All in all, we had the following findings:
-development at the 3rd trimester
-lateral location on the neck, far from midline and close to the ear
-hypervascular, without cardiac failure (not shown)
-homogenous on both MR and US
All these criteria led us to assume that this soft tissue mass was probably a congenital hemangioma, more specifically a rapidly involutive congenital hemangioma (RICH), which has a pseudotumoral appearance and is usually expected to involute spontaneously postnatally within the 1st year.
We performed a C-section to deliver the baby at 38 weeks of pregnancy due to concerns for normal delivery feasibility with the neck mass. The mass’s diameter was 8cm and it began to slowly involute: 5cm within the first postnatal month.
Congenital hemangiomas are a separate entity from Infantile hemangioma which do appear later in infancy and then involute. Congenital hemangiomas are divided into 2 main subtypes: 1) Rapidly Involutive (RICH), classically a pseudotumor differential diagnosis, often located on the scalp or on the neck next to an external ear, or on a limb next to a big joint such as the knee. Spontaneous involution is expected within 12-14 months. Some cases do ulcerate and do require percutaneous embolization though. In some cases, a partial involution may happen and these hemangiomas are called PICH (partial involutive congenital hemangioma). 2) Non involutive (NICH): flat shaped telangiectasic angioma-like. They are non involutive and may increase in size as the child grows. Being flat, most of NICH are not picked up on US prenatal screening.
Gorincour, G., Kokta, V., Rypens, F. et al. Imaging characteristics of two subtypes of congenital hemangiomas: rapidly involuting congenital hemangiomas and non-involuting congenital hemangiomas. Pediatr Radiol 35, 1178–1185 (2005). https://doi.org/10.1007/s00247-005-1557-9