Vulvar Leiomyoma in a young woman: A case report of a rare benign soft tissue tumor from Woldia,Ethiopia

Introduction

Leiomyomas are benign tumors arising from smooth muscle tissue, most commonly found in the uterus. However, when these tumors occur outside the uterus, they are referred to as extra uterine leiomyoma’s and are considered rare. Among these, vulvar leiomyomas are extremely uncommon, representing less than 0.03% of all gynecological neoplasms and approximately 0.07% of all benign soft tissue tumors in women.^1,2 These tumors are thought to originate from smooth muscle cells in the walls of blood vessels, erectile tissue, the round ligament, or remnants of the dartos muscle in the labia majora. ³

Due to their rarity, vulvar leiomyomas often pose a diagnostic challenge. Clinically, they can be mistaken for Bartholin’s gland cysts, epidermoid cysts, or other benign mesenchymal tumors such as lipomas or fibromas.^4,5 They typically present as slow-growing, firm, well-circumscribed masses, and while many are asymptomatic, some patients may report discomfort, dyspareunia, or local pressure effects depending on the size and location.^5–8

Diagnostic imaging, such as ultrasound or MRI, may assist in characterizing the mass, but definitive diagnosis is only possible through histopathological examination, which identifies the classical features of bland, spindle-shaped smooth muscle cells arranged in intersecting fascicles without evidence of malignancy.^9–11

Given the potential for recurrence and rare cases of malignant transformation into leiomyosarcoma, complete surgical excision with clear margins remains the mainstay of treatment.^12,13

This case report highlights a rare presentation of vulvar leiomyoma in a 19-year-old woman and reinforces the importance of histological confirmation in the evaluation of vulvar masses.

Surgical intervention

The mass was surgically excised under spinal anesthesia with clear margins (Figures 2 and 3).OPEN IN VIEWER

Figure 2.

Intraoperative Leiomyoma. Intraoperative photograph demonstrating the vulvar mass following surgical exposure. The lesion appears well encapsulated and clearly demarcated from surrounding tissues, facilitating complete excision.

OPEN IN VIEWER

Figure 3.

Intraoperative Leiomyoma case report image in Woldia comprehensive specialized hospital, 2025. Intraoperative image showing mobilization of the vulvar mass during surgical excision at Woldia Comprehensive Specialized Hospital. The tumor demonstrates a smooth surface and firm consistency, suggestive of a benign soft-tissue lesion.

Discussion

Leiomyomas are benign neoplasms arising from smooth muscle cells and are most commonly found in the uterus. Extra uterine leiomyomas, though histologically identical, are considerably rarer and can occur in unusual sites such as the gastrointestinal tract, skin, and genitourinary tract. Among these, Vulvar leiomyomas are exceptionally rare, accounting for less than 1% of all benign Vulvar tumors.^1,2

Due to their rarity and nonspecific presentation, Vulvar leiomyomas are often misdiagnosed preoperatively. The most common clinical misdiagnosis is a Bartholin’s gland cyst, especially when the lesion is located in the posterolateral aspect of the vulva.^15,16

In this case, the 19-year-old patient presented with a slow-growing, painless, firm Vulvar mass, which is typical for benign soft tissue tumors of this type. The absence of inflammatory signs or ulceration, and the mobility of the lesion, was suggestive of a benign process. However, given that clinical features alone cannot reliably distinguish between various Vulvar masses, surgical excision and histopathological evaluation were essential.

Histologically, Vulvar leiomyomas are characterized by spindle-shaped smooth muscle cells arranged in interlacing fascicles, often accompanied by areas of hyalinization, as seen in our case. The lack of cellular atypical, necrosis and a low mitotic index are key features distinguishing benign leiomyomas from leiomyosarcomas, which carry a poorer prognosis and require more aggressive treatment.^3,17,18

Some authors propose diagnostic criteria for differentiating benign from malignant smooth muscle tumors in the vulva, based on mitotic activity, cytologic atypia, and tumor necrosis. According to Nielsen et al., a tumor may be diagnosed as a leiomyosarcomas if it shows ≥5 mitoses per 10 high-power fields, moderate-to-severe atypia, and coagulative tumor cell necrosis. If none of these features is present, the tumor is classified as a Leiomyoma.^19,20

While imaging modalities such as ultrasound and MRI can help in preoperative assessment by delineating the size, depth, and consistency of the mass, they are not diagnostic. MRI, in particular, is useful in identifying the origin and composition of soft tissue masses and can be especially helpful in large or recurrent tumors to assess local infiltration. ⁹ However, these tools were not necessary in our case due to the small size and superficial location of the mass.

Surgical excision with clear margins remains the definitive and curative treatment for Vulvar leiomyomas. Incomplete excision may result in recurrence, though this is rare in benign cases. In our patient, the mass was completely excised, and no recurrence was noted at the six-month follow-up. Given the benign nature and complete excision, long-term surveillance may not be necessary, although some authors advocate for periodic clinical follow-up.^3,16

The young age of our patient is notable, as Vulvar leiomyomas are more commonly diagnosed in women aged 30–60 years. The etiology remains unclear, but hormonal influence particularly estrogen is suspected to play a role in tumor development and growth, as seen in uterine leiomyomas. Some studies report tumor expression of estrogen and progesterone receptors, suggesting a potential hormonal dependency.^21,22 However, receptor status was not assessed in this case, which may be a limitation in evaluating recurrence risk and potential hormonal management options.

Immunohistochemical staining, including smooth muscle actin (SMA), desmin, and h-caldesmon, is often used to confirm smooth muscle origin and differentiate leiomyoma from aggressive angiomyxoma or leiomyosarcoma. Although immunohistochemistry was not performed in this case due to classical morphology, its role is well established in diagnostically challenging cases.

This case underscores the importance of considering Vulvar Leiomyoma in the differential diagnosis of Vulvar masses, especially when clinical presentation is nonspecific. It also highlights the necessity of histopathological confirmation to ensure accurate diagnosis and guide appropriate.

Conclusion

Vulvar leiomyoma, although rare, should be considered in the differential diagnosis of vulvar masses in young women. Histopathological examination is essential for definitive diagnosis, and complete surgical excision offers excellent outcomes with minimal risk of recurrence.