Huge Subserosal Uterine Lipoleiomyoma – A Case Report and Literature Review.

Lipoleiomyoma is a rare benign variant of uterine leiomyoma, composed of an intimate admixture of adipocytes and mature smooth muscle cells, usually found in the uterine corpus and the tissue is easily recognizable on naked eye. Lipoleiomyoma represents 2.9% of all leiomyomas with an incidence of 0.03%–0.2%. They occur more in obese peri-menopausal and postmenopausal women. They may be asymptomatic or present with similar symptomatology as leiomyoma. Imaging plays a vital role in the diagnosis of benign pelvic tumors. Ultrasonography is usually the first line radiological imaging modality for diagnosis of female pelvic tumors but usually not specific in characterizing the tumour and may not be specific for the origin when the tumour is subserosal or pedunculated. Computed tomography (CT) and magnetic resonance imaging (MRI) are more specific in characterizing the fatty component and the uterine origin of the tumour. We present a case report of a solitary huge intramural uterine lipoleiomyoma manage successfully without complication.

Keywords: Leiomyoma; lipoleiomyoma; age; perimenopause; pelvic tumours.

Leiomyomas are common tumors of the uterus common in the reproductive age group originating from the smooth muscle layer of the uterine wall [1]. These benign monoclonal neoplasms are the commonest gynaecological tumour arising from smooth muscle cell in women of reproductive age [1].

Lipoleiomyomas are benign variants of leiomyomas occurring due to the fatty meta-morphogenesis of their smooth muscle cells [2‑4]. It has an incidence of 0.03%–0.2% and represents 2.9% of all leiomyomas [1]. Although most leiomyo­mas are seen in women of reproductive age, lipoleiomyomas are more common in older women. Unlike uterine fibroids that are described as benign monoclonal tumours arising from smooth muscle cells of the uterus [5], lipoleiomyomas are admixture of smooth muscles, fibrous tissue and fat cells in variable amount, separated by thin fibrous tissue [5, 6]. Accurate and proper choice of imaging to establish diagnosis can prevent unnecessary invasive intervention especially when asymptomatic with a heightened index of suspicion for other conditions associated with hyper-estrogenism which may co-exist [1].

A 29-year-old Para 1 lady presented with lower abdominal mass of six-year duration. There was no associated pain, infertility, or menstrual abnormalities. She was earlier diagnosed of suspected uterine fibroid during her last pregnancy about two years ago. The pregnancy was complicated with several episodes of abdominal pain; however, she carried the pregnancy to term and had an elective caesarean section. On examination, her uterine size was 24weeks, with firm nodular, mobile abdominopelvic mass.

She was requested to abdominopelvic MRI which revealed a huge solitary anterior intramural mass of 204 x 160mm with features suspicious of lipoleiomyoma. She had exploratory laparotomy and excision of the lesion which was found to be a huge solitary antero-fundal intramural fatty mass with fibrous partitions and convoluted surface having the gross resemblance of the brain covered by poorly vascularised capsular covering. The mass measured 20 x 16cm Histology confirmed a diagnosis of lipoleiomyoma.

Figure 1. Lipoleiomyoma seen intra-operatively

Figure 2. Excised lipoleiomyoma

-courtesy Dr Nwogu

Lipomatous uterine tumors are uncommon benign tumours. They can generally be subdivided into: Pure lipomas (composed of encapsulated mature fat cells), mixed lipomas or lipomas with mesodermal components (Lipoleiomyoma, Fibromyolipoma, Angiomyolipoma), Liposarcoma (the very rare and malignant form) [7].

Uterine lipoleiomyomas are rare benign tumors with an incidence of about 0.03%–0.2%3-9. Fatty metamorphosis of smooth muscle cells of leiomyoma into adipose tissue is the accepted aetiological factor rather than fatty degeneration [2-6]. Other theories suggest that these tumors may arise due to misplaced embryonic fat cells, perivascular extension of peritoneal or retroperitoneal fat, inclusion of fat cells into the uterine wall during surgery, metaplasia of smooth muscle or connective tissue cells into fat cells, fatty infiltration of the connective tissue, or due to lipocytic differentiation of primi­tive connective or mesenchymal totipotent cell [1, 3].

Malignant de­generation or transformation in uterine lipoleiomyoma is extremely rare, although it has been reported [8].

They are often seen in peri-menopausal or postmenopausal women [7, 9]. Most of the patients are asymptomatic [7] or present with signs and symptoms are similar to those caused by leiomyomas of the same size and location of the lesion such as abdominal pain, palpable abdominal mass, hypermenorrhoea, constipation, increased frequency of urine and urinary incontinence [6]. They present usually as solitary enlarged masses of varying sizes with the common site of occurrence in the corpus of the uterus and are usually intramural and may be Subserosal. Lipoleiomyomas can be found anywhere in the uterus or cervix, broad ligament, retroperitoneum, and ovary [11]. The average size of the lesion is usually between 5 and 10 cm. Concomitant uterine leiomyoma is commonly found, although this is not pres­ent in all patients [8].

Adipocyte differentiation in the myometrium has been observed under certain environmental conditions of the uterus such as preeclampsia and hyper estrogenic states [1].

Alteration in the lipid metabolism with menopause may be a factor in its development [6, 7].

Imaging is vital in determining the intrauterine location and fatty nature of lipoleiomyomas and to differentiate uterine lipoleiomyomas from cystic ovarian teratomas which is a common differential when lipoleiomyoma is Subserosal usually needing surgical excision, whereas lipoleiomyomas may not require intervention

Imaging by Ultrasonography commonly shows a well‑defined hyperechoic mass partially encased by a hypoechoic rind. The rind is thought to represent a layer or strip of myometrium surrounding the

fatty component. Tissue vascularity is often poor [7]. The presence of a sonographic halo around the mass representing compressed myometrial tissues around the margins of the tumor is typically seen in lipoleiomyoma. However, ul­trasound findings are not specific to the diagnosis [8]. A transvaginal ultrasonography may help rule out fat containing adnexal mass such as ovarian cystic teratoma seen on transabdominal scan by identifying its adnexal origin when small but may present a diagnostic dilemma when the mass is large where identifying organ of origin becomes difficult.

CT findings are more specific since it can clearly demonstrate fat component of the lesion. It usually shows more specific findings, revealing a well-circumscribed or well marginated mass with predominantly fatty component arising from the uterus [7,9]. It shows the fatty tissue with interspersed non fatty within the uterine mass. Although CT is more specific than ultrasound, it has its drawbacks, including inabil­ity to illustrate detailed uterine anatomy and confusion between an adnexal mass and a lesion arising from the uterus if the tumor is exophytic or pedunculated [8].

MRI is the imaging modality of choice and is the most useful modality in demonstrating the organ of origin. It is also the best imaging modality for diagnosing a lipomatous tumor [8]. The lipomatous nature of the lesion is suggested by a well circumcised mass which is hyperintense on T1-weighted images with a peripheral hypointense rim. It also appears hyperintense on T2-weighted images. The fatty components may be confirmed using fat-suppression techniques or sequence which demonstrates decrease in signal intensity in fat components of the lesion [6] and or chemical shift artifacts in the lesion [12].

Tissue characterization by MRI is superior to CT [13, 14]. The septa within the lesion can be seen on T1-weighted im­ages [13, 14]. MRI sometimes shows a peripheral low signal intensity rim which corresponds to a thin fibrous pseudo capsule which is not demonstrated on CT scan [13, 14].

MRI can also help differentiate uterine lipoleiomyoma from pure lipoma [13, 14]. Pure lipoma shows absence of non-adipose components, the presence of a homogeneous mass with a large amount of fat and signal decrease in the whole lesion on fat-saturated images on MRI.  Lipoleiomyoma on the other hand shows heteroge­neous signal intensity with adipose and non-adipose soft tissue content and decrease in signal limited to part of the lesion on fat-saturated images [14].

Differential diagnosis of lipoid pelvic tumors in the female pelvis include; benign cys­tic ovarian teratoma, malignant degeneration of a benign cystic ovarian teratoma, benign pelvic lipoma, benign non-teratomatous lipomatous ovarian tumor, fatty lymphadenopathy, degeneration of leiomyoma, extra-adrenal myelolipoma in pelvis, retroperitoneal cystic hamartoma, and well‑differentiated liposarcoma [7-15]. The most common of the differentials is benign cystic ovarian teratoma, which requires surgical excision unlike lipoleiomyoma which is a benign tumor and can be managed conservatively when asymptomatic [6].

Incidentally discovered asymptomatic uterine lipoleiomyoma can be managed conservatively and as such, it is important to rule out other fat‑containing pelvic tumors thereby prevent unnecessary surgical intervention [5]. Size and symptoms determine treatment. In symptomatic patients with large masses, medical management with analgesics and hormone regulation pills usually suffice while surgical options include myomectomy, hysterectomy, tumor embolization, myolysis and radiofrequency ablation [6-15].

Uterine lipoleiomyomas are benign uterine lesions and a specific type of leiomyoma with a considerable amount of adipocytes accounting for 2.9% of be­nign uterine leiomyomas. Its symptomatology may mimic leiomyomas and diagnosis may be difficult on imaging if found extrauterine. Fatty component of lipoleiomyomas is more specific on CT and MRI compared to ultrasonography. MRI having higher sensitivity, and specificity to fat and tissue characterization, is the modality of choice for confirmation of diagnosis. Patients with lipoleiomyomas are more likely to have many estrogen-related conditions including endometriosis, adenomyosis, polyps, endometrial hyperplasia, and gynaecologic malignancies. Small asymptomatic lipoleiomyoma do not require surgical management.

Lipoleiomyomas has a favorable outcome on follow up and histopathological evaluation must be performed on excised tissues to distinguish it from its differentials.

We are grateful to all the nurses, medical record staff, radiologists and theatre staff in our facility who contributed immensely to the patient care.

Authors contributions

All authors contributed to the conception of the case report. Literature search and review were performed by OA, NM, AK, OS. The first draft of the case report was written by NM and critically reviewed by OA and AK. All authors commented and reviewed the final draft of the case report.

Data availability

Not applicable for a case report.

Ethical approval

Not applicable for a case report.

Declaration of patient’s consent to use their images/photos

The authors certify that they have obtained all appropriate patient consent forms. In the form, she has given her consent for her images/photographs and other clinical information to be reported in the journal. She understands that her name and initials will not be published, and due efforts will be made to conceal her identity.

Declaration of Helsinki

Authors declare that the study was conducted in accordance with the ethical principles of the Helsinki Declaration.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Disclaimer (Artificial Intelligence)

We hereby declare that no generative AI technologies such as Large Language Models (ChatGPT, COPILOT, etc.) and text-to-image generators have been used during writing or editing of manuscripts.