[Clinicopathologic and immunohistochemical studies of midline malignant reticulosis in palate]

Fourteen patients (10 males and 4 females) with midline malignant reticulosis (MMR) in palate were studied. The symptoms were most commonly swelling and ulceration. In some cases, the lesion involved nasal, maxillary sinus and facial skin, but no regional lymph nodes were involved. A necrotizing infiltration of atypical lymphoid cells (ALCs) mixed with inflammatory cells was confirmed as the histopathologic feature of MMR. In 2 of 14 cases, ALCs formed a continuous sheet in several high-power fields with a few inflammatory cells. This overlapping feature may be a transitional form between MMR and malignant lymphoma. Immunohistochemical staining results indicated that in 10 of 14 cases, ALCs were CD3 positive; in 7 of 14 cases, ALCs were UCHL1 positive; and in all 14 cases, ALCs were L26 negative. We deem MMR a T-cell lymphoma in substance, but it should be treated as a histopathologic entity distinct from malignant lymphoma.