Primary thyroid lymphoma is a genuine medical rarity. The thyroid gland is packed with lymphatic tissue, particularly in people with chronic autoimmune inflammation such as Hashimoto’s thyroiditis, and on rare occasions a lymphoma can originate there directly rather than spreading from elsewhere in the body. Diffuse large B-cell lymphoma, or DLBCL, is the most common aggressive subtype of non-Hodgkin lymphoma overall, but when it presents as the first and only site of disease in the thyroid, it belongs to a small subset of so-called primary extranodal lymphomas. Because so few patients exist, no large randomized trials have ever defined a single standard of care. Treatment decisions are instead stitched together from small case series, registry data, and extrapolation from how DLBCL is managed at other anatomical sites. That evidence gap is precisely what the Hamburg team set out to address by pairing their patient’s story with a structured sweep of the published literature.

The clinical picture in 2017 was textbook for the disease in its most dangerous form. The patient’s enlarged thyroid was compressing her airway, explaining the dyspnoea and cough, while involvement of the recurrent laryngeal nerve that runs alongside the gland accounted for her hoarseness. Staging investigations placed her at Ann Arbor stage IE, meaning the lymphoma was confined to a single extranodal organ, and her International Prognostic Index score of 2 indicated intermediate risk. Histopathological analysis classified the tumor as the non-germinal-center B-cell-like, or non-GCB, subtype, a molecular categorization based on the cell of origin that carries prognostic weight in DLBCL generally. Establishing that classification reliably, the authors emphasize in their review, depends on obtaining an adequate tissue sample — ideally a core needle biopsy or a surgical biopsy — because fine-needle aspirates often cannot provide enough architectural and immunophenotypic detail to distinguish DLBCL from other thyroid malignancies or from inflammatory conditions.

First-line therapy followed the established chemoimmunotherapy playbook. The patient received R-CHOP, the workhorse regimen combining the anti-CD20 monoclonal antibody rituximab with cyclophosphamide, doxorubicin, vincristine, and prednisone, together with prophylactic treatment directed at the central nervous system. Rituximab’s arrival two decades ago transformed outcomes in DLBCL by targeting the CD20 surface protein found on malignant B cells, and the literature review confirms that rituximab-containing chemoimmunotherapy remains the backbone of first-line treatment for primary thyroid DLBCL as well, occasionally supplemented with radiotherapy to the thyroid bed. Surgery, by contrast, played essentially no therapeutic role: across the reviewed literature, operations were largely confined to obtaining diagnostic tissue rather than attempting resection, a notable departure from how many solid thyroid cancers are managed with near-total thyroidectomy.

The initial response was complete remission, and for six years the patient remained disease-free. Then came the twist that makes this case report valuable to practicing hematologists. Rather than recurring locally in the same gland or spreading to distant lymph nodes, the lymphoma re-emerged as an isolated relapse in the contralateral thyroid lobe — the opposite side of the gland from the original tumor. Isolated late relapses of primary thyroid DLBCL are vanishingly rare; the review notes that relapsed or refractory disease in general, and central nervous system involvement in particular, are uncommon events in this patient population. The contralateral pattern raises intriguing questions about clonal biology: whether the relapse represented re-seeding from an occult residual clone within the gland or a truly independent second primary lymphoma arising in the same chronically inflamed tissue environment.

Treating a relapse six years after the original diagnosis posed a practical dilemma. Because the patient had already received anthracycline-based chemotherapy and rituximab, the team chose an off-label regimen abbreviated Pola-R-miniCHP. The key ingredient is polatuzumab vedotin, an antibody-drug conjugate that ferries a potent cytotoxic payload, monomethyl auristatin E, directly to CD79b, a component of the B-cell receptor complex expressed on malignant cells. Polatuzumab-based combinations have reshaped the landscape of relapsed and refractory DLBCL since demonstrating survival benefits in randomized testing, and the miniaturized chemotherapy backbone in this regimen was designed to reduce cumulative toxicity in an elderly patient. The gamble worked: the contralateral relapse again melted into complete remission, giving the patient two separate cures from the same rare disease across nearly a decade.

The literature review that accompanies the case report assembles the fragmented evidence base into a coherent picture. Reported five-year overall survival rates for primary thyroid DLBCL span a wide range, from 57 percent to 88 percent, reflecting heterogeneity in patient age, stage, histological subtype, and treatment era across the small published series. The better end of that spectrum approaches outcomes for early-stage DLBCL at more conventional nodal sites, underscoring that when the disease is caught while confined to the thyroid and treated promptly with modern immunochemotherapy, long-term survival is a realistic expectation. The authors also highlight that central nervous system relapse, a feared complication of aggressive DLBCL, appears infrequently in this population, which has implications for how aggressively clinicians need to pursue CNS-directed prophylaxis at diagnosis.

What the review cannot yet deliver is a definitive, evidence-based treatment guideline, and the authors are candid about why. The rarity of primary thyroid DLBCL means that every published series is small, retrospective, and vulnerable to selection bias. Randomized trials enrolling patients with this specific presentation are practically impossible to mount. Their proposed way forward is registry-based research, particularly studies that group primary extranodal DLBCLs of various origins together to achieve analyzable patient numbers while still capturing the distinctive features of thyroid disease. Such registries could clarify outstanding controversies, including the optimal role of radiotherapy consolidation, the necessity and duration of CNS prophylaxis, the value of molecular risk stratification, and how best to manage the rare relapses like the one documented in this report.

For the broader oncology community, the case carries several practical lessons. First, a rapidly enlarging thyroid mass with compressive or neurological symptoms in an older patient, especially one with background autoimmune thyroid disease, should prompt consideration of lymphoma alongside the more common carcinomas — because the diagnostic and therapeutic pathways diverge sharply, and inappropriate upfront surgery can delay the correct treatment. Second, adequate tissue via core needle or surgical biopsy is not a formality but the linchpin of accurate subtyping. Third, relapsed primary thyroid DLBCL, while exceptionally uncommon, may be amenable to the same novel agents that have improved salvage therapy for DLBCL elsewhere, as the successful off-label use of a polatuzumab-based regimen here demonstrates. The report thus functions as both a caution and an encouragement: vigilance at first presentation and flexibility at relapse can yield complete remissions even in a disease so rare that no guideline exists to follow.

The Hamburg authors, writing from one of Germany’s major university cancer centers, published their work open access so that clinicians encountering their own rare cases can consult the full analysis. As targeted immunotherapies continue to migrate from relapsed settings into frontline treatment across the lymphoma spectrum, the experience documented in this single patient may foreshadow how primary thyroid DLBCL is managed in the coming decade — with antibody-drug conjugates and other precision agents potentially joining or even replacing legacy regimens, and with international registries finally assembling enough patients to turn anecdote into evidence.

Subject of Research: Primary thyroid diffuse large B-cell lymphoma: diagnosis, treatment, and relapse management

Article Title: Primary thyroid diffuse large B-cell lymphoma: a case report and focused review of the literature

Article References: Kirkgöz, K., Weisel, K., Bokemeyer, C., & von Kroge, S. (2026). Primary thyroid diffuse large B-cell lymphoma: a case report and focused review of the literature. Annals of Hematology. https://doi.org/10.1007/s00277-026-07303-7

Image Credits: AI Generated

DOI: 10.1007/s00277-026-07303-7

Keywords: primary thyroid lymphoma, diffuse large B-cell lymphoma, DLBCL, rituximab, R-CHOP, polatuzumab vedotin, thyroid cancer, non-Hodgkin lymphoma, relapse, chemoimmunotherapy, extranodal lymphoma, Annals of Hematology

Diffuse large B-cell lymphoma, or DLBCL, is the most frequent subtype of non-Hodgkin lymphoma, accounting for approximately 30 to 40 percent of all cases. For two decades, the frontline standard of care was R-CHOP, a five-drug immunochemotherapy combining the monoclonal antibody rituximab with three chemotherapeutic agents and a corticosteroid. Despite countless attempts to improve upon it with novel agents, R-CHOP remained essentially unchallenged until the POLARIX trial demonstrated that swapping vincristine for polatuzumab vedotin—a targeted antibody-drug conjugate directed against CD79b, a signaling component of the B-cell receptor—produced significantly superior outcomes. That result transformed Pola-R-CHP into the new global standard for previously untreated DLBCL, and the regimen was approved in China in April 2023 for adult patients.

Yet the POLARIX trial enrolled only patients with international prognostic index scores of 2 through 5, meaning patients considered to have intermediate or high-risk disease. The IPI is a well-established scoring system that predicts prognosis in DLBCL using five factors: age, tumor stage, number of extranodal sites involved, performance status, and serum lactate dehydrogenase levels. Patients scoring 0 or 1 are conventionally labeled low-risk and represent approximately 30 percent of newly diagnosed cases. Because they were excluded from the pivotal trial, this substantial population became a critical evidence gap. The problem is compounded by the fact that low IPI scores do not guarantee biological simplicity. Many of these patients carry molecular and pathological features known to undermine standard therapy, including bulky tumors, double-expressor lymphoma, and abnormalities of the TP53 gene, the so-called guardian of the genome.

The new study, led by Yuhong Ren and Peng Liu of Zhongshan Hospital, Fudan University, together with colleagues across China, set out to fill that gap using real-world data. Between June 2023 and July 2025, the researchers enrolled 118 consecutive previously untreated DLBCL patients with IPI scores of 0 or 1 who received at least one cycle of Pola-R-CHP. The median age was 53.5 years, with patients ranging from 17 to 87 years old. Despite their formally low-risk classification, the cohort was biologically heterogeneous and carried a surprising burden of adverse features: 51.7 percent had the non-germinal center B-cell-like subtype, 24.6 percent had double-expressor lymphoma, 9.3 percent had double-hit or triple-hit lymphoma, 25.4 percent showed high P53 expression, 12.7 percent had bulky disease, and 62.7 percent had extranodal involvement.

The treatment protocol followed a well-defined structure. Each 21-day cycle comprised polatuzumab vedotin at 1.8 milligrams per kilogram of body weight, rituximab at 375 milligrams per square meter, cyclophosphamide at 750 milligrams per square meter, doxorubicin at 50 milligrams per square meter or epirubicin at 70 milligrams per square meter, and prednisone at 100 milligrams orally for five consecutive days. Patients received a median of six cycles. Efficacy was assessed using whole-body fluorodeoxyglucose PET/CT or contrast-enhanced CT imaging after three to four cycles and again at the end of treatment, with responses graded according to the 2014 Lugano classification, the international standard for lymphoma response assessment.

The results were remarkable. Among the 68 patients who had completed end-of-treatment evaluation at the data cut-off of August 2025, 63 achieved a complete response, yielding a complete response rate of 92.6 percent. The overall response rate reached 98.5 percent at end of treatment and 98.9 percent at interim assessment, with 78.2 percent of interim-evaluated patients already in complete remission after just three to four cycles. Only two patients experienced disease progression during follow-up, both of whom had central nervous system involvement, and no deaths occurred at a median follow-up of 7.1 months. Importantly, the 50 patients without end-of-treatment assessment had not progressed, died, or been lost to follow-up; they were simply still undergoing treatment or awaiting imaging, meaning the missing data reflected short follow-up rather than treatment failure.

Perhaps most striking was the consistency of responses across molecular subgroups. Exploratory analyses showed broadly similar response rates at both interim and end-of-treatment time points among elderly patients, those with the non-germinal center subtype, extranodal disease, double-expressor lymphoma, and double-hit or triple-hit lymphoma. The one exception was the high P53 expression subgroup, where the complete response rate was numerically lower at 78.6 percent compared with 96.9 percent in patients with low or absent P53 expression. This finding aligns with the well-documented biology of TP53 alterations, which are associated with genomic instability and chemoresistance in lymphoma. However, the researchers caution that the small number of evaluable patients in this subgroup prevents definitive conclusions, and they suggest that the bystander effect of antibody-drug conjugates—the ability of the drug payload to diffuse into neighboring tumor cells that may not express the target antigen—could theoretically help overcome the clonal heterogeneity that drives resistance.

Safety data from all 118 patients showed a tolerable profile without unexpected toxicity compared with the POLARIX trial. Any grade 3 or 4 adverse event occurred in 24.6 percent of patients. The most common adverse events overall were anemia in 68.6 percent, leukopenia in 47.5 percent, and decreased neutrophil count in 39.8 percent, the vast majority of which were mild to moderate. The most frequent severe toxicity was neutropenia, affecting 21.2 percent of patients at grade 3 or 4—a manageable side effect routinely addressed with dose adjustments and growth factor support in clinical practice. No new safety signals emerged, reinforcing the regimen’s established risk-benefit profile in a broader and more diverse population than the original trial captured.

The study’s authors place their findings in context by comparing them with other real-world cohorts and historical R-CHOP data. Published complete response rates for frontline Pola-R-CHP and R-CHOP in low-risk patients range from 80.6 to 96.5 percent, and the current results sit comfortably at the upper end of that spectrum. Notably, the Chinese cohort carried a heavier burden of adverse features than a comparable R-CHOP cohort from a Chinese phase 3 trial, with higher rates of impaired performance status, advanced stage disease, and double-expressor lymphoma, yet still achieved outstanding responses. The researchers acknowledge the inherent limitations of a retrospective, single-arm design conducted exclusively in China, including potential selection bias and immature survival data, and they emphasize that a conservative sensitivity analysis counting all unevaluated patients as non-responders still yielded a complete response rate of 85.1 percent.

The implications reach beyond the numbers. Roughly a third of DLBCL patients worldwide fall into the IPI 0-1 category, yet they remain underrepresented in clinical trials and continue to experience late relapses even in limited-stage disease, a pattern that contrasts with the survival plateau seen in advanced-stage patients. This study provides the first multicenter real-world evidence that Pola-R-CHP is both effective and tolerable in this population, even when adverse biological features are present. The authors call for prospective randomized trials to precisely define the magnitude of benefit, and for molecular subtyping strategies to better identify which low-risk patients harbor hidden resistance mechanisms. For now, the message for clinicians is clear: the antibody-drug conjugate revolution in lymphoma treatment appears to extend to nearly every patient who walks through the door, not just those who fit the narrow criteria of a registration trial.

Subject of Research: Frontline Pola-R-CHP treatment of low-risk diffuse large B-cell lymphoma

Article Title: Pola-R-CHP in previously untreated DLBCL with international prognostic index score 0–1: a multicenter real-world retrospective study in China

Article References: Ren, Y., Liu, J., Lin, Z., Shou, L., Zeng, H., Wu, D., Zeng, Z., Zhou, F., Bao, L., Jing, H., Jiang, S., Liu, H., Shen, J., Yu, W., Zhou, H., Xu, J., Zhang, Y., Wang, T., Huang, H., … Liu, P. (2026). Pola-R-CHP in previously untreated DLBCL with international prognostic index score 0–1: a multicenter real-world retrospective study in China. Clinical Cancer Bulletin, 5(1), Article 21. https://doi.org/10.1007/s44272-026-00073-3

Image Credits: AI Generated

DOI: 10.1007/s44272-026-00073-3

Keywords: diffuse large B-cell lymphoma, Pola-R-CHP, polatuzumab vedotin, antibody-drug conjugate, international prognostic index, real-world study, R-CHOP, double-expressor lymphoma, TP53, complete response, non-Hodgkin lymphoma, immunochemotherapy