Miscellaneous: Poster Abstract: Anaplastic large cell lymphoma ALK negative vs. peripheral T cell lymphoma (NOS) - diagnostic dilemma

Middle aged female presented with generalised lymphadenopathy and fever for last one month. Peripheral blood findings were within normal limits. There was no extra nodal involvement. FNAC performed initially from a cervical node suggested possibility of Hodgkin's lymphoma and a whole node biopsy was performed. Histopathogical examination revealed effaced nodal architecture and a polymorphous population of lymphocytes, plasma cells, neutrophils and scattered large mononuclear cells with prominent nucleolus. An initial panel of CD3, CD20, LCA, CD15, CD30 and PAX5 was performed. The large atypical cells were positive for LCA, CD3 and CD30 with variable positivity for CD15. CD 30 showed Golgi and membranous staining. These large atypical cells were negative for PAX5 and CD20. In view of above findings, Hodgkin's lymphoma was ruled out and a possibility of Non- Hodgkin's lymphoma was considered. Further IHC markers were performed which included CD2, CD5, CD7, EMA, Alk, CD10 and KI67. CD5 showed variable positivity. The cells of interest were negative for CD2, CD7, ALK and EMA. Ki 67 index was 70-80%. Overall histological and IHC findings favoured Alk negative Anaplastic large cell lymphoma. Differential diagnosis considered was peripheral T cell lymphoma (NOS). Hodgkin's lymphoma, peripheral T cell lymphoma (NOS) and anaplastic large cell lymphoma share common histomorphological findings. With careful analysis of Immunohistochemistry, it is easier to categorise Hodgkin's lymphoma. ALK negative anaplastic large cell lymphoma and peripheral T cell lymphoma (NOS) are difficult to categorise and show overlapping features. We in this case have discussed clinical, histomorphological and IHC pattern of Alk negative Anaplastic large cell lymphoma.