Solitary fibrous tumor (SFT) is an uncommon neoplasm of pleural and extrapleural site of origin formed by cells with fibroblastic features. This tumor exhibits a spectrum of biological behavior and can occur at any age with the peak in the sixth and seventh decade of life. Most of these tumors grow slowly and their clinical behavior is mostly benign; however, up to 20 % of patients develop local recurrences and/or distant metastases.
We performed a retrospective study of 54 cases of SFTs. We investigated morphologic characteristics, proliferation activity evaluated using Ki-67 immunostain and existence of NAB2-STAT6 fusion gene together with Ki-67, TPX2, and hTERT mRNA expression levels. The aim was to define relationships between proliferation activity and biological potential and progression of the disease. Recently, several alterations within the TERT gene have been detected in human tumors. The most frequent alteration in the TERT gene, somatic promoter mutation, has been described. We measured Ki-67, TPX2, and hTERT mRNA levels using quantitative real-time reverse transcription PCR (RQ-RT-PCR). Determination of hot spot promoter mutation in TERT was analyzed.
NAB2-STAT6 fusion transcript was found in 46/54 cases (85%) of amplifiable samples. The mRNA expression of Ki-67 correlated with local recurrences (p = 0.025) and biological behavior of the tumor (p = 0.0027), but did not correlate with the type of the NAB2/STAT6 fusion (0.24). The level of Ki-67 mRNA correlated with IHC established results (p = 0.02). The TPX2 mRNA expression did not correlate with local recurrences (p = 0.26) nor with biological behavior of the tumor (p = 0.062). The mRNA hTERT expression correlated well with biological behavior of the tumor (p < 0.0001). The majority of SFTs with benign behavior were without detectable expression of hTERT mRNA. A majority of the patients with hTERT expression had also somatic promoter mutation C228T or less frequently C250T. We observed a significant association between increased Ki-67 and hTERT mRNA levels and the SFTs with malignant potential.
Detection of hTERT mRNA expression and its promoter mutation at routine practice might lead to a better estimation of a biological potential of SFTs.
Clinical trial identification
Legal entity responsible for the study
Ministry of Health, Czech Republic.
Supported by the Project (Ministry of Health, Czech Republic) for conceptual development of research organization 00064203 (University Hospital Motol, Prague, Czech Republic).
All authors have declared no conflicts of interest.