1. c. In taking biopsies of the lungs, tips of lobes and lingual are to be avoided. Inflation of the surgical specimen with formalin should be performed to avoid specimen atelectasis, which makes assessment of interstitial lesions difficult. All of the remaining items should be performed, as well as sampling for electron microscopy.

2. b. Erdheim-Chester disease is a rare disease characterized by infiltration of histiocytes staining variably with S100, but not staining with CD1a. In addition to the foamy histocytes, the disease may also display presence of multinucleated histiocytes, eosinophils, plasma cells, and few lymphocytes. The main differential diagnosis of this disease is Langerhans cell histocytosis.

3. c. The oil red O stain reveals lipid droplets within macrophages. This is a feature found in aspiration pneumonia. Slides made from BAL material requires that they are not mounted using conventional methods including xylene washes, rather an aqueous mount is needed to retain lipid vacuoles.

4. e. Clara cells are columnar nonciliated bronchial cells with a role in surfactant and protease inhibitor production. Kulchitsky cells are basally oriented cells with numerous neuroendocrine granules, with unknown specific function to date. Serous and goblet cells secrete serous and mucinous excretions, respectively. Aschoff cells are found in rheumatic carditis.

5. e. Patients with systemic lupus erythematosus (SLE) present with pleuritis, siderophages, and capillaritis in the acute phase. A second presentation in SLE consists of a cellular plasmacytic/lymphocytic interstitial pneumonia with variable amounts of fibrosis, categorized as a nonspecific interstitial pneumonia. Giant cells and granulomas are however not present. The remaining disease entities contain the features noted in the question.

6. c. A diagnosis of pulmonary alveolar proteinosis (PAP) requires the exclusion of several possible entities including edema, infection, and the like. The intra-alveolar material present in PAP is PAS-positive, diastase resistant, excluding several other disease entities. Nocardia infection is known to be associated with PAP, hence its exclusion needs to be performed. The exudate in Pneumocystis pneumonia is foamier as compared with PAP. Autoantibodies to GM-CSF are found among adults with acquired PAP. Mutation on surfactant protein B is in the congenital form, and is lethal.

7. d. This H&E picture depicts hyaline membrane disease. The membrane may become fragmented and faintly basophilic by the action of bacteria. The lungs are usually firm and atelectatic and not emphysematous. The remaining entities are potential differential disease to be considered; however, each has unique features not depicted in this H&E.

8. e. The granulomas in WG are characterized by involvement of bronchovascular regions, including large vessels, inflammatory infiltrate rich in eosinophils, and a less-defined appearance compared with the granulomas in sarcoidosis. Early changes may be as subtle as neutrophilic capillaritis of the alveoli.

9. c. Rare pulmonary involvement with Whipple disease is known. Sheets of histiocytes with PAS positive granules along bronchovascular bundles are typically noted. Eosinophils are rarely seen.

10. e. The most significant injury is at the level of bronchioles and acini with obstructive necrotizing bron chiolitis. Late phase of the disease is characterized by fibrosis, metaplasia and atrophy.

11. e. Small cell carcinoma seldom presents as exophytic endobronchial lesions as would be noted with bronchial carcinoids. It usually presents with circumferential infiltration beneath the bronchial mucosa.

12. c. IPH is associated with the presence of large numbers of hemosiderin-laden macrophages in BAL specimens. Eosinophilia and iron deficiency anemia are seen, usually with normal renal function and no associated immunological diseases. Wegener granulomatosis should have components of giant cells, granulomata, and presence of ANCA positivity for confirmation.