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Parasitic leiomyomas: two case reports and review of literature
Gynecological Surgery volume 7, pages383–384 (2010)
Fibroids or leiomyomas are common tumours of the uterus. Very rarely, a subserous fibroid may detach from the uterus and attach itself to other structures. Such fibroids are called parasitic fibroids. We present two such rare cases of parasitic fibroids attached to the sigmoid colon and urethra, respectively.
A 39-year-old woman was referred with a feeling of a lump in the vagina and voiding difficulties. She felt the lump gradually increasing in size over the last year. She was, otherwise, in good health with no other medical, surgical or gynaecological problems.
On examination, the vulva looked healthy. A firm lump about 3 × 3 cm could be palpated in the lower third of the anterior vaginal wall. The lump was firm, mobile and non-tender on palpation.
The lump was excised through the anterior vaginal wall. It was attached to the urethra. There was no pedicle connecting the lump to the uterus.
Histology confirmed a leiomyoma.
A 52-year-old woman was referred with heavy periods over the last 3 years. She had no significant history apart from being sterilised.
On examination, the abdomen was unremarkable. Upon vaginal examination, the uterus was about 12-weeks size. Ultrasound showed a bulky uterus with multiple fibroids.
The woman underwent a total abdominal hysterectomy with bilateral salpingo-ophorectomy. On laparotomy, a 7 × 5 cm fibroid was found attached to the serosa of the sigmoid colon (Fig. 1). This was easily enucleated. Histology confirmed a leiomyoma.
Fibroids or leiomyomas are common benign tumours of the smooth muscle of the uterus. They are found in about 20–30% of women above the age of 35 years. They are subserous, intramural or submucus in location in the uterus.
Very rarely, a subserous fibroid may detach from the uterus to attach and receive its blood supply from other structures in the abdomen. The commonest source of blood supply for a parasitic fibroid is the omentum.
Extra-uterine leiomyomas are very rare. They may arise from the smooth muscle cells in the vulva, ovaries, urethra or urinary bladder.
Very few cases have been reported in modern literature. Kelly and Cullen reported 37 cases of parasitic fibroids way back in 1909. Odofin et al. reported a case in which such was removed by laparoscopy . Cases of torsion of a parasitic fibroid , ileal haemorrhage  and ureteral obstruction  due to parasitic fibroids have been reported.
Kang et al.  reported a case of retroperitoneal leiomyoma but this was thought to be of primary origin rather than parasitic. Several cases of parasitic leiomyoma after laparoscopic myomectomy have also been reported [6, 7].
We present two cases of parasitic fibroids, one of which was symptomatic and the other, asymptomatic. Location of the parasitic fibroid on the sigmoid colon and the urethra are very rare.
We thought the fibroid, attached to the sigmoid colon, to be parasitic as there were multiple fibroids on the uterus.
With the fibroid arising from the urethra, classifying the fibroid as a parasitic one rather than a primary leiomyoma of the urethra was more difficult. The ultrasound examination of the uterus in this woman showed fibroid changes but no definite fibroids. However, the leiomyoma was enucleated very easily which is why we thought it was probably a parasitic one rather than a primary fibroid arising from the urethra.
Parasitic fibroids should be included in the differential diagnosis of a pelvic mass.
Odofin O et al (2004) An unusual case of ectopic or parasitic leiomyoma excised by laparoscopic surgery. Int Surg 89:161–163
Brieger GM, MacGibbon AL, Peat BP (1995) Torsion of a parasitic fibroid. Aust NZ J Obstet Gynaecol 35(2):224
Rader JS et al (1990) Ileal haemorrhage caused by a parasitic uterine leiomyomas. Obstet Gynecol 76:531–534
Zaitoon MM (1986) Retroperitoneal parasitic leiomyomas causing unilateral ureteral obstruction. J Urol 135(1):130–1
Kang WD, Kim SM, Kim YH, Choi HS (2009) Three isolated, large retroperitoneal leiomyomas. Arch Gynecol Obstet. 280:499–501
Epstein JH, Nejat EJ, Tsai T (2009) Parasitic myomas after laparoscopic myomectomy: case report. Fertil Steril 91(3):932
Moon HS, Koo JS, Par SH, Park GS, Choi JG, Kim SG (2008) Parasitic leiomyoma in the abdominal wall after laparoscopic myomectomy. Fertil Steril 90(4):1201
Conflict of interest
There is no actual or potential conflict of interest in relation to this article.