The bone marrow agar section: a morphologic and immunohistochemical evaluation.

A technique for agar embedding of bone marrow aspirate particles is compared with the conventional aspirate smear and bone marrow biopsy by reviewing 503 consecutive bone marrow specimens. Immunohistochemical studies were performed on both agar sections and bone marrow biopsies on 43 paired specimens to compare the results between the two preparations. The results were also compared with traditional clot sections from ten control cases. Of the 382 cases with agar sections, 97.7% contained material in the agar that was diagnostic alone or supportive of the diagnosis made with the biopsy and aspirate smear. In two cases (0.4%), focal involvement by lymphoma was identified on the agar section but not in the biopsy sections or aspirate smears. The immunohistochemical studies showed superior immunoreactivity in agar sections by lymphoproliferative disorders when compared with bone marrow biopsy sections. Similar results between agar and conventional biopsy sections were found in cases of metastatic carcinoma and plasma cell dyscrasias.