it all fits

Cali's growth is a lymphangioma, specifically, a cystic hygroma (a subset of lymphangioma). From hindsight, the symptoms make total sense.

Here's wikipedia's entry for "lymphangioma," edited.

"Lymphangioma is a lymphatic malformation, a benign proliferation of lymph vessels. Lymphangiomas are fluid-filled sacs resulting from blockage of the lymphatic system.

It is often removed by a form of surgery using an electric current electrocoagulation for cosmetic reasons. It is rare, incidence being estimated at around one per 10,000 live births.

These tumors may occur anywhere, but around 75% occur in the head and neck regions, with a predilection for the left side. Most (around 90%) are either evident at birth or become evident before age two years."

We are returning to the hospital to meet with a lymphatic surgeon on Monday.