Rare extra-gastrointestinal stromal tumor of the vulva: a case report.

Introduction: Extragastrointestinal stromal tumors (EGISTs) are rare mesenchymal neoplasms that originate outside the gastrointestinal (GI) tract and share histologic and immunohistochemical features with gastrointestinal stromal tumors (GISTs). Occurrence in the vulva is exceptionally uncommon, with limited reports describing their clinical course and management. Recognition is critical due to potential for local recurrence and malignant behavior. Methods: We present the case of a 53-year-old woman with a history of invasive ductal carcinoma of the breast who developed a recurrent vulvar mass. Clinical evaluation, imaging, surgical excision, and pathologic evaluation with immunohistochemistry were performed. Molecular testing guided clinical management. Results: Initial excision of a 4 cm left labial mass demonstrated a spindle cell neoplasm with strong immunoreactivity for c-KIT, DOG-1, and CD34; and negative immunostaining for other markers. Next-generation sequencing showed a KIT exon 11 mutation. Surgical margins were positive, and MRI revealed a recurrent perineal lesion without metastasis. GI workup including endoscopy and colonoscopy was negative. The patient subsequently underwent radical vulvar excision with partial anal sphincter excision, followed by sphincter repair with colorectal surgery and labial flap reconstruction with plastic surgery. Pathology confirmed vulvar EGIST with spindle cell morphology and diffuse c-KIT/DOG-1 positivity. Postoperatively, the patient recovered well and was treated with adjuvant imatinib. Conclusion/implications: This case highlights the diagnostic and therapeutic challenges of vulvar EGISTs, an exceedingly rare entity that can mimic more common vulvar lesions. Comprehensive workup, wide excision with negative margins, and targeted therapy are essential. Increased awareness and reporting are needed to guide management.