Malignant transformation of ovarian mature cystic teratomas is reported to occur in about 1% of cases. The most common malignant evolution is that of squamous cell carcinoma and one of the least common is that of small cell carcinoma. We report a case of distant metastasis from a small cell carcinoma arising in a mature cystic teratoma. A 28-year-old nulliparous female presented with signs of supraclavicular lymph node metastasis. This is the first known case report of lymph node metastasis as an initial sign of cancer developing in a pre-existing mature cystic teratoma. Histologically, the tumor cells had microscopic features similar to those of pulmonary small cell carcinoma. This report gives a literature review, and the histological, immunohistochemical, flow cytometric and ultrastructural features are described.