Musculoaponeurotic fibromatosis of both bones of forearm.HH D'Souza, DV Kulkarni, BB Patel, AA Shivraman
Department of Orthopaedics & Pathology, Seth GS Medical College & KEM Hospital, Parel, Mumbai.
Desmoplastic fibroma is a rare primary tumour of bone. When it does occur, the sites of predilection are the long bones. The following is a case report of desmoplastic fibroma involving both bones of forearm in a 12 year old boy with a review of literature.
Keywords: Bone Neoplasms, pathology,radiography,surgery,Case Report, Child, Fibroma, Desmoplastic, pathology,radiography,surgery,Human, Male, Radius, Ulna,
Musculoaponeurotic fibromatosis (MAF) is identical histologically to desmoid tumours. However, the former term is more suitably applied to tumours with a special predilection for limbs and limb girdle.
Fewer than 100 cases have been reported of which 60% have been in the metaphysis of the long bones of the appendicular skeleton. There have been reports of desmoplastic fibroma involving either the radius alone or ulna, but involvement of both the bones of the forearm has never been reported which makes this a unique case.
A 12 year old boy presented with a swelling around the lower end of the left forearm which was painless and gradually increasing in size over a period of 6 months. There was no pain, discomfort or restriction of activity.
On examination, there was a diffuse enlargement of the lower one fourth of the left forearm with two distinct bulges, one over the ulna and the other over the radius extending both on the dorsal and volar aspect. The swelling was firm to bony hard in consistency and affecting both the radius and ulna [Figure - 1].
There was no warmth, tenderness or thrill felt. The radial and ulna artery pulsations were distinctly felt. The wrist and hand functions were well maintained. The forearm movements were however restricted with forearm fixed in midprone position.
X-rays showed presence of an intraosseous, well-defined, radiolucent, expansile lesion in the lower metaphysis of both radius and ulna with a delicate trabeculated soap bubble pattern. There was marked thinning of the cortex, which was regular and smooth, without any sign of recent periosteal reaction [Figure - 2]. The lesion did not cross the physeal plate.
With these X-ray features, conditions like ABC, hemangioma, chondromyxoid fibroma, GCT etc had to be ruled out. Giant cell tumour occurs after the closure of the epiphyseal plate and hence was ruled out. To rule out the presence of hemangioma an arteriogram was done which showed displacement of the radial and ulna artery with relative avascularity of the tumour [Figure - 3]. Needle biopsy of the tumour established the diagnosis of desmoplastic fibroma.
Since the growing ends of both bones of the forearm were involved, curettage of the lesion was done. The medullary cavity was found to be filled with an elastic mass, which was dense, rubbery and whitish grey. The mass adhered to the endosteal surface. After thorough curettage of the lesion, the defect was packed with chips of autogenous iliac bone.
Microscopic examination showed interlacing bundles of uniform spindle-shaped cells with pale oval nuclei and tails of eosinophilic cytoplasm. Some cells had inconspicuous nucleoli but there was no hyperchromasia or mitotic figures. There was a prominent collagen component seen as broad collagen bands. There was no osteoid tissue [Figure - 4].
In the postoperative phase extensive physiotherapy for wrist, hand and forearm was given one week after surgery. Patient had a good hand, wrist and forearm function 2 years after surgery, with no evidence of recurrence. [Figure - 5] & [Figure - 6]
The term "desmoid" was coined from the Greek word "desmos" meaning band or tendon by Mueller in 1836 The first description of a desmoid tumour is however credited to Mac Farlance in 1832.
Musculoaponeurotic fibromatosis is identical histologically to the desmoid tumour. The lesion appears as a firm painless swelling in a limb or limb girdle. Although it is more common in the second to fourth decade (premenopausal women predominantly), it does occur in children. The sex incidence in children is equal.
Radiologically they show a periosteal or juxtacortical bulge with focal cortical erosion. Extensive intraosseous invasion (as seen in this case) may occur in areas of soft tissue with tight compartments in close apposition to bone, as for example - in the region of the foot, ankle, wrist, forearm or leg. Grossly they are very firm and white with whorled appearance. The tumours are characterised by their slow but continuous growth and do not metastasise.
Two major problems are associated with musculoaponeurotic fibromatosis. First is the distinction from low grade fibrosarcoma. In desmoplastic fibroma, as has been mentioned previously, the collagenous matrix is composed of thick wavy interlacing bundles with small, sparse and spindle-shaped fibroblasts and uniformly oval and small nuclei. In low grade fibrosarcoma, the fibroblasts are long and spindle-shaped: the nuclei are, in contrast plump, elongated and hyperchromatic and are almost twice as large as those of desmoplastic fibroma.
The second problem is in determining effective treatment. The mainstay of treatment has been surgical excision of varying extent. Local excision, even if radical, may be followed by upto a 65% recurrence rate. Recent evidence suggests radiotherapy, which has been reserved for inoperable lesions may be of value as an adjunct to primary treatment. Limited local excision with adjunctive radiotherapy may decrease recurrence rate, minimise functional deficit and improve cosmesis. Radical local resection (compartmental or amputation) may be avoidable. In children, amputation may not result in cure because of the multicentric behaviour pattern and radiotherapy may lead to growth retardation. A shorter functional upper or lower limb is preferable to an amputation stump or a limb disfigured from radical excision.
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6]