Seok-Ju Seong

Rapid recurrence of uterine smooth muscle tumor of uncertain malignant potential as leiomyosarcoma

⁎ Corresponding author at: Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, Gangnam CHA Medical Center, CHA University, 650-9 Yoksam-dong, Gangnam-gu, Seoul 135913, Korea. Tel.: +82 2 3468 3677; fax: +82 2 558 1119. E-mail address: sjseongcheil@yahoo.co.kr (S.-J. Seong). A 28-year-old woman (gravida 1, para 0) presented to the Department of Obstetrics and Gynecology at Gangnam CHA Medical Center, CHA University, Seoul, Korea, with menorrhagia. She had no obvious medical illness and no history of surgery. Pelvic examination revealed ahard palpablemass in themidline of the pelvis. Transvaginal ultrasound revealed multiple intramural leiomyomata, including 3measuring 8.0×7.5 cm, 6.8×5.1 cm, and 6.0×5.8 cm. At laparotomy, the uterus was found to be enlarged to a size corresponding to 12 gestational weeks. Myomectomy was uneventful. Fragments weighing 195 g in total were obtained from the myomectomy. They were whitish-gray, solid, and firm tissue masses with whorled and rubbery cut surfaces. Four samples from these fragments were taken for microscopic analysis, which revealed diffuse moderate-to-severe atypia; however, the mitotic rate was low (b10 mitotic figures [MF]/10 high-power field [HPF]) and necrosis was not detected (Fig. 1A). Smooth muscle tumor of uncertain malignant potential (STUMP)wasdiagnosed from3 large resectedmasses,whereas most case reports describe a single or solitary STUMP mass with combined multiple benign leiomyomata [1,2]. The clinicopathologic recommendation was for close follow-up. On follow-up examination 6 months after the initial diagnosis, transvaginal ultrasound revealed an intramural mass measuring 6×5 cm. It was suspected to be a recurrent benign leiomyoma; however, 6 months later, ultrasound revealed that the mass had increased to 8×6 cm and cystic degeneration had developed. Imaging could not rule outmalignancy; as a result, total abdominal hysterectomy was performed. On initial examination, the pathologic findings from frozen sections of the uterus were similar to the pathology of the previous STUMP, so surgical staging was not performed. On permanent pathologic examination, the mass displayed diffuse moderate nuclear atypia similar to that of the STUMP (Fig. 1B). Focal necrosis (Fig. 1C) and an infiltrative border, neither of which was present in the STUMP, were also noted. The final pathologic diagnosis was of leiomyosarcoma. Following surgery, positron emission tomography and computed tomography were performed to look for evidence of distant metastasis. The results were negative. The woman underwent postoperative adjuvant chemotherapy, receiving 3 cycles of platinum-based multiagent chemotherapy with the following intravenous regimen, in addition to continued hydration: paclitaxel (175 mg/m) on day 1; cisplatin (75 mg/m) and ifosfamide (5 g/m) on day 2; and mesna (5 g/m on day 2 and 3 g/m on day 3). The cycles were repeated every 3 weeks. After 3 years of follow-up, the womanwas disease free and asymptomatic. Smooth muscle tumor of uncertain malignant potential is a rare variantuterine smoothmuscle tumorwithborderline features that reflect neither the benign leiomyoma nor the malignant leiomyosarcoma. The diagnosis of benign, borderline, or malignant uterine smoothmuscle tumors depends on histologic findings such as the number of MF and nuclear atypia, in addition to the presence of tumor cell necrosis [3].Most reports have indicated that STUMP is associated with a good prognosis and that relapses occur generally after a long disease-free interval of up to several years [4,5]. Bell et al. [4] categorized STUMPs into 3 groups: atypical leiomyomata with low risk of recurrence had diffuse moderate-tosevere atypia, a mitotic rate of less than 10 MF/10 HPF, and no tumor cell necrosis; atypical leiomyomata with limited experience had focal moderate-to-severe atypia, a mitotic rate of less than 20 MF/10 HPF, and no tumor cell necrosis; and smooth muscle tumors of low malignant potential had absent-to-mild atypia, a mitotic rate of less than 10 MF/10 HPF, and tumor cell necrosis. Most patients with tumors in the first or second categories had benign clinical courses; however, 1 in 4 patients with tumors in the third category had a malignant clinical outcome, indicating that tumor cell necrosis is an important factor in determining the malignant potential of tumors from histologic findings [4]. The present case fell into the first category: atypical leiomyomata with a low risk of recurrence. However, unlike the reported prognosis, there was rapid recurrence to malignant leiomyosarcoma after conservative surgery, with necrosis and other findings of a similar pattern of atypia and MF. The reported case is perhaps unique in that, initially, there were multiple rather than solitary STUMP masses. Therefore, unless the uterus is removed in cases in which there may be multiple STUMPs, a complete evaluation of the remnant STUMP may be difficult. The possibility of underdiagnosis may be raised in the present case, although all visualized masses were enucleated completely and were not adherent to the uterus. Owing to the low incidence of STUMP, its malignant potential and standard treatment modality are not yet established. When considering uterus-preserving treatment in cases in which STUMP is diagnosed from multiple uterine masses considered to be benign myomata, meticulous pathologic examination and short-term followup are recommended.