Table 2.

Summary of a case series reporting the clinicopathological features of leiomyomas of retroperitoneum.

	Authors; year of publication
	Billings et al.; 2001 [10]
Clinical feature
Age	Often of perimenopausal age (median, 44 years; range 16–72 years)
Gender	F >> M
Anatomical site	Primarily in the retroperitoneum; also in the mesentery/omentum
Histological feature
Architecture	Intersecting fascicles
Lesional cells	Mature smooth muscle cells, with bland, blunt-ended, or slightly tapered nuclei
Nuclear atypia	Absent; very focal, minimal atypia acceptable
Coagulative tumor cell necrosis	Absent
Mitotic activity	Low (mean, 1 mitosis/50 HPF; range, <1–10 mitoses/50 HPF)∗
Atypical mitotic figures	Absent
Other findings	Cystic and degenerative changes (more frequent than in counterpart in deep somatic soft tissue)
IHC
ER and PR	Positive

M, male; F, female; HPF, high power fields; IHC, immunohistochemistry; ER, estrogen receptor protein; PR, progesterone receptor protein. ^∗The authors concluded that a smooth muscle tumor of retroperitoneum with >10 mitoses/50 HPF should be regarded as “smooth muscle tumors of uncertain malignant potential.”