Cytomorphologic features of malignant solitary fibrous tumor with mediastinal involvement sampled by endoscopic and endobronchial ultrasound-guided fine-needle aspiration: A comparison of two cases

Research output: Contribution to journalArticle

Abstract

Solitary fibrous tumor (SFT) is an uncommon fibroblastic neoplasm with considerable risk of local recurrence. SFT is histologically characterized by bland spindled-to-epithelioid cells in alternating hyper- and hypocellular zones, a “patternless pattern,” ectatic “staghorn” vessels with variable edematous perivascular stroma, and thick ropey collagen. Cytologically, smears are variably cellular with spindled-to-epithelioid cells with oval nuclei, wispy cytoplasm, multiple inconspicuous nucleoli, and occasional nuclear pseudoinclusions. Small vessels and bare/stripped nuclei are generally present while mild atypia is not uncommon. STAT6 nuclear expression is the most useful immunohistochemical stain and is the product of a NAB2-STAT6 gene fusion. SFTs with mediastinal involvement may be diagnostically challenging due to proximity to vital structures and anticipated patient risks. Endobronchial and endoscopic ultrasound-guided fine-needle aspiration (EBUS/EUS-FNA) are minimally-invasive tissue sampling methods that provide diagnostic material while minimizing patient risk, and the mediastinum is accessible by both procedures. Small aspirate samples and SFT nonspecific features can compound the diagnostic difficulty, although familiarity with the cytologic, morphologic, immunophenotypic, and genetic features of SFTs assist the pathologist in confirming the diagnosis. Pathologists must also be aware of high-risk SFT features to ensure appropriate therapy and management. Case #1 describes a recurrent mediastinal SFT with high-risk features sampled by EUS-FNA. Case #2 describes a primary diagnosis of mediastinal SFT with malignant behavior made on an EBUS-FNA specimen.

Original languageEnglish (US)
Pages (from-to)821-827
Number of pages7
JournalDiagnostic Cytopathology
Volume47
Issue number8
DOIs
StatePublished - Aug 2019

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Keywords

  • STAT6
  • endoscopic ultrasound
  • fine-needle aspiration
  • mediastinum
  • solitary fibrous tumor

PubMed: MeSH publication types

  • Journal Article
  • Case Reports
  • Comparative Study

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