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Immunophenotyping of mature T/NK cell neoplasm presenting as leukemia.

INTRODUCTION
Mature T/NK cell lymphomas (MTNKL) presenting as leukemia are rare and show considerable overlapping of clinical, morphological and immunophenotypic features.


AIM
Critical analysis of the morphology and immunophenotypic profile of MTNKL.


MATERIALS AND METHODS
We reviewed 380 consecutive cases of mature lymphoid neoplasm that presented as leukemia and were diagnosed on morphology and immunophenotyping of bone marrow and/or peripheral blood samples.


RESULTS
Peripheral blood and bone marrow involvement was seen in all cases. MTNKL constituted 4% (nine cases) of all mature lymphoid neoplasms presenting as leukemia. It included four cases of T-large granular leukemia (T-LGL), two of T-cell prolymphocytic leukemia small cell variant (T-PLL), two of adult T-cell leukemia/lymphoma (ATLL) and one of primary cutaneous gamma delta T-cell lymphoma (PCGDTCL). T-LGL revealed CD4-/CD8+ phenotype in three, and CD4+/CD8+ phenotype in one case. CD56 was absent in all the cases of T-LGL. One case of T- PLL small cell variant showed CD4+/CD8- phenotype, while the other revealed CD4-/CD8+ phenotype. Both cases of ATLL showed CD4+/CD8+/CD25+ phenotype. The single case of PCGDTCL showed CD4-/CD8- phenotype pattern. CD3 and CD5 were expressed in all MTNKL. CD7 was absent in three cases of T-LGL. TCRalpha/beta was performed in three cases of T-LGL and was positive in all. TCRalpha/beta was also seen in both the cases of T-PLL small variant. However, TCRalpha/beta was seen in the single case of PCGDTCL.


CONCLUSION
Mature nodal T/NK cell neoplasms are rare and MTNKL presenting as leukemia are even rarer. There is an overlap between the immunophenotypic profiles of different MTNKL subtypes and elaborate T/NK cell panels are required for their evaluation.