CD30+ TIA-1+ ALK+ anaplastic large cell lymphoma:: Studies of three cases by flow cytometry analysis, immunohistochemistry and electron microscopy

Anaplastic large cell lymphoma (ALCL) has recently been recognized as a distinct clinicopathologic entity of CD30(+) large cell lymphomas, restricted to T or null cell lineage. They may or may not express the anaplastic lymphoma kinase (ALK) protein, and most of them express cytotoxic granule-associated protein (e.g. TIA-1). We report three such cases studied by flow cytometry analysis (FCM), immunohistochemistry (IHC) and electron microscopy (EM). According to the new WHO classification, two cases were primary systemic ALCLs of which one case was of small cell variant (case 1) and the other case was a common variant (case 2). The third case (case 3) was primary cutaneous ALCL which showed a giant cell rich pattern. IHC combined with FCM indicated that all cases were T/null cell phenotypes, and all were positive for CD30, TIA-1 and ALK protein (p80). Electron microscopically, three types of cytotoxic granules (dense core, multivesicular and intermediate types) were seen in all cases. In conclusion, the three cases with differ,ent morphologic variants of ALCL share the same clinical, phenotypical, cytogenetic and ultrastructural characteristics. These results further support the view that ALK-positive ALCL is a distinct clinicopathologic entity.