Case Author(s): michael quinn, md and farrokh dehdashti, md , 4-10-98 . Rating: #D2, #Q4

Diagnosis: sarcoid and colon cancer metastases

Brief history:

47 yo male with colon carcinoma


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Full history/Diagnosis is available below

Diagnosis: sarcoid and colon cancer metastases

Full history:

47 yo old male with prior colon cancer who had two suspicious liver lesions on CT scan. The PET study was performed to evaluate these lesions as well as other possible sites of disease. Other pertinent clinical history was not provided at the time of the study.




There are multiple foci of abnormal activity throughout the body. The known liver abnormalities are metabolically active. Additionally, marked perihilar and mediastinal activity is present. Smaller foci are seen in the porta hepatis, retroperitoneum, inguinal regions, right axillary region, and right supraclavicular region.


Given the patients prior history of colon carcinoma, the abnormalities in the liver are suspicious for metastases as they display marked glucose metabolism. However, the remainder of the abnormal foci distributed throughout the chest, abdomen, and pelvis would be an unusual appearance of colon cancer metastases. A better explanation would be that of a more systemic process. After contacting the referring physician, it was found that the patient also carried an underlying diagnosis of sarcoidosis. Sarcoidosis is a chronic granulomatous inflammatory disease that is of unknown origin. While it commonly affects the lungs, nearly any tissue in the body may be affected. The initial inflammatory infiltrate consists of mononuclear cells, with subsequent formation of granulomas in the affected tissues. These granulomas may go on to resolve or lead to fibrosis. During the inflammatory phase there is increased glycolysis related to the metabolic activity of the cellular infiltrate. This is reflected in the increased activity seen in these same regions on PET-FDG studies during this phase. However, this is a nonspecific finding which may also be seen at other sites of inflammation (i.e. infection) as well as in malignancies. FDG uptake has been seen in vitro to be accumulated by leukocytes, lymphocytes and macrophages and FDG uptake is seen in vivo at sites of infection. Therefore, a concern exists for false positive interpretation for metastases in patients with coexisting malignancy and a systemic metabolic disease such as sarcoid. Use of other imaging modalities to discern the two as well as knowledge of likely routes of metastatic spread help to decrease the risk of overcalling the extent of tumor spread.


1. Lewis and Salama, Uptake of Fluorine-18- Fluorodeoxyglucose in Sarcoidosis. J Nucl Med 1994; 35:1647-1649

1. Alavi et al (Editorial) Is There A Role For PET-FDG Imaging In The Management Of Patients With Sarcoidosis? J Nucl Med 1994; 35: 1650-1652

Differential Diagnosis List


ACR Codes and Keywords:

References and General Discussion of PET Tumor Imaging Studies (Anatomic field:Vascular and Lymphatic Systems, Category:Inflammation,Infection)

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Case number: pt019

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