Primary Hepatic Actinomycosis Mimicking Hepatic Malignancy with Metastatic Lymph Nodes by F-18 FDG PET/CT

Abstract

Actinomycosis is a rare infection caused by gram-positive, anaerobic bacteria. It commonly manifests as a cervicofacial disease, but is also encountered as thoracic and abdominopelvic forms [1]. Hepatic involvement is usually secondary to abdominal actinomycosis infection. Primary hepatic actinomycosis accounts for 5 % of all cases of actinomycosis [2] and can be considered when there is no sign of primary involvement of the abdominal area or elsewhere in the body [3]. Symptom onset is typically subacute and the disease follows a chronic and indolent course. Usual clinical findings include fever, right upper quadrant pain, and weight loss [4]. Actinomycosis may appear as a solid enhancing mass on CT images [3–5], and hepatic actinomycosis may mimic a primary or metastatic tumor clinically or radiologically [3, 6]. These lesions are called inflammatory pseudotumors and cannot be differentiated from malignant tumors by radiological examination alone [3]. Definitive diagnosis is based on the demonstration of sulfur granules in a biopsy specimen or of aspirated pus and Gram-stained smears of anaerobic cultures [3, 5]. A 27-year-old man was admitted with a 3-day history of fever and weight loss (14 kg/ 2 months) (Fig. 1). Laboratory tests showed mild anemia; hemoglobin 119 g/L, elevated white blood cell count of 23,060/mm (83.1 %), AST 33 U/L, ALT 45 U/L, and γ-GT 155 U/L. CA 19–9 was 3.4 μ/mL and CEA was 1.0 ng/mL.