Granular Cell Tumour of the Breast: A Rare Mimicker of Carcinoma

Granular cell tumour of the breast is an uncommon benign neoplasm that can closely mimic carcinoma on clinical examination and imaging. We describe a 60-year-old woman who presented with a painless palpable lump in the upper inner quadrant of the left breast. Mammography demonstrated an irregular mass categorised as Breast Imaging-Reporting and Data System (BIRADS) 4, and ultrasonography was BIRADS 5. Breast magnetic resonance imaging (MRI) showed a 27×20 mm irregular, spiculated, heterogeneously enhancing lesion. Ultrasound-guided core biopsy established the diagnosis of granular cell tumour. The patient underwent breast-conserving wide local excision, and final histopathology revealed a poorly circumscribed tumour composed of cells with abundant eosinophilic granular cytoplasm, with negative margins and no atypical features. Postoperative recovery was uneventful. Surveillance mammography at 12 months was unremarkable, and at 24 months, the patient remains asymptomatic with a normal clinical breast examination and no evidence of recurrence. This case underscores the potential for granular cell tumour to imitate malignancy and highlights the importance of imaging-pathology concordance to avoid overtreatment. When a tissue diagnosis is secured preoperatively, breast-conserving surgery with margin negativity is usually sufficient, and routine clinical and age-appropriate imaging follow-up can document durable control. Our patient's two-year disease-free course supports a conservative, margin-oriented approach to management in similar presentations.