Chondromyxoid Fibroma (CMF) is slow-growing but mostly benign tumour. It is usually seen in the metaphysis of a long bone. World Health Organization (WHO) Classification of Bone and Soft Tissue Tumours (2002) defines CMF as ''benign tumour with lobules of spindle or stellate-shaped cells with abundant myxoid or chondroid intercellular material [1].

Chondromyxoid fibroma is a rare bone tumour accounting for <1% of primary bone neoplasms [2]. It is commonly found in older children and young adults between the age group of 10 to 30 years [3,4,5]. It is associated with high local recurrence and malignant transformation is rare (less than 2%). The most common site affected is the knee, tibia and femur, others are the flat and facial bones and sparsely in bones of the feet and hand [6-9]. Its occurrence in calcaneum is rarely seen.So here we report a case of a male patient, presented with cystic swelling and pain in the left foot, diagnosed as CMF on excisional biopsy.

A 20years old male presented in orthopaedic department of Dr RPGMC, Tanda with complaint of painful swelling in the left lateral aspect of the foot for 4 months. There was no significant past history of trauma, fever, TB (tuberculosis) or any previous surgery. The swelling was gradual in onset, progressive in nature with pain aggravates on walking. On palpation, there was a firm swelling on the antero-lateral aspect of the foot (size 10x10x7cm) with irregular margin and hyperpigmented overlying skin, fixed to underlying muscle (Figure 1). Movement was restricted at the ankle and subtalar joint with no associated neurovascular deficit.

On radiographic examination, a radiolucent, eccentric lesion with a sclerotic margin in the calcaneum was seen (Figure 2). MRI shows a multilobulated lesion on anterolateral aspect of foot measuring up to 7.5x6.8x10.1cm causing displacement and encasement of tibialis anterior, extensor hallucis longus and extensor digitorum longus and abutting cortex of talus, navicular and medial cuneiform (Figure 3). Histology after biopsy suggestive of interlacing fascicles of benign spindle cells in fibro myxoid stroma. The patient underwent wide local excision with extensor retinaculum repair with flap. Histology of excised tissue suggestive of fibromatosis with myxoid changes with all the margins infiltrated by tumour. Patient was then referred to radiotherapy department for further management where patient was taken up for local radiation.

Soft tissue and bone tumours of the foot are not rare, but their diagnosis is usually delayed due to common findings with pseudo tumour lesion. The occurrence of CMF in the foot is likely uncommon. It is seen more frequently in males; it is   usually benign   with   no reports of  metastases [10]. 

Figure 1: (a) Swelling on the antero-lateral aspect of the foot. (b) Radiolucent, eccentric lesion with a sclerotic margin in the calcaneum.

Figure 2 (a&b): Multilobulated lesion on anterolateral aspect of foot.

Figure 3: Displacement and encasement.

For establishing an accurate diagnosis of the tumour, a thorough clinical, radiological and histopathological examination is very essential. CMF presents as an oval, osteolytic, expansile lobulated lesion with précised margins and a sclerotic rim as seen in an x-ray. However cortical changes and breakthrough to the destruction of the cortex are best evaluated on CT [11,12]. Histopathology is a gold standard investigation in the diagnosis of CMF.

Treatment options include intralesional curettage with bone grafting, additional cementation and amputation [6]. Complete removal of the chondromyxoid fibroma by resection is very important to prevent the high rate of recurrence. The excised tissue should be preferably sent for histopathological examination for exact characterisation of disease and to know about the margin status. Accordingly, patient can be taken up for further management in form of re-excision if feasible or radiotherapy if necessary.

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