A unique case of inflammatory myofibroblastic tumor of the liver manifesting with biloma: A case report

Anaplastic lymphoma kinase (ALK)-negative hepatic inflammatory myofibroblastic tumors (IMTs) harboring the ETS variant transcription factor 6-neurotrophic receptor tyrosine kinase 3 (ETV6-NTRK3) fusion gene and manifesting with biloma are extremely rare, and their biological behavior is unclear. The present study reports the case of a 45-year-old female with ALK-negative IMT of the liver harboring the ETV6-NTRK3 fusion gene and manifesting with biloma. Computed tomography of the abdomen confirmed the lesions to be a low-density mass, measuring 11.2x8.5x10.5 cm, located in the left lobe of the liver, and a lower-density mass, measuring 8.5x6.1x5.9 cm, located in the interior of the tumor. As the suspicion of a malignancy remained high, surgical resection of the left hepatic lobe, including the tumor, was undertaken. Intraoperatively, a tumor (12x10x9 cm), with an unclear boundary, incomplete capsule and fish-like texture, was found in the left lateral lobe of the liver, and a biloma, measuring 8x6 cm, was identified inside the tumor. Pathological examination revealed spindle cell proliferation with infiltration of chronic inflammatory cells and mucinous degeneration. Immunohistochemical studies showed negativity for ALK, CD117, CD34, discovered on GIST-1, desmin, smooth muscle actin, S-100, CD21, pan-cytokeratin, epithelial membrane antigen, CD23 and CD35, but positivity for vimentin staining, and 5% Ki-67-positive cells. Fluorescence in situ hybridization studies assessing characteristic genetic rearrangements using ALK, RET, ROS1, MDM2, MGEA5 and ETV6 break-apart assays, revealed the presence of the ETV6-NTRK3 fusion oncogene and negativity for ALK, RET, ROS1, MDM2 and MGEA5. The patient was discharged 7 days post-operatively, without any adjuvant treatment. No recurrence of symptoms was noted at the 3-year follow-up. To the best of our knowledge, this is the first report of biloma in an ALK-negative IMT of the liver, which may increase our understanding of hepatic IMT.