A 24-days-old male newborn was brought the emergency department for the sudden appearance of left preauricular swelling. Gestation was complicated with preeclampsia, and he was born via vaginal delivery at 37 weeks. Postnatal period proceeded uneventfully. There was no history of fever or other clinical symptoms. Trauma and contact with household animals were denied.
On examination, there was a soft left parotid enlargement measuring approximately two centimeters, with well-defined limits and painless to touch. The integrity and color of the overlying skin was preserved with no signs of fluctuation (Figure 1). There were no adenopathies or other remarkable findings at the physical examination. Ultrasound revealed an increase in the size of the parotid gland, presenting an ovoid shape and homogeneous structure, with no evidence of focal changes or ductal ectasia. The blood count was normal, except for the presence of neutropenia (910/?L), CRP <0,60mg/L.
Figure 1. Soft left preauricular enlargement, measuring approximately 2cm, with well-defined limits and painless to touch.
What is the most probable diagnosis?