Squamous-cell carcinoma
Squamous-cell carcinoma, also known as epidermoid carcinoma, comprises a number of different types of cancer that begin in squamous cells. These cells form on the surface of the skin, on the lining of hollow organs in the body, and on the lining of the respiratory and digestive tracts.
The squamous-cell carcinomas of different body sites can show differences in their presented symptoms, natural history, prognosis, and response to treatment.
By body location
has been associated with SCCs of the oropharynx, lung, fingers, and anogenital region.Head and neck cancer
About 90% of cases of head and neck cancer are due to SCC.Skin
is the second most common skin cancer, accounting for over 1 million cases in the United States each year.Thyroid
Primary squamous-cell carcinoma of the thyroid shows an aggressive biological phenotype resulting in poor prognosis for patients.Esophagus
may be due to either esophageal squamous-cell carcinoma or adenocarcinoma. SCCs tend to occur closer to the mouth, while adenocarcinomas occur closer to the stomach. Dysphagia and painful swallowing are common initial symptoms. If the disease is localized, surgical removal of the affected esophagus may offer the possibility of a cure. If the disease has spread, chemotherapy and radiotherapy are commonly used.Lung
When associated with the lung, it is typically a centrally located large-cell cancer. It often has a paraneoplastic syndrome causing ectopic production of parathyroid hormone-related protein, resulting in hypercalcemia, but paraneoplastic syndrome is more commonly associated with small-cell lung cancer. It is primarily due to smoking.Penis
, primarily HPV 16 and 18, are strongly implicated in the development of SCC of the penis.Three carcinomas in situ are associated with SCCs of the penis:
- Bowen's disease presents as leukoplakia on the shaft. Around a third of cases progress to SCC.
- Erythroplasia of Queyrat, a variation of Bowen's disease, presents as erythroplakia on the glans.
- Bowenoid papulosis, which histologically resembles Bowen disease, presents as reddish papules.
Prostate
When associated with the prostate, squamous-cell carcinoma is very aggressive. It is difficult to detect as no increase in prostate-specific antigen levels is seen, meaning that the cancer is often diagnosed at an advanced stage.Scrotum
is a squamous cell carcinoma of the skin of the scrotum.Vagina and cervix
spreads slowly and usually stays near the vagina, but may spread to the lungs and liver. This is the most common type of vaginal cancer.Ovary
or squamous ovarian carcinoma is a rare tumor that accounts for 1% of ovarian cancers.Bladder
Most bladder cancer is transitional cell, but bladder cancer associated with schistosomiasis or large bladder stone is often SCC.Eye
and corneal intraepithelial neoplasia comprise ocular surface squamous neoplasia.Diagnosis
, physical examination and medical imaging may suggest a squamous-cell carcinoma, but a biopsy for histopathology generally establishes the diagnosis. TP63 staining is the main histological marker for squamous-cell carcinoma. In addition, TP63 is an essential transcription factor to establish the identity of the squamous cells.Classification
Cancer can be considered a very large and exceptionally heterogeneous family of malignant diseases, with squamous-cell carcinomas comprising one of the largest subsets. All SCC lesions are thought to begin via the repeated, uncontrolled division of cancer stem cells of epithelial lineage or characteristics. SCCs arise from squamous cells, which are flat cells that line many areas of the body. Some of which are keratinocytes. Accumulation of these cancer cells causes a microscopic focus of abnormal cells that are, at least initially, locally confined within the specific tissue in which the progenitor cell resided. This condition is called squamous-cell carcinoma in situ, and it is diagnosed when the tumor has not yet penetrated the basement membrane or other delimiting structure to invade adjacent tissues. Once the lesion has grown and progressed to the point where it has breached, penetrated, and infiltrated adjacent structures, it is referred to as "invasive" squamous-cell carcinoma. Once a carcinoma becomes invasive, it can spread to other organs and cause the formation of a metastasis, or "secondary tumor".Tissue of origin
The International Classification of Diseases for Oncology system lists a number of morphological subtypes and variants of malignant squamous-cell neoplasms, including:- papillary thyroid carcinoma
- verrucous squamous-cell carcinoma
- papillary squamous-cell carcinoma
- squamous-cell carcinoma
- large-cell keratinizing squamous-cell carcinoma
- large-cell nonkeratinizing squamous-cell carcinoma
- small-cell keratinizing squamous-cell carcinoma
- spindle-cell squamous-cell carcinoma It is also known as spindle-cell carcinoma, and is a subtype characterized by spindle-shaped atypical cells.
- adenoid/pseudoglandular squamous-cell carcinoma
- intraepidermal squamous-cell carcinoma
- lymphoepithelial carcinoma.
Other histopathologic subtypes
- Erythroplasia of Queyrat
- Marjolin's ulcer is a type of SCC that arises from a nonhealing ulcer or burn wound. More recent evidence, however, suggests that genetic differences exist between SCC and Marjolin's ulcer, which were previously underappreciated.
- adenoid squamous-cell carcinoma is characterized by a tubular microscopic pattern and keratinocyte acantholysis.
- basaloid squamous-cell carcinoma is mostly found in or near the tongue, tonsils, or larynx, but may also occur Basaloid [squamous cell lung carcinoma|in the lung] or elsewhere.
- clear-cell squamous-cell carcinoma is characterized by keratinocytes that appear clear as a result of hydropic swelling.
- signet ring-cell squamous-cell carcinoma is a histological variant characterized by concentric rings composed of keratin and large vacuoles corresponding to markedly dilated endoplasmic reticulum. These vacuoles grow to such an extent that they radically displace the cell nucleus toward the cell membrane, giving the cell a distinctive superficial resemblance to a "signet ring" when viewed under a microscope.