Local recurrence of an ossifying fibromyxoid tumour in the hand

A 37-year-old female presented with a slowly enlarging painless lump at the superficial palmar aspect of her right 5^th metacarpal. She had a lump surgically resected at the same site 17 years previously with the pathology reporting it as a neurofibroma.

Magnetic resonance imaging (MRI) showed a well-circumscribed lobulated heterogeneous soft tissue mass within the subcutaneous tissues (Fig.1a-d). A thin layer of fat is seen separating the mass from the underlying deep tissues. The deep aspect of the mass demonstrated intermediate signal intensity on T1 weighted imaging and intermediate to high signal intensity on STIR weighted imaging. Superficially within the mass were foci of low signal intensity on T1 and STIR weighted imaging. Computed tomography (CT) images (Fig. 1e+f) showed a soft tissue mass with calcification superficially corresponding to the low T1 and STIR signal intensity on MRI.

Ossifying fibromyxoid tumour (OFMT) is a rare soft tissue tumour first described by Enzinger et al. in 1989 [1]. The most common location is within the subcutaneous tissues of the extremities but less commonly is found to involve the trunk and head and neck region. OFMT is classified as a neoplasm of uncertain origin but had previously been suggested to possibly be nerve sheath, myoepithelial or cartilaginous in origin [2].

Clinical presentation of OFMT is usually with a painless well-circumscribed subcutaneous lump measuring around 4-5cm. There is a slight male predilection with median age of approximately 50 years old [3].

CT imaging of OFMTs typically shows a subcutaneous mass with peripheral intralesional ossification. This ossification corresponds to areas of low signal intensity on both T1 and T2 weighted MR images. The myxofibrous component of the tumour demonstrates intermediate signal on T1 weighted imaging and intermediate to high signal on T2 weighted imaging. Occasionally areas of internal haemorrhage are seen which are seen as high signal intensity on both T1 and T2 weighted imaging [4].

OFMT are benign tumours however it has been found that a subset shows atypical histopathological features which correspond to them exhibiting more aggressive behaviour with higher local recurrence and metastatic rates [5]. Core biopsy was performed on this tumour which showed a bland spindle cell tumour, difficult to classify but no evidence of morphological features associated with malignant behaviour. A review of the previously excised specimen from this site was carried out which found features consistent with an ossifying fibromyxoid tumour. In view of these new findings, the core biopsy was felt to likely represent OFMT recurrence. The patient proceeded to surgical excision with the specimen confirmed to be in keeping with OFMT.

This lesion showed no atypical histopathological features so is quoted to have local recurrence rates of 0-12% and metastatic rates of 0-4% [6,7]. The histopathological differential diagnosis includes malignant peripheral nerve sheath tumours which would explain the histological diagnosis of the original tumour in this patient excised 17 years ago [3].

Management of these lesions is usually with complete surgical excision with clinical follow-up, especially if histopathological malignant features are identified.

This case has shown the typical radiological features of a OFMT, a rare soft tissue tumour. It has shown that local recurrence of these tumours can occur even after long time intervals, in this case 17 years. Although OFMT is a rare tumour, it should be considered in the differential of a painless well-defined slow-growing subcutaneous soft tissue mass with peripheral calcification.

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