Vulvar leiomyoma in a postmenopausal woman

Abstract

Leiomyomas of the uterus are the most common benign tumours of women in the reproductive age group, affecting up to 40%–50% of women older than 35. In postmenopausal women, the incidence is much lower with an estimated incidence of 1%–2% in women in the 60–80 years old age group. Vulvar leiomyomas are much rarer than their uterine counterparts, accounting for only 0.03% of all gynaecological neoplasms and 0.07% of all vulvar tumours. These tumours are well-circumscribed, painless, solitary growths that affect females of all ages. Given the presentation and rarity of vulvar leiomyomas, they are often misdiagnosed as a Bartholin gland cyst, abscess or even cancer preoperatively. We present a case of a woman in her 70s with a 1.5 cm firm mass that was palpated on the left lower vaginal side wall and was initially suspected to be a Bartholin gland cyst or abscess. Initial treatment included antibiotics and an incision and drainage. Two weeks later, the mass had grown to 3 cm in size. Wide excisional biopsy revealed the mass to be a vulvar leiomyoma.

Background

The vulva is the external portion of the female lower genitourinary tract consisting of structures including labia minora, labia majora, vestibular bulbs and Bartholin glands. Leiomyomas are well-circumscribed, benign soft-tissue tumours of mesenchymal origin. Located within the uterus, leiomyomas, commonly referred to as fibroids, are tumours that affect 40%–50% of women older than age 35 who are in the reproductive age group but only 1%–2% of women in the 60–80 years old age group.¹ Vulvar leiomyomas are much rarer, accounting for only 0.03% of all gynaecological neoplasms and 0.07% of all vulvar tumours.² Vulvar leiomyomas arise from the smooth muscle in the round ligament, erectile tissue and dartos muscle.² Histologically, these tumours typically demonstrate bland spindle-shaped cells.³ The affected age range is from 15 to 73 years with a mean of 41 years.^{2 4} These tumours present a diagnostic challenge as they are usually misdiagnosed as a Bartholin gland cyst, abscess or even cancer preoperatively.

Case presentation

A G3P2012 postmenopausal woman in her 70s presented to the clinic with primary concerns of a 3-month history of a newly developing vaginal lump on the left vulva and burning in the clitoral region. The mass was tender to palpation without radiation of the pain, and it was first noted during twice weekly application of vaginal oestrogen for the treatment of vaginal atrophy and genitourinary symptoms of menopause. She had been using topical oestrogen intermittently for the previous 8 years. She was uncertain of what year she had started oral oestrogen therapy for the symptomatic management of menopause but had stopped around 15 years prior. She restarted oral oestrogen in about 7 years ago to treat her vaginal atrophy and genitourinary symptoms of menopause. On examination, a 1.5 cm firm mass was palpated on the left lower vaginal side wall, just proximal to the introitus, concerning a Bartholin gland cyst or abscess. An incision and drainage were attempted in clinic. An incision was made with minimal drainage and scant bleeding noted. The area on palpation was noted to be woody without evidence of loculation. She was treated with sulfamethoxazole–trimethoprim 800–160 mg tablets two times a day for 10 days.

The patient presented to the clinic 2 weeks after the initial presentation for follow-up. During this time, the mass of concern had increased in size from her previous visit and was now palpated to be 3 cm in size. The decision was made to proceed with definitive surgical management with excision and possible marsupialisation in the operating room.

The surgery was performed with a preoperative differential diagnosis including a Bartholin gland cyst, abscess or malignant process of the vulva. During excision, the mass was noted to be firm and well defined, with a white glossy surface. The lesion was removed in its entirety without complication. On gross examination of the mass as seen in figure 1, tissue was noted to be 3×4 cm in size and firm without cystic components. Sectioning revealed a glossy to whorled cut surface. Histopathological examination of the tissue revealed benign smooth muscle consistent with leiomyoma and showed intersecting fascicles of bland spindled cells with uniform cigar-shaped nuclei and abundant eosinophilic cytoplasm. Rare mitoses were present without concern for malignancy in figure 2. Delicate vasculature throughout the lesion and scattered dystrophic calcifications were also observed in figure 3.

Figure 1.

Gross image of vulvar mass following excision.

Figure 2.

H&E at 40× magnification shows bland spindled cells with uniform cigar-shaped nuclei, indicative of a leiomyoma.

Figure 3.

H&E at 4× magnification showing dystrophic calcifications.

Outcome and follow-up

The patient was evaluated 2 weeks following surgery for routine postoperative care. Examination of external genitalia appeared normal with the surgical area healing well.

Discussion

Leiomyomas are benign tumours originating from smooth muscle tissue. They most commonly develop from the smooth muscle cells of the uterine myometrium, the thick muscular layer of the uterus. Since leiomyomas are simply an overgrowth of smooth muscle tissue, they have the theoretical ability to develop in nearly any location within the body; however, locations outside of the uterus are rare.

Uterine leiomyomas are the most common tumour of the pelvis in women. Leiomyomas originating in the vulva are much rarer, with only a few hundred cases found in the medical literature. Just as leiomyomas of the uterus are less common in postmenopausal women, vulvar leiomyomas are less common in postmenopausal women with only one other case report in literature to our knowledge.⁵ The patient was a woman in her 60s who was seen and treated at the Department of Gynecology, First Affiliated Hospital, Xi'an Jiaotong University (Xi'an, China). Unlike the patient in our case report, this patient had no history of hormone replacement treatment.⁵

Due in part to their rarity, leiomyomas of the vulvar region are commonly misdiagnosed in clinic as Bartholin gland cysts, fibromas or even soft-tissue sarcomas as their presentations of a vaginal lump with possible pain, redness and swelling can be very similar. On examination, vulvar leiomyomas usually present as a firm, non-tender, semimobile mass. Features that may support the diagnosis of a leiomyoma include inverted labia minora and firm consistency while an everted labia minora and cystic consistency of the swelling may support the diagnosis of a Bartholin gland cyst.⁶ Transperineal ultrasound is helpful in helping to narrow the diagnosis, and MRI can be of use in differentiating benign versus malignant masses. Leiomyomas will characteristically show as isointense to muscle on T1-weighted images with low-signal intensity seen on T2-weighted images.⁶

Treatment consists of an excisional biopsy, often after treatment options for cysts and/or abscesses (antibiotics, incision and drainage) have failed. Long-term follow-up is recommended, although recurrence is uncommon, and most excisions are curative.

Through histological evaluation, it is thought that vulvar leiomyomas may originate from smooth muscle cells within dartos, blood vessels, the round ligament or around hair follicles.^{3 4} It has been speculated that vulvar leiomyomas express oestrogen and progesterone receptors. Vulvar leiomyomas have been observed to grow with pregnancy, strengthening the hypothesis that they are driven by oestrogen and progesterone receptors.^{1 4} In addition, the decreased incidence in postmenopausal women also strengthens the theory of oestrogen dependence. The chronic use of topical and systemic oestrogen in our patient may have played a role in the development of her vulvar leiomyoma. However, there have also been case reports of postmenopausal women who have seen the growth of a vulvar leiomyoma without oestrogen or progesterone therapy.^{3 4} The dartos muscle, smooth muscles around blood vessels and hair follicles, and round ligament lack intrinsic oestrogen and progesterone positivity. Thus, further studies are needed to determine the origin of vulvar leiomyomas and the effects of hormones on vulvar leiomyomas.

Learning points.

• It is important to maintain a broad differential when approaching vulvar lesions. Although Bartholin gland cysts are more common, vulvar leiomyomas or vulvar cancer should also be considered.

• Wide excisional biopsy of a rapidly growing lesion that is unresponsive to antibiotics and incision and drainage is essential in diagnosing and treating a vulvar leiomyoma.

• Additional research needs to be completed to determine the risk factors and pathophysiology of vulvar leiomyoma.

• Although very rare, vulvar leiomyomas are possible in postmenopausal women.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).