Pulmonary tumor thrombotic microangiopathy (PTTM) is a rare complication occurring during tumor dissemination that can lead to severe, commonly unrecognized pulmonary hypertension, right-sided heart failure, and sudden death. Histologically, it is characterized by tumor microthrombi within small arteries and arterioles and associated fibrocellular and fibromuscular intimal proliferation. Gastric adenocarcinoma is the most common tumor type with this association. Of gynecologic malignancies, a single case of ovarian clear cell carcinoma has been linked to PTTM. We report 2 patients who underwent surgery with a preoperative diagnosis of pelvic mass. After surgery, the patients had unexplained progressive respiratory failure that led to their death. Autopsy revealed typical features of PTTM with tumor lymphangitic spread and microscopic tumor emboli within the lung arteries. In both cases, the primary tumor was an ovarian serous neoplasm of low malignant potential with widespread dissemination, 1 with microinvasion and progression to low-grade serous carcinoma. In this last case, mutational analysis for KRAS and BRAF genes was performed to confirm the association between the ovarian and the extraovarian tumor and rule out other primary tumors more commonly associated with this disease. PTTM is a distinct pathologic entity with very few cases reported in the literature, especially involving ovarian tumors. We report 2 cases of low-grade ovarian serous neoplasm, not previously reported with this association.