What causes a tan-white discoloration on the heart and lungs?

Tan-White Discoloration on Heart and Lungs: Causes

The most common causes of tan-white discoloration affecting both the heart and lungs are histiocytic neoplasms, particularly Erdheim-Chester disease (ECD), which characteristically produces xanthomatous (yellowish-brown) infiltration of multiple organs including pericardium, myocardium, and lung parenchyma. 1

Primary Differential Diagnosis

Erdheim-Chester Disease (Most Likely)

• ECD produces characteristic yellow-brown or xanthomatous tissue infiltration that appears as tan-white discoloration grossly 1
• Cardiovascular involvement occurs in 50-70% of patients, manifesting as pericardial infiltration with effusion or myocardial infiltration (right atrial pseudotumor in 30-37% of cases) 1
• Pulmonary involvement is seen radiologically in approximately 50% of cases, presenting as mediastinal infiltration, pleural thickening, interlobular septal thickening, or ground-glass opacities 1
• Cutaneous manifestations include yellow-brown xanthomatous papulonodules and plaques, most commonly around the eyes as xanthelasma-like lesions 1
• Unlike pulmonary Langerhans cell histiocytosis, there is no association with cigarette smoking 1

Langerhans Cell Histiocytosis (LCH)

• Pulmonary involvement occurs in up to 20% of patients with histiocytic neoplasms 1
• Cardiac involvement is almost never seen in LCH, making it less likely when both organs are affected 1
• Cutaneous manifestations may include xanthomatous lesions appearing as red to purple nodules with a yellowish hue 1
• Strong association with cigarette smoking in pulmonary LCH 1

Rosai-Dorfman Disease (RDD)

• Skin and subcutaneous involvement occurs in 50% of patients, presenting as red-to-brown macules, papules, or xanthomatous nodules 1
• Cardiac involvement is less frequent than in ECD but more common than in LCH 1
• Endocrine and respiratory manifestations are very infrequent 1

Alternative Causes of Tan-White Lung Discoloration

Organizing Pneumonia Patterns

• Dense fibrosis or organizing pneumonia can appear white or tan on gross examination 1
• The tumor bed in post-neoadjuvant therapy specimens may show tan-white fibrotic changes that must be distinguished from viable tumor 1
• Organizing pneumonia consists of granulation tissue within small airways and alveolar ducts with surrounding chronic inflammation 1

Pulmonary Alveolar Proteinosis

• Characterized by accumulation of phospholipoproteinaceous material in alveoli 1
• BAL effluent yields sandy-colored or light-brown fluid from affected segments 1
• Histology reveals alveolar filling by granular lipoproteinaceous substance staining deep pink with periodic acid-Schiff stain 1
• Does not typically involve cardiac tissue 1

Diagnostic Approach

Imaging Evaluation

• CT chest with contrast is mandatory to characterize the extent of cardiac and pulmonary involvement 2, 3
• For cardiac assessment, echocardiography should be performed to screen for pericardial effusion and myocardial infiltration 1
• HRCT findings in ECD include mediastinal infiltration, pleural thickening, interlobular septal thickening, and ground-glass opacities 1

Tissue Diagnosis

• Bronchoscopic or surgical lung biopsy is necessary for definitive diagnosis 1
• Histologic examination should specifically look for foamy histiocytes with xanthomatous features characteristic of histiocytic neoplasms 1
• Immunohistochemistry for CD1a (positive in LCH) and CD68 (positive in ECD and RDD) helps differentiate between histiocytic disorders 1

Laboratory Assessment

• BAL with CD1a staining (>5% diagnostic for LCH) 1
• Evaluation for BRAF V600E mutation (present in 50-70% of ECD cases) 1

Critical Pitfalls to Avoid

• Do not assume bilateral lung involvement excludes unilateral processes, as histiocytic neoplasms can present asymmetrically 2
• Do not dismiss xanthomatous skin lesions as benign xanthelasma without systemic evaluation, as they may indicate underlying ECD 1
• Do not attribute tan-white cardiac masses to simple pericardial effusion without tissue characterization, as infiltrative processes require specific treatment 1
• Do not delay tissue diagnosis when imaging shows characteristic patterns, as early treatment of histiocytic neoplasms improves outcomes 1