Primary pulmonary follicular lymphoma

Primary malignant lymphomas of the lung are very rare. Most of them are extranodal marginal zone B-cell lymphoma of MALT type. Primary follicular lymphoma of the lung is extremely rare. A 50-year-old woman presented with cough and sputum, and consulted to a private hospital, where she was pointed out to have abnormal lung shadow by chest X–P. She was admitted to our hospital for scrutiny. Imaging modalities including CT, MRI, and PET revealed a small (15 mm in diameter) nodule in the right middle lobe beneath the pleura. No other tumors were found by these techniques. A biopsy revealed a lymphoid proliferation. Clinical cytology was negative. A wedge resection with wide margins was performed. Grossly, the resected lung specimen contained a white solid mass measuring 12 × 13 × 13 mm. Microscopically, the mass was composed of follicular proliferation of atypical lymphocytes. There were no tingible body macrophages, and normal follicular polarity was absent. Mild infiltrative growth from the surrounding lung was present. Lymphoepithelial lesions were not recognized. The atypical lymphocytes consisted of centrocytes, centroblasts, and small lymphoid cuffs. The centroblasts are seen in 3–5 per a high power field. The immunophenotypes were CD45 +, CD5 +, CD10 +, CD23 +, cyclin D1 −, CD20 +, CD21 +, CD79α +, bcl-2 +, bcl-6 −, CD3 −, CD45RO −, CD30 −, CD15 −, κ-chain +, and λ-chain −. The Ki-67 labeling was 36%. The overall appearances suggested that the lesion was primary pulmonary follicular lymphoma, grade I. Discussion of differential diagnosis from nodular lymphoid hyperplasia, extranodal marginal zone lymphoma of MALT type, and mantle cell lymphoma was made.