[Spindle cell hemangioma: a clinicopathological and molecular analysis of eight cases].

To investigate the clinicopathological and genetic characteristics of spindle cell hemangioma (SCH). The clinical, morphological and immunohistochemical features of 8 SCHs diagnosed from January 2013 to September 2021 in West China Hospital, Sichuan University, Chengdu, China were retrospectively analyzed. Hotspot mutations for IDH1 codon 132 and IDH2 codon 172 were tested in 4 SCHs and 29 other non-SCH lesions using Sanger sequencing. The 8 cases occurred in patients with a wide age range, from neonate to 46 years (mean 28 years, median 32 years). Both genders were equally affected. The course of the disease spanned from half a year to 31 years. Two SCHs were recurrent tumors. All tumors involved the distal extremities (4 of foot, 2 of ankle and 2 of hand). Six cases were presented as a single lesion and 2 cases as multiple lesions. The tumor diameters were 1-5 cm. All the 8 SCHs were typically composed of cavernous vascular space and solid components consisting of slit-like vessels, spindle cells and epithelioid endothelial cells which often exhibited cytoplasmic vacuolation. These two alternating components and the vacuolated epithelioid endothelial cells were the distinctive diagnostic clues for SCH. Vascular endothelial cells including epithelioid cells in the solid areas expressed CD31 (8/8), ERG (4/4), CD34 (5/8) and D2-40 (2/3). The spindle cells expressed SMA (8/8). Neither endothelial cells nor spindle cells expressed HHV8 (0/7), Desmin (0/5) or S-100 (0/3). Mutations were revealed in 2 SCHs, with IDH1 mutation (p.R132C) and IDH2 mutation (p.R172G), respectively. The IDH1/2 gene hotspot mutations were not found in the remaining 2 SCHs or the other 29 non-SCH lesions. Simple excisions were performed for 7 cases, and partial resection for 1 case. Follow-up information was obtained in 6 cases, with follow-up time ranging from 5 to 90 months (average, 46 months). No metastasis occurred in the 6 cases. No recurrence occurred in cases treated with simple excision. The residual lesions of the patient who received partial resection were stable. SCH is rare and should be differentiated from a variety of benign and malignant vascular lesions. An accurate diagnosis of SCH is clinically important and can be achieved by combining clinical information and typical pathological presentation. IDH1/2 gene hotspot mutations are specific to SCH in vascular lesions. Genetic detection is helpful in the diagnosis of challenging cases.