Adenoid cystic carcinoma of the breast - Discordant size on imaging and pathology: A case report and review of literature

INTRODUCTION: Adenoid cystic carcinoma (ACC) is an uncommon tumour of the breast. It is known for its rare lymph node involvement and distant metastasis. A triple-negative breast cancer that has a favorable prognosis compared to other triple negative ductal carcinomas, it accounts for approximately 0.1–1% of all breast cancers. PRESENTATION OF CASE: We report a case of a 69-year-old female with a palpable left breast mass who underwent multiple imaging modalities with significant size variance between the studies. Breast conserving therapy (BCT) was performed with axillary sentinel lymph node biopsy (SLNB) followed by radiation therapy (RT). Pathological examination confirmed the tumour as ACC. DISCUSSION: ACC, known as an persistent if low-grade malignant tumour of salivary gland, is considered to have low-malignant potential in the breast. It is a very rare subtype and from this scant data, there is minimal mention about size discrepancy between imaging modalities such as ultrasound and MRI. No consistent MRI features have been demonstrated, with the exception of T2 hyperintensity in larger lesions and T2 iso-intensity in smaller lesions. Ultrasound demonstrates primarily a hypoechoic or heterogenous mass with minimum vascularity, consistent with our radiographic findings. CONCLUSION: ACC is a rare entity in breast cancer pathology. Its size can be highly variable as measured by various radiographic modalities, and final Pathology from the surgical specimen is, as always, required for an accurate tumoral diameter. With that caveat, careful utilization of pre-operative imaging modalities is critical in pre-surgical planning to choose the appropriate surgery.