CONTENTS:

3.8.5 Mesenchymal Lung Tumor
i. Nerve Sheath Tumor (Schwannoma)
ii. Leiomyoma
iii. Chondroma
iv. Lipoma
v. Granular Cell Tumor
3.8.6 Benign Neuroendocrine Tumors: ‘Tumorlets’ and Benign Carcinoid Tumors
 

 
Forward to 4A Atypical and In-Situ Lung Conditions .   Back to 3E Infectious and Vascular Lung Conditions .

Why did Mozart kill his chickens? Because they always ran around going Bach! Bach! Bach!

3.8.5 Mesenchymal Tumors of the Lung

The lung contains mesenchymal elements in the form of nerves, smooth muscle, cartilage and fat.  Although benign (and malignant) mesenchymal tumors are rare,  they must be considered,  particularly when a diagnosis of a solitary pulmonary nodule (SPN) has been made on CT imaging of the lung.

i. Nerve Sheath Tumor (Schwannoma)

This is a rare type of lung tumor (<0.2%) and is histologically similar to schwannomas of other sites.

ii. Leiomyoma

Primary, solitary, pulmonary leiomyomas may be endobronchial or parenchymal.   A multiple smooth muscle lung tumor of the lung in women who have a history of uterine leiomyomas are more likely part of a condition called ‘benign metastasizing leiomyoma’.

I don’t have a facebook account so I just go around announcing what I’m doing at random times. I’ve got 3 followers so far but I think two are cops.

iii. Chondroma

Chondromas are benign lung tumors composed of cartilage without cellular epithelial elements and without other mesenchymal elements.  Cartilage seen in association with othe types of cell may represent hamartoma.

iv. Lipoma

In the lung, lipomas may be endobronchial (more commonly) or intraparenchymal.  Histologically, in order to make the diagnosis of lipoma, the tumor should be composed only of fat cells.  Components that include cartilage or epithelial cell ingrowth raises the possibility of an ‘adipose tissue–rich’ hamartoma.

v. Granular Cell Tumor

This benign lung tumor is also known as ‘granular cell myoblastoma.’   When present in the lung, these benign tumors are seen predominantly in males and are usually central tumors.

The histology of granular cell tumor shows large cells with abundant granular eosinophilic cytoplasm and bland nuclei.  They are periodic acid Schiff (PAS)-positive; using immunohistochemistry, they are S100-positive, vimentin-positive and cytokeratin-negative.   These benign tumors are thought to originate from neural Schwann cells and not muscle cells.

Because of their central location, granular cell tumors are more likely to be symptomatic, with cough or hemoptysis.   They are often irregular in outline and locally ‘invasive‘ and so can recur after conservative resection, but they do not metastasize.

Do you know, I walk two miles a day. One to the donut shop, and one home.

3.8.6 Benign: ‘Tumorlets’ and Benign Carcinoid Lung Tumor

There are neuroendocrine cells in normal bronchi; enterochromaffin cells, or ‘Kulchitsky cells.’  It is now believed that neuroendocrine tumors arise from these neuroendocrine cells.  There is a spectrum of tumor presentation, from benign tumorlets and carcinoids to low-grade neuroendocrine carcinoma to high-grade neuroendocrine carcinoma (‘small cell’ or ‘oat cell’ carcinoma’). It is not necessarily the case that benign tumors will progress to malignant ones in the case of neuroendocrine tumors.

A ‘tumorlet’ is a benign neuroendocrine cell proliferation in the lung that is < 5 mm in diameter.  Tumorlets may be found incidentally as lung nodules on imaging, but because of their location, they may produce symptoms of bronchial obstruction (cough). Tumorlets occur in individuals between 60 to 70 years of age and are more common in women.   The histology shows bland neuroendocrine cells with no mitoses or necrosis.

A carcinoid tumor is a benign neuroendocrine tumor that is  >5 mm diameter.  Although these may also be found incidentally on imaging, because of their increased size, they are more likely to present with symptoms of bronchial obstruction. The histology shows bland neuroendocrine cells with no mitoses or necrosis.

Diffuse, idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a very rare pulmonary condition featuring a proliferation of neuroendocrine cells within the lung.  In most cases, it is found in non-smokers and is asymptomatic.

In 2010, Koo and colleagues described in detail the radiological features shown by the spectrum of benign neuroendocrine proliferations in the lung.   A useful diagnostic histology marker from neuroendocrine cells is immunohistochemical staining for chromogranin.

News – A coach containing session musicians has overturned on the motorway, drivers may expect lengthy jams.

References:

Koo CW, Baliff JP, Torigian DA et al. (2010). Spectrum of pulmonary neuroendocrine cell proliferation: diffuse idiopathic pulmonary neuroendocrine cell hyperplasia, tumorlet, and carcinoids. AJR Am J Roentgenol 195(3), 661-8. (Retrieved 6^th February 2015): http://www.ajronline.org/doi/full/10.2214/AJR.09.3811

Beasley MB, Brambilla E, Travis WD .(2005). The 2004 World Health Organization classification of lung tumors. Semin Roentgenol 40:90–97. (Retrieved 5^th Feb 2015): http://www.ncbi.nlm.nih.gov/pubmed/?term=Beasley+MB+2005

More references for this section are on this page .

Patient Information:

MacMillan.Org Neuroendocrine tumours (NETs) (Retrieved 15^th April 2015): http://www.macmillan.org.uk/Cancerinformation/Cancertypes/Neuroendocrine/Overview.aspx

Web MD Lung Disease & Respiratory Health Center: Benign Lung Tumors and Nodules. (Retrieved 13^th April 2015): http://www.webmd.com/lung/benign-lung-tumors-and-nodules

More patient information for this section is on this page.

Forward to 4A Atypical and In-Situ Lung Conditions .   Back to 3E Infectious and Vascular Lung Conditions .