Mesenteric Fibromatosis

The term desmoid was first used by Muller [1] to describe the tendon-like aspect and the hard consistency of this type of proliferation (desmos in Greek means band). Desmoid tumours (DTs) are classified as extra- or intra-abdominal. The extra-abdominal DTs arise from fascial or musculoaponeurotic structures predominantly of the abdominal wall (Fig. 1a, b, c) and occasionally of the shoulder girdle, chest wall, inguinal region and extremities. They present as a firm, smooth, painless, progressively growing mass. Imaging investigations are useful in better defining the extent of the tumour which displays an iceberg growth with only a small proportion being clinically manifest. Interestingly, multiple extra-abdominal DTs are frequently discovered in very young patients under the age of 3 [2]. The intra-abdominal DTs develop in the folds of the mesentery or the meso-colon (Fig. 2a, b) even reaching the retroperitoneal tissue or they may grow exclusively in this region. These proliferations are usually single, round or oval in shape and up to 60 cm in size. Rather than a mass, a thickening of the mesentery that appears to be covered with hard white spots and causes retraction of the peritoneal folds is frequently reported in familial

Colon Polyp
Fig. 1a. Tc scan revealing a large and invasive desmoid mass arising within the abdominal wall. b Lateral view of the abdomen showing a protruding desmoid mass along the scar of the previous prophylactic colectomy. c Desmoid mass specimen.
Desmoid MesentericMesenteric Fibromatosis

adenomatous polyps (FAP) patients. This process has been variously referred as mesenteric fibrosis or mesenteric fibromatosis [3-5]. However, whitish, thin plaque-like areas of the mesenteric folds have been frequently identified in FAP patients undergoing laparotomy (Fig . 3a, b). It has been suggested that these mesenteric abnormalities represent precursor lesions of mesenteric fibromatosis and mesenteric DT [6, 7]. A model of stepwise progression for DT development similar to the adenoma-carcinoma sequence observed for colorectal cancer has been proposed. A prospective study of 42 patients with FAP undergoing laparotomy was made performing a detailed examination of the small-bowel mesentery and biopsy of the lesions. Plaquelike areas of peritoneal thickening were observed in 30% of these patients and areas of diffuse mesenteric fibromatosis in 16%. Histology was similar to that of other desmoids [6]. The patients with mesenteric fibromatosis had undergone a significantly higher number of previous abdominal operations than those without [6].

Helical abdominopelvic CT scanning and MRI was employed to characterize and follow up these precursors. It has been suggested that rapidly growing DTs have high signal intensity on T2-weighted images [8]. Mesenteric fibromatosis were identified in 21% of asymptomatic patients. At the follow-up (median 27 months), patients with desmoid precursor lesions (DPLs) had a significantly greater degree of mesenteric fibromatosis and DT formation than the control group [7]. Furthermore, CT findings consistent with mesenteric fibromatosis were observed on reviewing the scans of patients subsequently developing DTs [9].

Intra-abdominal DTs can be associated with DTs arising in the abdominal wall. The similarity of intraabdominal DTs to extra-abdominal DTs is evident in

Mesenteric Fibromatosis
Fig. 3a. Tc scan shows a large desmoid mass arising within the mesentery. b Intra-operative view of desmoid mass
Table 1. Data of literature on operated desmoid tumours in familial adenomatous polyposis

Author

Jones

Lofti

Penna

Gurbuz

Rodriguez-

Kadmon

Heiskanen

Soravia

Ho

(year)

et al. [14]

et al. [15]

et al. [13]

et al. [2]

Bigas et al. [16] et al. [17]

et al. [18]

et al. [19]

[20]

(1986)

(1989)

(1993)

(1994)

(1994)

(1995)

(1997)

(2000)

(2002)

Patients ( )a

29 (8.9)

24 (13)

29 (12)

83 (10)

24 (38)

29 (17)

29 (14)

97 (12.4)

11 (1)

Male/female

7/22

7/17

16/13

36/47

15 /9

10/19

12/17

38/59

5/6

ratio

Family history NA

3(12.5)

NA

49 (59)

NA

3 (10.3)

4 (13.7)

41 (42.2)

NA

Pregnancy

NA

11 (65)

NA

22 (66)

NA

2 (10)

10 (59)

33 (60)

NA

Site

Mesen

Mesen-

Mesen-

Abd. 60,

Mesen-

Mesen-

Mesen-

Mesen-

Mesen-

tery 21

tery 24

tery 25

Extra-

tery 8

tery 19

tery 15

tery 49

tery 3

Abd. wall 5

Abd.

Abd. 11,

Abd.

Abd.

Abd.

Abd.

Abd.

Both

wall 4

Both

wall 5,

wall 15

wall 10

wall10,

wall 4

sites 4

sites 3

Both

Extra-

Other

Both

NA 9

sites 11

abd. 2

sites 4

sites 31,

Extra-abd.

Mean age

29.8

34

32

31

28.5

34.5

28

29.9

33

at DT occurrence at DT occurrence

DT 2

development: mean tine from colectomy (years)

Recurrence 25 (85) after surgery

"Rate of operated patients. NA, not available; DT, desmoid tumour; Abd, abdominal the fact that these growths are histologically identical, they never metastasize and usually occur shortly after an abdominal operation. In the series from the polyposis registries of Denmark and Finland, DTs are located intra-abdominally in 50%, in the abdominal wall in 40% and on the extremities in 10% [10].While DTs are rare in the general population (two to four cases/million/year), they represent a major extraintestinal manifestation of FAP. The risk for a FAP patient of developing a DT is one thousand times that of the general population [2]. The incidence increases steadily with age until the fifth decade of life [11]. Only a few patients manifest a DT before the diagnosis of colonic polyposis. The growth of DTs usually occurs after the colectomy and the mean age at diagnosis varies between 29 and 32 years in patients collected in the registries of the most important institutions [2]. The cumulative risk of DT developing 10 years after prophylactic colectomy is 16% and the cumulative lifetime risk is around 21% [12].

The true incidence of DTs in FAP is unknown. The incidence usually ranges between 7 and 12% when a retrospective review of surgical FAP series is considered [2,12,13]. In these studies, the diagnosis is generally made on clinical evidence of an abdominal mass. However, considering that several mesenteric DTs are asymptomatic or are discovered fortuitously on radiographic abdominal examination, the incidence is probably higher than usually reported. Furthermore, it is not clear whether mesenteric fibro-matoses are always considered in these clinical series.

In our experience, DTs or their precursors such as mesenteric fibromatosis, retroperitoneal fibrosis or simply mesenteric fibrotic thickening have been found in 40 out of the 97 (41.2%) FAP operated patients. Twenty-seven patients (27.8%) developed abdominal wall or mesenteric DTs. The probable explanation of this relatively high frequency of desmoid reaction lies in a more accurate and prospective investigation. (Tables 1 and 2).

Table 2. Desmoids (D), fibromatosis (FB) and desmoid precursor lesions (DPL) in 40 out of 97 FAP patients (personal experience)

Abdominal wall D Mesenteric D Mesenteric FB Mesenteric DPL Retroperitoneal FB

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