415 Predictive factors for the diagnosis of intravascular large B-cell lymphoma among suspicious cases: A single-center retrospective analysis

Intravascular large B-cell lymphoma (IVLBCL) is a type of extranodal lymphoma in which tumor cells proliferate in microvessels. It lacks lymphadenopathy and develops with nonspecific symptoms such as fever of unknown origin, general malaise, neurological symptoms, and respiratory symptoms, and is often difficult to diagnose. The random skin biopsy is a relatively non-invasive procedure to detect large tumor cells in microvessels. In this study, we conducted a retrospective analysis of patients who underwent the random skin biopsy under the suspicion of IVLBCL during January 2010 and March 2022 to evaluate the predictive factors for the diagnosis of IVLBCL in our facility. We collected the final diagnosis, the presence or absence of fever, central nervous system symptoms, respiratory symptoms, and gastrointestinal symptoms, brain, lung, liver, spleen, and lymph node abnormalities in diagnostic imaging, and blood data including white blood cell counts, hemoglobin levels, platelet counts, lactate dehydrogenase (LDH) levels, soluble IL-2 receptor (sIL-2R) levels, and ferritin levels. Fifty-three patients were enrolled in this study and 8 patients were finally diagnosed as IVLBCL. Among them, seven cases were diagnosed based on the random skin biopsy and the remained one case was diagnosed by the autopsy. The onset age of IVLBCL patients ranged from 66 to 85 years old (median: 77.4 years old) and the male-to-female ratio was 1:1. Other diagnoses included diffuse large B-cell lymphoma in 8 cases, other lymphomas in 2 cases, neurodegenerative diseases in 10 cases, adult-onset still disease in 6 cases, other diagnoses in 9 cases, and unknown diagnosis in 10 cases. Patients with IVLBCL showed significantly higher LDH levels and sIL-2R levels and lower platelet counts compared to patients with other diagnoses. Other than LDH and sIL-2R levels, both of which are widely-known disease markers of malignant lymphoma, it may be good to keep in mind that the low platelet count may also indicate IVLBCL diagnosis in suspicious cases.