Presence of lymphocyte membrane surface markers on “small cells” in a pineal germinoma

A 16‐year‐old boy was operated on via an occipital transtentorial craniotomy for a pineal tumor. Routine histological examination of the tissue revealed it to be a germinoma, as characterized by the presence of two cell populations: large cells and small, lymphoidappearing cells. The cells were evaluated in a singlecell suspension for the peresence of lymphocyte membrane surface markers; small cells exclusively were found to have such markers; A T‐lymphocyte membrane marker was present in 81% of the small cells, whereas 15 to 18% of the small cells had a Blymphocyte membrane marker.