A 53-year-old Cambodian woman presented with nodular masses on the right arm suggestive of a sarcoma-type malignancy. The masses were excised and identified as multiple benign eccrine poromas. The patient re-presented after two years with large relapsed tumours and axillary lymph node involvement. A forequarter amputation was undertaken. Histology confirmed the diagnosis of a porocarcinoma, which was likely to be due to malignant transformation of the original poromas. The size and multiplicity of the tumours represents a highly unusual presentation of these rare eccrine neoplasms.