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Background: Pancreatic neuroendocrine neoplasms (NENs) are tumors with histopathologic and prognostic heterogeneity that pose difficulties in establishing standards for diagnosis, classification, and treatment. Among NENs, well-differentiated neuroendocrine tumors (NETs) have been classified as grade 1, 2, and 3 in the most recently released World Health Organization classification. Although well-differentiated NETs are associated with relatively better prognosis, they have a potential for malignant behavior such as extrapancreatic spread, metastasis, or recurrence. The present study aimed to evaluate clinical and histomorphologic findings of patients with well-differentiated pancreatic NETs and to identify histopathologic findings effective in predicting nodal metastatic progression., Methods: The study group consisted of 54 patients diagnosed with well-differentiated NET. All preparations and blocks of the patients were examined for the following histopathologic parameters: tumor diameter, microscopic tumor growth pattern (solid, trabecular, acinar, and mixed), cellular features (clear, eosinophilic, oncocytic, peliotic, and pseudopapillary), stromal changes (calcification, lymphocytic infiltration, and stromal hyalinization), presence of necrosis, perineural invasion, lymphovascular invasion, mitotic activity, and Ki67 proliferative index., Results: Lymph node metastasis was present in 7 patients. Lymph node metastasis was significantly associated with tumor diameter of >2 cm ( p = 0.012), Ki67 proliferative index of >20% ( p = 0.022), grade 3 tumors ( p = 0.002), presence of dense stromal hyalinization ( p = 0.034), and mild lymphocytic infiltration ( p = 0.041)., Conclusion: The present study revealed that the new findings such as presence of dense stromal hyalinization and absence of remarkable lymphocytic infiltration could be predictive morphologic findings for the development of lymph node metastasis.

Introduction: Sclerosing adenosis is a form of adenosis characterized by lobulocentric architecture, glandular and stromal proliferation in which the stromal component compresses and distorts the glandular structures. Atypical epithelial proliferations such as atypical lobular hyperplasia, lobular carcinoma in situ, and ductal carcinoma in situ may accompany areas of sclerosing adenosis. We present a case of ductal carcinoma in situ and sclerosing adenosis with metastatic carcinoma on sentinel lymph node., Case Description: A 40-year-old woman presented with a palpable mass in her left breast. Radiologic studies showed a lesion suggesting malignancy in the left breast and atypical lymph node in the left axillary region. Left lumpectomy and sentinel lymph node biopsy was performed. Histopathologic examination revealed lobulocentric lesions with glandular proliferation and hyalinizing stroma in between. Foci of high-grade cribriform and solid type ductal carcinoma in situ were observed. Sentinel lymph node biopsy showed micrometastasis in one lymph node section. Based on these findings, the patient was diagnosed with high-grade ductal carcinoma in situ with sclerosing adenosis. However, the presence of micrometastasis in the lymph node suggested occult invasion that we were not able to detect., Conclusion: Ductal carcinoma in situ with sclerosing adenosis can mimic invasive carcinoma both radiologically and histologically. It should be kept in mind that there may be occult invasive carcinoma in patients with ductal carcinoma in situ whether the lesion is accompanied by sclerosing adenosis or not. Multiple sections and immunohistochemical studies can be of help.