Sclerosing epithelioid mesenchymal neoplasm of the pancreas – a proposed new entity

Olca Basturk, Britta Weigelt, Volkan Adsay, Jamal K. Benhamida, Gokce Askan, Lu Wang, Maria E. Arcila, Giuseppe Zamboni, Noriyoshi Fukushima, Rodrigo Gularte-Mérida, Arnaud Da Cruz Paula, Pier Selenica, Rahul Kumar, Fresia Pareja, Christopher A. Maher, John Scholes, Yoshinao Oda, Donatella Santini, Leona A. Doyle, Iver PetersenUta Flucke, Christian Koelsche, Samuel J. Reynolds, Aslihan Yavas, Andreas von Deimling, Jorge S. Reis-Filho, David S. Klimstra

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

We have encountered pancreatic tumors with unique histologic features, which do not conform to any of the known tumors of the pancreas or other anatomical sites. We aimed to define their clinicopathologic features and whether they are characterized by recurrent molecular signatures. Eight cases were identified; studied histologically and by immunohistochemistry. Selected cases were also subjected to whole-exome sequencing (WES; n = 4), RNA-sequencing (n = 6), Archer FusionPlex assay (n = 5), methylation profiling using the Illumina MethylationEPIC (850k) array platform (n = 6), and TERT promoter sequencing (n = 5). Six neoplasms occurred in females. The mean age was 43 years (range: 26–75). Five occurred in the head/neck of the pancreas. All patients were treated surgically; none received neoadjuvant/adjuvant therapy. All patients are free of disease after 53 months of median follow-up (range: 8–94). The tumors were well-circumscribed, and the median size was 1.8 cm (range: 1.3–5.8). Microscopically, the unencapsulated tumors had a geographic pattern of epithelioid cell nests alternating with spindle cell fascicles. Some areas showed dense fibrosis, in which enmeshed tumor cells imparted a slit-like pattern. The predominant epithelioid cells had scant cytoplasm and round-oval nuclei with open chromatin. The spindle cells displayed irregular, hyperchromatic nuclei. Mitoses were rare. No lymph node metastases were identified. All tumors were positive for vimentin, CD99 and cytokeratin (patchy), while negative for markers of solid pseudopapillary neoplasm, neuroendocrine, acinar, myogenic/rhabdoid, vascular, melanocytic, or lymphoid differentiation, gastrointestinal stromal tumor as well as MUC4. Whole-exome sequencing revealed no recurrent somatic mutations or amplifications/homozygous deletions in any known oncogenes or tumor suppressor genes. RNA-sequencing and the Archer FusionPlex assay did not detect any recurrent likely pathogenic gene fusions. Single sample gene set enrichment analysis revealed that these tumors display a likely mesenchymal transcriptomic program. Unsupervised analysis (t-SNE) of their methylation profiles against a set of different mesenchymal neoplasms demonstrated a distinct methylation pattern. Here, we describe pancreatic neoplasms with unique morphologic/immunophenotypic features and a distinct methylation pattern, along with a lack of abnormalities in any of key genetic drivers, supporting that these neoplasms represent a novel entity with an indolent clinical course. Given their mesenchymal transcriptomic features, we propose the designation of “sclerosing epithelioid mesenchymal neoplasm” of the pancreas.

Original languageEnglish
Pages (from-to)456-467
Number of pages12
JournalModern Pathology
Volume33
Issue number3
DOIs
Publication statusPublished - Mar 1 2020

All Science Journal Classification (ASJC) codes

  • Pathology and Forensic Medicine

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