Primary ovarian leiomyoma: an unlikely differential diagnosis of adnex

Authors

Abstract

Introduction Primary ovarian leiomyoma is a rare benign ovarian tumor seen in women aged 20 to 65 years. It is generally asymptomatic and is often incidentally diagnosed during pelvic imaging or after pathological examination following surgery.
Case Presentation A 47-year-old patient with secondary infertility presented to the hospital with complaints of abnormal uterine bleeding and abdominal pain. Imaging suggested a diagnosis consistent with thecoma/fibroma. During the total abdominal hysterectomy and bilateral salpingo-oophorectomy surgery, macroscopic and microscopic examination of the specimen sent for pathological evaluation led to the diagnosis of primary ovarian leiomyoma.
Conclusion This case highlights the importance of considering paraovarian and intraovarian leiomyomas in the differential diagnosis of pelvic masses. Preoperative imaging, including high-resolution ultrasound (US) and computed tomography (CT), plays a critical role in the initial evaluation of these masses, while laparotomy and histopathological examination are necessary for definitive diagnosis and treatment.

Keywords

Introduction

Primary ovarian leiomyoma is a rare benign ovarian tumor seen in women aged 20 to 65 years. It is generally asymptomatic and is often incidentally diagnosed during pelvic imaging or after pathological examination following surgery. We present a case of a patient with abnormal uterine bleeding, abdominal pain radiating to the lumbar region, and secondary amenorrhea, where imaging suggested a dominant diagnosis of thecoma or fibroma, but the final diagnosis was primary ovarian leiomyoma. This case highlights the potential for misdiagnosis of pedunculated uterine leiomyoma, ovarian, and paraovarian fibromas/fibrothecomas. In ovarian leiomyomas, determining the exact location through ultrasound (USG) or computed tomography (CT) is difficult, and the location can only be determined through operative and histopathological examination ¹.

Case Presentation

The patient is a 47-year-old female who presented to our hospital with abnormal uterine bleeding, lower abdominal pain radiating to the back, and discharge. Her gravida is 3, and her parity is 2. She has a history of normal vaginal deliveries and one abortion. Other than that, her surgical history includes a dilation and curettage for an endometrial polyp, an iliolingual/genitofemoral/iliohypogastric nerve block for lower back pain due to bulging in 2022, and the use and removal of an intrauterine device (IUD). The patient has a history of irregular menstruation and secondary amenorrhea. She is on vitamin B12 supplementation and antihypertensive medication. She does not use oral contraceptives, estrogen supplements, or beta-adrenergic bronchodilators. Her Ca125, CEA, and Ca19-9 levels were found to be normal. On transvaginal ultrasound and magnetic resonance imaging (MRI), a solid mass was observed in the right ovary. In the abdominal MRI taken 10 months ago, the size of the right ovary was increased, measuring 60x30 mm. A 32x30 mm T2A hypointense nodular lesion was observed in the right ovary. Minimal free fluid was observed around the right ovary. The lesion is located near the uterus. The pelvic mass was not attached to the uterus. It did not show contrast enhancement. In the differential diagnosis, ovarian lesions (thecoma, fibroma) were considered, and though less likely, a pedunculated fibroid was also considered. Minimal free fluid was observed around the right ovary. Due to the presence of multiple fibroids and related complaints, a total abdominal hysterectomy with bilateral salpingo-oophorectomy was performed. A specimen was separately sent to us, consisting of a 4.8x4.6x4.5 cm right fallopian tube with a fibroid and paratubal cyst and a 7x4.3x3.2 cm ovary adjacent to it. The specimen also included a 7x1x0.6 cm left fallopian tube and a 7x3x1.8 cm left ovary. The cervical opening measured 2 cm in diameter, the intercornual distance was 4.5 cm, the anteroposterior diameter was 5.2 cm, and the superior-inferior diameter was 15.3 cm. The total abdominal hysterectomy and bilateral salpingo-oophorectomy specimen also included the following measurements: the endocervical canal was 3.2 cm, the endometrium was 0.2 cm, and the myometrium was 5.2 cm. Coronal sections showed more than ten myomatous lesions with nodular features, ranging in size from 0.1 cm to 3.8 cm,
without capsules (Figure 1). Nabothian cysts were observed on the cervix. A 4 cm mass with A myomatous appearance was seen on the right ovary’s cut surface. The right ovary also showed subcapsular cysts, corpus luteum, and corpus albicans. Both fallopian tubes had a hemorrhagic appearance, and paratubal cysts were present around the tubes. The tumor was macroscopically located intraovarian, distinctly separated from the uterus, and showed no adhesions or infiltration into surrounding tissues. Histopathologically, the mass lesion exhibited the classic features of leiomyoma (a round, unencapsulated tumor formed by a proliferation of spindle-shaped cells with intersecting morphologies). No atypical cells, pleomorphism, or necrosis were observed in the tumor (Figure 2). In the histochemical study, using PAS staining, suspicious nodular lesions were found to be located intramurally and intraovarian, with an intralesional mitotic rate of 1 per high-power field (Figure 2). Histological examination also revealed that the tumor primarily originated in the ovary (Figure 3). Therefore, based on the histopathological findings, the tumor was diagnosed as a primary ovarian leiomyoma.

Discussion

Pelvic masses in women are a common clinical and radiological problem. Although the diagnosis is often made through physical examination, these lesions are usually further evaluated using radiological methods such as ultrasound (US) or computed tomography (CT). In most cases, these masses are associated with uterine adnexal structures, and the majority are seen as ovarian masses. The ovaries and fallopian tubes may appear normal, but masses originating from the paraovarian and paratubal regions or from ligaments and related structures have also been reported. These can result from various pathological processes. Sometimes, pedunculated subserous (exophytic) uterine leiomyomas can lose their connection to the uterus due to necrosis or torsion and subsequently attach to another pelvic structure, forming parasitic leiomyomas ². These parauterine leiomyomas are quite rare, with a prevalence of 2.4% (22/928) reported in one study. They are typically located in the paracornual area, posterior or superior to the point of attachment of the round ligament of the uterus, or in the lateral and posterolateral parametrium, with 6/22 cases found in the perisalpinx, extending to the middle ampullary region ³.
Ovarian leiomyomas (primary ovarian leiomyomas) are rare solid tumors of the ovary, constituting 0.5–1% of benign ovarian tumors. Ovarian leiomyomas are usually unilateral and typically smaller than 3 cm in diameter ⁴. Our case was 32x30 mm. About 80% of cases occur in premenopausal women, unlike our case. These tumors are usually asymptomatic and are discovered incidentally, or, as in our case, they may present with lower abdominal pain and menorrhagia ⁵. In contrast, large ovarian leiomyomas may present with symptoms such as hydrothorax, hydronephrosis, ascites, or a slight elevation of tumor markers (CA 125). The definitive diagnosis of these lesions is difficult preoperatively because there are no pathognomonic imaging findings or symptoms. On ultrasound, ovarian leiomyomas appear isoechoic with the myometrium, making it difficult to differentiate them from pedunculated uterine leiomyomas or other solid ovarian tumors. In our case, the differential diagnosis leaned more towards thecoma or fibroma ⁴. MRI can sometimes assist in the diagnosis of ambiguous pelvic masses, and in our case, it showed a well-defined solid tumor in the pelvis with low signal intensity on both T1 and T2-weighted images. The tumor is often diagnosed following an oophorectomy performed for a suspected solid ovarian mass, followed by histological examination. Accurate diagnosis requires identification of the tumor’s smooth muscle structure. Additionally, unilateral leiomyomas are more dominant, and bilateral ovarian leiomyomas have been reported in pediatric and young adult patients ⁶. Consistent with the literature, our patient was 47 years old and had unilateral ovarian leiomyoma. Extrapelvic leiomyomas are associated with a history of hysterectomy or morcellated myomectomy ¹. Our patient also had a history of previous intrapelvic surgical procedures. Furthermore, ovarian leiomyomas often occur in conjunction with uterine leiomyomas. This finding suggests that both lesions may share a similar etiological background in sensitive patients ⁷.
Large parauterine tumors can be distinguished from intramural leiomyomas with parauterine extension by three criteria: (a) they should not be covered by the perimetrium externally, and this perimetrium should not show continuity with the perimetrium covering the adjacent uterus, (b) their juxtauterine borders should be able to separate slowly from the uterus, and (c) histologically, there should be no direct continuity between the tumor and the outer myometrium ³.
Ovarian leiomyomas, apart from being associated with uterine leiomyomas, may also have a secondary origin. For example, many patients with primary ovarian leiomyomas in the literature are nulligravid, suggesting that estrogen may play a role in the development of these lesions. Our patient, however, had three pregnancies, which is inconsistent with the literature, but she had a history of secondary amenorrhea. Another possible mechanism suggests that the tumor may originate from abnormal ovarian tissue during development ⁴. Histologically, our case showed a tumor that developed from ovarian tissue containing follicles and inclusion cysts. Other proposed mechanisms include the tumor originating from smooth muscle cells in the hilus of the ovary, smooth muscle cells in the ovarian cortical stroma, or undifferentiated germ cells. Additionally, cortical smooth muscle metaplasia has been implicated, and it is also suggested that the tumor may originate from the corpus luteum or ovarian connective tissue ⁴. In a paper by Sujata S. Kumbhar and colleagues, tubal uterine leiomyomas have been reported to arise from muscularis of the fallopian tube or the blood vessels supplying the fallopian tube ⁸.
Microscopically, these tumors are composed of tightly woven clusters of fusiform cells exhibiting smooth muscle cell staining characteristics. The cells show elongated cytoplasmic fibrils and cigar-shaped vesicular nuclei. Interstitial collagen is found to be denser in postmenopausal cases. The strong and widespread positive staining for SMA, which is characteristic for leiomyomas, is used to identify the smooth muscle origin in ovarian leiomyomas. Thecoma should also be considered in the differential diagnosis, but it does not show SMA staining ³. Ovarian leiomyomas should also be differentiated from leiomyosarcomas, for which mitotic count, necrosis, and cytological atypia are distinguishing features. In our case, none of these criteria were observed ³.

Limitations

The fact that the number of cases is odd is within the limits of our study.

Conclusion

This case highlights the importance of considering paraovarian and intraovarian leiomyomas in the differential diagnosis of pelvic masses. Preoperative imaging, including high-resolution US and CT, plays a critical role in the initial evaluation of these masses, while laparotomy and histopathological examination are necessary for definitive diagnosis and treatment. This rare tumor of the ovary should be considered in the preoperative diagnosis and differential diagnosis of solid ovarian masses.

Declarations

References

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About This Article

Received:

January 10, 2025

Accepted:

May 26, 2025

Published Online:

July 9, 2025