Differential Diagnosis for Unilateral Underarm Mass
Single Most Likely Diagnosis
- Breast Cancer Metastasis: This is the most likely diagnosis given the presence of a unilateral underarm mass and clusters of lymph nodes on ultrasound. Breast cancer often metastasizes to the axillary lymph nodes, and a mass in this area could be a sign of advanced disease.
Other Likely Diagnoses
- Lymphoma: Lymphoma can present with lymphadenopathy (enlarged lymph nodes) in the axilla, and the clusters of lymph nodes on ultrasound are consistent with this diagnosis.
- Cat Scratch Disease: This is a bacterial infection caused by Bartonella henselae, which can cause lymphadenopathy, particularly in the axilla.
- Tuberculosis: TB can cause lymphadenopathy in the axilla, although it is less common than other forms of TB.
Do Not Miss Diagnoses
- Melanoma Metastasis: While less common than breast cancer, melanoma can also metastasize to the axillary lymph nodes, and a diagnosis of melanoma would have significant implications for treatment and prognosis.
- Sarcoma: Soft tissue sarcomas can present with a mass in the axilla, and while rare, this diagnosis would require prompt and aggressive treatment.
Rare Diagnoses
- Castleman Disease: This is a rare disorder that can cause lymphadenopathy, including in the axilla.
- Kimura Disease: This is a rare, benign condition that can cause lymphadenopathy and eosinophilia, particularly in Asian males.
- Rosai-Dorfman Disease: This is a rare, benign condition that can cause lymphadenopathy, particularly in the axilla.
Management and Diagnosis for Each Differential Diagnosis
- Breast Cancer Metastasis: Diagnosis would involve a biopsy of the lymph node, and management would depend on the stage and type of breast cancer.
- Lymphoma: Diagnosis would involve a biopsy of the lymph node, and management would depend on the type and stage of lymphoma.
- Cat Scratch Disease: Diagnosis would involve a combination of clinical presentation, laboratory tests (e.g. PCR), and imaging studies. Management would typically involve antibiotics and supportive care.
- Tuberculosis: Diagnosis would involve a combination of clinical presentation, laboratory tests (e.g. AFB smear, culture), and imaging studies. Management would typically involve anti-TB medications.
- Melanoma Metastasis: Diagnosis would involve a biopsy of the lymph node, and management would depend on the stage and type of melanoma.
- Sarcoma: Diagnosis would involve a biopsy of the mass, and management would depend on the type and stage of sarcoma.
- Castleman Disease: Diagnosis would involve a biopsy of the lymph node, and management would depend on the type and severity of the disease.
- Kimura Disease: Diagnosis would involve a combination of clinical presentation, laboratory tests (e.g. eosinophil count), and imaging studies. Management would typically involve surgical excision and supportive care.
- Rosai-Dorfman Disease: Diagnosis would involve a biopsy of the lymph node, and management would typically involve supportive care and monitoring.