Unusual Metastases to the Axillary Lymph Nodes on Cytology: Cases That Mandate Out-Of-The-Box Thinking!

INTRODUCTION

The thorax, breast, arm, and upper abdominal wall above the umbilicus drain into the axillary lymph nodes. The breast is typically the most frequent primary site for axillary lymph node metastases. While breast cancer is the most frequent primary site for axillary lymph node metastases, metastases from non-mammary sites, though rare, may also occur. In this study, we aimed to analyze the cytomorphological and clinical characteristics of non-breast cancers metastasizing to axillary lymph nodes, diagnosed by fine needle aspiration cytology (FNAC).

METHODS

Using computerized electronic records, we retrospectively identified cases of non-breast malignancies metastasizing to the axillary lymph nodes. Slides were reviewed, and the distinct cytomorphological features of each entity were tabulated.

RESULTS

A total of 24 cases of non-breast primary cancers metastasizing to axillary lymph nodes were identified. These included six squamous cell carcinomas from the upper limb, four lung adenocarcinomas, three squamous cell carcinomas of the head and neck region, two high-grade serous carcinomas of the ovary, two soft tissue sarcomas (one from the upper limb and one from the back), and one case each of squamous cell carcinoma of the lung, gallbladder adenocarcinoma, malignant melanoma of the great toe, primary cutaneous neuroendocrine tumor, clear cell renal cell carcinoma, oropharyngeal carcinoma, and nasopharyngeal carcinoma.

CONCLUSION

This study underscores the importance of considering non-breast primaries in the differential diagnosis of axillary lymph node metastases. Accurate diagnosis of these unusual tumors requires meticulous cytomorphological evaluation, a thorough clinical history, relevant radiological investigations, and the judicious use of immunocytochemical markers.