Retroperitoneal Knee Pain: An Unusual Case Report and Review of an Ancient Schwannoma.

Schwannomas are nerve sheath tumors that occur in Schwann cells. They are usually benign, but malignant transformation can occur. Symptomatology depends on the involvement of the surrounding tissues or the mass effect of the tumor. We describe a case of a 28-year-old man who initially presented with right iliac fossa pain associated with radiating pain over the anterior and lateral aspect of his right knee. Following subsequent investigations, we found a retroperitoneal schwannoma of the right lateral femoral cutaneous nerve. The key to our diagnosis was the referred pain to his right knee, which gave us a clue of possible neuropathic pain. Our patient highlights the need to consider a unified diagnosis when faced with an incongruent set of symptoms. Magnetic resonance imaging is the diagnostic modality of choice for the diagnosis of schwannomas. Treatment is directed towards symptomatic control. Surgery, radiation, and, in rare instances, chemotherapy are the major treatment modalities employed.

Silastic injection for vocal fold medialization resulting in a false-positive finding on F18 FDG-PET/CT.

A false-positive uptake of F18-fluorodeoxyglucose (FDG) on positron-emission tomography/computed tomography (PET/CT) can result in confusion and misinterpretation of scans. Such uptakes have been previously described after injection of polytetrafluoroethylene (Teflon) into the vocal folds. Similarly, vocal fold injection of silicone elastomer (Silastic) can result not only in a false-positive FDG uptake on PET/CT, but also in chronic inflammation. We report a case of increased FDG uptake in a vocal fold after Silastic injection that was misinterpreted as a malignancy in a 70-year-old woman who had metastatic carcinoma of the stomach.

The Role of PET/CT in Advanced Malignant Melanoma.

Positron emission tomography/computed tomography (PET/CT) with fluorodeoxyglucose demonstrates a high sensitivity and specificity for detecting both locoregional and distant metastases in patients presenting with AJCC stages III and IV disease. PET/CT also plays an important role in the detection of recurrence particularly in high-risk group patients, and this should be the modality of choice in investigating patients for suspected recurrence. The role of PET/CT in response assessment and follow-up still has to be defined, and cost-effectiveness analysis is required to strengthen its role.