Abstract

Endometriosis is an enigmatic disease which affects 10% of reproductive age women and commonly involves pelvic organs. Extrapelvic endometriosis involving the anterior abdominal wall is rare and even rarer is the involvement of the rectus abdominis muscles. Abdominal wall endometriosis can be explained by grafting of the endometrial cells to the abdominal wall during laparotomy or pelvic surgery, particularly caesarean section. It can pose a diagnostic dilemma when it presents as a lump in the abdomen and has to be differentiated from the abdominal wall tumours.

We report two cases of rectus muscle endometriosis following caesarean section in women of reproductive age group.

Introduction

Endometriosis, first described by Rokitansky in 1860 is defined as the presence of functioning endometrial tissue in anatomic locations other than the uterine cavity,1 with the maximum prevalence in the third and fourth decade of life.1-5 Overall prevalence, including both symptomatic and asymptomatic women, is estimated to be 5-10%.1-5

The most common sites of occurrence are in the pelvis such as ovaries, fallopian tubes, pouch of Douglas and uterine ligaments.1-4 Extra pelvic abdominal sites include the rectosigmoid ileum and appendix.1 The abdominal wall is an uncommon site of extrapelvic endometriosis where it usually develops in an old surgical scar. Endometriosis involving the rectus abdominis muscle is rare.2-7 Until now only few such cases have been described in the medical literature.2-10 We present two cases of endometriosis involving the rectus abdominis muscle.

Case Report

Case 1: A 33 year old female presented with anterior abdominal wall swelling of six months duration. The lump had developed six years after a caesarean section. She failed to notice variation in the size of the mass in relation to the menstrual period.

She did not have any other complaints related to abdomen.

On examination, the abdomen was non-tender with an ill-defined lump, just below the umbilicus measuring 4.0 x 3.5 cm, tender, firm to hard and non-reducible. Clinically the diagnosis of desmoid tumour was entertained.

Case 2 : A woman of 26 years was referred to surgery for evaluation of bulge in the anterior abdominal wall. The bulge did not appear to fluctuate in size in relation to her menstrual period. There was history of previous caesarean section five years back but no history of abdominal or systemic complaints. Examination revealed a tender, immobile, firm, lump of 3.0 x 1.5 cm, left side to the anterior rectus sheath. USG showed a diffuse mass at the muscular plane measuring 3 x 3 x 1.5 cms, not communicating with abdominal cavity. The preoperative diagnosis was suture granuloma.

Fig. 1 : Gross specimen of case 1 and case 2 measures 4 x 3 x 1.5 cm and 5.5 x 4 x 1.5 cm respectively. The cut surface of both specimens was firm, grayish white with focal brownish areas.		Fig. 2 : Cystically dilated endometrial glands lined by low cuboidal to flattened epithelium involving muscle fibres.
Fig. 3 : Cystically dilated glands involving muscle fibres with lymphoid infiltrate and fibrosis but sparing subcutaneous fatty tissue.

Pathological findings

Gross examination : The resected specimens of case 1 and case 2 measured 5.5 x 4 x 1.5 cm and 4 x 3 x 1.5 cm respectively and were not covered with skin. Cut surface of both was firm, grayish white with brownish areas.

Microscopy : The histomorphology was similar in both the cases. The endometrial glands and stroma involved the muscle fibres with extensive fibrosis and myxoid change. There were focal intra and extra glandular haemorrhages with the presence of haemosiderin laden macrophages and absence of involvement of the subcutaneous fatty tissue.

Discussion

The extra pelvic endometriosis was first documented in 1899 by Russell and has been described in virtually every organ in the body including skin, spleen, brain, liver, lung, extremities and anterior abdominal wall.4-10

The occurrence of abdominal wall scar endometriosis is uncommon with an incidence of 1.6%.1 The true incidence of caesarean section scar endometriosis is difficult to determine, but ranges from 0.03% to 0.4%.1-5 Endometriosis in patients with scars, is more common in the abdominal skin and subcutaneous tissue compared to muscle and fascia. Endometriosis involving only the rectus muscle and / sheath is very rare with only few case reports.2,5,10 in the literature, since it was first described by Coley in 1993.2

Endometrosis is a complex disorder with multifactorial causes, such as tubal retrograde spread, coelomic metaplasia of peritoneal cells, traumatic implantation and vascular and lymphatic spread.2,4 The presence of endometrial tissue in the rectus muscle in the present study can be explained on the basis of traumatic implantation theory.

The classical presentation is that of a parous woman complaining of a painful nodule, varying with menses at the incision site. In this case both women were para one and had previous history of caesarean section. They presented with tender, abdominal mass but the history of cyclic pain or fluctuation in lump size in relation to menstrual period was not elicited which may be secondary to lack of awareness.

Abdominal wall endometriosis can mimic incisional hernia, suture granuloma, abscess, haematoma and benign or malignant abdominal wall tumour.1,4 The histopathological examination will be helpful in establishing the diagnosis of endometriosis as it is usually not suspected prior to surgery, which happened in present study.

Gross pathological findings of endometriosis depend on the location and duration of the disease. The abdominal wall lesions are grayish white, with several pinhead-sized central red cores, and have evidence of old and recent haemorrhages within the mass.8 The gross appearance of the lesions in our cases was characteristic of endometriosis with histomorphology of glands, stroma haemorrhage, haemosiderin-laden macrophages and fibrosis. The presence of myxoid change and decidual reaction were an unusual findings in one of the cases. The danger lies in confusing such type of endometriosis with that of metastatic carcinoma due to presence of stromal mucin and solid areas of decidual reaction. The features of absence of cytologic atypia, presence of endometrial stroma and glands lined by atrophic epithelium, will rule out carcinoma.

Medical and surgical therapies have been used in the treatment of this process. The wide surgical excision of the lesion as performed in our patients is recommended to prevent recurrence.4,9

In conclusion, although rare endometriosis should be considered in any woman of childbearing age with a painful or tender incision mass, especially if there is a history of abdominal surgery. Imaging studies such as USG, CT or MRI are non specific, thus, a biopsy is necessary to make a definitive diagnosis.

References

1. Satrtoff DM, La Vorgna KA, McFarland MM. Extrapelvic endometriosis presenting as a hernia : Clinical reports and review of the literature. Surgery 1989; 105 : 109-12.
   
2. Coeman V, Sciot R, Breuseghen Van. Rectus abdominis endometriosis: a report of two cases. Brit J of Radio 2005; 78 : 68-71.
   
3. Brenner C, Wohlgenueth S. Scar endometriosis : Surg Gynecol Obstet 1990; 170 : 538–40.
   
4. Ideyi SC, Schein M, Niazi M, Gerst PH. Spontaneous endometriosis of the abdominal wall. Dig Surg 2003; 20 : 246-88.
   
5. Picod G, Boulanger L, Bounoua F, Ledeec F, Duval G. Abdominal wall endometriosis after caesarean section : report of fifteen cases. Gynecol Obstet Fertil 2006; 34 (1) 8-13.
   
6. Gordon CW, Singh KB. Caesarean scar endometriosis : a review. Obstet Gynecol Surv 1989; 42 : 89-95.
   
7. Roberge RJ, Kntor WJ, Scorza L. Rectus abdominis endometrioma. Am J Emerg Med 1999; 17 (7) : 675-77.
   
8. Chatterjee SK. Scar endometriosis : a clinicopathologic study of 17 cases. Obstet Gynecol 1980; 56 : 81-84.
   
9. Seydel AS, Sickel JZ, Warner ED, Sax HC. Extrapelvic endometriosis : diagnosis and treatment. Am J Surg 1996 ; 171 : 239-41.
   
10. Benchimol D, et al. Endometriosis of the rectus abdominis muscles. Ann Chir 2000; 125 : 880-83.

*Registrar; **Associate Professor; ***HOD; +Observer; LTMGH Sion Hospital, Mumbai 400 022