Differential Diagnosis for Septated 5mm Breast Cyst

Single Most Likely Diagnosis

• Simple Breast Cyst: This is the most common diagnosis for a septated breast cyst, especially given its small size (5mm). Simple breast cysts are benign fluid-filled sacs that can be single or multiple, simple or septated, and are very common in women, particularly those of reproductive age.

Other Likely Diagnoses

• Complicated Breast Cyst: While simple cysts are more common, a complicated cyst could present similarly, especially if it has septations. Complicated cysts may contain debris or blood, which can sometimes be seen as septations on imaging.
• Intracystic Papilloma: Although less likely for a small cyst, an intracystic papilloma could potentially present as a septated cyst, especially if the papilloma is small and located within a cyst.

Do Not Miss Diagnoses

• Phyllodes Tumor: While rare, phyllodes tumors can present as cystic lesions with septations. They are important to consider because they can be malignant, and missing them could have significant consequences.
• Cystic Carcinoma: Although uncommon, some breast carcinomas can present with cystic components, including septations. It's crucial to consider this diagnosis to ensure timely and appropriate management.

Rare Diagnoses

• Hemangioma: A vascular lesion like a hemangioma could potentially appear as a septated cystic structure on imaging, although this would be an unusual presentation.
• Lymphangioma: Similarly, a lymphangioma, which is a benign lesion of the lymphatic vessels, could present as a cystic structure with septations, but this is exceedingly rare in the breast.