PTPRC and Interstitial pneumonitis: Lung microscopy revealed diffuse interstitial thickening with thin collagen fiber deposits on MT- and VG-stained sections, and with predominantly lymphomonocytic (CD45 positive) cell infiltrates plus some neutrophils and eosinophils, alveolar type II (proSP-B positive) cell hyperplasia and abundant clusters of intra-alveolar macrophages (CD68-positive) with a foamy, PAS-positive cytoplasm, a pattern corresponding to desquamative interstitial pneumonitis (DIP).