Unusual synchronous liver and brain abscesses infected by rare Aerococcus viridians in a patient with pulmonary arteriovenous malformations on FDG PET/CT: A case report and literature review

PET/CT Variants and Pitfalls in Liver, Biliary Tract, Gallbladder and Pancreas

A wide variety of pathological anomalies may occur in the liver, biliary system, and pancreas. It is a necessity to use many different imaging techniques in order to distinguish such varied pathologies, especially those from malignant processes. Positron Emission Tomography/Computed Tomography (PET/CT) is an imaging method that has proven its diagnostic value in oncology and can be used for different clinical purposes. Fluoro-18 fluoro-2-deoxy-D-glucose has a wide range of uses as a dominant radiopharmaceutical in routine molecular imaging, however, molecular imaging has started to play a more important role in personalized cancer treatment in recent years with new Fluoro-18 and Gallium-68 labeled tracers. Although molecular imaging has a strong diagnostic effect, the surprises and pitfalls of molecular imaging can lead us to unexpected and misleading results. Prior to PET/CT analysis and reporting, information about possible technical and physiological pitfalls, normal histological features of tissues, inflammatory pathologies, specific clinical features of the case, treatment-related complications and past treatments should be evaluated in advance to avoid misinterpretation. In this review, the physiological and pathophysiological variants as well as pitfalls encountered in PET/CT imaging of the liver, biliary tract, gallbladder, and pancreas will be examined. Other benign and malignant pathologies that have been reported to date and that have led to incorrect evaluation will be listed. It is expected that the devices, software, and artificial intelligence applications that will be developed in the near future will enable much more effective and faster imaging that will reduce the potential causes of error. However, as a result of the dynamic and evolving structure of the information obtained by molecular imaging, the inclusion of the newly developed radiopharmaceuticals in routine practice will continue to carry new potentials as well as new troubles. Although molecular imaging will be the flagship of diagnostic oncology in the 21st century, the correct analysis and interpretation by the physician will continue to form the basis of achieving optimal performance.

Unusual disseminated Talaromyces marneffei infection mimicking lymphoma in a non-immunosuppressed patient in East China: a case report and review of the literature

Background

Talaromyces marneffei infection is an important opportunistic infection associated with acquired immune deficiency syndrome (AIDS). However, it is unusual in patients with non-AIDS and other non-immunosuppressed conditions. We report a case of delayed diagnosis of disseminated T. marneffei infection in non-AIDS, non-immunosuppressive and non-endemic conditions.

Case presentation

We describe a previously healthy 24-year-old man who complained of a 3-month history of intermittent diarrhea and a recent week of uncontrollable high fever. The HIV antibody test was negative. Enhanced abdominal computed tomography (CT) and integrated ¹⁸F-2-deoxy-2-fluoro-D-glucose position emission tomography/computed tomography (FDG PET/CT) both suspected malignant lymphoma. However, a large number of yeast-like cells were found in macrophages in cervical lymph node samples by hematoxylin and eosin stain and silver hexamine stain. Subsequent blood culture suggested T. marneffei infection. Metagenomic Next Generation Sequencing (mNGS) results suggested T. marneffei as the dominant pathogen. Unfortunately, the patient continued to develop acute liver failure and died due to adverse events associated with amphotericin B.

Conclusions

Early diagnosis in HIV-negative patients who are otherwise not immunosuppressed and endemic poses a serious challenge. T. marneffei infection is an FDG-avid nonmalignant condition that may lead to false-positive FDG PET/CT scans. Nevertheless, integrated FDG PET/CT is necessary in patients with fever of unknown origin in the early period to perform earlier biopsy for histopathology and culture in highly avid sites and to avoid delays in diagnosis and treatment.

Concomitant Liver and Brain Abscesses Caused by Parvimonas Micra

Anaerobic infections have been reported to be responsible for 3-10% of pyogenic liver abscesses in Korea, and reported anaerobes include Fusobacterium, Bacillus fragilis, and Bacteroides melaninogenicus. Parvimonas micra is an anaerobic, Gram-positive, non-spore-forming bacterial species and a constituent of normal flora on skin, vagina, gastrointestinal tract, and oral cavity that can cause opportunistic infections. However, it has only rarely been reported to be a cause of liver abscess; only one such case has been reported in Korea. We experienced a case of concomitant liver and brain abscesses caused by Parvimonas micra in a non-immunodeficient 65-year-old female patient without diabetes or periodontal disease. Parvimonas micra infection was confirmed by blood culture using VITEK^® 2 cards and by bacterial 16s ribosomal RNA gene sequencing. We conclude that we should not overlook anaerobes as a cause of liver abscess.