Primary follicular immunoblastic lymphoma (FIBL) is an extremely rare lymphoma. The positive expression of CD10 suggests the lymphoma originating from germinal centers (GC) and CD138-positive expression generally indicates plasmablastic or plasmacytic differentiation. We report such a rare case in a Chinese female patient and analyze the clinicopathologic and immunohistochemical features of this disease. PET-CT examination was performed to detect signs of systemic lymph node metastasis. We also discussed the differential diagnosis of FIBL from follicular lymphoma (FL) and reactive follicular hyperplasia (RFH). As a rare variant of human follicular lymphoma, FIBL is featured by a neoplastic overgrowth of intrafollicular immunoblasts. Compared with FL, FIBL has a greater chance to evolve into diffuse large B-cell lymphoma with therefore a poorer prognosis.