ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 E-PS-15-014 A rare case of neuroendocrine transdifferentiation in cutane- ous melanoma D. Pisani, J. Scerri, S. Baldacchino* *Cellular Pathology, Department of Pathology, Mater Dei Hospital, Malta Background & objectives: Neuroendocrine transdifferentiation is a rare event in cancer pathogenesis and refers to the phenomenon whereby a non-neuroendocrine malignancy differentiates along the neuroendocrine route. Herein we present a case of neuroendocrine transdifferentation in a primary cutaneous melanoma. Methods: Case is clinically and pathologically evaluated accompanied by immunohistochemistry. This case treats a 45-year-old male, with a history of a malignant melanoma excised from the left anterior shin in 2015 and multiple in transit metastatic lesions in subsequent years. On follow-up routine radionucleotide imaging studies performed in 2019, he was found to have uptake in a right inguinal lymph node. Results: Histological analysis showed a tumour with striking neuroendocrine morphology that showed immunohistochemical co-expression of neuroendocrine and melanocytic markers. A retrospective review of the patient’s histology confirmed that the original melanocytic lesion was conventional epithelioid melanoma in vertical growth phase with no evidence of neuroendocrine dif- ferentiation on morphological or immunohistochemical grounds. Retrospective analysis of two in-transit metastases on the right shin (2017) and the right side of the leg (2019) showed subtle morphological transdifferentiation of the melanocytic tumour with progressively increasing immunohistochemical expression of neu- roendocrine markers. BRAF mutational analysis on the first in- transit metastatic lesion, uncovered the 1799T>A (p.Val600Glu) mutation, which mutation has been conserved on the subsequent metastatic groin tumour. Conclusion: This phenomenon has been best described in high grade prostatic adenocarcinoma, often after extensive therapy, representing a possible treatment resistance mechanism. Neuroendocrine transdifferentation, however, is vanishingly rare in melanocytic neoplasms. De novo neuroendocrine transdifferentiation typically represents an aggressive clinicopathological phenotype. Nonetheless, this patient was kept on dual BRAF inhibitor therapy and remains disease free to date. The mutational evolution of this tumour will be studied by Whole Genome Sequencing to elucidate potential drivers of the neuroendocrine phenotype. Funding: The Project: “Molecular switch underpinning Neuroen- docrine Transdifferentiation in malignant neoplasms – MOLNET” (REP-2021-021) is financed by the Malta Council for Science & Technology, for and on behalf of the Foundation for Science and Technology, through the FUSION: R&I Research Excellence Programme E-PS-15-015 Precision proteomics for the characterization of follicular- patterned thyroid neoplasms entities D. Seminati*, I. Piga, G. Capitoli, L. Principi, V. L’Imperio, G. Casati, S. Galimberti, F. Magni, F. Pagni *University of Milano-Bicocca, School of Medicine and Surgery, Pathology Unit, San Gerardo Hospital, ASST Monza, Italy Background & objectives: Noninvasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP) are low-risk thyroid lesions most often with RAS-type mutations. The current histological diagnostic criteria are still debated. In this study we’ll characterize NIFTP lesions by MALDI-MSI to highlight proteomic signatures. Methods: Archived FFPE samples from eight NIFTP (5 RAS- mutated and 3 RAS-WT) and one goiter were analysed by MALDI- MSI using rapifleX MALDI Tissuetyper equipped with a Smart- beam 3D laser at 2kHz frequency. Mass spectra were acquired in reflectron-positive mode. Images of FFPE NIFTPs tissues were acquired with 50 μm spatial resolution. CHCA matrix was removed, digested peptides were identified by nLC-ESI-MS/MS. Results: Considering the proteome of the entire tissue sections, unsu- pervised segmentation analysis highlighted i) the presence of the nodu- lar lesions that arose in the context of normal thyroid parenchyma, with spectra clustered under separate nodes, ii) under the nodule nods, a further separation enlightened the presence of NIFTP and hyperplastic lesions, with spectra being clustered under separate nodes. The pro- teomic data complexity was investigated and unsupervised principal component analysis highlighted specific patterns of the two NIFTP entities. ROC analysis highlighted that five ions were able to discrimi- nate RAS-mutated and RAS-WT NIFTP. These results underline the MALDI-MSI capability of detecting proteomic signatures within regions that are indistinguishable at the microscopic level. Conclusion: Spatial-proteomics is an outstanding approach to dif- ferentiate NIFTPs from other follicular-patterned features and to characterize classic and atypical cases, highlighting the potential role of Matrix-Assisted Laser Desorption/Ionization (MALDI)- Mass Spectrometry Imaging (MSI) technology as a support to tra- ditional pathology. Funding: Ricerca Finalizzata GR-2019-12368592 E-PS-15-016 The impact of pre-analytical factors on DNA quantification L. El Moutaoukkil*, R. Ben Tayeb, I. Toughrai, B. Benjelloun, S. Bardai, L. Chbani *Laboratory of Biomedical and Translational research, Faculty of Medicine and Pharmacy Fez, Morocco Background & objectives: Attaining high-quality genomic DNA is considered one of the most important phases in molecular oncology diagnoses, the aim of our study is to evaluate the influence of cold ischemia and fixation time on the DNA quantity of cancer digestive specimens. Methods: 32 FFPE blocks of colorectal cancer, liver cancer, Pan- creaticoduodenectomy, and gastric cancer tissues were obtained and macro-dissected. We used the following cold ischemia times: less than 1 hour (CIT-1), and 96 hours (CIT-5). 24 hours (FT-1) and one week (FT-4) for the fixation times. We applied a fluorometric procedure (Qubit 3.0) to determine the quantity of the collected DNA samples. Results: The correlation between normal and tumour tissue was statistically significant for pre-analytical parameters evaluated with a strong influence on tumour tissue. For fixation times, the correlation between both (FT-1) and (FT-4) was significant with p = 0.059. For cold ischemia times, the value p = 0.028 was significant for both (CIT-1) and (CIT-5). The Qubit detected the lowest DNA concentrations in all prolonged fixation samples (FT- 4) with an average of 1,55 ng-μl. The highest DNA concentrations were in samples with less than one hour of cold ischemia duration with an average of 159 ng-μl. Conclusion: our preliminary research revealed that these pre-ana- lytical parameters have a significant impact on the concentration and DNA quantification, as well as its variation depending on the type of tissue with more marked consequences on tumour tissue. S308