Gallbladder mucinous carcinoma in a child with metachromatic leukodystrophy, case report and literature review.

BACKGROUND: Metachromatic leukodystrophy (MLD) is an autosomal recessive genetic disorder caused by arylsulfatase A (ARSA) deficiency. Patients with MLD exhibit a high prevalence of gallbladder polyps and intestinal metaplasia. Although these precancerous lesions may progress to malignancy over time, gallbladder cancer is rarely diagnosed in children. Here, we present a case of gallbladder mucinous adenocarcinoma in a 5-year-old child, detailing its clinical, imaging, pathological, and genetic characteristics. To our knowledge, this is one of the earliest documented instances of pediatric gallbladder mucinous adenocarcinoma in MLD. CASE PRESENTATION: A 5-year-old male patient was admitted with a recurrent intermittent epigastric pain for over six months. Imaging examinations revealed an enlarged gallbladder and thickened gallbladder wall. The patient underwent cholecystectomy, and histopathological analysis confirmed mucinous adenocarcinoma with low-grade intraepithelial neoplasia. A low frequency (6.31%) of somatic KMT2C gene mutations (c.2922A > T, p.L974F) was detected in the tumor tissue. Ten months later, the patient was readmitted due to the onset of abnormal neuropsychiatric behaviors and significant regression in both cognitive and motor function. Brain MRI revealed multiple, bilateral, symmetrical abnormal signals within the cerebral white matter. Whole exome sequencing (WES) identified a homozygous missense variant (c.640G > A; p.Ala214Thr) in the ARSA gene. A diagnosis of MLD was established bases on clinical and molecular findings. CONCLUSION: Pediatric gallbladder cancer is extremely rare. Although the role of low-frequency (6.31%) KMT2C variant in carcinogenesis is uncertain. When accompanied by neurological symptoms, there is high suspicion for an underlying genetic etiology. Radiological imaging plays a critical role in providing indications for the diagnosis of leukodystrophy. And genetic testing is helpful in detecting germline variations and somatic mutations in tumor tissues.