Linear spiradenoma with focal malignant transformation.

Malignant spiradenoma is an exceedingly rare adnexal tumour clinically characterized by rapid enlargement of a pre-existing, long-standing benign spiradenoma. Microscopic examination typically reveals a continuum between benign spiradenoma and areas of malignant transformation. Biological behaviour is unpredictable and it should be regarded as a potentially lethal neoplasm. Treatment recommendations require radical surgical excision. The reported case of a 23-year-old female illustrates the malignant transformation of a 1.5 cm nodule within a large linear spiradenoma almost covering the frontal aspect of the lower leg. In reviewing the literature, malignant transformation seems to occur slightly more often in multiple than in solitary spiradenomas. It is unclear whether excision restricted to the malignant area is an advisable treatment option in comparison to total excision of all spiradenoma nodules. In the presented case, the transformed area was excised. The patient is free of recurrence after 2 years.