Cytomorphological semen analysis is an essential part of the diagnostic work-up for male infertility. Apart from the assessment
of sperm morphology, it should include the qualitative evaluation of cellular elements other than spermatozoa. Appropriate
staining of routine semen smears allows one to differentiate “round cells” (which need to be differentiated with regard to
their type and cytomorphological abnormalities) from the completely distinct population of leukocytes, such as neutrophils
and macrophages. Moreover, erythrocytes, epithelial cells as well as agglutination of spermatozoa can be identified.
Classification of sperm morphology and its diagnostic and prognostic value are still a matter of debate. According to current
WHO recommendations, strict criteria defining morphologically normal spermatozoa are widely used in andrology laboratories.
Whereas official reference values are pending, recent studies suggest threshold values of 8–10% normal forms to distinguish
between fertile and infertile men.
With regard to abnormal forms, head defects, neck and mid-piece defects, tail defects, and cytoplasmic droplets are considered
as main categories and recorded for each spermatozoon. Beyond this descriptive approach, systematic analysis of the phenotype
and degree of sperm pathology, e.g. by means of the Düsseldorf classification, may highlight underlying disorders of spermatogenesis
and/or epididymal function. Ultrastructural evaluation allows further characterization of “systematic” defects affecting the
majority of spermatozoa in a semen sample.Moreover, correlations between abnormal sperm morphology and chromosomal abnormalities
should be taken into consideration when performing intracytoplasmic sperm injection (ICSI).