Background: Vulvar dermatofibrosarcoma is a rare fibrous tumor of intermediate grade malignancy, with a tendency for local recurrence, and rarely metastasizes. Management should be multidisciplinary. This is a report of an apparently benign vulvar mass with delayed diagnosis of vulvar dermatofibrosarcoma. Case report: A 42-year-old woman was referred to our hospital because of a vulvar tumor lasting 16 years, although several gynecological procedures and a total laparoscopic hysterectomy had been performed two years before. During this long period the lesion did not change morphological features and remained asymptomatic. Only a benign vulvar mass was diagnosed. Then, the swelling became evident showing erythematous skin with an aspect of “peau d’orange”, leading the patient to consult a specialist. A firm vulvar swelling was observed in the anterior third of right labia majora continuing with about 3 cm of cord on top, quite movable above the underlying tissue but not on the overlying tissue. A wide excision was performed. The pathological examination showed positive margins. One month later an extensive deeper excision was performed. Histology confirmed a diagnosis of dermatofibrosarcoma. Immunohistochemistry was strongly positive for CD34. Conclusion: Vulvar lesions always require complete pathologic examination even in case of features of benign tumor to exclude a dermatofibrosarcoma. The role of the pathologist is essential to ensure negative microscopic margins and to avoid local recurrence.