Multifocal Nodular Fatty Infiltration of the Liver in a Child—A Benign Condition Masquerading as a Malignant Liver Tumor

To the Editor; Most fatty liver conditions involve the entire liver, with only rare cases presenting as focal nodular lesions known as multifocal nodular fatty infiltration of the liver (MNFIL) [1]. This represents a distinct subtype of hepatic steatosis, exhibiting imaging features similar to metastatic liver tumors. Diagnosing such cases poses significant challenges and is prone to misdiagnosis. This distinct fatty liver form is rarely reported in adults and is even more uncommon in children [2, 3]. We present the first pediatric case of MNFIL to enhance pediatricians’ awareness of this condition and reduce misdiagnosis. A previously healthy 13-year-old male presented to a primary care hospital with intermittent abdominal pain lasting more than 1 month. His body temperature was within the normal range. Physical examination revealed a weight of 47 kg and height of 166 cm. No abnormalities were found on abdominal examination. Abdominal ultrasonography revealed multiple hyperechoic masses of varying sizes in the liver parenchyma (Figure 1A,B). One mass occupied the first and second hepatic hilum, measuring 10 × 6 × 10 cm, and involved the entire caudate lobe. Abdominal computed tomography (CT) showed a liver attenuation value of 60 Hounsfield units (HU). The regions with multiple lesions had an attenuation of 31 HU, and the spleen measured 55 HU (Figure 1C,D). The patient was referred to a tertiary pediatric specialty clinic the following day. Laboratory tests showed normal white blood cell count, C-reactive protein level, liver function indices, and levels of alpha-fetoprotein and neuron-specific enolase. Contrast-enhanced magnetic resonance imaging (MRI) revealed multiple large, irregular liver masses with iso- to mildly hyperintense signals on T1-weighted and mildly hyperintense signals on T2-weighted images. Most of the fat-suppressed signals were reduced, and internal linear high-signal areas were observed (Figure 1E,F). The patient underwent an ultrasound-guided aspiration biopsy of the hepatic lesion. Postoperative histopathology revealed hepatic steatosis, predominantly of the macrovesicular type, accompanied by mild-to-moderate hepatocellular swelling (Figure 1I,J). At the 1-year follow-up, contrast-enhanced abdominal MRI showed no change in the size of the lesions compared to previous imaging. The patient is currently asymptomatic. Literature Review: A PubMed search for “multifocal nodular fatty infiltration of the liver, MNFIL” yielded six case reports spanning 26 years from 1999 to 2025. All cases involved adult patients with MNFIL; no pediatric cases were reported (details in Table 1). Hepatic steatosis is a highly prevalent condition in the general population and is typically asymptomatic. Severe cases may be associated with underlying conditions such as diabetes mellitus, metabolic disorders (e.g., porphyrias), and exposure to certain medications [1, 9]. Multifocal nodular fatty infiltration of the liver (MNFIL) is a rare subtype of hepatic steatosis [10]. Due to its imaging features, MNFIL can be easily mistaken for hepatic metastases or malignant tumors. Such misdiagnosis may lead to unnecessary and potentially harmful interventions, particularly in pediatric patients. In terms of differential diagnosis, the spectrum of multiple hepatic lesions in children differs significantly from that in adults. Therefore, particular caution is required in both the diagnostic evaluation and clinical management of pediatric patients. In adults, hepatic metastases are more common, with their incidence increasing with age and closely related to the nature and timing of the primary malignancy. In children, liver metastases may originate from tumors such as neuroblastoma, nephroblastoma, Wilms tumor, and adrenocortical carcinoma. These metastatic lesions typically appear as multiple hepatic nodules with irregular margins. On contrast-enhanced CT, characteristic signs such as the “bull's-eye” or “starry sky” appearance may be observed. These lesions generally demonstrate greater density than those seen in fatty infiltration. Positron emission tomography‒computed tomography (PET-CT) often reveals multiple hypermetabolic nodules, with simultaneous identification of the primary tumor site [11]. In the present case, there was no personal or family history of malignancy. Furthermore, PET-CT did not reveal a primary tumor (Figure S1). As such, metastatic liver disease was effectively ruled out. The diagnosis of MNFIL remains challenging. A single imaging modality is often insufficient to fully characterize the lesions [12]. Therefore, clinical context—including the patient's presentation, past medical history, and family history—must be taken into account. Abdominal ultrasound is highly sensitive but lacks specificity. MRI is the preferred modality for further evaluation [11]. Histopathological confirmation through biopsy is essential, particularly to exclude malignancy. However, open surgical biopsy or lesion resection should be avoided due to the potential for unnecessary trauma in pediatric patients. MNFIL should be included in the differential diagnosis of multiple hepatic lesions, particularly when the clinical presentation is not consistent with advanced malignancy. As MNFIL is a benign condition, the primary treatment approach involves etiologic management and lifestyle modifications. As the initial screening for porphyria in this patient was negative, regular follow-up with imaging is recommended to monitor changes in lesion size. Additionally, hepatotoxic exposures should be avoided to prevent further liver damage. In conclusion, diagnosing MNFIL is challenging. However, open biopsy or further lesion resection should be avoided to prevent harm to the pediatric patient. Multifocal nodular fatty infiltration of the liver should be considered in the differential diagnosis of multiple hepatic lesions, particularly when clinical presentations are inconsistent with advanced malignancy. The patient's parents gave written consent to the release of the medical history and images. We are grateful to the patient and his family who have made this research possible. The authors declare no conflicts of interest. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.