We report a case of a 54-year-old Caucasian woman with an earlier diagnosis of Peutz-Jeghers Syndrome (PJS) and sex cord tumor with annular tubules (SCTAT). The sex cord stromal tumors showed aggressive malignant behavior with repeated recurrence and metastasis. This is an unusual behavior of SCTAT in patients with PJS, with only 2 such cases reported earlier. Genetic analysis revealed that the patient has a new (unreported earlier) missense mutation of the LKB1 gene. A review of the literature reporting the clinicopathologic features and biologic behavior of SCTAT in patients with and without PJS is presented. We discuss the presentation and management of this case and highlight the importance of considering the possibility of aggressive behavior of these tumors in the management of patients with PJS.