Background: Pancreatic ductal adenocarcinoma differs from other solid tumors with its unique immunosuppressive microenvironment and non-immunogenic feature. There are not many studies in the literature investigating the effect of these features on prognosis. Aims: To investigate the prognostic value of tissue-resident memory T cells, tumor microenvironment features, and tumor-associated immune cells in resected pancreatic ductal adenocarcinomas. Study Design: Retrospective cross-sectional study. Methods: Of 138 patients diagnosed with pancreatic ductal adenocarcinoma between 2011 and 2018, 81 were included in the study. Specimens from operated patients were reassessed separately as peritumoral and intratumoral areas for tissue resident memory cells and tumor microenvironmental elements (tumor infiltrating lymphocytes, tumor stroma, CD204+ macrophages, PDL1+ immune cells). Disease-free survival and overall survival were defined from the date of operation to the date of recurrence and the date of first diagnosis to the date of death, respectively. If the patient was alive, the last visit date was taken into account. Results: The median age at diagnosis was 63 (range: 40-78). The median follow-up period was 18.9 months (range: 1.4-80.4 months). Median overall survival was 23.7 months (1.4-80.4 months) and median disease-free survival was 10.8 months (1.4-74.4 months). Patients with higher intra-tumoral tissue-resident memory cell counts had a longer survival trend than those having lower values (25.6 months vs. 18 months, respectively, P = .84). According to microenvironmental evaluations, lower stromal score (defined as stroma having less desmoplasia and rich in cells) and presence of peritumoral Crohn’s-like inflammatory response were associated with higher survival (29.2 months vs. 19.7 months for low vs. high stromal scores, respectively, P = .16 and 30.2 months vs. 18.1 months for the presence of Crohn’s-like inflammatory response P = .13). Decreased survival was observed in tumors with increased CD204+ tumor-associated macrophages which were immunosuppressive elements of the microenvironment (12 months vs. 26.3 months for intra-tumoral assessment, P = .29). Conclusion: Tissue-resident memory T cells and other microenvironmental features may be prognostic in resectable pancreatic ductal adenocarcinomas. Further studies with larger cohorts are needed for validation.

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BACKGROUND This is a case of aggressive Langerhans cell histiocytosis (LCH) with an atypical intracranial location. OBSERVATIONS In this report, the authors present the diagnosis and treatment of a 12-year-old male patient diagnosed with LCH. The patient was admitted to the emergency department with left-sided facial palsy, and a solid lesion with mass effect in the pons was found. A biopsy was performed via suboccipital craniotomy, and the diagnosis was LCH. A chemotherapy regimen was started since the LCH sample was the resistant type. The patient showed improvement in his neurological deficit following treatment. LESSONS This rare localized and aggressive case’s diagnosis process and treatment choices may apply to future cases.