Single-Patient Case Report Links Advanced Colorectal Cancer to Later Lymphoma

A 63-year-old man remained alive more than 10 years after treatment for stage IV sigmoid colon cancer with multiple liver metastases, according to a retrospective single-patient case report. His unusual course included chemotherapy that enabled resection, complete remission from the colorectal cancer, a second primary peripheral T-cell lymphoma, not otherwise specified, and lymphoma recurrence in 2026. The report documents the patient’s observed outcomes but cannot establish how frequently the same sequence occurs or whether its treatment produced the unusually long survival. It also emphasizes that control of the two malignancies was not uniformly favorable: the lymphoma initially entered complete remission, then recurred and became widespread even as the patient continued to survive beyond the original colorectal diagnosis.

The patient first noticed small amounts of bright-red blood on toilet paper after defecation in 2012 and did not pay much attention to it. By October 2015, he had developed substantially increased bowel frequency, approximately five stools per day, thinner stool and persistent dull lower-abdominal pain. Colonoscopy revealed a space-occupying lesion in the sigmoid colon, and pathological examination confirmed adenocarcinoma. Chest and abdominal CT identified the primary tumor and multiple hepatic space-occupying lesions, the largest measuring 8 cm, while upper-abdominal MRI also showed multiple intrahepatic metastatic tumors. The resulting diagnosis was sigmoid colon adenocarcinoma with liver metastases, classified as cT4N1M1, stage IV. Initial marker measurements were CEA at 277.80 μg/L and CA19-9 at 96.09 U/mL, with AFP within the normal range. Testing of the primary sigmoid tumor found wild-type KRAS, NRAS, BRAF and PIK3CA.

After review by a multidisciplinary team, the physicians recommended conversion therapy, an approach intended to shrink initially unresectable tumors sufficiently to permit an operation. The patient declined targeted treatment because of financial constraints. Beginning on November 12, 2015, he instead received four cycles of modified FOLFIRI chemotherapy every two weeks, with irinotecan, leucovorin and 5-fluorouracil adjusted according to his age, general condition and body surface area of 1.71 m². The regimen included 280 mg irinotecan, 600 mg leucovorin and a 600 mg bolus of 5-fluorouracil on day 1, followed by 3.25 g of 5-fluorouracil infused over 46 hours. Grade I leukopenia and granulocytopenia occurred. CT after four cycles showed significant shrinkage of the intrahepatic lesions, assessed as a partial response, allowing the treatment team to proceed with surgery. Because this was an individual observation without a comparison group, the response cannot establish that the same regimen would enable resection in other patients.

On January 15, 2016, the patient underwent special hepatic segmentectomy under general anesthesia. The surgeons found multiple post-chemotherapy nodules, including one measuring 8 by 6 cm in the right posterior lobe, another measuring 2 by 1.5 cm in the left lateral lobe and a 0.5-cm lesion in the right anterior lobe. No vascular invasion or bile-duct tumor thrombus was observed. Postoperative pathology identified metastatic adenocarcinoma with negative surgical margins, indicating an R0 resection, and no perioperative complication was documented. The patient then received four additional cycles of FOLFIRI. On April 7, laparoscopic-assisted radical sigmoidectomy and complex intestinal adhesiolysis were performed. Pathology showed a grade II infiltrative tubular adenocarcinoma measuring 3 by 3 by 0.5 cm that invaded the serosa. Both margins were negative, as were all 14 sampled peritumoral intestinal lymph nodes. No perioperative complications were documented, and the patient completed another four cycles of FOLFIRI after surgery.

An evaluation on May 16, 2016 found no recurrence and established a complete response with no evidence of disease. CEA and CA19-9 had returned to their normal ranges, and imaging showed no identifiable residual disease. The patient then entered regular scheduled follow-up. The report interprets the sequence of conversion chemotherapy followed by radical surgery as an individual clinical success, but it does not identify a single cause of the long-term outcome. The authors note that negative margins, a node-negative primary tumor and low subsequent marker levels were favorable features. They also distinguish the patient’s course from population-level survival estimates and emphasize that results from one case cannot be compared directly with outcomes from chemotherapy plus targeted treatment. His transition from unresectable disease to no evidence of disease was therefore a documented outcome rather than proof of a general effect.

During surveillance in 2021, a newly enlarged left inguinal lymph node raised concern that the colorectal cancer had returned. A needle biopsy on June 15 instead identified peripheral T-cell lymphoma, not otherwise specified, or PTCL-NOS. The diagnosis was supported by the tumor’s morphology and an immunophenotype showing T-cell markers, including CD3, CD4, CD8, CD7 and TIA-1, as well as CD30 positivity. B-cell markers CD20 and PAX-5 were absent, as were ALK and EBER, while the Ki-67 proliferation index was approximately 95%. PET-CT on June 29 found a roughly 14-mm left inguinal node with an SUVmax of 9.1, but no increased FDG metabolism at the previously operated intestinal or hepatic sites. The distinct pathological findings, the six-year interval and the clinical course supported classification as a metachronous second primary lymphoma rather than a colorectal metastasis.

From July through October 2021, the patient received six cycles of CHOP chemotherapy—cyclophosphamide, vincristine, epirubicin and prednisone—at three-week intervals. CT after three cycles showed a partial response, with the inguinal node decreasing from 14 mm to 9 mm; after six cycles, the node remained 9 mm and the assessment of partial response was maintained. He then received local radiotherapy to the left inguinal region, delivering 50 Gy in 25 fractions, with no reported side effects. A PET-CT on January 12, 2022 showed reduced volume and FDG metabolism in the treated nodes, resulting in an assessment of complete response. No abnormal FDG metabolism was reported at the intestinal anastomosis or in the liver. The patient remained under close follow-up, and the lymphoma remained in remission for approximately four years before recurrence became evident in 2026.

Routine CT on March 9, 2026 revealed multiple enlarged retroperitoneal and left external iliac lymph nodes, some with necrosis, compared with the scan from March 20, 2025. A March 17 biopsy again showed PTCL-NOS, with CD30, CD4, BCL-2 and partial CD3 positivity, CD20 and CD19 negativity, and a Ki-67 index of about 95%. CEA and CA19-9 remained within their normal ranges. Whole-body PET-CT on July 29 showed extensive renewed lymphoma activity involving the right tonsil, lymph nodes at multiple sites, the bladder wall, peritoneum, subcutaneous tissues, muscles and several bones. The reported SUVmax values ranged from 3.4 to 22.8, and the scan was assigned a Deauville score of 5. Bone-marrow aspiration on August 17 showed no lymphoma involvement. Continued lymphoma chemotherapy with or without local therapy was recommended, but the source does not report the outcome of that treatment.

The case highlights a difficult diagnostic boundary between recurrence or metastasis and a new primary cancer in people previously treated for colorectal cancer. Histopathology and immunohistochemical staining were central to identifying PTCL-NOS, while imaging documented the location and extent of disease. The authors identify a key limitation: molecular clonality analysis was not performed, so the genetic relationship between the colorectal adenocarcinoma and lymphoma was not directly assessed. PTCL-NOS is a heterogeneous group of mature T-cell lymphomas that do not fit into specifically defined subtypes. In this patient, the approximately 95% Ki-67 index indicated a highly proliferative phenotype, and recurrence after initial complete remission demonstrated that the early response did not produce durable lymphoma control. Population studies cited in the report associate CHOP-treated PTCL-NOS with five-year overall survival of approximately 20% to 36%, but those estimates cannot be applied directly to this individual. At the last reported follow-up on August 31, 2026, the patient was alive, with overall survival measured from the October 29, 2015 colorectal diagnosis exceeding 10 years.

Subject of Research: Long-term survival in advanced colorectal cancer followed by metachronous peripheral T-cell lymphoma

Article Title: Rare metachronous advanced colorectal cancer coexisting with lymphoma: a case report with over 10-year survival

Article References: Ma, Y., Han, T., Lin, X., & Xiao, X. (2026). Rare metachronous advanced colorectal cancer coexisting with lymphoma: a case report with over 10-year survival. Frontiers in Oncology, 16, Article 1952530. https://doi.org/10.3389/fonc.2026.1952530

Image Credits: AI Generated

DOI: 10.3389/fonc.2026.1952530

Keywords: case report, colorectal cancer, liver metastases, T-cell lymphoma, multiple primary cancers, conversion therapy, FOLFIRI chemotherapy, surgical resection, lymphoma recurrence, long-term survival, Rare, metachronous