Intravascular lymphomas are rare disease conditions that exhibit neoplastic lymphoid cells that are confined mainly to the lumens of small capillaries and medium-sized vessels. The majority of the intravascular lymphomas are of B-cell origin, but they can include NK/T-cell and CD30+ immunophenotypes. In the histologic differential diagnosis are benign proliferations such as intralymphatic histiocytosis and intravascular atypical CD30+ T-cell proliferation. In this review, we discuss the clinical, histopathologic, and molecular findings of intravascular B-cell lymphoma, intravascular NK/T-cell lymphoma, intralymphatic histiocytosis, and benign atypical intravascular CD30+ T-cell proliferation.

Intravascular large B-cell lymphoma (IVLBCL) is a rare type of aggressive B-cell non-Hodgkin lymphoma that poses a great diagnostic challenge due to its highly heterogenous clinical manifestations. Although 18F-fluorodeoxyglucose (FDG) is widely used as a diagnostic tool for patients suspected of having lymphoma, as it reveals FDG-avid lesions, the FDG avidity of IVLBCL has not been extensively characterized. Here, we present a comprehensive report of FDG avidity in IVLBCL and its association with clinicopathological features and survival. This descriptive observational study included consecutive patients aged at least 18 years diagnosed with IVLBCL in Peking Union Medical Hospital across 9 years. Among 50 screened IVLBCL patients, 42 had undergone 18F-FDG PET/CT to detect possible lesions for biopsy before pathological diagnosis; their FDG PET/CT (positron emission computed tomography, PET/CT) reports were retrospectively reviewed. The primary endpoint was the clinical description of FDG avidity of newly diagnosed intravascular large B-cell lymphoma and frequency. A total of 73.8% patients showed FDG-avid lesions, with a median SUVmax of 7.4 (range 1-27.7), which was lower than that for other aggressive lymphomas. Clinicopathological features were the same between the FDG-avid group and the non-FDG-avid group, except that the latter had a higher Ki-67 index (median 90% in the nonavid group vs. 80% in the avid group, P = 0.043). The overall survival rate was not different between the PET/CT groups. Our findings demonstrate that FDG PET/CT is a useful diagnostic tool for detecting FDG-avid lesions in IVLBCL patients. A random skin biopsy is essential for assisting in the diagnosis of IVLBCL, even for those with negative PET/CT.

Intravascular large B-cell lymphoma (IVLBCL) is a rare and highly malignant non-Hodgkin B-cell lymphoma with uncommon clinical presentation and poor prognosis. The diagnostic pitfall of IVLBCL is mainly due to the fact that subtle histological changes could be easily overlooked, in addition to its rare occurrence, non-specific and variable clinical presentations, and the absence of significant mass lesions. The purpose of this study is to further explore the clinicopathologic and molecular features of IVLBCL to ensure an accurate diagnosis of this entity. Here, we retrospectively present the data of the four new cases and the literature cases. The age ranged from 23 to 92, with a medium age of 67 and a male-to-female ratio of 1:1. The clinical manifestations are extremely variable, including fever, night sweats, weight loss, anemia, thrombocytopenia, unexplained hypoxemia, impaired consciousness, and skin lesions, as well as the extremely low levels of serum albumin, high levels of serum lactate dehydrogenase (LDH), soluble interleukin-2 receptor (sIL2R), and ferritin. Morphologically, 99.9% of cases showed a selective growth pattern with large, atypical lymphocytes within the lumen of small blood vessels. In addition, vast majority of cases were positive for CD20, CD79a, PAX5, MUM1, and BCL6, and a subset of cases expressed BCL2 and CD5, whereas CD3 and CD10 were typically negative. Ki-67 proliferative index ranged from 20% to 100%. To sum up, we have conducted comprehensive case reports, to the best of our knowledge, this is the largest reported cohort of IVLBCL cases. Comprehensive assessments and more IVLBCL cases are required for early diagnosis and prompt treatment.