1-2-3-4 Sign FDG PET Sign in Sarcoidosis

Area of Science:

• Radiology
• Nuclear Medicine
• Oncology

Background:

• Sarcoidosis is a multisystem granulomatous disease often affecting the lungs and lymph nodes.
• Characteristic imaging findings like the lambda sign on FDG PET/CT can suggest sarcoidosis.
• FDG PET/CT is valuable for assessing disease extent and guiding treatment.

Purpose of the Study:

• To define the prevalence and imaging characteristics of the lambda sign and 1-2-3-4 sign in sarcoidosis.
• To analyze FDG-avid periportal and portocaval lymphadenopathy in sarcoidosis patients.
• To evaluate the diagnostic utility of these findings in differentiating sarcoidosis.

Main Methods:

• Retrospective analysis of FDG PET/CT scans from sarcoidosis patients.
• Assessment for the presence of the lambda sign and FDG-avid periportal/portocaval lymph nodes.
• Analysis of nodal distribution, metabolic activity (SUVmax), and frequency of the 1-2-3-4 sign.

Main Results:

• The lambda sign was identified in a significant portion of patients.
• FDG-avid periportal and/or portocaval lymph nodes were observed in a subset of cases.
• The complete 1-2-3-4 sign was rare; however, periportal/portocaval nodes showed FDG uptake similar to intrathoracic nodes.

Conclusions:

• FDG-avid periportal and portocaval lymphadenopathy can be present in sarcoidosis, complementing typical intrathoracic findings.
• The complete 1-2-3-4 sign is uncommon in sarcoidosis.
• Recognizing these FDG PET/CT patterns enhances diagnostic confidence and helps differentiate sarcoidosis from other causes of lymphadenopathy.