Myospherulosis. Fine needle aspiration cytologic findings in 19 cases.

An analysis was made of 19 cases of myospherulosis seen on fine needle aspirates of mammary and subcutaneous tissue masses. Myospherulosis, best seen with the Papanicolaou stain, appeared as 4 microns to 7 microns spherules that were homogeneously smooth or contained one or more internal dense bodies. The spherules were dispersed singly or aggregated into sac-like structures. Myospherulosis accompanied 16 benign and 3 malignant conditions. In two aspirates, myospherulosis was seen simultaneously with breast carcinoma; in another, fat necrosis with myospherulosis masked an underlying breast malignancy. In 10 of the 12 aspirates from patients with previous tissue trauma, it accompanied evidence of fat necrosis and mesenchymal repair; in 4 aspirates, no other underlying condition was apparent. These findings indicate that myospherulosis is not an uncommon finding in fine needle aspirates of fatty sites; it often accompanies fat necrosis and mesenchymal repair. The presence of myospherulosis in aspirates of clinically suspicious masses does not exclude an underlying malignancy.