Pancreas
Other tumors
Sclerosing epithelioid mesenchymal neoplasm


Topic Completed: 18 August 2020

Minor changes: 18 August 2020

Copyright: 2019-2020, PathologyOutlines.com, Inc.

PubMed Search: Sclerosing epithelioid mesenchymal neoplasm

Aslihan Yavas, M.D.
Olca Basturk, M.D.
Page views in 2019: 14
Page views in 2020 to date: 412
Cite this page: Yavas A, Basturk O. Sclerosing epithelioid mesenchymal neoplasm. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/pancreassclerosingepit.html. Accessed September 29th, 2020.
Definition / general
  • A novel indolent pancreatic neoplasm with unique morphologic / immunophenotypic features and a distinct methylation pattern, different from both epithelial and mesenchymal neoplasms described in other anatomical sites (Mod Pathol 2020;33:456)
  • First described in 2020 (Mod Pathol 2020;33:456)
Essential features
  • Indolent
  • Well circumscribed tumor with a geographic pattern of epithelioid cell nests alternating with spindle cell fascicles
  • Vimentin (diffuse), CD99 (diffuse) and cytokeratin (AE1 / AE3 and CK18, dot-like) expression
  • Lack of abnormalities in any of key genetic drivers
  • Mesenchymal transcriptomic features and distinct methylation signature
Epidemiology
Sites
Clinical features
  • Nonspecific symptoms
Laboratory
  • Serum tumor markers (CA19.9 and CEA) within normal limits
Prognostic factors
Gross description
  • Well circumscribed and solid, usually confined to the pancreatic parenchyma
  • White-tan and firm cut surface
  • Median tumor size: 1.8 cm (Mod Pathol 2020;33:456)
Gross images

Images hosted on other servers:
Well circumscribed solid lesion

Well circumscribed solid lesion

Microscopic (histologic) description
  • Solid neoplasms associated with extensive fibrosis and dense lymphoid aggregates at the periphery (Mod Pathol 2020;33:456)
  • Entrapped pancreatic parenchyma may be seen at the periphery or within the tumor
  • Density of tumor cells varies significantly, not only among tumors but also throughout each tumor, creating a geographic appearance of hypercellular and hypocellular areas with collagenous stroma
  • No true epithelial structures such as glands, papillae or pseudopapillae (Mod Pathol 2020;33:456)
  • Most cells are epithelioid to spindled with scant cytoplasm and round to oval nuclei with open chromatin
    • Others display more irregular, hyperchromatic nuclei
  • Occasional mitotic figures may be seen
Microscopic (histologic) images

Contributed by Olca Basturk, M.D.
Overall appearance

Overall appearance

Well circumscribed lesion

Well circumscribed lesion

Peripheral dense lymphoid aggregates

Peripheral dense lymphoid aggregates

Entrapped pancreatic parenchyma

Entrapped pancreatic parenchyma

Hypercellular and hypocellular areas

Hypercellular and hypocellular areas


Sheets of epithelioid cells

Sheets of epithelioid cells

Atypical spindle cells

Atypical spindle cells

Dense hyaline fibrosis

Dense hyaline fibrosis

Membranous CD99 expression

Membranous CD99 expression

Dot-like CK18 expression

Dot-like CK18 expression

Positive stains
Electron microscopy description
  • Nonspecific findings; occasional desmosomes, perinuclear tonofilaments and abundant rough endoplasmic reticulum (Mod Pathol 2020;33:456)
Molecular / cytogenetics description
  • No recurrent somatic mutations, amplifications or deletions in any known oncogenes or suppressor genes (Mod Pathol 2020;33:456)
  • Activation or enrichment of pathways related to the extracellular matrix, tight junctions, adherens junctions and TGFβ signaling by Gene Set Enrichment Analysis (Mod Pathol 2020;33:456)
  • A unique cluster by unsupervised analysis of the methylation profiles (Mod Pathol 2020;33:456)
Molecular / cytogenetics images

Images hosted on other servers:
Genomic and transcriptomic characterization

Genomic and transcriptomic characterization

Sample pathology report
  • Pancreas and duodenum, pancreaticoduodenectomy:
    • Sclerosing epithelioid mesenchymal neoplasm (see comment)
    • Comment: The tumor is confined to the pancreatic parenchyma and measures 2.2 cm in greatest dimension. Adjacent pancreas reveals atrophy. Surgical margins are free of tumor. 16 benign lymph nodes are identified (0/16).
Differential diagnosis
Board review style question #1

Which one of the following stains is positive in sclerosing epithelioid mesenchymal neoplasm of the pancreas in the figure shown above?

  1. CD34
  2. CD99
  3. DOG1
  4. MUC4
  5. S100
Board review answer #1
Board review style question #2
Which one of the following microscopic features is seen in sclerosing epithelioid mesenchymal neoplasms of the pancreas?

  1. No entrapped pancreatic parenchyma is seen within the tumors.
  2. They are composed of epithelioid cells only.
  3. They are predominantly hypocellular tumors.
  4. They have well circumscribed borders.
  5. True epithelial structures such as glands, papillae and pseudopapillae are common.
Board review answer #2
D. They have well circumscribed borders.

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Reference: Sclerosing epithelioid mesenchymal neoplasm
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