Searching for the primitive tumor of a peritoneal carcinomatosis (PC) is no easy task even considering the multiple modern diagnostic procedures at our disposal. Without the primary site of a neoplasm it is often difficult to establish the prognosis and a treatment regimen. In PC the most frequent primitive tumors are ovarian neoplasms in women and gastrointestinal neoplasms in men. We present a case report of a 70-year-old Caucasian woman who was referred to our department for diagnosis and management of a PC. A fine-catheter aspiration cytology of the peritoneal implants was performed and provided histologic evidence of an ovarian papillary type carcinoma. This case is suggestive of what has been called in recent literature extraovarian peritoneal serous papillary carcinoma. Absent or insignificant histology of the ovaries of primary in-situ ovarian carcinoma is one diagnostic criterion. This patient had no evidence of ovarian disease considering ultrasound imaging and computer tomography. Unfortunately, since both laparotomy and laparoscopy were contraindicated, histology of the ovaries is lacking.