Differential Diagnosis
- Single most likely diagnosis
- Tuberculous lymphadenitis: The presence of a non-tender anterior neck fluctuant mass, a positive PPD (4mm) which indicates exposure to tuberculosis, and biopsy findings of giant cells are highly suggestive of tuberculous lymphadenitis. The history of being on a farm could imply exposure to tuberculosis from animals, but the key findings point towards tuberculosis.
- Other Likely diagnoses
- Cat-scratch disease: Although less likely given the biopsy findings, cat-scratch disease can cause lymphadenopathy and is associated with exposure to cats, which could have occurred on the farm. However, the presence of giant cells and a positive PPD makes this less likely.
- Mycobacterium avium complex (MAC) infection: This could be considered given the farm exposure and the presence of a fluctuant mass with giant cells on biopsy. However, the positive PPD and the clinical context make tuberculous lymphadenitis more likely.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Lymphoma: Although the clinical presentation and biopsy findings do not strongly suggest lymphoma, it is a diagnosis that could be devastating if missed. The presence of a fluctuant mass and systemic symptoms (if present) could warrant further investigation to rule out lymphoma.
- Atypical mycobacterial infections: These can present similarly to tuberculosis and can be seen in immunocompromised individuals or those exposed to contaminated water or soil. Given the farm exposure, this is a consideration, but the positive PPD and clinical context make it less likely.
- Rare diagnoses
- Sarcoidosis: This condition can cause lymphadenopathy and granulomatous inflammation, which could include giant cells. However, the clinical context and the specific findings make this a less likely diagnosis.
- Toxoplasmosis: Typically causes lymphadenopathy without fluctuance, and the biopsy findings would not typically include giant cells in the context provided. This diagnosis seems less relevant given the clinical scenario and biopsy results.