First published online August 20, 2007
British Journal of Radiology (2007) 80, 750-756
© 2007 British Institute of Radiology
doi: 10.1259/bjr/53719785
Uptake characteristics of fluorodeoxyglucose (FDG) in deep fibromatosis and abdominal desmoids: potential clinical role of FDG-PET in the management
S Basu, MBBS, DRM, DNB
1
N Nair, MD
1 and
S Banavali, MD
2
1 Radiation Medicine Centre (BARC), 2 Department of Medical Oncology, TATA Memorial Hospital, Parel, Bombay 400 012, India
Correspondence: Dr Sandip Basu, Radiation Medicine Centre (BARC), Tata Memorial Hospital Annexe, Jerbai Wadia Road, Parel, Bombay 400 012, India. E-mail: drsanb{at}yahoo.com
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Abstract
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In this preliminary report, we explore the uptake pattern of fluorodeoxyglucose (FDG) in fibromatosis and hypothesize the potential clinical role of FDG-positron emission tomography (PET) in the management of this benign but locally aggressive heterogeneous group of soft-tissue tumours. Five patients were studied (two men and three women, age range 23–35 years), among whom were three cases of deep musculoskeletal fibromatosis, one of abdominal fibromatosis (abdominal desmoid) associated with familial adenomatous polyposis (Gardner's syndrome) and one case of both deep musculoskeletal fibromatosis and abdominal desmoid. The FDG uptake in the lesions was heterogeneous in four cases and relatively homogeneous in one case. The uptake ranged from low to moderate grade with areas or foci of relatively avid FDG uptake. The maximum standardized uptake value (SUVmax) observed was up to 4.7; the avidity probably related to the biological aggressiveness and tendency for recurrence, characteristic of fibromatosis. A dual-point FDG-PET carried out over four active foci in two cases registered an increase in SUV ranging from 6.93% to 25.85% (mean 19.28%). Treatment monitoring with chemotherapy was carried out in two cases: the reduction in FDG uptake was consistent with the histological evidence of fibrosis and reduction in mitosis. Hence, a baseline FDG-PET can serve a valuable role in monitoring the effect of systemic pharmacotherapy in patients with recurrent progressive disease after unsuccessful local–regional treatment. The findings in this report can be extrapolated and have implications for studying the utility of FDG-PET in defining aggressiveness, guiding biopsy and defining excision site in a large tumour and in monitoring therapy in fibromatosis.
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Introduction
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Fibromatosis comprises a heterogeneous group of locally infiltrative clinicopathological processes usually characterized by the proliferation of generally mature fibroblasts associated with mature collagen [1–4]. With widely variable cellularity, the biological behaviour of these tumours varies in aggressiveness: superficial fibromatoses (SFs) are typically small and slow-growing, whereas deep fibromatoses (DFs) are usually large, more aggressive and demonstrate an infiltrative growth pattern with a frequent tendency towards involvement of adjacent structures and local recurrence after excision but no evidence of metastasis [1–4]. Recent DNA sequencing data demonstrate the presence of somatic 
-catenin or adenomatous polyposis coli (APC) gene mutations in virtually 100% of cases of Gardner's syndrome-associated fibromatosis (GAF) and also in the majority of DFs [5, 6]. No somatic mutations were identified in beta-catenin or APC genes in SF [5, 6]. These genetic differences are suggested to be responsible for the divergent clinical behaviours of SF in relation to DF and GAF, despite their similar clinical and histological morphological features [5, 6]. We herein study the uptake pattern of fluorodeoxyglucose (FDG) in fibromatosis and explore the potential clinical role of FDG-positron emission tomography (PET) in defining aggressiveness, guiding biopsy and excision site and in monitoring therapy.
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Methods and materials
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Five patients (two men and three women, age range 23–35 years) with fibromatosis were retrospectively reviewed in this study. There were three cases of deep musculoskeletal fibromatosis, one of intraabdominal fibromatosis (intraabdominal desmoid) associated with familial adenomatous polyposis (Gardner's syndrome) and one of both deep musculoskeletal fibromatosis and abdominal desmoid. Treatment monitoring was carried out in two patients. These patients were selected from five consecutive cases undergoing FDG-PET studies between September 2005 and May 2006.
The standard FDG-PET protocol was followed: patients fasted for at least 6 h and had a blood glucose level of <150 mg dl–1. Patients were imaged 60 min after the injection of 444 MBq FDG on a whole-body full-ring dedicated bismuth germanate (BGO)-based GE Advance PET scanner (General Electric Medical systems, Milwaukee, WI). Images were reconstructed using the attenuation-weighted ordered subsets expectation maximization (OSEM) algorithm. Images were interpreted visually as well as using semiquantitative standardized uptake value (SUVmax) analysis corrected for the body surface area. Two experienced PET readers independently scored the cases, and the means of the values were considered for the final analysis.
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Results
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The overview of the clinical profile of the patients with fibromatosis who were studied has been summarized in Table 1
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Case 1
A 25-year-old man presented with gradually increasing right gluteal swelling. He had been treated for this at his local hospital by wide excision 2 years previously. The histopathology impression was that of a fibromatosis. He complained of recurrent swelling at the same site. Local examination revealed a relatively firm soft-tissue non-tender mass of about 12 cm in diameter. CT of the pelvis and thigh revealed a large fairly well defined lobulated soft-tissue mass measuring 14.3x10.8 cm involving the right gluteus maximus muscle. The mass also infiltrated the right quadratus inferior muscle; the gluteus minimus and the medius muscles were spared. There was no intrapelvic extension or bony erosion. The right sciatic nerve appeared encased by the two components of the mass but had not been infiltrated. He was referred for a whole-body FDG-PET (Figure 1, upper panel) for disease evaluation, which revealed a large area of heterogeneous FDG uptake in the right gluteal (SUVmax 4.6) and right upper thigh region (SUVmax 3.7) corresponding to the clinically palpable and CT-described soft-tissue masses. Follow-up FDG-PET (Figure 1, lower panel) for treatment monitoring was carried out after he had been treated with a combination of methotrexate, vinblastine and tamoxifen. This showed a decrease in the relatively intense fair-sized focus at the superomedial aspect in the gluteus maximus muscle (the SUVmax reduced from 4.7 to 1.6, i.e. a reduction of 65.17%), whereas the right upper thigh focus revealed a marginal increase in SUV (from 3.7 to 3.8), which could be regarded as "no significant change". A biopsy from the region which showed reduction in uptake revealed evidence of fibrosis consistent with the FDG-PET finding of treatment response. The remainder of the uptake was, however, similar in pattern and degree of uptake as seen in the pretreatment FDG-PET.
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Figure 1. Upper panel: pretreatment whole-body FDG-PET showing a large area of heterogeneous FDG uptake in the right gluteal (SUVmax 4.68) and right upper thigh (SUVmax 3.73) regions corresponding to the clinically palpable and CT-described soft-tissue masses. Lower panel: follow-up FDG-PET for treatment monitoring showed a decrease in the relatively intense fair-sized focus at the superomedial aspect in the gluteus maximus muscle (the SUVmax reduced from 4.7 to 1.6, i.e. a reduction of 65.17%), whereas the right upper thigh focus revealed a marginal increase in SUV (from 3.7 to 3.8).
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Case 2
A 28-year-old woman with a recurrent case of fibromatosis. She had surgery twice previously, with the last being 5 months previously. Recent MRI of the right thigh showed a large heterogeneous mass with hypointense areas within and demonstrating post-contrast enhancement. The pretreatment FDG-PET (Figure 2, upper panel) showed a large area of heterogeneous FDG uptake in the right thigh, corresponding to the tumour described in the MRI of the right thigh. The SUVmax of three areas (arrows) which appeared relatively intense visually were 2.8, 2.4 and 2.4 (from proximal to distal). She was treated with a combination of methotrexate, vinblastine and tamoxifen and was referred for a follow up FDG-PET for treatment-monitoring purposes. The post-therapy FDG-PET (Figure 2, lower panel) registered a reduction in the FDG uptake. The SUVmax values in the post-therapy FDG-PET region of interest (ROI) drawn over the same area as in the pretherapy FDG-PET) were 2.3 (reduction of 17.26%), 1.8 (reduction of 25%) and 1.7 (reduction of 26.89%). There was evidence of fibrosis and reduced mitosis in the histopathology obtained from multiple biopsies.
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Figure 2. Upper panel: pretreatment FDG-PET showing large area of heterogeneous FDG uptake in the right thigh corresponding to the tumour described in the MRI of the right thigh. The SUVmax of three areas (arrows) which appeared relatively intense visually were 2.8, 2.4 and 2.4 (from proximal to distal). Lower panel: post-therapy FDG-PET registered a reduction in the FDG uptake. The SUVmax of the previous three prominent foci in the post-therapy FDG-PET (ROI drawn over the same area as in the pre-therapy FDG-PET) were 2.30 (reduction of 17.26%), 1.80 (reduction of 25%) and 1.7 (reduction of 26.89%).
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Case 3
A 23-year-old man presented with recurrent fibromatosis in the right shoulder region after a surgical excision approximately 2 years previously. Recent MRI of the right shoulder showed a large (13.1x10.7x9.2 cm) lobulated mass along the anterior and medial aspect of the right axilla. The lesion was hypointense in T1 weighted images and predominantly hyperintense on fat-suppressed T2 weighted images and displaced the pectoralis muscle anteriorly with a loss of cleavage line between the lesion and adjoining muscles. A similar smaller lobulated lesion was noted posterolateral to it along the medial aspect of the axilla. FDG-PET (Figure 3) showed a large focus of mild to moderately enhanced FDG uptake corresponding to the large mass. The avidity of uptake was more at its superior aspect (arrow). Another focus of smaller size and relatively lower FDG uptake was observed below the focus mentioned above. The SUVmax values obtained were 2.8 and 2.2 respectively.
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Figure 3. FDG-PET showing a large focus of mild to moderately enhanced FDG uptake corresponding to the clinically discernible large mass. The avidity of uptake is more at its superior aspect (arrow). Another focus of smaller size and relatively lower FDG uptake is observed below the above focus. The SUVmax values obtained were 2.8 and 2.2, respectively.
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Case 4
A 35-year-old woman who had surgery for abdominal desmoids (primary along the right external iliac vessel) 3 years previously presented with recurrent abdominal desmoids at the same location and a progressively increasing right gluteal swelling of 3 months' duration. MRI of the abdomen and pelvis showed a large (7.7x4.9x7.9 cm) lobulated mass deep to the gluteus maximus extending caudally up to the greater trochanter; there was no specific bony erosion and the neurovascular bundle was displaced posteriorly. Another fairly well circumscribed 3x3.5 cm nodular mass was noted along the course of the right common iliac vessels. The mass exhibited an isointense signal in the T1 weighted images and a predominantly hyperintense signal on T2 weighted images. Both of the lesions were biopsied and proven to be fibromatosis. Whole-body FDG-PET (Figure 4, upper panel) demonstrated moderately enhanced homogeneous uptake in both of the lesions; the SUVmax of the right gluteal mass was 3.6 and that of the abdominal desmoid was also 3.6. A limited delayed PET (obtained at 2.5 h after injection of FDG) of the right gluteal region (Figure 4, lower panel) revealed an increase in the SUVmax to 4.4 (24.71%).
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Figure 4. Upper panel: whole-body FDG-PET demonstrating moderately enhanced homogeneous uptake in both the lesions; the SUVmax of the right gluteal mass was 3.6 and that of the abdominal desmoid was also 3.6. Lower panel: a delayed limited PET (obtained at 2.5 h after injection of FDG) of the right gluteal region registered an increase in the SUVmax to 4.4 (increase of 24.71%).
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Case 5
A 25-year-old woman, diagnosed with familial adenomatous polyposis, who had undergone total colectomy with ileoanal anastomosis 2 years previously because of histopathology showing features of high-grade dysplasia, recently presented with multiple parietal and intraabdominal desmoid fibromatoses. A CT scan of the abdomen revealed multiple varying sized soft-tissue mass lesions scattered in the retroperitoneum, mesentery, intraperitoneal space and the anterior abdominal wall. A biopsy correlation of these revealed them to be desmoid tumours. The largest of these was in the right anterior aspect of the anterior abdominal wall (6.8x7.9 cm) in the right lumbar region. This was discernible in the FDG-PET (Figure 5, upper panel), which showed low-grade FDG uptake interspersed with a few tiny foci of relatively intense uptake, probably representing the mitotically active foci. The baseline SUVmax values, which were calculated by drawing the ROI from the three most prominent foci, were 3.8, 3 and 2.6. These were found to be more prominent in delayed limited PET (obtained at 2.5 h after injection of FDG) of the abdomen (Figure 5 lower panel), the SUVmax values being 4 (increase of 6.93%), 3.6 (increase of 19.80%) and 3.3 (increase of 25.85%) respectively. Hence the dual timepoint FDG-PET carried out over four foci in two patients registered an increase ranging from 6.93% to 25.85% (mean 19.28%).
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Figure 5. Upper panel: FDG-PET showing low-grade FDG uptake with a few tiny foci of relatively intense uptake interspersed within. The SUVmax calculated by drawing the ROI over the three most prominent foci were 3.8, 3 and 2.6. Lower panel: delayed limited PET (obtained at 2.5 h after injection of FDG) of the abdomen demonstrating the foci to be more prominent; the SUVmax values being 4 (increase of 6.93%), 3.6 (increase of 19.80%) and 3.3 (increase of 25.85%), respectively.
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The mean SUVmax values at 1 h in the liver and the mediastinal blood pool in these patients were found to be 2.4 and 2.4 respectively.
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Discussion
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Fibromatosis encompasses a wide range of fibrous lesions. It is characterized macroscopically by a pale, whorled and fibrous cut surface appearance; microscopically there is a proliferation of fibroblastic and myofibroblastic elements and abundant collagen between the tumour cells. Cellularity and mitotic activity are widely variable as is the collagen content in an individual lesion. Although they never metastasize, there is a strong tendency towards local recurrence and invasion of neurovascular structures, especially the deep fibromatoses and Gardner's syndrome-associated fibromatoses. The biological aggressiveness of deep fibromatoses and Gardner's syndrome-associated fibromatoses compared with superficial fibromatoses has been attributed to genetic differences [5, 6].
CT features of deep fibromatoses are frequently non-specific owing to the infiltrating growth pattern of the tumour, and MRI is regarded as the best imaging modality for evaluation and staging [4, 7–11]. Although MRI is excellent in defining lesion margins and the extent of the tumour, signal intensity characteristics have been variable; the commonest pattern is heterogeneous, with intermediate signal intensity essentially reflecting the percentage composition of the cellular tissue and the collagen content within the tumour [8–13]. Low signal intensity is related to the dense collagenous region, and high signal intensity on T2 weighted images is related to the relatively cellular areas. The more cellular areas also demonstrate gadolinium contrast enhancement [4]. Our observation on varying FDG uptake by the different parts of the same tumour probably reflects the varying proportions of active cellular tissue and collagen in the lesion. The areas of higher FDG metabolism are likely to represent more cellular and mitotically active areas.
Despite surgery and radiation therapy, 20–36% of patients with fibromatosis experience local recurrence [14, 15] and several novel pharmacological therapies (both cytotoxic and non-cytotoxic) are now being tried out in refractory cases [16, 17]. Induction of fibrosis and decreased cellularity have been proposed as early changes in the responding fibromatosis [16–18]; FDG-PET by its ability to depict metabolic changes may prove to be valuable in treatment monitoring and might be an early indicator of treatment response. The ability to assess the functionality of the tumour as a whole for treatment response is an advantage compared with biopsies. A solitary case report of FDG-PET detecting aggressive fibromatosis [19] has been described in the literature; also FDG uptake in fibromatosis has been described as part of a differential diagnosis between benign and malignant soft-tissue masses or musculoskeletal tumours [20, 21]. However, there has been no definitive study investigating the FDG uptake pattern and the possible clinical role of FDG-PET in fibromatosis, including treatment monitoring. This preliminary report may serve as a basis for carrying out further trials on this issue.
Received for publication November 14, 2006.
Revision received January 18, 2007.
Accepted for publication February 20, 2007.
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Abstract
Introduction
