Implementation of the recommended immunohistochemistry algorithm for classification of peripheral T-cell lymphoma, not otherwise specified into the prognostically significant GATA3 and TBX21 subtypes.

Although the algorithm is reproducible, a proportion of cases remains unclassifiable and may require additional investigation and gene expression profiling. The GATA3 subgroup was found to have a monomorphic population with a poor overall prognosis and thus requires a larger sample size for validation.