Background Fascin is an actin cross-linking protein, which is part of the cytoskeleton and involved in cell motility in several cell types. The differentiation of epithelial cells is greatly influenced by cell–matrix and cell–cell interactions, which play an important role in the normal organisation and stabilisation of epithelial cells and maintain the cells in a non-migratory state. The malignant conversion of epithelial cells results from a phenotypic switch to a migratory state, which allows tumour invasion beyond the basement membrane, as well as metastasis. Such a switch requires complex rearrangements of the actin cytoskeleton and is governed by multiple actin-binding proteins including fascin. In non-neoplastic lymphoid tissue, fascin expression is highly selective and is predominantly localised in dendritic cells, while lymphocytes, plasma cells, etc are uniformly non-reactive. However, all or nearly all Reed–Sternberg cells and their variants in all types of Hodgkin's lymphoma express fascin and are strongly immunoreactive for fascin.

Conclusion Lymphomas (Hodgkin's and non-Hodgkin's) are among the commonest malignancies seen in our practice. The Section of Histopathology at the Aga Khan University, Karachi is the largest centre for histopathology in Pakistan, a densely populated country with an estimated population of 170 million. The authors wanted to test the utility of Fascin in distinguishing between Hodgkin's lymphoma and morphologically closely related forms of non-Hodgkin's lymphoma such as diffuse large B cell non-Hodgkin's lymphoma and anaplastic large cell lymphoma in difficult cases. If found useful, this antibody could help us in reaching a correct diagnosis in difficult cases and allow appropriate patient management.