Lung Tumors Flashcards
Major Types of Primary Neoplasms of the Lung
- Carcinomas (about 90% of all primary lung neoplasms).
- Carcinoid tumors (about 5%).
- Other neoplasms (the rest; a diverse group with many rare entities).
Current Histologic Classification
- Small cell carcinoma (15% of cases).
All of the rest are “Non-small cell” carcinomas:
- Squamous cell carcinoma (30%).
- Adenocarcinoma (40%).
- Large cell carcinoma (10%)
- Other rare types of non-small cell carcinoma (5%).
Key concepts about the histologic classification of lung cancer
- All of the histologic types are believed to originate from the same progenitor (undifferentiated) cell.
- Two important histologic distinctions that dramatically change treatment:
a. Small cell carcinoma versus non-small cell carcinoma.
b. Adenocarcinoma versus squamous cell carcinoma.
Gross Appearance of Primary Lung Cancer
- Hilar - originate in large bronchi
- Peripheral
Gross Appearance of Primary Lung Cancer - Hilar
Some originate in large bronchi and are thought of as hilar; these are often a squamous cell carcinoma or small cell carcinoma.
a. Firm infiltrating solid gray-tan mass arises in intimate association with a large bronchus.
b. However, all histologic types of lung cancer may form a hilar mass, and one cannot tell them apart grossly
Gross Appearance of Primary Lung Cancer - Peripheral
Peripheral lung cancers are not associated with a large airway and are often subpleural with a scar that puckers or retracts the pleura adjacent to them, and most commonly are adenocarcinomas.
Histopathology of Small Cell Carcinoma
- Invasive sheets or nests of small undifferentiated malignant epithelial cells containing coarse chromatin but no prominent nucleoli, and very little cytoplasm.
- It originates from bronchial neuroendocrine (Kulchitsky) cells
Histopathology of Squamous Cell Carcinoma
•Invasive nests, sheets, or cords of large malignant epithelial cells with intercellular bridges and/or keratin formation (keratin pearls).
Histopathology of Adenocarcinoma
- Large malignant epithelial cells forming invasive glandular structures and/or intracytoplasmic mucin.
- Adenocarcinoma in situ is a slow growing low-grade variant of adenocarcinoma consisting of large malignant cuboidal or columnar cells that grow across alveolar septal surfaces without invading into the interstitium. This tumor used to be called “bronchiolo-alveolar cell,” but this term is obsolete.
Molecular Alterations in Adenocarcinoma
- kRAS- 30%: worse prognosis; no drug • EGFR (Epidermal Growth Factor Receptor)- 10-40%: especially nonsmoking, Asian, women: specific chemotherapy
- MET – 11%: specific therapy
- EML4-ALK- 5%: specific therapy
- ROS1, BRAF, others- 1-4% each
Adenocarcinoma in Situ
(previously Bronchiolo-Alveolar Carcinoma)
- Arises from bronchiolar (goblet or Clara) cell or type II pneumocyte
- Grows on alveolar septa—lepidic growth (no invasion); should be 100% survival
- May spread aerogenously (by inhalation)
- Solitary nodule, many nodules, pneumonia-like
Large vs. Non-small Cell Carcinoma
- not small cell, but not squamous or adeno? Then you must be large cell.
- Invasive sheets of large, undifferentiated malignant epithelial cells showing no squamous or glandular differentiation despite immunohistochemistry.
Complications of a hilar tumor
- Localized hyperinflation due to partial bronchial obstruction.
- Atelectasis due to total bronchial obstruction.
- Bronchiectasis due to bronchial obstruction and subsequent inflammation.
- Post-obstructive abscesses and/or pneumonia due to bronchial obstruction.
- Superior vena caval syndrome, caused by obstruction of the superior vena cava by tumor and secondary engorgement of the veins of the head and arms.
Complications of a Peripheral Tumor
- Pleural invasion and pleural dissemination, with pleuritis and effusion.
- Invasion of cervical sympathetic plexus producing Horner syndrome (exophthalmos, ptosis, miosis, and anhidrosis). Tumors that do this are called Pancoast tumors.
Clinical Course and Prognosis
- Common symptoms are cough, weight loss, chest pain, and dyspnea, all nonspecific.
- Many tumors are asymptomatic and are discovered on imaging studies performed for other reasons.
- About 3/4 of lung tumors are unresectable at the time of discovery.
- Small cell carcinoma responds dramatically to chemotherapy initially, but usually recurs quickly and eventually kills the patient.
- Some tumors secrete hormones such as ACTH, ADH, or serotonin, producing dramatic clinical symptoms related to the effects of the hormone produced. These scenarios are called paraneoplastic syndromes.
Carcinoid Tumor
- A low-grade malignant neoplasm derived from neuroendocrine cells, typically indolent and usually arising in younger patients, and not caused by cigarette smoking. The etiology is unknown.
- Usually arise in large bronchi, forming a well-circumscribed protruding mass that can obstruct the bronchial lumen.
- Locally invasive, but most do not metastasize or spread only to local lymph nodes.
- However, about 10% metastasize systemically. Behavior is extremely difficult to predict based on clinical or pathologic features.
- Most are cured by surgery.
Hamartoma
- The pulmonary hamartoma is actually a benign mesenchymal neoplasm, rather than a disorganized mass of mature tissues formed by an embryonic mistake as the name implies. The term “hamartoma” is a misnomer. Nevertheless, the term hamartoma is still used for this lesion.
- Most commonly occurs in adults.
- Typically a single well-circumscribed, spherical, peripheral lung nodule 3-4 cm in diameter (radiologists would call it a “coin” lesion).
- Histologically, the lesion usually consists of mature cartilage, mixed with other mature mesenchymal elements such as fat and smooth muscle, often with entrapped lung tissue.
Hematogenous metastasis
Carcinomas arising in other anatomic sites can spread to the lung through the vascular system. This usually produces multiple nodules in the lungs of varying sizes
Lymphangitic carcinomatosis
Diffuse MAlignant Mesothelioma
- A malignant neoplasm that arises from the mesothelial lining of the parietal or visceral pleural surface; usually grows diffusely along the pleural surface, forming a thick “rind” of tumor that covers the surface of the lung and inside surface of the chest wall.
- Most cases are related to asbestos exposure, with a 25-45 year latency period; NOT caused by cigarette smoking.
- Histologically, may form gland-like or papillary structures (epithelioid type of mesothelioma), spindle cells (sarcomatoid type), or both types of appearances (mixed type). Sarcomatoid and mixed types tend to be a bit more aggressive with a poorer prognosis than the purely epithelioid type.
- Usually fatal, usually within 2 years of diagnosis, and is relatively resistant to current chemotherapy agents and radiation.
- Similar tumors arise in the meso
