title: Fibromyxoid variant of endometrial stromal sarcoma with atypical bizarre nuclei.
abstract: Endometrial stromal sarcoma (ESS) is the second most common malignant uterine mesenchymal tumor. It affects women primarily in the perimenopausal age group. ESSs are morphologically heterogeneous. The distinction between uterine smooth muscle tumors such as cellular leiomyoma and myxoid leiomyosarcoma and low-grade ESS can be problematic when stromal sarcomas show prominent smooth muscle differentiation and abundant myxoid stroma, respectively. We herein present a rare case of fibromyxoid variant of ESS, which was misdiagnosed as hydropic leiomyoma on intraoperative frozen section examination. Grossly, the uterine mass consisted of intracavitary and intramural portions. The intracavitary portion with extensive hydropic degeneration mimicked a hydropic leiomyoma. In contrast, the intramural portion displayed an obvious tongue-like myometrial invasion. Histologically, the tumor consisted of both cellular (20%) and myxoid (80%) areas. In the cellular areas, oval to spindle-shaped tumor cells with bland nuclear features were found to surround concentrically a rich vascular network of arterioles, a characteristic of ESS. In addition, two relatively well-circumscribed nodular lesions showing atypical bizarre nuclei were identified in the myxoid area. Immunohistochemically, the tumor cells were diffusely and strongly positive for CD10. The present case indicates a wide morphological spectrum of ESS. Fibromyxoid variant of ESS should be considered in the differential diagnosis of intracavitary and/or intramural uterine mesenchymal tumors with myxoid differentiation. It is important to avoid confusion between fibromyxoid ESS and myxoid leiomyosarcoma because of the differences in their clinical course, treatment, and prognosis.
authors.affiliation: Department of Pathology, Severance Hospital, Yonsei University College of Medicine Seoul, Republic of Korea.
authors.forename: Hyun-Soo
authors.initials: HS
authors.lastname: Kim
authors.affiliation: Department of Gynecology and Obstetrics, Pusan National University Yangsan Hospital, Pusan National University School of Medicine Yangsan, Republic of Korea.
authors.forename: Gun
authors.initials: G
authors.lastname: Yoon
authors.affiliation: Department of Pathology, Severance Hospital, Yonsei University College of Medicine Seoul, Republic of Korea.
authors.forename: Yoon Yang
authors.initials: YY
authors.lastname: Jung
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine Seoul, Republic of Korea.
authors.forename: Yoo-Young
authors.initials: YY
authors.lastname: Lee
authors.affiliation: Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine Seoul, Republic of Korea.
authors.forename: Sang Yong
authors.initials: SY
authors.lastname: Song
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D001706:Biopsy; D002467:Cell Nucleus / Q000473:pathology*; D003951:Diagnostic Errors; D016889:Endometrial Neoplasms / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D005260:Female; D005350:Fibroma / Q000737:chemistry / Q000473:pathology* / Q000601:surgery; D005629:Frozen Sections; D006801:Humans; D007150:Immunohistochemistry; D007889:Leiomyoma / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D015260:Neprilysin / Q000032:analysis; D011237:Predictive Value of Tests; D018203:Sarcoma, Endometrial Stromal / Q000737:chemistry / Q000473:pathology* / Q000601:surgery
chemical_list: D014408:Biomarkers, Tumor; D015260:Neprilysin
keywords: Endometrial stromal sarcoma; atypical bizarre nuclei; fibromyxoid variant