Progressive transformation of germinal centers (PTGC) can mimic NLPHL clinically and histologically.
On low magnification, progressively transformed follicles are similar to NLPHL nodules in that they are composed of nonneoplastic mantle cells.
On low-power magnification, it may closely resemble NLPHL or PTGC (Figure 4).
Of these subtypes, lymphocyte-rich classical Hodgkin lymphoma (LRCHL) is the most difficult subtype to differentiate from NLPHL and misclassification has frequently been found in retrospective studies.
As the treatment and prognosis of this lymphoma differ markedly from NLPHL, appropriate classification is essential.
In excisional biopsies, these T-cell-rich areas often coexist with nodular areas and can be recognized and appropriately classified as NLPHL (Figure 6, A and B).
In small biopsies, including core biopsies, the distinction between NLPHL and THRLBCL can be treacherous.