C. Intravascular large B-cell lymphoma
Histopathologic evaluation revealed large round cells with scant cytoplasm and prominent nucleoli proliferating within blood vessels. Immunohistochemical analysis showed positivity for CD20, B-cell lymphoma (Bcl) 2, Bcl-6, cellular MYC, and multiple myeloma 1. The Ki-67 staining index was about 90%. The endothelial cells of the involved vessels expressed CD34 and CD31 and were negative for D2-40. Positron emission tomography scan results revealed no lymphadenopathy or metastases. No evidence of bone marrow involvement was found. The diagnosis of intravascular large B-cell lymphoma (IVLBCL) cutaneous variant was made. The patient was treated with 6 cycles of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) with a complete response. At her last follow-up, 1 year after treatment, she continued to be in remission.