Mature cystic teratomas (dermoid cysts) of the ovary are very rarely associated with androgen production. The source of androgens in these cysts may be tumours such as Sertoli-Leydig cell tumour or Leydig cell hyperplasia. In this study, we present a case of virilisation in a postmenopausal female patient, where Leydig cell hyperplasia in a mature cystic teratoma was found to be responsible for the production of testosterone. In addition, extensive areas of lipomatous differentiation were identified. These areas showed significant alterations in adipocytic morphology, and differential diagnoses such as spindle cell lipoma (SCL) and atypical lipomatous tumour (ALT) were excluded after additional workup. Adipose tissue is traditionally described as an energy reservoir, but recently it has become clear that adipose tissue is a complex endocrine organ with additional metabolic roles in whole body homeostasis. Exuberant proliferation of lipomatous tissue in this teratoma raises the possibility of a synergistic role of Leydig cells and adipocytes in the development of hyperandrogenism
