Lymphoma - mediastinal
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Core biopsy was performed.
The cores show sclerosis with an infiltrate of small lymphocytes, neutrophils, eosinophils and plasma cells. Within this background infiltrate are moderate numbers of atypical lymphoid cells whose morphology is not well preserved. These cells form a nodule and are large and pleomorphic with nuclear irregularities with many showing nuclear lobularity or multinucleation. Some cells have prominent eosinophilic nucleoli. Occasional binucleate cells are present.
Immunohistochemistry: The large atypical cells are negative for CD45, CD79a, ALK and CD3. There is variable CD20 staining with some cells positive and some negative. CD30 and CD15 are both positive. CD23 stains some large cells. EBER stain is negative.
Left mediastinal mass biopsy consisten with lymphoma.
Comment: the morphology of the large atypical cells, polymorphous background, and immunohistochemistry findings favour classic Hodgkin lymphoma over the differential diagnosis of mediastinal large B cell lymphoma. The CD23 positive staining is more typically seen however in mediastinal large B cell lymphoma as is the negative EBER stain.
This case illustrates how although pathology is considered the gold standard, even histology sometimes cannot establish a precise diagnosis 100% of the time.