Background

Uterine leiomyomas have received great attention in recent years; however, the exact pathogenesis of uterine leiomyoma growth is not completely uncovered. Several agents such as growth factors, cytokines, chemokines, estrogen, progesterone, and human chorionic gonadotropin (HCG) are suggested to be involved in the growth of these tumors [1, 2]. Uterine leiomyomas might be found during an ultrasound examination; however, sometimes patients refer with abdominal pain and discomfort or pregnancy-related complications, including placental abruption, retained placenta, preterm labor, or postpartum hemorrhage [1, 3].

Cotyledonoid dissecting leiomyoma, also known as Sternberg tumor, is a benign variant of leiomyoma with an unusual macroscopic appearance. It was reported for the first time in 1996 by Roth et al. [4]. Presently, only a few cases have been reported worldwide, in such a way that Jamal et al. call this tumor an uncommon form of a common disease [5]. The lesion usually shows an exophytic mass-like gross appearance of placental tissue and extends into the myometrium with dissection of myometrial fibers [6,7,8]. This gross appearance may mimic uterine malignancy [8, 9].

We report a case of cotyledonoid dissecting leiomyoma in a 55-year-old postmenopausal woman who presented with postmenopausal vaginal bleeding and underwent total abdominal hysterectomy along with bilateral salpingo-oophorectomy. This case report was written based on the reporting checklist for case report guidelines (CARE guidelines) [10], and written informed consent was obtained from the patient for publication of this case report and any accompanying images. Moreover, this study was approved by Birjand University of Medical Science’s Research Ethics Committee (approval ID: IR.BUMS.REC.1401.119).

Case presentation

A 55-year-old Iranian woman with a history of two pregnancies and two deliveries presented with postmenopausal vaginal bleeding, which began 4 months after menopause and lasted for 10 days. Laboratory tests showed moderate normochromic normocytic anemia (hemoglobin 9.8 g/dL, Mean Corpuscular Volume (MCV) 85 fl, Mean Corpuscular Hemoglobin (MCH) 27 pg, and Mean Corpuscular Hemoglobin Concentration (MCHC) 31.6 g/dL). On pelvic physical examination, a mass in the uterus was detected. The transabdominal ultrasound scan demonstrated two solid heterogeneous hypoechoic masses (141 mm × 110 mm and 81 mm × 61 mm) in the myometrium of the uterine fundus. No cystic lesion or mass was found in the adnexa. Hence, for evaluation of malignancy, the patient underwent an endometrial pipelle biopsy, which was normal. Finally, the patient underwent a total abdominal hysterectomy and bilateral salpingo-oophorectomy, and macroscopic and microscopic evaluations were performed.

Pathologic findings

Macroscopic

One tumoral tissue (140 mm × 120 mm × 120 mm) in the uterine fundus was found, originating from the myometrium, compressing the endometrial cavity. The tumor (measuring 35 mm × 30 mm × 30 mm) showed a multinodular appearance, which dissects the myometrium to the serosal surface and makes grape-like projections on the serosal surface of the uterine fundus (Fig. 1).

Fig. 1
figure 1

A Gross image of cotyledonoid dissecting leiomyoma, giving a placental appearance. B Cut section with multiple tan-white nodules. Variable-sized tan-white nodules dissect the myometrium to the serosal surface and make grape-like projections on the serosal surface of the uterine fundus

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The boundary between the tumor and the myometrium was unclear. No necrosis was found in the tumor. One polypoid lesion (15 mm × 10 mm × 20 mm) in the endometrial cavity was also seen. Two separated small intramural leiomyomas (15 and 10 mm) were seen in the left uterus wall. No pathologic findings were seen in the bilateral adnexa.

Histologic

The tumor showed multiple nodules composed of smooth muscle fibers arranged in fascicular and whorling structures. Cells showed eosinophilic cytoplasm and bland-looking plump nuclei. A significant stromal edema was seen. No necrosis was noted in the tumor. An intravascular growth was absent (Fig. 2). Mitotic activity was low (Ki-67 index < 5%) (Fig. 3). According to the above description, we came into the conclusion that the tumor was a cotyledonoid dissecting leiomyoma. An additional pathologic finding, in this case, was an endometrial polyp.

Fig. 2
figure 2

Microscopic images of dissecting nodules [hematoxylin and eosin (H&E) stain, magnification size: A ×100, B ×400]. The nodules are composed of benign-looking spindle cells without atypia, necrosis, or increased mitosis

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Fig. 3
figure 3

Immunohistochemical staining of cotyledonoid dissecting leiomyoma cells. Ki-67 staining slides show low mitotic activity (Ki-67 index < 5%)

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It should be noted that in 1-year follow-up period, no recurrence or any other related complications were found in the patient.

Discussion

Leiomyoma is the most common benign neoplasm of the female genital system. Cotyledonoid dissecting leiomyoma is a rare variant of leiomyoma with unusual macroscopic appearance, which may mimic malignancy due to its growth pattern in the uterus wall. This tumor was first reported in 1996 by Roth et al. [4]. To the best of our knowledge, this is the first report of cotyledonoid dissecting leiomyoma from Iran.

The age range of reported cases was 23–73 years [11]. Clinical presentations include abnormal uterine bleeding, pelvic mass, constipation, bloating, and weight gain. However, the most common presentation is abnormal uterine bleeding, which was found in our case [11].

Cotyledonoid dissecting leiomyoma has some variants:

  1. 1.

    Some reported cases of cotyledonoid dissecting leiomyoma had atypical cells; however, this microscopic finding cannot be diagnostic for malignancy without other criteria [12].

  2. 2.

    A new form of cotyledonoid dissecting leiomyoma named “cotyledonoid hydropic intravascular leiomyomatosis” is also described [13].

  3. 3.

    Another variant called “cotyledonoid leiomyoma” was described by Roth and Reed, which is similar to cotyledonoid dissecting leiomyoma, but lacks an intramural component [14].

  4. 4.

    Another author also described a variant called “intramural dissecting leiomyoma,” which lacks extrauterine placental-like component [15].

Disorganized smooth muscle fascicles as well as marked hydropic degeneration and extensive vascularity are the main key factors to diagnose cotyledonoid dissecting leiomyoma [16]. Cotyledonoid dissecting leiomyoma is a benign tumor, but its appearance is challenging for gynecologists, radiologists, and pathologists. Due to the unusual gross appearance of the tumor, one of the most important differential diagnoses is leiomyosarcoma. Classification of malignant smooth muscle tumors according to the study of Kempson and Hendrickson is based on tumor coagulation necrosis, mitotic activity (Ki-67 index), and cellular atypia [17]. According to the microscopic findings of our case (no necrosis, no cellular atypia, and low mitotic activity), leiomyosarcoma was excluded.

Table 1 provides a review of some cases of cotyledonoid dissecting leiomyoma with their ages, clinical presentations, tumor size, and tumor location. Despite the macroscopic and microscopic unusual appearance of cotyledonoid dissecting leiomyoma, no malignant behavior has been reported.

Table 1 A review of some cases of cotyledonoid dissecting leiomyoma
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Conclusion

Although the microscopic or macroscopic appearance of cotyledonoid dissecting leiomyoma might be malignant, no recurrence or aggressive behavior of this tumor has been reported until now. Therefore, the gynecologists, pathologists, and radiologists should be aware enough to recognize this rare variant of leiomyoma to prevent overtreatment. Although the gold standard treatment of this tumor in postmenopausal women is total abdominal hysterectomy and bilateral salpingo-oophorectomy, it is important to preserve fertility in young women who suffer from this lesion. Therefore, it is suggested to try to use frozen sections for better diagnosis.