Desmoid tumour of the distal forearm involving the distal radioulnar joint

Abstract

A 32-year-old woman presented with progressive pain and swelling of the left wrist for 6 months. Physical examination revealed a firm, tender, oval swelling over the left wrist. X-rays showed a pressure effect on the distal radius and ulna. Magnetic Resonance Imaging (MRI) revealed a well-defined, asymmetrical, dumbbell-shaped soft-tissue lesion involving the interosseous region of the distal forearm and extending until the distal radioulnar joint (DRUJ). Core needle biopsy confirmed the diagnosis of desmoid tumour. Marginal excision of the tumour was done. At the 2-year follow-up, the patient was doing well and had painless and improved left wrist motion. Desmoid tumour involving the DRUJ has not been previously reported. We, through this case, report new observation and discuss the epidemiology, investigation of choice, treatment modalities, and the need for a regular follow-up for appendicular desmoid tumours.

Background

Desmoid tumour, also called aggressive fibromatosis, is a rare benign tumour originating in the musculoaponeurotic tissue with a potential to infiltrate locally. Aggressive fibromatosis of the forearm is very rare and only a few reports have been published to date, none of which had involved the distal radioulnar joint (DRUJ).^1–4 We report a case of a middle-aged woman with desmoid tumour of the distal forearm extending until the DRUJ, and discuss its epidemiology, investigation of choice, treatment modalities, and the need for a regular follow-up.

Case presentation

A 32-year-old woman came to us with progressive pain and swelling of the left wrist for 6 months. There was no numbness in the hand or decrease in the grip strength. There was no history of trauma, fever, or weight loss. It was not associated with swelling in any other body part. Physical examination revealed a 4 cm × 3 cm oval swelling in the left wrist. The overlying skin was normal and there were no dilated veins. It was firm in consistency and diffusely tender with normal local temperature. The range of motion of the left wrist was restricted (dorsiflexion: 30°, palmar flexion: 30°, pronation: 45°, and supination: 45°). Cardiorespiratory, abdominal, and neurological examinations were normal.

Investigations

X-rays of the left wrist showed pressure effect on distal radius and ulna leading to concavity of the ulnar border of the distal radius and the radial border of the distal ulna (figure 1). Magnetic Resonance Imaging (MRI) revealed a well-defined, asymmetrical, dumbbell-shaped soft-tissue lesion involving the interosseous region of the distal forearm and extending until the DRUJ, which was hypointense on T1 weighted image and hyperintense on T2 weighted image (figure 2). All laboratory investigations were normal.

Figure 1.

(A, B) X-rays of the left wrist showed pressure effect on distal radius and ulna leading to concavity of the ulnar border of the distal radius and the radial border of the distal ulna.

Figure 2.

(A, B) MRI revealed a well-defined, asymmetrical, dumbbell-shaped soft-tissue lesion involving the interosseous region of the distal forearm and extending until the distal radioulnar joint.

A core needle biopsy was done from the dorsal aspect as it was the safer and more approachable side of the swelling. Histopathology revealed a fibrous tumour with abundant collagenous stroma, no nuclear hyperchromasia or cytologic atypia, no area of necrosis, and infiltration into the surrounding soft tissue. These features were suggestive of musculoaponeurotic fibromatosis (desmoid tumour).

Treatment

After informed consent, tumour resection was performed under general anaesthesia. The DRUJ was approached from both volar and dorsal aspects. Volarly, the modified flexor carpi radialis approach was used, and dorsally it was approached through a longitudinal incision along the line of the third metacarpal. The tumour was found to be incorporating the capsule of the DRUJ and the pronator quadratus muscle (figure 3). The median nerve and other superficial tendons were spared. Marginal excision was done along with biopsy tract excision. No surgical reconstruction was performed for the correction of the pressure effect. Histopathological examination confirmed the diagnosis and margins were found to be tumour free.

Figure 3.

Intraoperative image showing the tumour.

Outcome and follow-up

The patient was followed up at 1, 3 and 6 months, then subsequently at 6-month intervals. At the 2-year follow-up, she was doing well and had painless and improved left wrist motion (figure 4). There were no clinical or radiological signs of recurrence.

Figure 4.

At the 2-year follow-up. (A, B) show well-healed volar and dorsal surgical scars; (C, D) show dorsiflexion and palmar flexion at the left wrist joint.

Discussion

Desmoid-type fibromatosis (DF) is defined by the World Health Organisation (WHO) as an intermediate soft-tissue tumour characterised by clonal fibroblastic proliferation arising in the deep soft tissues.⁵ It tends to locally infiltrate and recur but is not associated with metastasis. The condition was first described by McFarlane in 1832 and is also known as aggressive fibromatosis. Constituting a soft tissue mass, it generally arises from muscle, fascia, or aponeurosis.

Typically diagnosed in young adults (peak incidence at 35–40 years), desmoid tumours are more common in pregnant women probably due to hormonal imbalance.⁶ The commonly involved sites are the abdominal wall, limbs, girdles, and mesenteric area. Desmoid tumours can cause severe pain, functional impairment and, rarely, can be life-threatening.⁷

Bone involvement of aggressive fibromatosis can be divided into two groups according to its primary origin: (a) extraosseous soft-tissue desmoid tumour causing pressure effect on the bone, and (b) intraosseous DF.⁸ Pathologists often use ‘aggressive fibromatosis’ for both DF and soft-tissue desmoid tumours.⁹ We classified our case as extraosseous based on the radiographic and intraoperative findings. Hence, we did marginal excision with sparing of the bony elements of the wrist joint.

MRI is considered the gold standard radiological investigation for diagnosing, assessing, and monitoring an extra-abdominal desmoid tumour. It allows accurate assessment of tumour size, local infiltration, and relationship to adjacent neurovascular structures.¹⁰ A desmoid tumour shows low-signal intensity on T1 weighted images and high-signal intensity on T2 weighted images.

The course of a desmoid tumour is often unpredictable. Spontaneous regression, long-lasting stable disease, or disease progression can occur. Though surgery is the mainstay of treatment, a more conservative ‘active surveillance’ approach has been recently recommended which avoids overtreatment of desmoid tumours that are stable, less symptomatic and could spontaneously regress. Considering the biology and unpredictable course of the tumour, active surgical or medical treatment should be considered only if there is persistent progression. Medical therapies include anti-hormonal agents like tamoxifen, tyrosine kinase inhibitors like imatinib, and chemotherapy. Due to inconclusive evidence, a definitive sequence of the existing systemic treatment options is still not proposed. In general, less toxic therapy is initiated followed by more toxic agents in a stepwise fashion. Indications for surgery are volumetric progression, symptom worsening (like in our case), and mesenteric or head and neck desmoid tumour (due to proximity to critical structures). Aim of surgery should be wide microscopic margins resection, but positive microscopic margins are acceptable when function or cosmesis is concerning.¹¹ Postoperative radiation therapy is frequently used after a positive margin and to avoid mutilating surgery. Patients need to be under regular follow-up as the tumour can locally recur.^{12 13}

Patient’s perspective.

When I first noticed the swelling in my left wrist, I thought it would get better with time. But when it started aching and increasing in size, I decided to seek treatment. After work-up, I was informed that I have a benign tumour which will need excision. After consulting my family members, I decided to get the surgery done. After the surgery, the pain decreased and I underwent physiotherapy. Now after 2 years of surgery, I have no pain and although I still can’t move my wrist fully, I can do my activities at home and work without any difficulty. I am aware that there are some chances that the tumour can recur and hence, I need to be under continued follow-up.

Learning points.

• Desmoid tumour, also called aggressive fibromatosis, is a rare benign tumour originating in the musculoaponeurotic tissue with a potential to infiltrate locally but not associated with metastasis.

• It is generally seen in young adults and commonly involves the abdominal wall, limbs, girdles, and mesenteric area.

• Bone involvement of aggressive fibromatosis can be divided into two groups according to its primary origin: (a) extraosseous soft-tissue desmoid tumour causing pressure effect on the bone, and (b) intraosseous desmoplastic fibroma.

• MRI is considered the gold standard radiological investigation for diagnosing, assessing, and monitoring extra-abdominal desmoid tumour.

• Surgical indications include volumetric progression and worsening of symptoms, and patients need to be under regular follow-up after surgery to monitor for signs of recurrence.