Cutaneous Involvement by Blastoid Mantle Cell Lymphoma Presenting as Cervical Abscess: A Rare Extranodal Diagnostic Challenge.

Mantle cell lymphoma (MCL) is a rare and heterogeneous subtype of B-cell non-Hodgkin lymphoma (NHL), defined by the t(11;14)(q13;q32) translocation leading to overexpression of cyclin D1. The blastoid variant represents a highly aggressive form, with a high mitotic index and unfavorable prognosis. Cutaneous involvement by mantle cell lymphoma is rare and may present with atypical clinical features, often leading to delayed diagnosis due to morphological overlap with other high-grade lymphomas and unusual extranodal presentations. We describe a 73-year-old male who presented with a solitary fluctuant swelling over the left cervical region clinically suspected to represent an abscess, without systemic symptoms or lymphadenopathy. Contrast-enhanced imaging revealed a localized lesion without additional lymphadenopathy. Histopathological examination of a core biopsy demonstrated medium to large atypical lymphoid cells. Immunohistochemistry showed strong expression of CD20, CD5, cyclin D1, SOX11, and a high Ki-67 proliferation index (~90%-95%), supporting a diagnosis of blastoid variant MCL. These cells were immunonegative for CD3, CD10, BCL6, and CD30, excluding other high-grade lymphomas. This case highlights an unusual presentation of blastoid mantle cell lymphoma, manifesting as an abscess-like cutaneous lesion of the neck and underscores the importance of histopathologic and immunophenotypic evaluation in atypical cutaneous swellings. Early recognition, facilitated by histopathological and immunophenotypic evaluation, is critical for initiating timely and appropriate treatment in such aggressive lymphomas.