Role of FNAC in Extramammary Tumors Metastatic to the Breast

Background: Metastasis to the breast of an extra-mammary origin is very rare. FNAC plays an important role in differentiating non-mammary breast metastasis from primary malignancy. This study aimed to analyze the cytomorphological criteria and its pitfalls in differentiating metastatic lesion of the breast from primary malignancy. Methodology: Retrospective analysis of 891 FNACs of the breast was performed for a time span of 3 years. A total of 12 cases were diagnosed on FNAC as secondary neoplasms to the breast. Clinical and radiological data, along with Pap and MGG stained smears of each case were examined and correlated with the histopathology of the primary tumor. Statistical analysis was carried out. All cases of primary breast malignancies were excluded from our study. Results: In 10 out of 12 cases, primary malignancies were identified as Plasma cell myeloma (one case), B-acute lymphoblastic leukemia (two cases), acute myeloid leukemia (one case); chronic myeloid leukemia (one case), Burkitt's lymphoma of the ovary (one case), Diffuse large B-cell lymphoma (one case), esophageal squamous cell carcinoma (one case), spindle cell sarcoma (one case) and squamous cell carcinoma of the cervix (one case). The remaining two cases in our study were misdiagnosed on cytology as metastasis and turned out to be breast primaries on histopathology. Conclusion: Our case series highlights the importance of FNAC to differentiate secondary lesions from primary breast malignancy and thus helps to avoid unnecessary surgery to the patient. It emphasizes on the need to keep in mind the possibility of metastatic breast neoplasms in the presence of unusual cytological features on FNAC.