The OxFAT score: A new score for predicting malignancy in foot and ankle tumours

A. Abboud, R. Colta, H. Branford White, A. Kendal, R. Brown

Background: Masses are not uncommon in the foot and ankle. Most of these masses are benign, often leading clinicians to underestimate their potential for malignancy.

Methods: We conducted a retrospective review of our clinical records, on patients with histologically confirmed musculoskeletal tumours of the foot and ankle, treated in a single nstitution between 2010 and 2019. The maximum diameter of each lesion was determined through MRI or Ultrasound analysis in centimeters. To develop a scoring system we compared the risk of malignancy with five criteria: site (proximal or distal to the first TMTJ), gender, age, composition and the diameter as observed.

Results: Our study included 496 patients, of whom 39 (7.9%) were identified as having malignancies. The incidence of malignancy demonstrated an increased propensity among male patients, patients over 50 years of age and lesions located proximal to the TMTJ. A ROC Analysis determined that lesions measuring over 2.85 cm had an increased risk of malignancy, with a PPV of 31.1%, a NPV of 94.2%, a Sensitivity of 0.82, and a Specificity of 0.62. These identified patterns of risk were employed to formulate a scoring system, aimed at facilitating informed clinical judgment in the referral of patients to regional tumor services.

Conclusion:  The new OxFAT scoring system highlights the importance of lesion size, site, age and gender of the patient in determining the risk of malignancy in lump in the foot and ankle. We propose this new scoring system to aid health care professionals in managing these patients. Based on our results any patient with a foot or ankle mass of less than 2.85cm, an OxFAT score < 4/7 and no malignant or sinister features on MRI or USS can be managed locally with excision biopsy. All other patients should be referred urgently to a Regional Tumour Service.