Experience with Endometrial Stromal Nodules (ESNs) is limited due to less than 2% of all uterine neoplasms and the literature on these lesions is inadequate. There is only one large series of ESNs which is reported with 60 cases in 1981 [4]. Recently, Dionigi published a series of 50 cases with endometrial stromal tumors which includes only 4 ESNs [5].

ESN usually occurs at premenopausal age, but can be observed over a wide age range, such as 23 to 86 years [5]. Our case was a 46-year-old perimenopausal woman and there was no need to protect fertility.

The preoperative diagnosis of ESNs is very difficult. Patients may have abnormal bleeding, lower abdomen, or pelvic pain. However, they can sometimes be asymptomatic [5]. Our patient had lower pain and abnormal vaginal bleeding. Also, no specific medical imaging is defined for an ESN in ultrasound or MRI examination so postoperative pathology is essential for the diagnosis of an ESN. The ESN is usually misdiagnosed as uterine fibroids, interstitial ectopic pregnancy or stromal hyperplasia. These tumors are well-circumscribed, solitary, encapsulated and usually found in myometrium with a size of 1 to 22 cm and an average size of 7 cm, but may also be located across endometrium as a polypoid mass [3,4]. In this case, the transvaginal ultrasound showed a few well-circumscribed masses, the biggest of which one was 6*6cm, which might be fibroids. ESN cases are generally diagnosed preoperatively as leiomyoma and adnexal mass [6]. Our preoperative diagnosis was leiomyoma in line with the literature, but postoperative pathology confirmed the ESN. In an endometrial biopsy material, the differences between an ESN and a low grade endometrial stromal sarcoma are almost impossible unless the tumor is too small, and the borders are fully evaluated in our case endometrial biopsy was diagnosed as late proliferative endometrium.

Differantial diagnosis of endometrial stromal nodules completely depends on the histopathological findings. Multiple preparate examination and serial cut sections must be performed. These stromal nodules have expansile, non-infiltrative margins with adjacent myometrium [7]. Lymphatic and vascular invasion is absent. Immunhistochemical expression includes CD10 positivity, SMA, caldesmon and desmine negativity (or weakly positivity).

In our case, the tumor expresses diffuse CD10. Only starburst pattern showed Desmin and Caldesmon positivity. The nodule was immunonegative with desmine and caldesmon in the regions other than these starburst areas.

Although ESNs are benign tumors, hysterectomy is the gold standard for total histological examination of the uterus to rule out malignancy [8]. On the other hand, Schilder et al. published a case report involving a successful hormone therapy of the endometrial stromal nodule to maintain fertility in a young nulliparous woman [9]. As a result, local excision and hormonal therapy can be successful in women of reproductive age who want to maintain fertility. Hysteroscopy can then be used to evaluate the full myometrial interface and to monitor tumor growth [10].

In conclusion, it is not easy to diagnose the ESN preoperatively because of its similarity to cellular leiomyoma. If the postoperative result shows the ESN, the prognosis is excellent. The gold standard is to perform hysterectomy in patients diagnosed with the ESN. This rare tumor should be considered among the differential diagnoses in patients with irregular vaginal bleeding and uterine fibroma. Since there is a few ESN in the literature, lots of studies are needed, which may improve the knowledge about the preoperative diagnosis or treatment and surgery options.