B41. Benign and metastatic tumors of the lung

Question 1

List the benign lung tumors

Answer 1

Benign lung tumors are rare, can all be removed surgically

1. Hamartoma
2. Adenoma
3. Solitary Fibrious Tumor
4. Desmoid tumor
5. Carcinoid tumorlets
6. Sclerosing hemangioma
7. Salivary gland-like tumors (The pleomorphic adenoma and the adenoid cystic carcinoma)

Question 2

What is a hamartoma

Answer 2

A collection of tissue that originates in the organ it is found in, that represents some tissue of the organ growing in a disorganized manner.

75% of all benign lung tumors are hamartomas

Usually composed of cartilage, connective tissue, and fat.

Usually asymptomatic but may cause compression effects or block bronchioles.

Will often have calcifications and appear as “coin lesions” on radiography.

Question 3

Describe solitary fibrous lung tumors

Answer 3

Solitary fibrous tumors

Rare mesenchymal tumors, arising from the visceral pleura in 80% or the parietal pleura in 20%.

Arises from fibroblast connective tissue cells of the pleura.

Are usually benign, but ~15% are malignant.

Question 4

Describe desmoid tumors

Answer 4

Benign fibroma type tumor

Slow growing and totally non-metastatic.

But may cause local invasion

Usually appear in the abdominal wall or muscles of the trunk and arms/legs.

Very rarely occur in the lung.

Question 5

Describe Carcinoid tumorlets

Answer 5

• Neuroendocrine tymors, arising from neuroendocrine cells of the respiratory mucosa.
• They are highly vascular and can cause hemoptysis and lots of bleeding on biopsy.
• Can be benign, locally invasive, or metastatic.
• Often cause obstruction and distal atelectasis.
• Very rarely metastasize.
• Even though they are neuroendocrine origin, they very rarely secrete any active hormones.
• Often form as tumorlets, nodular proliferation of the neuroendocrine cells smaller than half a centimeter. Unclear if it is a neoplasm or a hyperplasia, most people classify it as a hyperplasia.
• Are small, less than 0.5cm.

Question 6

Describe sclerosing hemangioma

Answer 6

Old name, now called pulmonary pneumocytoma.

four main histological components in varying proportions

• solid,
• papillary,
• sclerotic,
• haemangiomatous

Rare benign neoplasm of the lung.

Well circumscribed with a thin pseudocapsule. Benign.

Mostly in women.

Question 7

Describe Lung Adenomas

Answer 7

The 2nd most common benign lung tumor. Epithelial neoplasia that produces glandular patterns or benign tumors derived from glandular epithelium that are not exhibiting glandular patterns.

1. Alveolar adenomas: occuring in the peripheral regions, forming small cysts lined by type 2 pneumocytes, filled with fluid.
2. Bronchial gland adenomas:
   
   • ​Mucous gland adenoma
   • Adenoid cystic carcinoma - of the Salivary gland type.
3. Papillary adenomas:
   
   • ​of type 2 pneumocytes or Clara cells
4. Pleomorphic adenoma
   
   • ​Mixed cell type adenoma of serous gland cells and myoepithelial cells, both neoplastic.
   • Salivary gland type
   • Need to check salivary gland as these types may be metastases from there.

Question 8

What are the major metastatic tumors found in the lung?

Answer 8

First, almost every kind of metastatic tumor can go to the lung.

Second, metastatic tumors of the lung are more common than primary lung tumors.

The most common are: breast and colorectal carcinoma

• Breast
• GI tumors, Colorectal carcinoma
• Renal cell carcinoma
• Melanoma
• Uterine leiomyosarcoma
• Sarcoma
• Lymphoma
• Leukemia
• Germ cell tumors