predominantly mid-esophageal squamous cell carcinoma. Complete pathological response (pCR) was noted in 47% (44/93) patients. The kappa inter-rater agreement score for the Ryan system was substantial (0.774), while it was almost perfect agreement for tumor percentage assessment-based systems (Swisher, CROSS, and Becker). Only the mRCRG TRGs correlated significantly with prognosis, while the Ryan system did not. Tumor stage and pCR status did not correlate with DFS, though the nodal stage was clinically significant. CONCLUSION: Though the inter-rater concordance was optimal for all the TRG systems studied, only the mRCRG system showed prognostic significance, while the commonly used modified Ryan system did not. It may be worthwhile to look at further evaluating other systems like mRCRG for inclusion in minimum dataset reporting.

Definitive chemoradiation for oropharyngeal squamous carcinomas: Outcomes with intensity-modulated radiation therapy using simultaneous integrated boost, in a majorly p16 negative cohort.

BACKGROUND: The literature on modern-era outcomes of oropharyngeal squamous carcinoma (OPSCC) in India is limited. MATERIALS AND METHODS: We analyzed records of consecutive patients with OPSCC treated using a curative SIB IMRT regimen of 66 Gy/30#/6 weeks. RESULTS: One hundred fifteen patients from July 2011 to December 2018 were analyzed. Twenty of 69 patients tested positive for p16. In p16 positive patients, the K-M probability of being disease free and alive at 2 years, with at least one follow-up 3 months after treatment, was 83% (median not reached) compared with 48% if p16 was unknown/negative. Patients staged as IVB p16 negative had a 2-year DFS of 25%. Patients unfit for cisplatin and consequently received other agents had 2-year DFS estimated at 20%. CONCLUSIONS: Intensity-modulated radiation therapy (IMRT) with simultaneous integrated boost (SIB) and concurrent chemotherapy was feasible, with toxicity and disease control comparable to available literature. AJCC Stage IVB p16 negative disease had notably poor outcome.

Subcategorization of Perineural Invasion and Its Impact on Survival in Patients with Oral Squamous Cell Carcinoma.

BACKGROUND: Perineural invasion (PNI) is  recognized as a poor prognostic factor in oral squamous cell carcinoma (OSCC). However, the prognostic significance of further histologic  subcategorization of PNI is inconclusive. In this study, we determined the prognostic relevance of histologic subcategories of PNI and their correlation with the presence of other clinical and pathological parameters METHODS: This is a retrospective study of 207 homogeneously treated OSCC patients with histologically documented PNI from a single center. Univariate and multivariate survival outcomes, namely, local recurrence-free survival (LRFS), disease-free survival (DFS), and overall survival (OS) of patients with various subcategories of PNI,namely- number of foci, size of the involved nerve, extratumoral or intratumoral extent, and intraneural or perineural location-were determined. RESULTS: Within the histologic subcategories of PNI, tongue primary and presence of lymph node metastasis correlated significantly with the number of nerves involved with PNI. Larger size of involved nerve correlated with advanced tumor stage. Number of foci, extent, and location of PNI were not prognostically significant except size of the involved nerve which showed an inverse correlation with disease outcome as involvement of larger nerves displayed better outcomes in terms of DFS and LRFS but not of OS on multivariate analysis. Addition of adjuvant chemotherapy to radiotherapy emerged as a significant predictor of improved LRFS, DFS, and OS. CONCLUSIONS: Histologic subcategorization of PNI did not have prognostic relevance in our study. Involvement of even small nerves was associated with poor prognosis. Addition of chemoradiation was seen to improve prognosis.