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Endogenous Clostridium septicum endophthalmitis is a rare and fulminant ocular infection, usually encountered in immunocompromised or diabetic patients. It is also highly associated with both gastrointestinal and hematologic malignancies. We describe herein the detection of an adenocarcinoma of the cecum on PET/CT with F-FDG in a patient with an active endogenous C. septicum endophthalmitis of the right eye. FDG PET/CT should be considered for all patients with endogenous endophthalmitis to exclude an occult malignancy, especially colorectal cancer.

Hemangioendotheliomas are a heterogeneous group of vascular neoplasm that may affect the liver, bone, and soft tissues. Among its variants, pseudomyogenic hemangioendothelioma is rarely encountered. Pseudomyogenic hemangioendothelioma is usually characterized by multiple soft tissue lesions, with occasional bone lesions. Fewer than 20 cases with exclusive involvement of bone structures have been reported. We describe a case of pseudomyogenic hemangioendothelioma involving multiple bony structures but without soft tissue involvement in a 7-year-old girl, imaged with F-FDG PET/CT at diagnosis and during treatment with mammalian target of rapamycin inhibitors.

Fecal retention can be exacerbated in older patients, bedridden patients, as well as those receiving opioids analgesics or anticholinergic medications. It can lead to impaction, which can have serious consequences, sometimes even requiring surgical intervention. We describe herein the incidental detection of a giant hypometabolic fecaloma on PET/CT with F-FDG during the initial staging of a patient with osteosarcoma using opioids for pain management.

Prostate cancer (PCa) treatment monitoring usually relies on prostate-specific antigen to detect disease progression or relapse. PET/CT with prostate-specific membrane antigen (PSMA) ligands has shown high accuracy in detecting metastatic PCa lesions and could help assess response to therapy. We describe herein the early relapse detection of a hormone-sensitive metastatic upfront PCa treated with docetaxel on Ga-PSMA-11 PET/CT before biochemical progression. PSMA PET/CT should be considered to monitor PCa response to chemotherapy to detect early relapse, regardless of prostate-specific antigen levels, increasing the chances of finding low-volume oligoprogressive disease.

Nodular fasciitis is an uncommon benign mass-forming myofibroblastic proliferation, most frequently found in the upper limbs, with only rare intramuscular cases. We describe herein a case of chronic nodular fasciitis of the left triceps muscle with a low Ga-labeled prostate-specific membrane antigen (PSMA) ligand uptake on PET/CT. Ga-PSMA ligands bind to PSMA-expressing prostate cancer cells, but uptake has also been demonstrated in other solid neoplasms and various benign lesions. Nodular fasciitis should be included in the differential diagnosis of soft tissue lesions with variable Ga-PSMA uptake.

Objective: To investigate the association between Prostate-Specific Membrane Antigen (PSMA) expression changes on positron emission tomography-computed tomography (PET/CT) and the response to treatment following the start of enzalutamide or abiraterone in metastatic castration-resistant prostate cancer (mCRPC) patients., Methods: All consecutive 68 Ga-PSMA-11 PET/CT scans routinely performed at our institution during more than 4 years were retrospectively screened for inclusion. We included mCRPC patients with a baseline PSMA PET/CT performed less than 2 months before the start of either enzalutamide or abiraterone, and a follow-up PSMA PET/CT performed no more than a year after, while still under those novel antiandrogen drugs (NAD). The associated clinical records were reviewed. Patients were considered treatment responders if they presented decreasing PSA levels > 50% or a radiological response based on RECIST 1.1 criteria. PSMA expression changes on the follow-up PET/CT were assessed using per-patient dominant response criteria to classify patients as PSMA-responders (complete disappearance of pathologic PSMA uptake, or a decreased uptake of the majority of lesions) or PSMA-non-responders (new PSMA-expressing lesions, increased uptake of the majority of lesions, or stable PSMA expression of the disease). Descriptive statistics and measures of associations (two-sided Fisher's exact test and Phi coefficient) were calculated., Results: A total of 11 and 15 patients were included in the enzalutamide and abiraterone groups. Median follow-up was 110 (IQR 76-124) and 87 (IQR 71-242) days, respectively. All treatment responders (3 enzalutamide and 4 abiraterone) were considered PSMA-responders, and all treatment non-responders (8 enzalutamide, 11 abiraterone) were considered PSMA-non-responders. PSMA PET response was thus perfectly associated with conventional response criteria (p = 0.006, Phi = 1 for enzalutamide; p = 0.001, Phi = 1 for abiraterone). In our cohort, no PSMA expression flare phenomenon was detected on follow-up PET/CT scans at a median follow-up of 3 months. However, an early and short-lived flare cannot be excluded., Conclusions: This retrospective study suggests that, after a median follow-up of 3 months under enzalutamide or abiraterone, PSMA expression changes on PET/CT are strongly associated with response to treatment. Prospective studies are needed to better understand PSMA expression dynamics following the start of enzalutamide and abiraterone, along with the role of PSMA PET/CT in response assessment.

Fibrous dysplasia is an uncommon benign bone pathology with only rare potential for malignant transformation. We describe the heterogeneous uptake of fibrous dysplasia of a whole rib on Ga-labeled prostate-specific membrane antigen (PSMA) PET/CT. Ga-PSMA binds to PSMA-expressing prostate cancer cells, but it can also bind to the neovasculature of various solid tumors, as well as to some benign lesions. Ga-PSMA expression in fibrous dysplasia should not automatically be equated with malignant transformation or confused with prostate cancer metastases.

Radiation-induced sarcoma is a rare complication of radiation therapy. We describe the incidental detection of a radiation-induced undifferentiated soft-tissue sarcoma with increased uptake on Ga-labeled prostate-specific membrane antigen (PSMA) PET/CT in a prostate cancer patient previously treated with surgery and external-beam radiotherapy. Results were confirmed by histological analysis. Ga-PSMA is known to bind not only to PSMA-expressing prostate cancer cells but also to the neovasculature of various other solid tumors. A careful Ga-PSMA PET/CT review of previously irradiated areas is warranted so as not to miss radiation-induced sarcoma in prostate cancer patients.

Objective: The aim of this study was to assess the clinical relevance of imaging the lower limbs when using 2-(F)-fluoro-2-deoxy-D-glucose (F-FDG) positron emission tomography with computed tomography (PET/CT) for malignant cutaneous melanoma in patients without previously known or suspected primary or metastatic melanoma lesions in the lower limbs., Patients and Methods: We retrospectively assessed 880 consecutive F-FDG PET/CT scans performed for adult patients in a context of suspected melanoma spanning a period of 5 years. All scans were correlated with the associated patient records (clinical history, physical examinations, and pathology reports), as well as follow-up imaging examinations, up until at least 6 months after the end of the study., Results: Among the 461 whole-body scans included for analysis, 109 reported unusual activity in the lower limbs, but with at most 21 scans showing lower-limb lesions attributed to melanoma on follow-up. No scan showed melanoma lesions exclusively in the lower limbs, and in no case did imaging the lower limbs upstage a patient. Imaging the lower limbs changed the actual clinical management of the melanoma for only one patient, with precautionary local radiation therapy administered following the detection of an asymptomatic distal femur bone metastasis in an otherwise plurimetastatic patient headed for palliative care., Conclusion: Our study, the largest of its kind, confirms that, when using F-FDG PET/CT for staging, restaging, or surveillance of malignant cutaneous melanoma in patients without previously known or suspected lower-limb melanoma lesions, imaging the lower extremities offers little additional clinically relevant information and stopping the scan at the proximal thighs has essentially no clinical impact.