Primary mediastinal large cell lymphoma with sclerosis containing a large number of T cells - Differential diagnosis

Primary mediastinal large cell lymphoma with sclerosis (PMLS) occurs primarily in relatively young female patients. We report such a case in a 28-year-old woman with superior vena cava (SVC) syndrome. Because of the SVC syndrome, immediate diagnosis was highly desired. However, because of the small size of the mediastinal biopsy, lack of monoclonality by flow cytometric immunophenotyping (FCI), and areas that were rich in T cells, the diagnosis could be made only by immunohistochemical analysis (IH), which revealed the L-26(+), LCA(+) clusters of cells. We describe our findings and discuss the differential diagnosis. This case underscores the importance of always correlating the histologic and FCI findings and performing appropriate IH when indicated.