Presentation
Recent onset right neck hard swelling
Patient Data
Large 4.6cm cystic right level II lesion with internal non vascular mural nodule seen. Another abnormal appearing hypoechoic right level III lymph node with loss of fatty hilum and measuring 11mm in short axis seen.
No suspicious thyroid lesion seen.
Large cystic or necrotic lesion in right level 2 neck with post contrast enhancing internal solid component and irregular wall enhancement. In addition there is mildly enlarged right level III neck lymph node.
Except for prominent lingual tonsil , no other suspicious focal lesion in upper aero-digestive tract or larynx seen in MRI.
Asymmetric FDG avid lesion in right tonsil. The large right level necrotic lymph node showed increased uptake in peripheral wall and internal solid component.
Incidental focal increased uptake in proximal sigmoid colon noted for which colonoscopy was advised.
Histopathology report
Lymph node specimen shows a core of fibrocollagenous tissue with a small amount of moderately to poorly differentiated squamous cell carcinoma at one edge. No evidence of lymphoid tissue in the background. The appearances are consistent with metastatic squamous cell carcinoma.
Focal FDG uptake in proximal sigmoid colon was Tubulovillous adenoma polyp with low grade dysplasia.
Case Discussion
This case shows the high sensitivity for the detection of lesions, when combined 18F-fluoro-2-deoxyglucose positron emission tomography (FDG PET) computed tomography (CT) is used in addition to conventional magnetic resonance imaging in detecting the unknown primary tumor.
In a meta-analysis that compared FDG PET with CT, MRI, or sonography, FDG PET increased sensitivity for nodal metastases from 79% to 85% and increased specificity from 80% to 86%1
In evaluating cystic masses in adult patients, it is important to have a high suspicion for malignancy and not dismiss as congenital cysts or secondary to inflammation or infection
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