The histopathology, immunophenotype and clinical presentation in 35 cases of midline malignant reticulosis (MMR) were studied with 8 cases of midfacial non-specific inflammation as the control during immunohistochemical staining. The result showed that atypical lymphoid cells (ALC) of MMR could be divided into small, intermediate and large ALC subtypes basing on their sizes. Twenty-three of the 35 cases (65.7%) showed dominant small and medium-sized ALC proliferation, meanwhile, ALC infiltrating into the mucosa and vascular walls were also small and medium-sized cell predominant. Immunohistochemical study showed that the UCHL1 positive small lymphocytes proliferated predominantly in MMR; in contrast, many Ki-B5 positive lymphocytes appeared in midfacial inflammation. ALC of MMR in 27 cases (71%) also showed UCHL1 positive reaction but negative reaction to Ki-B5 and lysozyme. The result indicates that ALC of MMR belongs to T-lymphocyte origin and MMR may be a kind of peripheral T-cell lymphoma originated from mucosa-associated lymphoid tissue (MALT). The relations between MMR, malignant lymphoma and other related disorders of MALT are discussed.