Estudo clinicopatológico, imunofenotípico e genético do linfoma MALT de cavidade oral

Abstract

Lymphomas are solid malignant neoplasms that develop from lymphocytic lineage cells. The presentation of lymphomas in the oral cavity is uncommon and generally consists of non-Hodgkin lymphomas (NHL) of mature B-cell origin, representing about 3% of all extranodal lymphomas. Mucosa-associated lymphoid tissue (MALT) lymphoma, also known as MALT lymphoma, is a low-grade malignant neoplasm that originates from B lymphocytes located in the marginal zone of secondary lymphoid follicles, being the fourth most common type of NHL in the oropharyngeal region. Its morphological and immunohistochemical characteristics are sometimes nonspecific and may overlap with other entities, making the diagnosis of MALT lymphoma a significant challenge and requiring genetic studies for confirmation. This study aims to investigate in detail the clinical, histopathological, immunohistochemical, and molecular characteristics of a series of MALT lymphoma cases in the oral cavity. A cross-sectional observational study was conducted on a convenience sample of 11 cases of MALT lymphoma in the oral cavity, collected from the archives of the Oral and Maxillofacial Pathology Laboratory of the School of Dentistry at the Federal University of Minas Gerais (FAO-UFMG) and from cases received from other diagnostic centers for diagnostic consultation. Immunohistochemical reactions were performed to determine the B-cell lineage, and the proliferation index was evaluated using the Ki-67 marker, along with additional markers to exclude other types of lymphomas or reactive lymphoid processes. In five cases, fluorescence in situ hybridization (FISH) was performed to investigate the presence of MALT1 gene translocation, and the clinical and follow-up data of the patients were collected from their histopathological examination request forms. A total of 11 cases were retrieved, comprising three females and four males. Cases presented a wide age range of 35 to 75 years, with a mean of 58 years, involving the hard palate (3 cases), soft palate (2 cases), and floor of the mouth (3 cases). Histopathologically, all cases demonstrated a diffuse proliferation of small to medium- sized neoplastic cells that infiltrated normal structures. All tumors demonstrated a predominance of CD20-positive cells, but with a large number of CD3-positive reactive T lymphocytes. The expression of Bcl2 was positive in all cases and negative for CD5, Bcl6, and CD10, with a low Ki-67 proliferation index. Five cases were investigated for genetic translocation in the MALT1 gene, all of which were negative. Of the 11 collected cases, all underwent surgery as treatment. Thus, we can conclude that oral MALT lymphoma is an indolent neoplasm whose histopathological diagnosis is quite challenging, and the MALT1 gene translocation was not present in the evaluated sample.