Acquired gluteal myospherulosis secondary to intramuscular injections of petrolatum-based hormones: a case report diagnosed by fine-needle aspiration cytology.

A case of acquired myospherulosis of the right gluteal region diagnosed by FNA cytology is reported in a woman who had received a series of intramuscular injections of petrolatum-based hormones. The lesion is characterized by inflammatory pseudocystic nodules containing saccular formations with erythrocytes or "bags of marbles." It results from a physical process similar to the emulsion phenomenon between nonresorbent oily material and plasma. This process gives rise to sequestration of blood corpuscles by oily materials and thus development of foreign body granulomas.