Differential Diagnosis for Unilateral Underarm Mass
Single Most Likely Diagnosis
- Breast Cancer Metastasis: The presence of a unilateral underarm mass with clusters of lymph nodes, the largest measuring 4.7 cm, is highly suggestive of metastatic breast cancer, especially given the location and the fact that lymph node involvement is a common route of spread for breast cancer.
Other Likely Diagnoses
- Lymphoma: Both Hodgkin's and non-Hodgkin's lymphoma can present with lymphadenopathy, and the axillary region is a common site. The large size of the lymph nodes increases the suspicion for lymphoma.
- Infectious or Inflammatory Conditions: Conditions such as cat-scratch disease, tuberculosis, or sarcoidosis can cause lymphadenopathy. However, these conditions might not typically present with such large lymph nodes.
- Metastasis from Other Cancers: Although less common than breast cancer, other cancers (e.g., lung, melanoma) can metastasize to axillary lymph nodes.
Do Not Miss Diagnoses
- Tuberculosis: Although less likely in many regions, tuberculosis can cause significant lymphadenopathy and has a varied presentation. Missing this diagnosis could lead to significant morbidity and mortality.
- Sarcoma: Soft tissue sarcomas are rare but can present as a mass in the axilla. They are critical to diagnose early due to their potential for aggressive behavior.
Rare Diagnoses
- Castleman Disease: A rare disorder that involves an overgrowth of cells in the lymphatic system, which can cause lymphadenopathy.
- Kikuchi-Fujimoto Disease: A rare, self-limiting condition that causes lymphadenopathy, typically in the neck but can occur in the axilla.
- Kimura Disease: A rare, chronic inflammatory disorder that can cause lymphadenopathy and eosinophilia, more common in Asian males but can occur in females.
Each of these diagnoses has a different approach to management and treatment, emphasizing the importance of a thorough diagnostic workup, including biopsy of the lymph nodes, to establish a definitive diagnosis.