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