Background and Clinical Significance: Granular cell tumor (GCT), also known as Abrikossoff tumor, is a rare, typically benign neoplasm of Schwannian origin. Although these tumors can occur in various locations, breast involvement is uncommon, accounting for up to 15% of cases. Case Presentation: We report the case of a 23-year-old female who presented with a firm, non-tender, 1 cm palpable lump in the upper outer quadrant of the left breast, detected during routine examination without skin changes or axillary lymphadenopathy. Ultrasound imaging revealed a hypoechoic, well-defined nodule, while MRI demonstrated minimal contrast enhancement, supporting a benign process despite features that may mimic malignancy. A core needle biopsy showed a proliferation of polygonal cells with abundant granular eosinophilic cytoplasm, mild nuclear pleomorphism, and low mitotic activity (Ki-67 ≤2%). Immunohistochemical analysis confirmed the diagnosis with strong positivity for S100, SOX10, and vimentin, and negativity for carcinoma-associated markers. Conclusions: This case highlights the diagnostic challenges of breast GCT in young patients and underscores the importance of integrating imaging, histopathology, and immunohistochemistry to distinguish it from malignant lesions and guide appropriate management. Regular follow-up is recommended to monitor for recurrence.
