Primary Muscle Diffuses Large B-cell Lymphoma: A Rare Extranodal Presentation

Abstract

Malignant Non-Hodgkin lymphoma (NHL) is a common tumor, with extranodal involvement observed in nearly 40% of cases. Primary lymphomas of soft tissues, particularly those involving skeletal muscle, are extremely rare, with intramuscular involvement accounting for less than 1.5% of patients. This condition can affect individuals of all ages and is characterized by a wide diversity of clinical, morphological, and molecular presentations. The median age at diagnosis is around 60 years, with a slight male predominance. Its treatment combines surgical resection, chemotherapy, and radiotherapy. We report the case of a 60-year-old patient presenting with a primary muscular Diffuse large B-cell lymphoma located in the left psoas muscle, managed in our hematology department at Hôpital 20 Août 1953. Histopathological examination of the muscle biopsy revealed a diffuse lymphomatous process composed of large cells. Histology showed sheets of large atypical cells with moderately eosinophilic or sometimes clear cytoplasm, irregular nuclei, often prominently nucleolated, with nuclear indentations or clefts. Definitive diagnosis relies on histological examination of the muscle biopsy, which allows identification of the lymphomatous nature of the infiltrates and exclusion of other infiltrative muscular diseases. Most of these lymphomas exhibit a B-cell immunophenotype; however, two other reports of primary muscular lymphoma with a T-cell morphology have been described.