Autopsy case of CD4–/CD8– cutaneous T‐cell lymphoma presenting disseminated pagetoid reticulosis with aggressive granulomatous invasion to the lungs and pancreas

Pagetoid reticulosis is a rare cutaneous T‐cell lymphoma with striking epidermotropism similar to that present in Paget's disease. There are two forms of pagetoid reticulosis: localized and disseminated. Reported herein is an autopsy case of disseminated pagetoid reticulosis with CD4–/CD8– phenotype T cells and massive invasion of the lungs and pancreas. The abnormal cells in the epidermis expressed a protein derived from a rearranged T‐cell receptor β gene, and this feature was used to confirm the monoclonality of these cells by polymerase chain reaction. At present, the World Health Organization (WHO) classification system considers pagetoid reticulosis to be an indolent form of primary cutaneous T‐cell lymphoma and a variant of mycosis fungoides/Sézary syndrome with prominent epidermotropism. Some differences have been observed between pagetoid reticulosis and mycosis fungoides in terms of clinical course, tumor cell phenotype, and genetic findings; and these differences are highlighted in the present case. The relation between disseminated pagetoid reticulosis, CD4–/CD8– cutaneous T‐cell lymphoma, and γδ T‐cell lymphoma, including whether pagetoid reticulosis is a variant of mycosis fungoides, remains unclear.