#GIPathJC - The study demonstrates chemotherapy can significantly alter the Ki67 index in high grade neuroendocrine neoplasms - In post-treatment cases history and pre-treatment pathology facilitates the correct pathologic interpretation

#GIPathJC - More evidence is needed to determine prognostic implications of treatment-associated alterations - Until more evidence is available post-treatment PD-NECs should retain their originally established pre-treatment diagnostic classification

#GIPathJC morphology of pre-treatment and post-treatment samples fell in two categories -first category (n = 9) showed cellularity, atypia, and pleomorphism similar to pre-treatment samples -second category (n = 11), showed morphologic transformation of the neoplastic cells

#GIPathJC hopefully more physicians will know with our #GIPathJC!

#GIPathJC In 18/20 cases (90%), post-treatment samples showed areas with Ki67 index significantly lower than matched pre-treatment samples or <20% that would not qualify for high grade based on the WHO grading system

#GIPathJC -6 cases had post-treatment Ki67 index falsely suggesting a diagnosis of WD-NET G2 (3 cases) or G1 (3 cases). -Degree of heterogeneity in the post-treatment samples was marked, 15/20 cases showing heterogeneity, 12 had a heterogeneity score >1 (mean score = 2.4).

#GIPathJC -In 15/20 post-treatment samples, Ki67 index was <20%, at least focally (i.e., in a coldspot), and in 6 cases (30%) the overall Ki67 index based on the hotspot was <20%. -In 3 cases, the highest Ki67 index in the entire sample was ≤1%.

#GIPathJC -Ki67 index was calculated as the percentage of neoplastic cells with nuclear labeling in the areas of maximum (hotspot) and minimum (coldspot) staining -A mitotic count was performed in the areas of highest and lowest Ki67 labeling.

#GIPathJC -Due to observations of reduction in proliferation rate of neuroendocrine tumors following neoadjuvant therapy this study was conducted -20 cases with history of chemotherapy and/or radiation with pre and post treatment samples were included

#GIPathJC Though WD-NET can progress from grades 1 to 3, Often the recurrence or metastases of WD-NET is WD-NET, as opposed to progression to PD-NEC

#GIPathJC Ki67 index should be used for tumor grading, but is not by itself useful to distinguish between well differentiated neuroendocrine tumors (WD-NETs) and poorly differentiated neuroendocrine carcinomas (PD-NECs) particularly in high grade tumors or grade 3 WD-NET

#GIPathJC well differentiated neuroendocrine tumors (WD-NETs) are separated from poorly differentiated neuroendocrine carcinomas (PD-NECs) due to difference in clinical behavior, treatment, and molecular findings

#GIPathJC hello and welcome everyone! Thank you Dr. Vyas @Mvgs1706 for joining #GIPathJC

#GIPathJC @MatthewStachler