Trapped in the Vasculature: Delving into Intravascular B-cell Lymphoma.

Intravascular large B-cell lymphoma (IVLBCL) is a rare and aggressive variant of diffuse large B-cell lymphoma (DLBCL) in which neoplastic lymphoid cells proliferate within the lumen of small blood vessels involving any organ. The rarity and intravascular involvement of this lymphoma make this diagnosis difficult. Only 5% of these cases show atypical cells in peripheral blood. Some cases may present with hemophagocytic syndrome. Here, we report a case of IVLBCL diagnosed in a 65-year-old male who presented with vague symptoms of fever and fatigue. Peripheral blood smear showed approximately 5% atypical blast-like cells, which led to bone marrow examination. Flow cytometry immunophenotyping was done on aspirate followed by immunohistochemistry on trephine biopsy, and a diagnosis of IVLBCL was made (IVLBCL). Radiological evaluation was done by positron emission tomography (PET) scan, and cerebrospinal fluid (CSF) examination was done as part of the workup. Six cycles of R-CHOP chemotherapy were given with intrathecal methotrexate, and minimal residual disease (MRD) assessment was done twice. No recurrence of the disease was seen till 1-year follow-up post diagnosis. The case emphasizes that IVLBCL, being rare and aggressive, requires complete diagnostic workup in terms of laboratory and radiological studies, which play an important role in differential diagnosis and deciding the prognosis.