Monomorphic Epitheliotropic Intestinal T-Cell Lymphoma With Secondary Cutaneous Involvement: A Diagnostic Challenge

<jats:title>Abstract:</jats:title> <jats:p>A 45-year-old woman presented with a solitary breast nodule that histologically corresponded to a dense dermal/subcutaneous infiltration of atypical cytotoxic T-lymphocytes (CD3<jats:sup>+</jats:sup>, CD8<jats:sup>+</jats:sup>, CD56<jats:sup>+</jats:sup>, TIA-1+, CD5<jats:sup>−</jats:sup>, CD4<jats:sup>−</jats:sup>, CD30<jats:sup>−</jats:sup>, EBV<jats:sup>−</jats:sup>), resembling subcutaneous panniculitic T-cell lymphoma. The presence of TCRδ gene rearrangement and the absence of βF1 expression let to suspect the diagnosis of primary cutaneous γδT-cell lymphoma. As a consequence of jejunum perforation following chemotherapy treatment, a mucosal atypical lymphoid infiltration with marked epitheliotropism was observed in the resected intestinal sample, and the diagnosis of monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) was finally established. Disease progression appeared with multiple erythematous plaques showing a dense lichenoid atypical cytotoxic T-cell infiltrate with intense epidermotropism, mimicking primary cutaneous epidermotropic aggressive CD8<jats:sup>+</jats:sup> T-cell lymphoma. MEITL is an uncommon and aggressive peripheral T-cell lymphoma that often presents in adults with gastrointestinal symptoms. Secondary cutaneous involvement is a rare phenomenon that may show clinicopathologic and immunohistochemical features that overlap with different subtypes of primary cutaneous cytotoxic T-cell lymphomas. In the absence of gastrointestinal symptoms, the diagnosis may be challenging, and only the evidence of underlying MEITL may allow to establish the definite diagnosis.</jats:p>