Review of Potential Significance of Mutations of ADAMTS20, NF1 and PKHD1 Detected Using Next Generation Sequencing (NGS) in Dermal Fibrosarcoma Arising in Dermatofibrosarcoma Protuberans

We examined a status of fibrosarcoma arising in dermatofibrosarcoma protuberans of 64-year-old male patient. A dermal, solid, grayish-yellow, desmin-negative trichrome-bluish tumor measured 1.5 cm in diameter pT1a (edition 8 pTNM). It was composed of spindle cells. It was consistent with dermatofibrosarcoma protuberans (ICD-O3: 8832/3) in areas of low mitotic activity, low atypia and sustained CD34 positivity. CD34-negative texture with high mitotic index and atypia was consistent with the high grade sarcoma apparently of fibrous origin, given category of poorly differentiated fibrosarcoma. The high grade component was graded (G3) and scored according to French Federation of Cancer Centers Sarcoma Group (FNCLCC): total score of 6 points: tumor differentiation: 3 points + Mitotic count: 3 points (up to 26 mitoses/ 10HPF in high-grade fields), + no necrosis: 0 points. In low grade sarcomatous component ADAMTS20 (NM_025003: c.1661C>T, p.P554L) NF1 (NM_001042492: c. 2173G>T, p.E725X) and PKHD1 (NM_138694: c. 11074C>T, p.R3692X) were revealed with following allelic frequencies: 25%, 27% and 17%. In high grade component allelic frequencies of the same mentioned mutations were 30%, 30% and 14% respectively. In the light of our findings, none of detected mutations can be regarded as a mutation that would definitely induce phenotype of high malignancy, because ADAMTS20, NF1 and PKHD1 mutations were detected both in high grade sarcoma and in low grade areas of dermatofibrosarcoma protuberans. It also points that these mutations appeared on early stages of tumor development.