Evaluation of Solitary Lung Mass Vishal Sagar, M.D. Chicago Medical School Chicago, Illinois

Pulmonary Mass vs Pulmonary Nodule Most authorities consider a size of 3-4 cms as the cut off limit for differentiation between pulmonary mass and pulmonary nodule Reason for differentiation- different etiologic factors need to be considered if the size is greater than 3-4 cms

Classification of Etiologic factors in a Solitary Pulmonary Mass Developmental Infectious Neoplastic Inhalational Traumatic Immunologic

Developmental Intralobar sequestration Almost invariably contiguous to the diaphragm in the posterior bronchopulmonary segment Typically well defined margin Cyst formation relatively common Although cystic in nature, mass remains homogeneous until communication is established with contiguous lung as a result of infection

Infectious Granulomas Histoplasmosis Coccidiodomycosis Tuberculosis Atypical Mycobacteria Cryptococcosis Blastomycosis

Lung Abscess Predilection for posterior portions of upper or lower lobes Tends to be round Ill defined margins when acute but well defined when chronic No calcification Cavitation is common Etiology- usually Staph or anaeobes Mass may remain unchanged for many weeks

Other Infections Ascariasis Pneumocystis Carinii Aspergilloma Paragonimus Westermani Hydatid Cyst

Hydatid Cyst Causative organism- Echinococcus Granulosus Predilection for lower lobes Tends to have bizarre, irregular shape Calcification may be seen - though extremely rare

Neoplastic Benign Malignant Primary Lung Ca Metastatic

Benign Tumors Hamartoma Lipoma Fibroma

Characteristics that help determine benign nature of the pulmonary mass Age less than 35 Absence of risk factors like smoking or exposure to occupational carcinogens Small size of the mass ( Size of > 3 cms is associated with an 80% chance of malignancy) Doubling time < 20 Days or > 400 Days Certain patterns of calcification Diffuse Central Laminated Pop corn

Primary Pulmonary Carcinoma Even though all cell types of lung cancer can present as a solitary peripheral lung mass- it is most commonly seen in adenocarcinoma Margins tend to be ill defined Foci of calcification seen on CT in about 5% to 10% of large tumors Cavitation relatively common

Metastasis Uncommon for pulmonary metastasis to present as a solitary mass Tends to be sharply defined and lobulated Calcification is rare- almost exclusively restricted to metastatic osteogenic sarcoma or choondrosarcoma

Inhalational Foreign Body Inhalation Lipid Pneumonia Silicosis Coal Workers Pneumoconiosis Round Atelectasis

Foreign Body Inhalation Broken fragments of teeth Food particles Flowering heads of various grasses Oral medications Patients might give a history of recent dental work, general anesthesia or there might be a history of altered consciousness predisposing them to foreign body inhalation/aspiration

Lipid Pneumonia Inflammatory reaction associated with oil or fat in the alveoli Usually aspiration of mineral oil used as laxative Dependent portions of upper and lower lobes Well defined shape but often has a shaggy outer margin No calcification seen CT scan often allows specific diagnosis by demonstrating foci of fat attenuation

Silicosis Initially involves the periphery of the mid and upper lung zones Margins may be irregular and somewhat ill defined, simulating pulmonary carcinoma A background pattern of diffuse silicosis may be apparent Hilar lymph node enlargement is common and may be associated with “eggshell calcification”

Coal Workers Pneumoconiosis Marked predilection for upper lobes Shape- similar to large opacities of silicosis Calcification generally not seen May Cavitate A background of diffuse nodular or reticulonodular shadows is usually evident

Round Atelectasis Most commonly associated with asbestos exposure Lower zonal predominance, abuts localized area of pleural thickening Shape is generally round or oval No calcification CT shows the mass abutting a thickened pleura; vessels and bronchi curve toward the periphery of the mass

Traumatic Pulmonary Hematoma Usually deep to the point of maximal trauma It is generally sharply defined, round or oval- No calcification No cavitation Resolution may take several months

Immunologic Wegners Granulomatosis Sarcoidosis Extremely Rare for these to present as solitary lung mass

References Focal and Multifocal Lung Disease, ScientificAmerican Medicine, IV, 1-19 Textbook of Respiratory Medicine, 3rd Edition,Murray, Nadel, Mason, Boushey. Fraser and Pare's Diagnosis of Diseases of the Chest, 4th edition- Fraser, Muller, Colman, Pare. Textbook of Pulmonary Diseases, Fifth edition- G.L.Baum, Emanuel Wolinsky.