Histological background of dedifferentiated solitary fibrous tumour

Abstract

AimsDedifferentiation is a histological phenomenon characterised by abrupt transition of histology to a sarcomatous component with high-grade malignant potential in solitary fibrous tumour (SFT). The authors histologically reviewed SFT cases to reveal the histological background of dedifferentiated SFTs.MethodsClinicopathological and histopathological findings of 145 SFT cases were reviewed. Immunohistochemical staining and genetic analysis were also performed.ResultsThe non-dedifferentiated components showed a cellular component in 45 of 145 (31%), high mitotic rate (≥4/10 high-powered field) in 12 of 145 (8.2%) tumours, necrosis in 7 of 145 (4.8%) tumours, multinodular growth pattern in 39 of 132 (29.5%) available tumours and intratumoural fibrous septa in 37 of 131 (28.2%). Immunohistochemically, the non-dedifferentiated components were positive for CD34 in 128 of 141 (90.7%), bcl-2 in 101 of 133 (75.9%), nuclear pattern of β-catenin in 64 of 127 (50.3%) and p16 in 22 of 140 (15.7%). Loss of Rb protein expression was detected in 17 of 110 (15.4%) cases. Statistically, cellular component, multinodular structure, p16 overexpression and Rb protein loss were significantly associated with dedifferentiation. Moreover, cellular component and multinodular structure were significantly associated with p16 overexpression and Rb protein loss. All the non-deddifferentiated components showed wild type of p53 expression. The dedifferentiated components of all 10 dedifferentiated tumours presented positivity for p16 in 9 of 10 (90%) and mutational type of p53 in 5 of 10 (50%). Loss of Rb protein expression was detected in 6 of 10 (60%).ConclusionsThe authors propose that cellular or multinodular transformation may be associated with dedifferentiation. They also suggest that cellular and multinodular transformation may be associated with p16 overexpression and Rb downregulation.

Solitary fibrous tumor resembling pulmonary fractionation disease: A case report

“…[11,12] Immunohistological features include strong expression of CD34, CD99, and BCL-2 in > 90% of cases. [13,14] The genetic hallmark of SFT is the NAB2:: STAT6 gene fusion and immunostaining with anti-STAT6 antibodies have been reported to be useful for the diagnosis of SFT. [14] STAT6 immunostaining is the most sensitive and specific marker currently available in several studies.…”

Mesenchymal tumours of the pleura: review and update

“…28,29 Additionally, TERT promoter mutations have been reported to be correlated with aggressive clinicopathologic features. 27,[30][31][32] A small subset of solitary fibrous tumours undergoes dedifferentiation, transitioning into highgrade sarcoma, 9,27,[33][34][35] which appears generally nondistinctive, but rarely harbours heterologous osteosarcomatous or rhabdomyosarcomatous elements. 36,37 By immunohistochemistry, the dedifferentiated component may show overexpression of p16 and p53, loss of Rb, and loss of immunoreactivity for CD34 and STAT6, 27,[33][34][35] secondary to a complex genomic profile.…”

“…27,[30][31][32] A small subset of solitary fibrous tumours undergoes dedifferentiation, transitioning into highgrade sarcoma, 9,27,[33][34][35] which appears generally nondistinctive, but rarely harbours heterologous osteosarcomatous or rhabdomyosarcomatous elements. 36,37 By immunohistochemistry, the dedifferentiated component may show overexpression of p16 and p53, loss of Rb, and loss of immunoreactivity for CD34 and STAT6, 27,[33][34][35] secondary to a complex genomic profile. While the dedifferentiated component can show complete or partial loss of STAT6 immunoreactivity due to loss of NAB2::STAT6 chimeric protein expression, the NAB2::STAT6 chimeric DNA/ RNA fusion transcript can be retained and identified by sequencing analysis.…”