UNUSUAL TENDON SHEATH FIBROMA OF FOOT IN AN ADOLESCENT: A CASE REPORT

Introduction: Tendon sheath fibroma is a rare and slowly growing benign tumor commonly seen in the upper extremity (80%). It is frequently seen in the third to fifth decades of life and is more common in males. Tendon sheath fibroma has been reported to occur most likely after trivial trauma and more commonly in the plantar aspect of the region. The tumor size usually seen is <3 cm in diameter. To our knowledge, only twelve such cases have been reported around the foot and ankle. Case report: We describe a unique case of a benign, locally aggressive fibroma of the tendon sheath affecting the left foot in an adolescent — a 13-year-old girl presented with slow-growing swelling on her left foot for a year. Physical examination revealed a 7 × 5 cm swelling on the plantar aspect of the foot. MRI showed a well-defined mass seen in the flexor compartment around the 2nd and 3rd metatarsals abutting the flexor tendon sheath with iso signal intensity to muscle on T1-weighted images and homogeneously low signal intensity to muscle on T2-weighted images. After the biopsy, we went ahead with complete tumor excision. The histopathological specimen was composed of spindle cells arranged in bundles, fascicles, and a swirling pattern, and areas with varying cell density and abnormal hyaline degeneration confirming tendon sheath fibroma. The atypical features seen in our case were that this was found in an adolescent girl, with a size of 7 × 5 cm, which did not follow the usual pattern as seen in other patients. There were no signs of recurrence or any disability seen at 2 years of follow-up. Given the foot’s susceptibility to various lytic lesions and the overlapping clinical presentations, accurate diagnosis can be challenging. The foot’s complex anatomy can further obscure the condition, underscoring the need for heightened clinical suspicion when evaluating foot lesions. Conclusion: Looking at the nature of the histopathological diagnosis which has quite distinct features from usual tendon sheath fibroma we conclude that tumors may present with atypical characteristics leading to difficulty in histopathological diagnosis.