SRF-rearranged cellular perivascular myoid tumor:a clinicopathological analysis of two cases
Objective To investigate the clinicopathological features,immunophenotype,diagnosis and differential diagnosis of SRF-rearranged cellular perivascular myoid tumor.Methods Two cases of SRF-rearranged cellular perivascular myoid tumor diagnosed in the Department of Pathology,Fudan University Shanghai Cancer Center from October 2021 to March 2022 were collected.Immunohistochemical staining,fluorescence in-situ hybridization(FISH)and next-generation sequencing(NGS)were performed,and the literature was reviewed.Results Case 1,a 3-month-old boy presented with a painless tumor of the scalp,measuring about 2 cm in diameter.Case 2,a 3-year-old girl complained with a painless tumor of the knee,measuring approximately 1.5 cm in diameter.Microscopically,the tumor had a clear boundary and showed multinodular growth.The tumor was mainly composed of spindle cells arranged in long intersecting fascicles associated with thin,slit-like or branching ectatic vessels,focally forming hemangiopericytoma-like appearance.The tumor cells were abundant,but there was no obvious atypia.Mitotic figures(3-4/10 HPF)were noted.H-caldesmon and SMA were positive in both cases.Case 1 showed diffuse and strong positivity for Desmin,and focally for CKpan.Ki-67 proliferation index was 20％and 30％,respectively.FISH displayed NCOA2 gene translocation in case 1 and the RELA gene translocation in case 2.NGS detected the SRF-NCOA2 gene fusion in case 1 and the SRF-RELA gene fusion in case 2.Both patients underwent local excisions.During the follow-up of 5-14 months,case 1 had no local recurrence,while case 2 developed local recurrence 1 year post operatively.Conclusions SRF-rearranged cellular perivascular myoid tumor is a novel variant of perivascular cell tumor,which tends to occur in children and adolescents.The tumor forms a broad morphologic spectrum ranging from a pericytic pattern to a myoid pattern,and include hybrid tumors with a mixture of pericytic and myoid patterns.Due to its diffuse hypercellularity and increased mitotic figures and smooth muscle-like immunophenotype,the tumor is easy to be misdiagnosed as myogenic sarcomas.The tumor usually pursues a benign clinical course and rare cases may locally recur.
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