Microscopic and immunohistochemical staining features. Medium-sized atypical lymphoid cells totally replaced a lymph node (A) (Haematoxylin-eosin stain, ×400) with strong positivity of CD3, CD4, and Ki-67 labeling index (B–D). On the skin biopsy, atypical lymphoid cells showed typical epidermotropism (E) (Haematoxylin-eosin stain, ×200), and massive perivascular infiltration (F) (Haematoxylin-eosin stain, ×200) resembling Mycosis fungoides. A strong positivity of CD4 and Ki-67 labeling index were shown (G, H). Atypical lymphoid cell infiltration was evident in his liver biopsy (I) (Haematoxylin-eosin stain, ×100) with strong CD4 reactivity (J). The same findings were noted in his bone marrow biopsy (K) (Haematoxylin-eosin stain, ×200) with CD4 immunohistochemical study (L). The HTLV-1 infected ‘flower cells’ were apparent in his peripheral blood smear (Wright-Giemsa ×1,000) (M–P).