The case demonstrates PAH breast injections. Polyacrylamide hydrogel (PAH) was one of the substances historically used to augment breast tissue (along with paraffin and silicon). It was used in this patient 20 years ago in what was then the Soviet Union. The needle injection was via the axilla or inframammary fold into the submammary space.
Not a common finding in Western Canada but I suppose it depends where you work. This case showed migration of the PAH from the submammary space toward the left axilla where it formed a palpable mass lesion.
The reference below is a very readable historical summary of the augmentation of breast tissue (and other protuberances) and well worth reading for some perspective if you are involved in senology. To my mind also a social commentary on who we are and who we would like to be.