Intravascular Large B-Cell Lymphoma With Exclusively Cutaneous Involvement, Colonizing Pre-Existing Hemangiomas: A Rare Case With Aberrant HMB45 Expression

Intravascular large B-cell lymphoma (IVLBCL) is a rare and aggressive subtype of non-Hodgkin lymphoma. It is characterized by the presence of neoplastic lymphoid cells within blood vessels. We report a rare case of IVLBCL with exclusively cutaneous involvement colonization of hemangiomas. A 55-year-old man with a history of cutaneous angioma consulted dermatology because of the growth of some of the hemangiomas in recent months. Histologic examination revealed a dermal proliferation of small- and medium-sized vessels with lumina occupied by large pleomorphic cells with B immunophenotype and aberrant expression of HMB-45. Biopsy of a pre-existing hemangioma may be useful in the diagnosis of suspected cutaneous IVLBCL. The cutaneous variant has a better prognosis. It is also important to note that unexpected protein expression or loss of expression in malignant tumors may be a risk factor for misdiagnosis.