Four cases of a pelvic mass due to the development of benign hyperplas
ia within ectopic prostatic tissue are reported. They presented a hypo
echoic homogeneous or heterogeneous pattern on transrectal ultrasonogr
aphy and a high signal intensity on T2-weighted spin-echo sequences on
MR. On CT the density was similar to that of prostatic tissue. No rec
ent imaging findings of this rare entity have been described in the li
terature. Possible aetiologies are discussed. Even if it is a rare eve
nt, the correct diagnosis can be reached. It is important for radiolog
ists to consider the presence of this lesion because of its benign nat
ure.