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Pulmonary Pathology Online

Pathology of Squamous Cell Carcinoma of the Lung

- Type of Non-Small Cell Lung Cancer (Non-Small Cell Lung Carcinoma)

Dr Sampurna Roy MD

 

Squamous cell carcinoma (SCC) of the lung is a type of non-small cell lung cancer (non- small cell lung carcinoma - NSCLC ) demonstrating squamous (epidermoid) differentiation.

 

Squamous cell carcinoma of the lung can be divided into two types according to the location of the primary site -

The central type and the peripheral type :

Morphologically, peripheral SCCs are smaller, have fewer mitoses, less prevalent lymphatic invasion, and a more intense stromal reaction. Improved survival in patients with peripheral SCC may be due to a more favorable stage at the time of initial treatment.

According to a study the patient population of the peripheral type was older, with a lower pathologic stage, lower lymphatic vessel involvement, and lymph node metastasis.

Based on the histologic growth pattern, the peripheral type was classified under three subgroups as follows:

1)  the alveolar space-filling type, 2)  the expanding type, and 3)  the combined type.

Among these three types, the alveolar space-filling type showed neither lymphatic vessel invasion nor lymph node metastasis and had the most favorable prognosis.

The central and peripheral types of lung squamous cell carcinoma have different clinicopathologic characteristics and should be classified under respectively different categories.

 

In the past Squamous Cell Carcinoma (SCC) was historically considered to be the most common lung neoplasm, however Adenocarcinoma (ADC) is currently the most common histologic subtype of NSCLC.

Squamous cell carcinoma is tumour is usually associated with prolonged tobacco use.

Despite the association of many genetic alterations with lung cancer, the precise molecular mechanisms of tumorigenesis remains unclear.

Most cases arise in or near the hilus of the lung.

In comparison to solid squamous lung carcinoma patients with cavitating squamous lung carcinoma present with high grade tumours that may initially simulate infectious processes, leading to late diagnosis despite long standing symptoms and presentation with advanced disease.

Microscopically, the tumour is graded as well, moderately and poorly differentiated on the basis of the amount of keratinization and presence of intercellular bridges.

Keratin may be seen in isolated cells or more commonly  as "keratin-pearls".

This tumour is diagnosed as mixed carcinoma when components of adenocarcinoma and/or small cell carcinoma are present in substantial amount. 

- Small cell variant :   

Particular challenges may occur in diagnosis of the combined small cell carcinoma with non-small cell carcinoma variant of small cell carcinoma, and distinction between the small cell squamous cell variant of poorly differentiated squamous cell carcinoma and small cell carcinoma.

A primary immunohistochemistry panel including TTF-1, p63, and high molecular weight keratin is an efficient and powerful supplement to morphology for distinguishing between small cell carcinoma and poorly differentiated squamous cell carcinoma.

A primary immunohistochemistry panel including TTF-1, p63, and high molecular weight keratin is an efficient and powerful supplement to morphology for distinguishing between small cell carcinoma and poorly differentiated squamous cell carcinoma.

- Clear cell variant shows cellular glycogen in some cells while others contain keratin.

- Well-differentiated papillary type.

- Pseudovascular adenoid squamous cell carcinoma

- Basaloid types are more aggressive

- Spindle cell squamous carcinoma (sarcomatoid carcinoma) 

- Lymphoepithelioma-like carcinoma

To define early stage lung cancer as curable, it should be defined as T1N0M0, peripheral squamous cell carcinoma, or central squamous cell carcinoma without pericartilage layer invasion.

Minimal tumour nest (MTN) sizes are defined as large (>6 tumor cells), small (2-5 tumor cells) or single cell.

According to a study the 5-year disease-free survival rate was significantly worse in patients with single cell nests than in those with small nests.

The MTN size is a useful prognostic factor for small peripheral squamous cell carcinomas.

Tumours with a single cell invasive component appear to be highly malignant, and should be distinguished from invasive cancers with a low malignant potential (tumours with large or small tumour nest components).

 

Further reading:

Surgical pathology of early stage non-small cell lung carcinoma.

Non-Small Cell Lung Carcinoma Biomarker Testing: The Pathologistís Perspective

Histologic prognostic factors for small-sized squamous cell carcinomas of the peripheral lung.

Reevaluation and reclassification of resected lung carcinomas originally diagnosed as squamous cell carcinoma using immunohistochemical analysis

Characterization of cell-type specific profiles in tissues and isolated cells from squamous cell carcinomas of the lung.

Clinicopathologic features of peripheral squamous cell carcinoma of the lung.

Cavitating squamous cell lung carcinoma-distinct entity or not? Analysis of radiologic, histologic, and clinical features.

The clinicopathological features of peripheral small-sized (2 cm or less) squamous cell carcinoma of the lung.

Clinicopathologic characteristics of peripheral squamous cell carcinoma of the lung.

Pseudovascular adenoid squamous cell carcinoma of the lung: clinicopathologic study of three cases and comparison with true pleuropulmonary angiosarcoma

Early squamous lung cancer and longer survival rates.

Peripheral vs central squamous cell carcinoma of the lung. A comparison of clinical features, histopathology, and survival.

 

 

Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)

 

 


 

 

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