What is the role of genetic studies in the diagnosis of malignant solitary fibrous tumors (SFTs) of the pleura?

Updated: Dec 25, 2019
  • Author: Joseph F Tomashefski, Jr, MD; more...
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Answer

There has been a single report of SFT occurring in a mother and daughter. [80] A wide variety of karyotypic abnormalities, including both numerical and structural abnormalities, have been identified in SFTs.

Cytogenetic abnormalities are more common in malignant than in benign SFTs. A few numerical imbalances such as extra copies of chromosome 8, gain of chromosome 21, and loss or partial deletions of chromosomes 1, 6, 9, 13, 15, 17, 18, and X and structural rearrangements of 4q1, 9p22-23, 9q22, 9q31-32, and 12q24 have been shown to be recurrent. However, at this time, no consistent chromosomal abnormality has been reported for SFT. [81]

Further genetic studies of SFT are necessary to define the presence or absence of useful diagnostic cytogenetic markers.

In regard to other molecular markers, Schirosi et al noted a lack of immunohistochemical expression of SFTs for EGFR and expression of CD117/KIT in 3.4% of cases. PDGFR-alpha and PDGFR-beta were detected in 97.7% and 86.5% of cases, respectively. High p53 staining was noted in 20.4%. Fluorescence in situ hybridization (FISH) analysis for SYT rearrangement was uniformly negative in SFTs. [10]

More recently, NAB2-STAT6 gene fusion has been identified, in which there is intrachromosomal inversion involving 12q13.3. [7]  "The derived immunohistochemical detection of nuclear STAT6 expression has high diagnostic value in distinguishing SFTs from histologic mimics," although pitfalls exist. "NAB2-STAT6 fusions yield numerous transcript subtypes associated with the clinicopathological variations." [7]


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