pulmonary signet ring adenocarcinoma

Synopsis

 Rare as a pure subtype and uncommon (around 2%) as a component of mixed adenocarcinomas.
 Younger average age when predominant as a component compared to average age of lung cancer patients in general
 Unlike the other subtypes, this variant is defined by cytology—the classic signet-ring morphology.
 Intracytoplasmic material stains with PAS diastase, mucicarmine, and Alcian blue @ pH 2.7—indicating both neutral and acid mucins
 Over 95% of tumors express CK7 and over 80% express TTF-1 but are negative for CK20; also positive for CEA, MUC1 and MUC5AC—a staining profile that helps distinguish this as a primary lung tumor versus metastasis from breast, gastric and colon primaries.
 This is the most aggressive mucinous-type lung adenocarcinoma.
 Tumors with at least 50% signet-ring component have a poorer 5-year survival rate compared to the typical adenocarcinoma prognosis.