A 79-year-old male visited the outpatient department for a screening colonoscopy. A 4.5 × 2.0 cm lobulated polypoid mass was detected 20 cm above the anal verge in the sigmoid colon (Fig. 1A). The lesion in the colon was a localized mass with suspicion of lymphoma. Due to inconclusive biopsy results, endoscopic submucosal dissection (ESD) was performed for both diagnostic and therapeutic purposes. After admission, ESD was performed (Fig. 1B). Endoscopic ultrasound revealed a hypoechoic lesion located between the mucosal and submucosal layers (Fig. 1C). Pathologically, the specimen showed a thickened mucosa and monomorphic small lymphoid cell infiltration in the expanded lamina propria with nondestructive glands (Fig. 1D, 2A). These lymphoid cells expressed CD3+, CD5+, CD8+, low Ki-67 expression (less than 5%), CD20−, CD79a−, CD4−, CD56−, granzyme B−, CD10−, BCL6−, CD30−, cyclin D1−, and EBV-encoded small RNA by in situ hybridization (Fig. 2B–H). The molecular pathology identified monoclonal T-cell receptor (TCR) β, δ, and γ gene rearrangement, leading to a diagnosis of indolent T-cell lymphoproliferative disorder of gastrointestinal tract (iTLPD-GI). The patient was asymptomatic, and given the successful endoscopic resection and the low morbidity associated with the disease, we opted for follow-up observation without further treatment [1]. The patient remains alive for three years. Initially described as iTLPD-GI, it was reclassified as indolent T-cell lymphoma of the gastrointestinal tract (iTCL-GI) in the 5th edition of the WHO classification [2–4].