腹壁の低異型紡錘形細胞腫瘍の稀な提示

Spindle cell neoplasms are morphologically distinct sets of mesenchymal tumors characterized by elongated, spindle-shaped cells arranged in fascicles. They may be benign or malignant and can arise in various anatomical locations. Their variable histological pattern and non-specific clinical features make the diagnosis difficult, particularly when they occur in rare sites such as the anterior abdominal wall. We present a case of a 50-year-old male patient who presented with a progressively enlarging right lower abdominal mass over two years, recently becoming painful and ulcerated with purulent discharge. He had a history of a similar lesion over the right leg 20 years prior, which was excised and suspected to be an implantation dermoid. Examination revealed a 10 x 15 cm pedunculated, firm-to-hard, bosselated mass in the right lower anterior abdominal wall without regional lymphadenopathy. CT imaging demonstrated a multilobulated, heterogeneously enhancing soft tissue lesion in the subcutaneous plane (8.9 × 5.2 × 9.0 cm), without intra-abdominal extension and small umbilical hernia. Biopsy revealed a low-grade spindle cell neoplasm. Wide local excision with hernia repair was performed successfully. Histopathology confirmed the diagnosis, and the patient remains recurrence-free on follow-up.  Spindle cell neoplasms at uncommon sites, such as the anterior abdominal wall, may clinically mimic benign lesions, making diagnosis challenging. Imaging may be misleading, highlighting the importance of the tissue biopsy for definitive diagnosis. Early histopathological confirmation and complete surgical excision are critical for optimal outcomes in rare spindle cell neoplasms.