Anaplastic large cell lymphoma arising in bone - Report of a case of the monomorphic variant with the t(2;5) (p23;q35) translocation

Anaplastic large cell lymphoma (ALCL) represents approximately 2% of all no n-Hodgkin lymphomas according to the recent Non-Hodgkin Lymphoma Classifica tion Project. As defined in the revised European-American classification of lymphoid neoplasms (REAL), ALCL is a neoplasm of T-cell or null-cell linea ge; 20% to 60% of cases are associated with the t(2;5)(p23;q35) translocati on. ALCL commonly involves nodal as well as a wide variety of extranodal si tes, although primary or secondary involvement of bone is rare. We describe the case of a 71-year-old man with stage IE T-cell ALCL, monomorphic varia nt, arising in the left anterior fifth rib and involving adjacent soft tiss ue without other sites of disease. The monomorphic histologic features hind ered the initial recognition of this neoplasm as ALCL. However, strong unif orm CD30 antigen expression and subsequent demonstration of the t(2;5)(p23; q35) translocation and anaplastic lymphoma kinase (ALK) immunoreactivity le d to the correct diagnosis. We identified only 5 reported cases of T-cell a nd null-cell ALCL arising in bone and only 2 of these cases involved a sing le bone site. All 5 previously reported cases were ALCL of the classic type . We report a case of ALCL that is unique to our knowledge. This case of mo nomorphic ALCL was localized to bone and tumor cells contained the t(2;5)(p 23;q35) translocation.