transillumination

Illumination generally with an otoscope in a darkened room across tissue (generally the scrotum &/or one of the testicles). The light source is placed directly against the tissue. The transmittance of light across the tissue suggests tissue of relatively low density. Failure to transilluminate across a tissue mass (i.e. testicular or scrotal mass) is suggestive of a neoplasm.

References

Webster's Ninth New Collegiate Dictionary, Miriam-Webster Inc. Springfield, MA 1990