Renal Cell Carcinoma Presenting as Isolated Deltoid Muscle Metastasis 12 Years After Radical Nephrectomy Detected on 18F-FDG PET/CT

The Hot Pleura: Isolated Pleural Metastases From Renal Cell Carcinoma

Renal cell carcinoma (RCC) is the most common solid renal malignancy that metastasizes typically to lungs, bones, liver, adrenals, and lymph nodes. Isolated pleural metastases of RCC are extremely rare, with only few cases reported in the literature. We report one such case of a 60-year-old woman, a known case of RCC of the left kidney who underwent nephrectomy, and on follow-up, PET/CT scan revealed diffuse thick nodular hypermetabolic left pleural thickening, which was later biopsied and turned out to be pleural metastases from RCC. No other site of metastases was found.

18F-FDG PET/CT detects Metastatic Renal Cell Carcinoma Masquerading as Primary Breast Malignancy

We present the case of a 36-year-old woman who underwent ¹⁸F-FDG PET/CT with suspicion of a primary breast malignancy. However, PET/CT detected an occult renal cell carcinoma with metastases to the thyroid, breast, lungs and lymph nodes. Thyroid and breast metastases are atypical metastatic sites of renal cell carcinoma. Breast metastases from extra mammary tissue are extremely rare, more so from renal cell carcinoma. Histopathologic confirmation of the breast lesions is imperative to avoid unnecessary mastectomy and imaging can help in raising the suspicion of metastatic involvement versus primary breast malignancy.

Relationship Between the Elevated Muscle FDG Uptake in the Distal Upper Extremities on PET/CT Scan and Prescan Utilization of Mobile Devices in Young Patients

It is common to notice increased FDG activity in the muscles of the forearms or hands on PET/CT images. The purpose of this study was to determine relationship between the prevalence of increased FDG activity in the forearms or hands and using mobile devices prior to the FDG PET/CT study.

METHODS

A total of 443 young patients with ages between 5 and 19 years who underwent FDG PET/CT scan were included in this retrospective analysis. All patients had FDG PET/CT with their arms within the field of views. The images were reviewed for elevated activity in the muscles of the distal upper extremities (DUEs), which include forearms and hands. The preimaging questionnaire/interview records regarding using mobile devices prior to FDG PET/CT were also reviewed and compared with the imaging findings.

RESULTS

Most patients (72.0% [319/443]) used mobile devices more than 60 minutes in the period of 24 hours prior to the FDG PET/CT study. Elevated uptake in the muscles in the DUEs was observed in 38.6% (123/319) of these patients. In contrast, among 124 patients who did not use the mobile devices or used the mobile device minimally prior to the study, only 6.5% (8/124) of them had elevated FDG activity in the DUEs. The difference persisted following stratification analysis for sex, age, and serum glucose level in our patient population.

CONCLUSIONS

Increased FDG uptake in the muscles of the DUEs in young patients is commonly seen in those who used mobile devices prior to PET/CT study. Recommendation should be considered to reduce using mobile devices prior to FDG PET/CT study in young patient population.

Presentation of Unusual Tracheal Metastasis on Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography after 9 Years in Postnephrectomy Patient of Renal Cell Carcinoma: A Case Report and Review of Literature

Tracheal metastases from renal cell carcinoma (RCC) are extremely rare. Most common primary malignancy metastasizing to this unusual location usually comes from lung region while it is rare to have tracheal metastases from nonpulmonary malignancies such as breast, thyroid, colorectal carcinoma, and melanoma. The lesions detected on fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography/computed tomography (PET/CT) scan, especially in the head and neck region, soft tissue, and muscular compartment during follow-up of RCC patients raise the possibility of metastatic lesions in these regions, though rarely encountered. F-18 FDG PET/CT proved to be a valuable noninvasive imaging tool in detecting the very unusual distant metastases and multisystem involvement many years after nephrectomy in RCC in a single session in the present case.

Multiple and solitary skeletal muscle metastases on 18F-FDG PET/CT imaging

OBJECTIVE

The aim of this study was to investigate the features and patterns of skeletal muscle metastases (SMM) detected with F-fluorodeoxyglucose (F-FDG) PET/computed tomography (PET/CT).

PARTICIPANTS AND METHODS

Our database was analyzed for patients with pathologically proven malignancy, who underwent F-FDG PET/CT in our institution. The patients with SMM were included in the study group on the basis of the final diagnosis confirmed by follow-up or histopathology. Images were acquired using a PET/CT system Biograph mCT S(64)-4R. CT was performed without contrast enhancement.

RESULTS

The selected group included 31 patients (1.7% of the database, which consisted of 1805 patients). A total of 233 lesions were found. The prevalence of SMM evaluated in specific primary malignancies was the highest in melanoma (6.9%), followed by carcinoma of unknown primary (4.4%), colorectal cancer (4.1%) and lung cancer (2.8%). Three patterns of skeletal muscle metastatic involvement were observed: multiple SMM accompanied by other metastases (64.5%), solitary lesion associated with other metastases (29%) and isolated intramuscular lesions (two cases, 6.5%). Isolated SMM represented recurrence of the malignant disease. In patients with extraskeletal metastases, solitary or multiple SMM did not affect tumor staging.

CONCLUSION

Solitary SMM are less common than multiple on F-FDG PET/CT imaging. SMM are usually associated with other metastases and do not affect tumor staging. The cases of isolated SMM are very rare. Nevertheless, in patients with a diagnosis of malignant disease, a solitary, F-FDG avid intramuscular focus should be suspected to represent metastasis.