Incidence rate and clinicopathological features of 62 atypical fibroxanthomas in a North‐Western Spanish population

BACKGROUND/OBJECTIVES: Atypical fibroxanthoma (AFX) is a mesenchymal neoplasm of unknown incidence. It has been determined that AFX is a tumour with low aggressiveness as long as it is properly diagnosed. Our objectives were to exclude pleomorphic dermal sarcomas or other skin tumours incorrectly diagnosed as AFX in our centre after applying strict diagnostic criteria and to assess the behaviour of appropriately diagnosed AFX. METHODS: We conducted an observational retrospective analysis of 73 patients diagnosed with AFX in our centre between 1998 and 2018. After selecting cases fulfilling AFX criteria, we made an analysis of predictive factors for local recurrence. Crude and sex-adjusted incidence rates were calculated. RESULTS: Out of 73 cases, 62 were eventually diagnosed as AFX. We examined for absence of tumour necrosis, lymphovascular or perineural invasion and infiltration of deep structures. Cytokeratin AE1-AE3, desmin and CD34 were negative in all cases. The remaining tumours were reclassified. The incidence of AFX in our health-care area was estimated at 0.59 cases every 100 000 inhabitants per year. In our series, 72.6% of the patients were men with mean age at diagnosis of 81 years. Average tumour diameter was 12 mm. The most common location was head and neck (96.8%). Only four local recurrences were detected over a mean of 47-month follow-up. CONCLUSIONS: We report a series of AFX in our health-care area. We verify its indolent course when it is properly diagnosed.