Systemic ALK-negative anaplastic large cell lymphoma with distinctive myxoid change and DUSP22 rearrangement.

Systemic anaplastic lymphoma kinase-negative (ALK-) anaplastic large cell lymphoma (ALCL) comprises a genomically heterogeneous disease that is considered a distinct entity by the 2016 World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues. Other than lymph nodes, systemic ALK- ALCL may affect extranodal tissues, sites where the inflammatory background may be especially prominent. In this scenario, myxoid change is exceptional in systemic ALK- ALCL. We describe a rare case of systemic ALK- ALCL with distinctive myxoid changes, carrying specific chromosomal aberrations that affect the clinical outcome. Careful morphological, immunohistochemical, and molecular workup is mandatory because a myxoid background should not be a reason to ignore the possibility of a lymphoma. Finally, extensive correlation with staging and the detection of prognostic biomarkers such as DUSP22 and TP63 rearrangements are essential for the diagnosis and prediction of clinical outcome in ALK- ALCL.

ALK-negative anaplastic large cell lymphoma with "Hodgkin-like" cytomorphology and nuclear expression of PAX5.

Anaplastic lymphoma kinase negative systemic anaplastic large cell lymphoma (ALK-ALCL) is a CD30+ T-cell malignant lymphoma which may involve both lymph nodes and extranodal tissues, showing important clinical differences from ALK-positive ALCL (ALK + ALCL). ALK- ALCL is considered a specific entity by the 2016 World Health Organization (WHO) classification of hematolymphoid neoplasms.We describe an exceptional case of ALK- ALCL with a striking "Hodgkin-like" cytomorphology and a very uncommon nuclear expression of PAX5.