Here we present a report of 61-year-old female patient. Uterus with left appendages was removed together with clinically tagged "tumor of right ovary" and then extensively sampled and routinely processed with Hematoxylin-Eosin (HE) and some additional staining. There was discernible oviduct adherent to grayish, solid, polycyclic 22 cm in diameter focally necrotic tumor to be diagnosed high-grade conventional leiomyosarcoma FNCLCC (Fédération Nationale des Centres de Lutte Contre le Cancer) G3 pT2b, according to 7th edition pTNM, according to World Health Organization (WHO) 2013 International Classification of Diseases for Oncology (ICD-O): 8890÷3, in nearby of right oviduct. Grade of differentiation was given according to FNCLCC classification: grade 3 {point score: 6 = 1 [microscopically necrosis comprised 10% of the tumor] + 3 [high mitotic index eight mitoses÷one high-power field (HPF) in hot spots in HE slides; Ki67 labeled approximately 60% of tumor cells] + 2 [histopathological type: conventional leiomyosarcoma]}. The staging was more appropriate for pT2b (7th edition pTNM) for deeply seated sarcoma of soft tissues, in examined samples, there was no trace of microscopically evident ovarian texture) rather than pT1a for ovarian tumors. The tumor was alpha-smooth muscle actin (α-SMA)-positive. Detected epithelial membrane antigen (EMA) immuno-reactivity indicates a possible change in mesenchymal origin. Next generation sequencing revealed tumor protein p53 (TP53) mutation C275Y (7577114 C>T). Each soft tissue malignancy should be carefully reported with appropriate choice of staging and precisely graded with internationally acknowledged classification.