Indolent natural killer-cell lymphoproliferative disorder of the gallbladder: a rare case report

Background Indolent natural killer (NK)-cell lymphoproliferative disorder (iNKLPD) is a rare, recently defined neoplasm that is typically challenging to diagnose preoperatively. We report a rare case of iNKLPD arising in the gallbladder. Case presentation A 61-year-old woman presented with right upper abdominal pain and a positive Murphy’s sign. Ultrasonography revealed wall thickening (0.6 cm) and a submucosal, tumor-like lesion at the gallbladder neck, along with several hyperechoic shadows suggestive of stones. Histopathological examination revealed coagulative necrosis in the mucosal lamina propria and diffuse infiltration of tumor cells into the muscular layer. The tumor cells were medium in size, with inconspicuous or small nucleoli. Immunohistochemically, the cells were positive for CD3, CD2, CD56, CD43, TIA-1, perforin, and granzyme B, and negative for CD5, CD20, CD79a, pan-CK, Bcl-6, CD10, MUM1, and cyclin D1. Both Epstein–Barr virus-encoded RNA in situ hybridization (EBER ISH) and T-cell receptor (TCR) gene rearrangement analysis by PCR were negative. Based on these findings, a pathological diagnosis of iNKLPD of the gallbladder was established. The patient remained recurrence-free at 36 months after surgery. Conclusion We herein present a rare case of iNKLPD primarily occurring in the gallbladder. Given its atypical clinical and pathological features, iNKLPD requires careful distinction from other lymphomas or inflammatory lesions to prevent misdiagnosis. Furthermore, due to its indolent nature, accurate recognition is crucial to avoid the potential risk of overtreatment.