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Intravascular large B-cell lymphoma (IVLBCL) is a rare variant of extranodal diffuse large B-cell lymphoma (DLBCL). It is characterized by proliferation of blastic, neoplastic B cells within the lumina of small-or intermediate-sized blood vessels and capillaries. 1 IVLBCL may potentially involve any organ and is often widely disseminated. Two major patterns have been recognized. In Western patients, predominantly the skin and the central nervous system (CNS) are involved, whereas in Asian countries, the disease often involves multiple other organs and is accompanied by hemophagocytosis. 2 Additionally, a cutaneous variant, with skin-limited disease at time of diagnosis, has been described in younger, Western women. 3 Standard treatment of IVLBCL consists of rituximab-containing chemotherapeutic regimens, demonstrating an estimated 3-year overall survival (OS) of 60% to 81%. 4,5

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Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT) and primary cutaneous follicle center lymphoma (PCFCL) are cutaneous B-cell lymphomas (CBCL) with different clinical characteristics and behavior. PCDLBCL-LT is the most aggressive CBCL with a relatively poor prognosis. In nodal diffuse large B-cell lymphoma (DLBCL), rearrangements of the MYC gene, especially in combination with a second hit in BCL2 and/or BCL6, and double protein expression of MYC and BCL2 (DE) are adverse prognostic factors. As the clinical significance of these factors in CBCL is largely unknown, we studied the frequency and prognostic value of MYC rearrangements and DE in a cohort of 44 patients with PCDLBCL-LT and 17 patients with PCFCL. Compared with nodal DLBCL (9% to 14%), the PCDLBCL-LT patients had a high incidence of MYC rearrangements (32%), but only 2 patients (4%) had a second hit, both with BCL6. PCDLBCL-LT patients with a MYC rearrangement showed an inferior disease-specific survival (Log-rank, P=0.036) and disease-free survival (Log-rank, P=0.028), but no significant adverse effect on overall survival (Log-rank, P=0.157) at 5 years compared with patients without a MYC rearrangement. DE, present in 65% of the PCDLBCL-LT patients, was not associated with reduced survival. In the PCFCL group, MYC rearrangements and DE were not detected. In conclusion, this study identifies a high incidence of MYC rearrangements in PCDLBCL-LT compared to nodal DLBCL and further shows that a MYC rearrangement is an inferior prognostic marker in these patients. Therefore, our data suggest that it is useful to perform MYC-FISH in all newly diagnosed PCDLBCL-LT patients.