15 Unknown Primary Tumors
Shahram Bouyadlou and Peter S. Conti
History
38-year-old male who has a history of low-grade fever and episodic night sweats pre- sents with an abnormal CT. Evaluation for malignancy is requested.
Findings
There is extensive adenopathy within the mediastinum involving the paratracheal, sub- carinal, pericardial, and the AP window nodes (Figure 15.1.1). There are also hyper- metabolic nodes within the gallbladder fossa adjacent to the pancreatic head near the common bile duct. A right internal mammary, as well as a perigastric node, are mod- erately positive. The periaortic nodes within the celiac axis are also active. There is abnormal activity involving the pleural base and possibly soft tissue on the left of the chest wall. No abnormalities are seen in the liver and spleen. No definite bony lesions are seen.
Impression
Extensive metastatic lymphadenopathy along with soft tissue disease. Differential diagnosis included lymphoma vs. metastatic disease from an unknown primary. Dis- seminated granulomatous disease is a less likely possibility.
Discussion
A patient should be considered to have carcinoma of unknown primary site when a tumor is detected at one or more metastatic sites and routine evaluation fails to define a primary tumor site. In evaluation of a patient with suspected malignancy, history would be the key to develop the differential diagnosis. The clinical findings along with imaging studies are complementary.
In this case the patient is a young male with constitutional symptoms of night sweats and low-grade fever. The initial diagnosis of infection (most likely TB) is more likely.
The abnormal mediastinal lymphadenopathy on CT without lung involvement leads more toward malignancy. The anatomically based imaging modalities have sig- nificant shortcomings, particularly their lack of specificity when abnormal findings are present.
Case 15.1
155
Lymphoma may be multifocal and widespread, where there is a need for a non- invasive whole body imaging capability. Ga-67 has been successfully used for high- grade lymphoma but carries limitations for abdominal evaluation. With the introduction of F-18 FDG PET these limitations have been overcome. Studies have demonstrated that FDG shows good visualization of Hodgkin’s and non-Hodgkin’s lymphoma, and that there is a direct correlation between quantitative FDG uptake and poor prognosis. The highest FDG uptake is seen in the most clinically aggressive tumors.
The clinical presentation and imaging findings will place this case in the category of highly suspicious for malignancy (lymphoma preferably), however one must still con- sider infection (e.g., advanced TB) in this case.
156 Part II Clinical Cases
FIGURE15.1.1.
History
44-year-old male who has a history of an inflammed left buttock. The CT revealed swelling in multiple muscles in the pelvis. Evaluation for malignancy is requested.
Findings
There is extensive hypermetabolism in the left obturator internis piriformis muscle (Figure 15.2.1) extending to the gluteus minimis and left iliacus muscles which presents as an irregular border soft tissue mass adjacent to the sclerotic iliac/ischium lesion on CT (Figure 15.2.2). There is also a focus of intense activity in a right inguinal node (Figure 15.2.3).
The generalized uptake in the left lower extremity (Figure 15.2.4), more in the calf, is suggestive of venous stasis, possibly thrombophlebitis secondary to a pelvic
Case 15.2
FIGURE15.2.1.
FIGURE15.2.2. FIGURE15.2.3.
FIGURE15.2.4.
malignancy superiorly. The mild uptake in the gastroesophageal junction is due to inflammatory changes.
Impression
Bulky adenopathy seen involving the muscle groups mentioned above with additional right groin lymphadenopathy, compatible with lymphoma vs. sarcoma.
158 Part II Clinical Cases
