Basosquamous Carcinoma Arising from the Vulva: A Case Report

Basal cell carcinoma (BCC) is a common skin cancer; however, it accounts for less than 1% of all BCC cases in the vulva [1]. Basosquamous cell carcinoma (BSC) is a metatypical form of BCC characterized by a combination of histologic features from both BCC and squamous cell carcinoma (SCC). BSC is rare in the vulva [2]. The etiology of BCC commonly includes factors related to ultraviolet exposure, while hypotheses for vulvar localization have implicated syphilis, chronic irritation or infection, trauma, arsenicals, and radiotherapy [3]. Clinical examination alone cannot differentiate BSC from BCC; definitive diagnosis relies on histology often aided by immunohistochemistry. We report the case of a woman presenting with BSC of the vulva at the age of 59. To the best of our knowledge, this is the sixth reported case.

A 59-year-old woman, gravida 3 para 2, with a history of hypertension, type 2 diabetes, dyslipidemia, and hyperuricemia, was referred to our cancer institute for a 3-year history of a slow-growing and painful vulvar lesion.

Physical examination revealed a 35 mm nodular, ulcerating, and non-pigmented lesion on the anterior part of the right edge of the labia majora that did not extend to the urethral meatus. No lichen lesions were observed. The cervico-vaginal examination showed no abnormalities, and there were no palpable inguinal lymph nodes. A biopsy of the vulvar lesion was performed, confirming BSC. A cervical smear was also conducted and showed no abnormalities. Staging assessments revealed no evidence of metastasis.

The patient underwent a partial radical vulvectomy with sentinel lymph node biopsy from the right groin. The macroscopic examination revealed a 3-cm nodular, tender, and non-pigmented lesion arising from the labia majora (Fig. 1). Microscopically, the epidermal carcinomatous proliferation organized into well-defined lobules that ulcerated the surface and infiltrated the reticular dermis. The tumor cells were basaloid with nuclei exhibiting a palisading arrangement at the periphery of the lobules. Mitoses were rare, and no lymphovascular invasion was identified. In some areas, squamous differentiation was observed within these lobules, with tumor cells forming clusters surrounded by layers of keratin. The histological examination revealed distinct features characteristic of BSC, including prominent basaloid cell islands and areas demonstrating significant squamous differentiation. These features were sufficiently evident to support a definitive diagnosis without immunohistochemical analysis (Fig. 2).

The excision margins were tumor-free. Six lymph nodes were identified in the lymph node biopsy sample; all were negative for metastases. The Responsible Clinical Panel (RCP) has concluded that no additional adjuvant therapy is necessary. The patient has been undergoing regular surveillance for 6 months with no signs of recurrence.

Vulvar cancer represents only 3%–5% of female gynecological cancers and is predominantly of squamous cell type (90%–92% of cases) [4]. BSC is a non-melanoma skin neoplasm first described in 1894 by Beadles [5‒7]. The majority of BSC cases (80%) are located in the head and neck region, with only 5 cases involving the vulva documented in literature: 3 cases described by Stewart et al. in 1960, 1 case reported by Kimball et al. in 2006, and another by Hughes et al. in 2021 [8‒10].

Clinically, BSC does not present any particularities; diagnosis is commonly made through biopsy [11]. It often manifests as an indolent ulcerated lesion with or without loco-regional lymphadenopathy.

Histology plays a crucial role in confirming the diagnosis since this tumor type contains both basal cell and squamous cell components with a transition zone between them. Immunohistochemical studies are positive for Ber-EP4, AE1, and AE3 markers in the basal cell area and AE1, AE3, and CAM5.2 markers in the squamous area. The transition zone predominantly shows reduced marking of Ber-EP4 correlating with the transition from basal to squamous zones aiding differentiation from other diagnoses such as collision tumors [12, 13].

The prognosis for BSC is more serious compared to BCC due to its metastatic potential; recent studies indicate that, while BSC recurs less frequently than skin SCCs overall, its metastatic potential remains significant. Bowman et al. reported a prevalence of metastatic disease at the presentation of 7.4% for BSC compared to less than 0.1% for BCC and 0.87% for SCC; additionally, BSC exhibits local aggressiveness comparable to pure SCC and BCC [14‒16].

In vulvar carcinoma specifically, various studies investigate multiple biological markers as prognostic factors; markers such as p63, Ber-EP4, and EMA can provide insights into biological behavior and treatment response in vulvar cancers specifically [5, 17, 18]. Because of its rarity, there is no consensus on managing both skin and vulvar BSC; however, surgery remains first-line treatment. For skin BSC, authors recommend wider excision margins than those typically used for BCC to achieve better disease control [5, 16]. Sentinel lymph node biopsy is recommended by certain authors; however, there are insufficient data in the literature to assess its benefits [5]. Radiotherapy can be indicated if surgical treatment is not feasible initially or in case of positive surgical margins without the possibility of re-resection [5].

Chemotherapy is restricted to locally advanced forms; immunotherapy may be discussed within multidisciplinary teams for patients who have exhausted other options [5]. The patient’s clinical presentation and the predominant histological features, BCC or SCC, are important factors in this decision. Additionally, the use of immune checkpoint inhibitors has gained traction in treating various skin cancers, including BSC, especially for patients who have exhausted other treatment options [19].

BSC represents a rare entity within skin cancers in the vulvar region; this case report highlights the importance of accurate histological diagnosis essential for differentiating BSC from other malignancies such as BCC and SCC. As BSC exhibits more aggressive behavior compared to typical BCC, understanding its prognosis and treatment options is vital. Current treatment strategies primarily involve surgical excision with considerations for wider margins in certain cases while emerging therapies such as immunotherapy may provide additional options for advanced or recurrent disease. Future research should focus on establishing standardized management protocols while exploring novel therapeutic agents’ efficacy in improving patient outcomes; given its rarity collaboration among multidisciplinary teams remains crucial for optimizing care tailored to patients’ specific needs. This case adds to the limited literature on vulvar BSC emphasizing the need for continued investigation into its biological behavior therapeutic strategies.

A timeline summarizing key events related to this patient’s diagnosis and treatment has been included as Figure 3 for enhanced readability.

This case study was reviewed and approved by the Local Ethic Committee of Salah Azaiez Institute, Tunis, Tunisia, on May 22, 2024, Approval No. ISA/2024/13. Written informed consent was obtained from the patient for publication of this case report and any accompanying images. The CARE Checklist has been completed by the authors for this case report, attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000541967).

The authors have no conflict of interest to report.

The authors received no financial support for the research, authorship, and/or publication of this article.

Turki Haykal and Ghazouani Ayoub contributed to the collection of patient data. Saadallah Fatma, Zemni Ines, Mansouri Houyem, and Ben Diab Tarek collaborated on the literature search related to the manuscript and the writing of the manuscript. Sahraoui Ghada was responsible for photographing surgical specimens, capturing images with the microscope, and describing the various figures.

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.