Mucosa-associated Lymphoid Tissue Lymphoma of a Labial Minor Salivary Gland in an Immunocompetent Child: A Rare Case Report

Mucosa-associated lymphoid tissue (MALT) lymphoma is a low-grade B-cell lymphoma that is exceptionally rare in children, particularly when involving minor salivary glands. A case is presented of a 13-year-old immunocompetent girl who presented with a firm, painless mass on the lower lip, initially suspected to be a mucocele. Histopathological examination revealed dense infiltration of atypical lymphoid cells with lymphoepithelial lesions. Immunohistochemical staining showed CD20 positivity, CD3 negativity, and a low Ki-67 proliferation index. Polymerase chain reaction analysis confirmed B-cell monoclonality, supporting a diagnosis of MALT lymphoma. The lesion was completely excised, and no recurrence was observed during an 18-month follow-up. This case underscores the importance of considering malignant lymphoproliferative disorders in the differential diagnosis of persistent oral lesions, particularly given their potential to mimic benign entities like mucocele or reactive lymphoid hyperplasia. Accurate diagnosis is therefore required and depends on the careful integration of histopathological, immunophenotypic, and molecular findings. This comprehensive diagnostic approach can confirm the diagnosis and guide management, as conservative surgical excision may be sufficient for localized, low-grade cases.