TZ collected the patient clinical data. Castleman disease, pulmonary hyalinizing granuloma, secondary amyloidosis 1.?Introduction Castleman disease (CD), also called angiofollicular lymph node hyperplasia, is an uncommon disease of unknown etiology and intrapulmonary CD has been reported in a few cases.[1,2] In 1980, Plavnick et al reported systemic amyloidosis with CD.[3] The condition is fairly rare that intrapulmonary CD can mimic tumor or even metastatic adenopathy. In this case, a female patient presenting with multiple pulmonary nodules developed amyloidosis secondary to intrapulmonary CD, and was misdiagnosed as pulmonary hyalinizing granuloma (PHG) previously. In the patient, preoperative diagnosis was hard and repeated invasive attempts, especially surgical biopsy was required for pathological diagnosis. 2.?Case statement An 18-year-old female student was referred to our hospital presented with dry cough and dyspnea on exertion for 6 months. The patient denied fever, hemoptysis, excess weight loss, or tobacco use. Past medical history included immune thrombocytopenia for 3 years before the visit, for which she received 1.5 years of oral glucocorticoid. Laboratory examinations revealed iron deficiency anemia (hemoglobin?=?90?g/L), platelet count of 6??109/L, and total white cell count of 4.4??109/L. Urinalysis, liver function, electrolytes, and creatinine were within normal ranges. Her erythrocyte sedimentation rate ( 140?mm/h), C-reactive protein (150.1?mg/L), and serum IL-6 (7.3?pg/mL), IL-8 (279?pg/mL), tumor necrosis factor- (175.0?pg/mL) were significantly elevated. Serum measurement of immunoglobulins showed elevated total IgG of 27.59?g/L, while serum IgG4, M protein, serum, and urine immunofixation electrophoresis and light chain were negative or normal. Hypocomplementemia (C4?=?0.079?g/L), positive antinuclear antibodies (titer 1:160), and positive Coombs test were found. Additional clinically relevant autoantibodies, (1C3)–D-glucan, galactomannan, interferon gamma release assay, and tumor markers were unfavorable or normal. Pulmonary function assessments revealed restriction and decreased diffusing capacity with forced vital capacity of 2.05?L (65.9% predicted), total lung capacity of 2.83?L (68.9% predicted) and diffusing capacity for carbon monoxide of 28.8% predicted. Chest computed tomography (CT) showed multiple well-defined nodules randomly distributed in both lung fields and mediastinum lymphadenopathy, with no significant pleural effusion (Fig. ?(Fig.1).1). Bronchoscopy exhibited Carisoprodol no endobronchial pathological lesions, and a culture of bronchoalveolar lavage fluid showed no evidence of tuberculosis or fungal contamination. Carisoprodol Cytological evaluation was unfavorable for malignant cells. A CT-guided percutaneous lung biopsy was performed, and histopathological examinations revealed some defining features for hyalinizing granuloma, including homogenous hyaline lamellae around small blood vessels and dense infiltrates of lymphocytes, plasma cells with frequent lymph follicle formation (Fig. ?(Fig.2).2). The patient was diagnosed with PHG, and Carisoprodol received prednisone 1?mg/kg/d Carisoprodol and tacrolimus. Unfortunately, 6 months after initiation of therapy with prednisone gradually tapered, neither pulmonary lesions nor platelet level revealed remarkable interval switch. As detailed investigations in medical center failed to uncover any more underlying condition, the patient underwent video-assisted pulmonary wedge biopsy. Open in a separate window Physique 1 Chest CT showing multiple bilateral lung nodules. CT = computed tomography. Open in a separate window TNF-alpha Physique 2 Histopathology of the pulmonary mass demonstrating bundles of hyalinized collagen fibers surrounding small vessels and lymphoplasmacytic infiltration (HE stain, 40). HE = hematoxylin and eosin. Intraoperatively, multiple white and tough-elastic nodules were found in the upper and lower lobes of lung, partially fused to mass, with pulmonary Carisoprodol parenchyma edema surrounded. One isolated lesion was dissected from your left upper lobe, which contained 2 nodules. The diameters of nodules were 1 and 2?cm, and specimens were sent for microorganism culture and pathological examination, respectively. Microorganism culture was unfavorable. Pathologic exam revealed nodular interstitial pink deposits in lungs which stained.