Intravascular B-cell lymphoma with hypercalcemia as the initial presentation.

Intravascular B-cell lymphoma (IVLBCL) is a rare subtype of extranodal diffuse large B-cell lymphoma, which is characterized by the growth of lymphoma cells within blood vessel lumina without nodular lesions, and which predominantly affects elderly patients. IVLBCL is characterized by B-symptoms and a variety of systemic symptoms due to focal obstruction of blood flow, but may be difficult to diagnose due to its peculiar intravascular localization and the lack of nodular lesions. While hypercalcemia is one of the complications of various types of cancerous diseases, it has rarely been reported as the first presentation of IVLBCL. In this report, we present the case of a 71-year-old male with IVLBCL who showed hypercalcemia accompanied by elevation of serum parathyroid hormone-related protein (PTH-rP) as the initial presentation. Interestingly, immunohistochemical staining revealed that the intravascular lymphoma cells expressed high levels of PTHrP. Six courses of immunochemotherapy, consisting of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP), and two courses of high-dose methotrexate induced complete remission (CR) and retained CR for 4 months. We also reviewed other IVBCL cases in which hypercalcemia was the initial presentation. We suggest that IVLBCL, although rare, should be considered as a possible causative in hypercalcemia of unknown underlying disease.