Spontaneous rupture of the spleen is occasionally seen as the presenting event in infectious mononucleosis (IM). Diagnosis of these cases can be very challenging.
We describe the morphologic and immunohistochemical findings in a series of seven splenectomy specimens removed after spontaneous rupture in patients with IM. Most cases were submitted for a second opinion since the histology of the cases suggested malignant lymphoma.
All the cases showed similar findings, with red pulp expansion occupied by activated T and B cells, including scattered large lymphocytes with both T- and B-cell markers, together with a polymorphic background rich in cytotoxic T cells. Clonality analysis revealed T-cell receptor clonal patterns in four of the six cases evaluated.
IM should be considered a possible diagnosis in any case of splenic rupture whose histology suggests possible aggressive lymphoma.