Non-Gynecologic Cytology
Respiratory specimens
Sputum, bronchial washings and brushings, and BAL are reported as negative, atypical, suspicious, or malignant, with an attempt to type non-small cell versus small cell carcinoma. Small cell carcinoma shows molding, crush artifact, salt-and-pepper chromatin, and scant cytoplasm; adenocarcinoma forms three-dimensional clusters with prominent nucleoli; squamous carcinoma shows dense cytoplasm, keratinization, and bridges. Watch contaminants: oral squamous cells in sputum and macrophages in BAL are frequent false-positive traps. Curschmann spirals and Charcot-Leyden crystals point to asthma, not infection.
Serous fluids
The central problem is reactive mesothelial cells versus adenocarcinoma. Mesothelial cells are cohesive but show windows, rounded contours, and two-tone cytoplasm; adenocarcinoma shows tight three-dimensional balls, high nuclear-to-cytoplasmic ratio, and prominent nucleoli. Immunopanels: mesothelial markers include calretinin, CK5/6, WT-1, and D2-40; epithelial markers include MOC-31, Ber-EP4, CEA, and B72.3. Never diagnose mesothelioma on cytology alone.
Urine and CSF
Urine follows the Paris System: NHGUC, AUC, SHGUC, HGUC, and unsatisfactory. Catheterized specimens are not screening tests. In CSF, malignant cells must be separated from reactive lymphocytes and ependymal cells; cytospin and cell blocks improve yield.
Trap and rule of thumb
The commonest trap is overcalling reactive mesothelial cells as adenocarcinoma in a patient with cirrhosis or heart failure. If cells form flat sheets with windows and two-tone cytoplasm, think mesothelium and confirm with a panel - morphology plus an epithelial marker, never morphology alone.