Histologic and cytologic analysis of TPM3-ALK–positive lymphoma and leukemic cells in blood from tTA/pBIL-TA double-transgenic mice. Hematoxylin and eosin staining on tissue sections from lymph node, spleen, kidney, lung, liver, and skin. The lymph node architecture is obliterated by abnormal lymphoid cells showing slightly irregular nuclei and scanty cytoplasms (A, original magnification ×50; B, original magnification ×1000). In the spleen, lymphoma cells are predominantly localized in the white pulp and show comparable morphologic features as seen in the lymph nodes. Note scattered megakaryocytes (arrow) (C, original magnification ×50; D, original magnification ×640). Wright-Giemsa–stained smear of peripheral blood showing presence of circulating abnormal lymphoid cells (E right, original magnification ×1000) compared with normal circulating lymphoid cells from control age-matched tTA littermate mice (E left, original magnification ×1000). All animals presented with skin nodules consisting of a hyperplasia of the epidermis, suggesting a keratoacanthoma-like lesion (F right, original magnification ×50) in comparison with normal skin from control age-matched tTA littermate mice (F left, original magnification ×50). (F right) As shown, a lymphomatous infiltration (arrow) was sometimes observed in the dermis below the keratoacanthoma-like lesion. Infiltration of various intensity was also found in kidney (G, original magnification ×400; arrow), lung (H, original magnification ×100; arrow), and liver (I, original magnification ×400; arrow).