Pediatric mucosa-associated lymphoid tissue (MALT) lymphoma of lip: a case report and literature review

Mucosa-associated lymphoid tissue (MALT) lymphoma is listed in the new World Health Organization classification as extranodal marginal zone B-cell lymphoma of MALT. Most cases occur predominantly in adults and are rare in children or adolescents. We report, with a review of earlier literature, a MALT lymphoma of the lower lip in a 7-year-old immunocompetent child. The patient had a sessile, indurated, and firm mass on the lower lip without regional lymphadenopathy. Microscopically, dense lymphoid cell infiltrates composed of small- to medium-sized centrocyte-like cells and plasmacytoid cells infiltrating around scattered reactive germinal centers were observed, with formation of typical lymphoepithelial lesions. Immunohistochemical staining demonstrated positivity of atypical lymphoid cells for CD20, CD43, CD79a, and Bcl-2 and negativity for CD3, CD5, CD10, CD23, Ki-1, Bcl-10, and ALK. Cytoplasmic kappa light chain restriction was demonstrated. We conclude that this case represents the youngest patient with a MALT lymphoma of the lip.