Intramuscular capillary-type hemangioma: Diagnosis, treatment, and outcomes. A French multicentric retrospective study of 66 cases

Purpose: Intramuscular capillary-type hemangiomas (ICTHs) are rare entities, belonging to the group of intra-muscular "hemangiomas." The diagnosis remains challenging. We aimed to assess the diagnostic criteria, treatments and outcomes of ICTHs.Methods: This retrospective study collected all cases of ICTH followed up in 9 French hospital centers, reviewed by an adjudication expert group.Results: Among 133 patients screened, 66 with ICTH were included. The median age of patients at diagnosis was 28.0 years, interquartile range (21.0---36.0). The lesion, mainly presenting as a gradually increasing mass (83.9%), was painless (88.9%) and was located in the head and neck (42.4%). MRI (available in all cases) mainly revealed a well-delineated lesion, isointense to the muscle on T1-weighted images, with enhancement after contrast injection; hyperintense on T2-weighted images; and containing flow voids. Among the 66 cases, 59 exhibited typical ICTH features and 7 shared some imaging features with arteriovenous malformations. These latter were larger than typical ICTHs and more painful and appeared on imaging as less well delimited and more heterogeneous tissue masses, with larger tortuous afferent arteries, earlier draining vein opacification and mild arteriovenous shunting. We propose to name these lesions arteriovenous malformation (AVM)-like ICTH. Pathological reports were similar in typical and AVM-like ICTH, showing capillary proliferation with mainly small-size vessels, negative for GLUT-1 and positive for ERG, AML, CD31 and CD34, with low Ki67 proliferation index (<10%), and adipose tissue. The most frequent treatment for ICTH was complete surgical resection (17/47, 36.2%), preceded in some cases by embolization, which led to complete remission.Conclusions: ICTH can be diagnosed on MRI when it is typical. Biopsy or angiography are required for atypical forms.