Analysis of infantile hemangioma without proliferation after birth.

Infantile hemangiomas (IHs) are the most common benign tumors of infancy, occurring in approximately 5-10% of the population. Among what appear to be typical IHs with proliferative and involuting phases, we noticed that there are also IHs that are already present at birth and regress without proliferating. We therefore aimed to determine the frequency and clinical characteristics of this type of IH. A retrospective study was conducted on 176 lesions of 137 Japanese patients with IH. As a result, six lesions (3.4%) in three patients with IH (2.1%) were already present at birth and lacked subsequent proliferation. Analysis of the clinical characteristics of IHs without proliferation revealed that they are significantly less common in the head and neck region, which is the preferred site of the tumor, than typical IHs with proliferation (0% vs. 42.9%, p < 0.05 by Fisher's exact test). This suggests that when the clinical course of IH is uncommon, their distribution can also be atypical. Furthermore, all of the IHs without proliferation were superficial types, and there were no deep types in this cohort. This study demonstrates that the clinical course of IH can be diverse, and that very rarely there can be a type of IH that does not grow after birth. It may be necessary to consider conducting a detailed interview for the growth history at the first visit for the possibility of such a type of IH without proliferation, as it is likely that they can be followed up without the need for treatment.