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

Primary thyroid diffuse large B-cell lymphoma (DLBCL) is a rare subset of primary extranodal DLBCL. Thus, there are limited evidence-based specific recommendations regarding its diagnosis and treatment. We present a case report of a patient with relapsed primary thyroid DLBCL, followed by a focused literature review covering key epidemiological, diagnostic, and therapeutic aspects. In 2017, a 74-year-old woman was diagnosed with primary thyroid non-GCB-type DLBCL (Ann Arbor IE, IPI 2) after presenting with dyspnoea, hoarseness, and cough. Treatment with R-CHOP and CNS prophylaxis achieved complete remission. Six years later, an isolated relapse occurred in the contralateral thyroid gland. The patient was treated with Pola-R-miniCHP (off-label), resulting in complete remission again. In the focused literature review core needle or surgical biopsy was found to be important for reliable histopathological characterization, while first-line treatment mainly consisted of rituximab-containing chemoimmunotherapy, occasionally combined with radiotherapy. Surgery was largely limited to diagnostic purposes. Reported 5-year overall survival rates ranged from 57% to 88%, whereas relapse or refractory disease and central nervous system involvement were rare. Registry-based studies, especially those focusing on primary extranodal DLBCL, are necessary to develop evidence-based treatment guidelines for these patients.