Lung Carcinoma: High-Yield Pathology
Lung cancer is the leading cause of cancer-related mortality globally. Classification is essential for determining management (Small Cell vs. Non-Small Cell).
1. Classification & Key Associations
| Type | Location/Histology | Key Features/Paraneoplastic |
|---|---|---|
| Small Cell (SCLC) | Central; Kulchitsky cells. | ACTH (Cushing), SIADH. Amplification of the MYC oncogene. |
| Squamous Cell | Central; Keratin pearls. | PTHrP (Hypercalcemia). |
| Adenocarcinoma | Peripheral; Glandular. | Most common, associated with smoking and scarring. |
| Large Cell | Peripheral; Anaplastic. | Diagnosis of exclusion; aggressive. |
2. Exam Must-Knows
- Pancoast Tumor: Located in the apex (superior sulcus). Can compress the cervical sympathetic plexus, leading to Horner syndrome (ptosis, miosis, anhidrosis).
- Superior Vena Cava (SVC) Syndrome: Obstruction of the SVC, commonly by central lung masses (SCLC or Squamous), leading to facial plethora, JVD, and upper extremity edema.
- Adenocarcinoma In Situ: Formerly known as Bronchioloalveolar carcinoma; grows along alveolar septa (lepidic growth pattern).
Pathology Board Hint: For NEET PG and USMLE, memorize the “Central” vs. “Peripheral” locations: SCLC and Squamous are Central (think “S” for SCLC/Squamous/Small cell/Syndrome), while Adenocarcinoma is Peripheral.