Myospherulosis in Japan. A report of two cases and an immunohistochemical investigation.

We report two cases of myospherulosis and offer review of the Japanese literature. Case 1 was a 41-year-old woman with cystic tumors under the fascia of the right major gluteal muscle. Case 2 was a 36-year-old man with subcutaneous cystic tumors in the right buttock. The characteristic saccular structures enclosing numerous small spherules were observed in the cysts. These spherules measured 5-7 micron in diameter and stained with Masson trichrome, Giemsa, Papanicolaou, and alizarin red S for hemoglobin. The myospherules also stained positively by the immunohistochemical method for hemoglobin. These findings support the contention that the spherules and parent bodies were derived from erythrocytes altered by foreign lipids or fat.