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.

Objective:To investigate the clinicopathological features, pathologic diagnosis and differential diagnosis of florid vascular proliferation (FVP) of the intestinal tract.Methods:Ten cases of FVP of the intestinal tract diagnosed from 2010 to 2020 at Fudan University Shanghai Cancer Center were collected. The histomorphology and immunohistochemical staining were evaluated and the relevant literature was reviewed.Results:There were five males and five females, aging from 28 to 76 years (mean 51.0 years; median 50.5 years). Five cases occurred in the colon, three cases in the small intestine, and one each case in the inguinal region and cecum. Clinically, the patients mainly presented with abdominal pain, diarrhea and hematochezia. Seven of nine patients with imaging data showed associated intussusception. Microscopically, the lesion presented lobular growth of florid proliferation of small vessels extending through the bowel wall. The vascular channels were lined with bland endothelial cells with no nuclear atypia and infrequent mitoses. The overlying mucosa showed chronic ulceration. Immunohistochemically, endothelial cells of FVP were positive for CD31, CD34, ERG and Fli1, the stromal spindle cells expressed SMA, and the Ki-67 proliferation index was low (5%-30%). None of 4 patients with follow-up information had local recurrence.Conclusions:FVP is a rare benign vascular proliferation lesion which often occurs in the intestinal tract and is associated with intussusception. Accurate pathologic diagnosis of FVP requires close combination of radiological examinations. FVP is easily misdiagnosed as a true vascular tumor, especially angiosarcoma. It is necessary to better understand FVP to avoid misdiagnosis.