PAX5-NEGATIVE HODGKIN-LIKE LYMPHOMAS: A DIAGNOSTIC CHALLANGE

Hodgkin lymphoma (HL) is a lymphoma that arises from peripheral B lymphocytes. However, the neoplastic cells, Hodgkin cells and Reed-Sternberg cells, typically lack most B-cell markers, usually preserving the expression of the transcriptional factor PAX5, only phenotypic clue of B-cell origin. Morphologically similar cells to those diagnostic Hodgkin and Reed-Sternberg cells can also be observed in other lymphocytic proliferations, including Anaplastic Large Cell Lymphoma (ALCL), which originates from T lymphocytes and which share many features with HL, like strong CD30 expression and usually loss of T-cell markers. However, their clinical course is dramatically different with curability rates of \>90% for classical HL and an unfavorable prognosis for ALCL. PAX5 expression in HL and cytotoxic molecules expression in ALCL tumor cells may be a useful aid for diagnosis. However, in some cases the differential diagnosis is difficult owing to absence of these established markers. Furthermore, clonality analyses on classical HL were focused on Ig regions while TCR clonality has not yet been usefully explored. Studying the TCR clonal status of tumor cells, correlating it with a more comprehensive immunophenotypic profile and investigating the presence or absence of characteristic rearrangements (such as the JAK2 rearrangement, typical of ALCL lymphomas) could help to resolve the immuno-morphological overlap of the two entities and identify a possible repetitive pattern based on morphological, phenotypic and genetic characteristics. To this aim we intend to involve the Pathological Anatomy of Tubinga to increase the number of cases and achieve statistical significance, given the relative rarity of this entity