Cytoplasmic droplets are normal structures of human sperm but are not well preserved by routine procedures for assessing sperm morphology

BACKGROUND: There is a discrepancy between the use of terminology employed by clinicians and basic scientists concerning the cytoplasmic droplets of sperm. Most clinicians consider their presence on sperm to be indicative of abnormal sperm, whereas basic scientists consider them to be attributes of normal sperm. METHODS: The presence of cytoplasmic droplets on human sperm was examined using conventional air-dried, fixed and stained sperm smears and in living and fixed wet preparations. RESULTS: Cytoplasmic droplets were found on the majority of motile sperm and in fixed preparations but only half of them were found in air-dried smears. There was no relationship between the presence of abnormally large cytoplasmic droplets, indicative of abnormal sperm, and the droplets found on living cells. CONCLUSION: The term 'cytoplasmic droplet' is confusingly used to describe two different sperm structures: large amounts of retained, excessive cytoplasmic remnants, that survive the air-drying procedure and are observed on abnormal sperm in conventionally stained sperm smears, and osmotically sensitive vesicles that are present on normal living sperm. A plea is made to retain the term 'cytoplasmic droplet' for the latter structure of normal sperm and to use the term 'excess residual cytoplasm' to describe the abnormally retained cytoplasm observed on abnormal sperm in smears.