Case report: An unusual observation of elastophagocytosis in a patient with cutaneous CD5⁺ diffuse large B cell lymphoma

A Japanese man in his mid-60s reported having a subcutaneous mass for a period of 8 months, after which it gradually enlarged in size and was surgically extirpated. The resected tumor was 10 × 8 mm in size, and the cut surface was smooth, solid, and whitish. Histologi-cal analysis revealed the presence of medium to large lymphoid cells that had proliferated to form a solid mass. The diffuse proliferating cells stained positive for CD20, CD79a, and CD5, but were negative for CD3, CD30, and CD10, and the MIB-1 index was very high. On the basis of these findings, the tumor was diagnosed as cutaneous CD5⁺ diffuse large B cell lym-phoma. Interestingly, detailed analysis revealed elastophagocytosis, with scattered, fragmented elastic fibers engulfed by macrophages that were intermixed with tumor cells. These macrophages were mostly multinucleated giant cells, apparently forming part of a foreign body-type reaction. Elastic fiber staining clearly revealed positively stained fragmented fibers in the cytoplasm of the macrophages, which were densely positive for CD68, in sharp contrast to the CD68-negative tumor cells. The final diagnosis was cutaneous CD5⁺ diffuse large B cell lymphoma exhibiting unusual elastophagocytosis. The patient's clinical course was good, and the tumor disappeared completely after 3 cycles of rituximab, cyclophos-phamide, doxorubicin, vincristine, and prednisone (R-CHOP) therapy with radiation.