Abscess

• RLL>RML>LLL;

• PMN, debris, microphage, bacteria and aspirates;

• Atypical squamous metaplasia mimics squamous cell carcinoma;

• Culture or special stains necessary.

Granuloma

• Causes: TB, atypical mycobacteria, sarcoid, fungi, aspirate, granulomatosis and cancer;

• Nodular collections of epithelioid histocytes: elongated nuclei, fine chromatin, tiny nucleoli and fibrillar cytoplasm;

• Reactive atypia or squamous metaplasia may lead to false positive diagnosis;

• Culture of special stains necessary.

Pulmonary Infarct

• Peripheral of the lesion: marked reactive atypical glandular cells--mimic adenocarcinoma;

• Center: squamous metaplasia, regeneration or repair--mimics SCC; (Hint: few atypical cells, continuum from benign to atypical)

• Numerous histocytes contains hemosiderin, lipid or RBC;

• Chronic or acute inflammation, necrosis or granulation.

Hamartoma

• 75% of benign lung tumors; located in subpleural parenchyma;

• Well-demarcated, lobulated, sometimes calcified (popcorn);

• Cartilaginous or fibromyxoid aspirate (mimics pleomorphic adenoma);

• May contain bronchial cells with reactive atypia--mimic carcinoma (Hint: clean background, no necrosis)

• Other: fat, muscle.

Inflammatory Pseudotumors

• Mainly in young patient;

• Inflammatory cells and myofibroblasts; edematous, myxoid, fibrous or hyalinized stroma;

• Fibroxanthoma (xanthogranuloma): prominent histiocytes;

• Plasma cell granuloma: plasma cell predominant; DDX-plasmacytoma: pure population, moderately-differentiated; monoclonal;

Pseudo lymphoma

• Polyclonal, mixed variable mature cells;

• Benign reactive follicles;

• Non-invasive, no hilar adenopathy.

Sclerosing Hemangioma (Type II Pneumocytoma)

• Sheets or single uniform bland cells in a bloody background; cells surrounding small vessels or sclerosing cores;

• Round, columnar cell with moderate amount of granular cytoplasm; may show smaller, cuboidal, signet-ring or spindle cells;

• Nuclei: round, oval with fine chromatin, may have distinct nucleoli;

• DDX-Bronchioloalveolar carcinoma, papillary carcinoma: monophase, more cellular, more atypical.

Reference

• The art and science of cytopathology. Richard M Demay, MD. 1996