Presented byMajor Dr /Moamen Khalifachest specialist in military academy
Introduction Lung cancer is the leading cause of cancer deaths worldwide. If we can define and detectpreneoplastic lesions, we might have a chance of improving survival.
Despiteadvances in therapy; the over all survival rate for lung cancer patients only 15 % due to relatively advanced stage of the disease at diagnosis Why? Screening can detect small asymptomatic nodules (2-3 mm) But!!!!!!!! It already malignant
.Lung cancer consists of 4 major types including : 1- Squamous cell carcinoma, 2- Adenocarcinoma, 3-Large cell carcinoma, 4-Small cell carcinoma.
The sequential preneoplastic changes have been well defined for: 1)Centrally arising squamous cell carcinomas, 2)Peripheral adenocarcinomas While!!!!
No preneoplastic lesions have been defined For Small Cell Lung Carcinoma
Definition of preneoplasia Preneoplasia is used to identify groups of phenotypically altered cells. Preneoplastic changes have been shown to consistently reflect sequential steps in carcinogenesis. They include specific alteration in bronchial mucosa and epithelial alveolar layer. (Microscopically visible )
The Origen Preneoplastic lesions of the lungs may start in; The basal layer of the bronchial mucosa or In the bronchial glands As well as in bronchioalveolar epithelial layer (Clara cells &type 2 pneumocytes ) And may also affect neuro-endocrine cells in bronchial mucosa
Why we do our best to define and detect preneoplastic lung lesions ? Because
Lung cancer could be identified earlier at a preneoplastic stage, before: 1)Angiogenesis, 2)Invasion and Micrometastases can occur we might have a greater chance of improving survival.
What are the preneoplastic lesions of the lungs ? The World Health Organization (WHO) recently published a tumor classification system that defines three different preneoplastic lesions of the bronchial epithelium: 1) Squamous Dysplasia (SD) and Carcinoma In Situ (CIS), which may be precursors to Squamous Cell Carcinoma (SCC); 2)Atypical Adenomatous Hyperplasia (AAH), which may be the progenitor lesion for Adenocarcinoma (particularly peripheral);
3)Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIP-NECH), which may progress to carcinoid Additional possible preneoplastic lesions and conditions include: Basal cell hyperplasia and squamous metaplasia (progressing to SD and CIS); Adenomatous hyperplasia(progressing to AAH); Angiogenic squamous dysplasia(consisting of microscopic projections into the bronchial lumen, surfaced by squamous dysplasia); and Pulmonary fibrosis.
Carcinoma in situ full thickness sever cytological atypia with chaotic appearance
Atypical adenomatous hyperplasia lesion found in centriaciner zone and showing alveolar wall thickening and increased numbers of alveolar lining cells
Data supporting the preneoplastic nature of lesions 1)Circumstantial evidence (lesions found in association with malignancies or in patients with high risk of developing lung cancer). 2)Genetic evidence (genetic similarities found between tumors and their associated preneoplastic lesions).
Circumstantial evidence Patients with primary cancer in the lung or upper aero digestive tract have an increased RISK of developing synchronous or second primaries This risk is likely to be related to chronic exposure of the bronchial tree to Carcinogens.
Cigarette smoke causes a field change in the mucosa with mutations demonstrable even in histologically normal areas ('field cancerization'). After smoking cessation, many of these mutations seem to persist indefinitely, so risk of lung cancer never reverts to that of a lifelong nonsmoker Thus
Broad areas of the tracheobronchial tree in high-risk patients are prone to premalignant or multifocal malignant change. The finding of these presumed premalignant lesions in cancer-bearing lungs or in patients at high risk of developing lung cancer is circumstantial evidence of the lesions' preneoplastic nature, and supports the field cancerization theory
Several studies have shown an increased incidence of squamous metaplasia and dysplasia in the lungs of smokers. In contrast, we still have little information about the incidence of AAH or DIP/NECH in either smoking or nonsmoking populations.
Genetic evidence Alterations in gene expression and chromosome structure known to be associated with malignant transformation can be demonstrated in squamous metaplasia, dysplasia and CIS, as well as in AAH. These changes can be seen both as proof of the preneoplastic nature of the lesions, and as possible markers of transformation
Cell proliferation markers and cell cycle regulators Hyperproliferation and loss of cell cycle control seem to be early events in malignant transformation. Staining for proliferation markers (PCNA and Ki-67) increased with increasing atypia in both squamous cell dysplasia and AAH
Normal bronchial mucosa, The first column shows hematoxylin and eosin (H&E) tissue staining The second column shows staining for the proliferation marker, Ki-67. Ki-67 is essentially negative in normal tissue.
The picture of AAH shows low (40×) and high (400×, inset) power images inThe first column. The images show increased Ki-67 in AAH inthe second column
The H&E staining of squamous dysplasia shows relatively normal mucosa on the left of the image and severe dysplasia on the right. In severe dysplasia,there is considerable cellular pleiomorphism The images show further increased Ki-67 in squamous dysplasia
coarse uneven chromatin, and little cell maturation. Vertical nuclei and mitotic figures are present in the lower two thirds of the mucosa. In invasive carcinoma the cytological aberration is extreme, mitoses occur at all levels of the mucosa, and maturation is absent.
DNA ploidy Studies in both squamous cell metaplasia/dysplasia and AAH have shown progressive, increased aneuploidy with increasing atypia A few studies have shown aneuploidy of chromosome 7 in both the bronchial epithelium of patients with high risk for lung cancer (smokers, uranium miners) and in preneoplastic lesions, with an increase in the percentage of aneuploid cells from preinvasive to invasive lesions
Telomerase Telomerase is thought to play a role in conferring immortality on tumor cell populations. It may prevent progressive telomere shortening and therefore cellular senescence. In adult somatic cells telomerase is inactive, whereas the enzyme is activated and expressed in most human cancers. They found telomerase activity in 95–100% of CIS and invasive disease, in 70 to 80% of both hyperplasic and dysplastic bronchial epithelium, and in only 20% of normal epithelium. When they assayed activity, they found preinvasive lesions had enzyme activity only 3–4 times normal, whereas in invasive disease, activity was more than 40 times normal.
k-ras genes The ras genes play an important role in signal transduction and cellular proliferation (through the mitogen-activated protein kinase pathways) and were among the first oncogenes identified. Mutation of k-ras is found in about 30% of non-small cell carcinoma, and is more common in adenocarcinoma than in squamous cell carcinoma. Accordingly, studies have found k-ras mutation more commonly in AAH than inSD.
FHIT The FHIT gene (fragile histidine triad tumor suppressor gene) is frequently deletedin many carcinomas, including lung This gene encodes a protein that hydrolyzes diadenosine triphosphate to ADP and AMP in vitro. Although the in vivo function of this protein is not known, it may play a role in cell death through apoptosis and/or may affect cell proliferation. Loss of FHIT protein is the most frequent alteration in non-small cell lung carcinoma and precancerous lesions (both squamous cell and adenocarcinoma). The frequency of loss increases as the grade of dysplasia increases
Genomic alterations and LOH studies The most common and earliest changes in both squamous cell carcinoma and adenocarcinoma seem to involve allele-specific loss of genome at 3p and 9p and perhaps 17q, among others.These changes involve all regions of the respiratory tract, and occur with increasing frequency with increasing atypia. Loss of heterozygosity (LOH) at this locus was found in atypical carcinoids as well.
Methylation Recently, there has been increased interest in the significance of the methylation of genes and their promoters. Aberrant methylation of gene promoters can silence gene expression. In an animal model exposed to tobacco carcinogen, methylation was frequent in preneoplastic lesions. In human lung cancer, p16, p53 and k-ras promoter hypermethylation has been seen. Aberrant methylation of the promoter regions of other tumor suppressors may also play a role in carcinogenesis.
Other possible markers of transformation Increasing neovascularization and vascular count has been found with increasing dysplasia of lesions of the bronchial tree Accordingly, expression of vascular endothelial growth factor was found to increase from normal tissue to SD to CIS to invasive cancer Changes in the extracellular matrix may also distinguish normal, preinvasive, and malignant lesions. Many other proteins have been found to have either increased or decreased expression, correlating with increasing histopathologic abnormality.(fatty acid synthase, thrombomodulin and epithelial cellular adhesion molecule)
SQUAMOUS LESIONS The spectrum of mucosal abnormalities associated with squamous cell carcinoma has been known for many years. These include basal cell hyperplasia, squamous metaplasia, dysplasia, and carcinoma in situ, which are all usually seen in the background of invasive squamous cell carcinoma of the large airways. However, the same mucosal abnormalities may be detected in smokers without evidence of carcinoma. The frequency of these lesions in smokers correlates with the number of cigarettes smoked. These lesions are preinvasive and reversible,which means that they may not necessarily progress into invasive carcinoma and may regress if an individual quits smoking.
Morphologic Entities 1)Goblet cell hyperplasia: May be seen in a background of carcinoma. It consists of an increased number of goblet cells in the bronchial mucosa. In goblet cell hyperplasia, the goblet cells are frequently adjacent to one another and may appear multilayered, the nucleus is basally located, the chromatin is dense, and the cytoplasm is abundant
2) Basal cell hyperplasia: Is characterized by expansion of the basilar zone of bronchial mucosa. Nuclei are small, round, and stratified in the lower levels of the mucosa. Cytoplasm is scant. Goblet cells and cilia are maintained at the luminal surface
Transbronchial biopsy showing goblet cell hyperplasia (left) and basal cell (reserve cell) hyperplasia (right) in a patient with a history of squamous cell carcinoma of the lung. An intact thickened basement membrane is present (hematoxylin-eosin,
3) Immature squamous metaplasia: Is similar to basal cell hyperplasia except that the metaplastic epithelium occupies nearly the full thickness of the epithelium. In comparison to mature squamous metaplasia, cells have less cytoplasm and are nonkeratinized. Ciliated cells may be retained on the epithelial surface, but goblet cells are usually depleted.
4)Mild squamous dysplasia : Is characterized by mildly increased epithelial thickness, with slightly enlarged cells showing mild anisocytosis and pleiomorphism. The basilar zone is expanded with cellular crowding in the lower third. The intermediate zone is intact and distinct, and cells show superficial flattening. Chromatin is finely granular. Nuclei show minimal angulation and are vertically oriented in the lower third. Nucleoli are absent. Mitoses are absent or very rare
5)Moderate squamous dysplasia Is characterized by moderately increased epithelial thickness, with moderately enlarged cells, although in some cases cells may be small. Moderate anisocytosis and pleiomorphism are common features. The basilar zone is expanded with cellular crowding in the lower two thirds. The intermediate zone is confined to the upper third of the epithelium, and cells show superficial flattening. Similar to mild dysplasia, chromatin is finely granular and nucleoli are absent. However, nuclei are angulated with grooves and lobulations and are vertically oriented in the lower two thirds. Mitoses are present in the lower third.
6)Severe squamous dysplasia : Is characterized by markedly increased epithelial thickness. The basilar zone is expanded with cellular crowding into the upper third. Cells are large with marked anisocytosis and pleiomorphism. No or little maturation is seen from base to luminal surface. Intermediate zone is attenuated, and cells show superficial flattening. In contrast to mild and moderate dysplasia, the chromatin is coarse and uneven. Prominent nuclear angulation and folding are present with nuclei vertically oriented in the lower two thirds. Nucleoli are frequently present. Mitoses are present in the lower two thirds
7)Squamous carcinoma in situ May not be necessarily associated with increased epithelial thickness. Cells are usually markedly increased in size and may show marked anisocytosis and pleiomorphism. Usually there is no progression of maturation from base to luminal surface the epithelium has a monotonous appearance. The basilar zone is expanded with cellular crowding throughout the epithelium. Nucleoli may be present or inconspicuous. Mitoses are present through the full thickness of the epithelium.
GLANDULAR LESIONS Recently, substantial attention has been paid to AAH that is considered to represent the adenoma in a putative ‘‘adenoma-carcinoma’’ sequence in the lung periphery leading to the development of non mucinous BAC and invasive peripheral adenocarcinoma. These lesions are detectable on high-resolution computed tomography scan as small, ground glass densities
What is Atypical Adenomatous Hyperplasia? (AAH) The WHO defines AAH as a localized proliferation of mild to moderately atypical cells lining involved alveoli and sometimes respiratory bronchioles, resulting in focal lesions in peripheral alveolated lung, usually less than 5 mm in diameter.
Histology of AAH Discrete parenchymal lesion arising often in the centriacinar region . The alveolar septa are lined by rounded, cuboidal, low columnar cells with round to oval nuclei showing either Clara cell or type II pneumocyte differentiation. Intranuclear inclusions are a frequent feature and may be seen in up to 25% of the cells . Ciliated and mucin producing cells are absent. Mitoses are extremely rare. Cellularity and atypia are variable. The majority of the lesions show a discontinuous lining of the alveolar septa with cells showing minimal atypia, whereas in some cases cells may be more continuous exhibiting moderate atypia. Pseudopapillae and tufts may be present.
A, Atypical adenomatous hyperplasia is a centriacinar lesion usually identified in a peripheral lung parenchyma.