Smooth muscle hyperplasia of testicular adnexa is a benign non-neoplastic process in which there is excessive smooth muscle in the paratestis or spermatic cord clinically mimicking a neoplasm. The smooth muscle bundles are arranged concentrically around efferent ductules or vessels. The lesions may grow to as much as 6-7 cm in size. In this image, normal testis is seen on the left; the smooth muscle bundles are seen on the right and spermatic cord vessels are sandwiched between the two. Ref: Smooth Muscle Hyperplasia of the Testicular Adnexa Clinically Mimicking Neoplasia : Clinicopathologic Study of Sixteen Cases. Barton JH, Davis CJ, Sesherhann IA, Mostofi FK. Am J Surg Pathol 23(8):903-909, 1999.