Role of Immunostaining in Detecting Extra-Pattern and Subtle Lymphomatous Infiltration in Bone Marrow Biopsies of NHL Patients

Introduction: Immunohistochemistry (IHC) enables the examination of a greater number of trephine biopsy levels and is helpful in determining additional scattered malignant cells. The aim of this study is to detect extra-pattern and subtle lymphomatous infiltration in bone marrow biopsies using CD20 and CD3 immunostaining. Patients and Methods: This study was conducted on 100 newly diagnosed Non Hodgkin Lymphoma (NHL) patients. Their bone marrow trephine biopsies were assessed on routine histology [Hematoxylin and Eosin (H & E)], and were further subjected to IHC using CD20 and CD3. Results: Pattern of involvement by H & E was highlighted by IHC. It showed additional interstitial pattern in 9 cases, parasinusoidal streaks in one case and highlighted a patchy pattern in another case with interstitial involvement on H & E. IHC also detected subtle infiltrations on additional 5.5% cases compared with histology alone. It helped in differentiating reactive (12 cases) and malignant lymphoid infiltration (33 cases). Conclusion: CD20 and CD3 immunostaining performed routinely on bone marrow trephine biopsies has the ability to reveal extra-pattern of infiltration and improve detection of subtle lymphoid involvement. A combined procedure identifying several distinctive features, in particular histotopography and IHC, provides a promising way of discriminating reactive from neoplastic lymphoid infiltrates in bone marrow trephine biopsies.