Primary Endometrial Lymphomas: A Systematic Review

<b>Background:</b> Primary endometrial lymphomas (PELs) are exceedingly rare and diagnostically challenging lesions. <b>Objective:</b> To assess the clinicopathologic features of PELs. <b>Methods:</b> We adhered to the PRISMA-2020 guidelines for reporting systematic reviews. A PubMed literature search (1956-2025) was conducted using keyword combinations including "endometrium" and "lymphoma," "lymphoid proliferation," or "lymphoproliferative lesions." Only original articles published in the English peer-reviewed journals were considered. The inclusion criteria were: (i) studies involving human subjects, and (ii) studies published in the English language. Reviews, editorials, meeting abstracts, and non-English publications were excluded. <b>Results:</b> We identified 42 studies for our analysis, collectively reporting 58 cases of PELs. Abnormal uterine bleeding was the main complaint. Non-Hodgkin lymphoma (57 cases) and Hodgkin lymphoma (one case) were identified. In most cases, lymphoma was the sole lesion. In five cases, lymphoma coexisted with, preceded, or followed endometrial carcinoma. Histologically, PELs either diffusely involved the endometrium (50 cases) or were localized to endometrial polyps (eight cases). Marginal zone lymphoma (MZL) was the most frequently reported type, followed by diffuse large B-cell lymphoma (DLBCL). Other rare types included intravascular large B-cell lymphoma, NK/T-cell lymphoma, T-cell lymphoma, and low-grade B-cell lymphoma. <b>Conclusions:</b> Our study indicates that MZL and DLBCL were the most common types of PELs. Other extremely rare subtypes were also identified. Moreover, some PELs developed in the background of endometrial polyps and, in exceptional cases, in association with endometrial carcinoma. Radiological findings were critical for provisional diagnosis, staging, and follow-up. Key modalities included ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), and 18F-fluoro-2-deoxyglucose positron emission tomography/CT (18F-FDG PET/CT).