Metastasis in the subcarinal lymph node with unknown primary tumor

Area of Science:

• Oncology
• Thoracic Surgery
• Diagnostic Imaging

Background:

• A 59-year-old male with a history of stage 3A anaplastic large cell T-cell lymphoma presented with an unusual finding.
• Positron Emission Tomography-Computed Tomography (PET-CT) revealed an isolated metabolically active lesion in a subcarinal lymph node.

Observation:

• Endobronchial ultrasound-guided fine-needle aspiration (EBUS-FNA) of the subcarinal lymph node diagnosed well-differentiated squamous cell carcinoma.
• Despite the diagnosis, no primary tumor was discernible on initial PET-CT imaging.

Findings:

• Mediastinoscopy confirmed the squamous cell carcinoma diagnosis in the subcarinal lymph node.
• Further surgical exploration via thoracotomy revealed an inoperable metastasis infiltrating adjacent vital structures (trachea, esophagus, aorta).

Implications:

• This case represents a unique instance of isolated subcarinal squamous cell carcinoma without an identifiable primary tumor.
• The findings challenge conventional diagnostic paradigms for metastatic squamous cell carcinoma, particularly in patients with prior malignancy.
• Further research is warranted to elucidate the potential origins and management strategies for such rare presentations.