Squamous cell carcinoma of the skin overview

# Overview
Squamous cell carcinoma  is a malignant tumor of epithelium that shows squamous cell differentiation. This type of cancer can be visualized if it is on the skin, lips, inside the mouth, throat or esophagus. It is characterized by red, scaly skin that turns into an open sore.Reports of non-melanoma cancer date back to biblical times. Percival Pott was the first person to report the malignant nature of squamous cell carcinoma in adolescent British chimney sweeps. This was the first described occupational and exposure-related risk factor for squamous cell carcinoma. Later, other occupational and exposure associations were reported when there were reported incidences of squamous cell carcinoma in mule spinners, and it was therefore called mule spinner's disease. French surgeon Jean-Nicholas Marjolin, in 1828, first described this carcinoma arising in traumatic scars, and subsequently any squamous cell carcinoma associated with burns was termed Marjolin's ulcer. Squamous cell carcinoma of the skin is a slow growing invasive non-melanoma skin tumour, which is caused mainly by prolonged exposure to sunlight and other forms of UV radiation. Patients undergo staging as a routine part of their diagnosis and treatment. Staging of the lesion assists the physician to choose which form of treatment strategy suits the patient. Squamous cell carcinoma (SCC) is type of non-melanoma skin cancer. The cancer arises as a result of uncontrolled growth of the squamous cells in the epidermis of the skin. Squamous cell carcinoma is most commonly caused by long term exposure to sunlight and other forms of UV radiation. Male sex, fair skinned people, smokers, the elderly, and people who have previous history of a skin cancer are particularly prone to the development of this non-melanomatous skin cancer. It accounts for 20% of all non-melanomatous tumors, and is fairly invasive  contrary to its counterpart, basal cell carcinoma. Squamous cell carcinoma typically presents as a non-healing ulcer or growth on a sun exposed area of the skin. Squamous cell carcinoma (SCC) is one of the most common subtypes of skin cancer. Its main risk factors include prolonged exposure to sunlight and/or UV radiation. Most of the affected individuals are elderly. The risk factors for the Squamous cell carcinoma (SCC) include prolonged sunlight exposure, UV radiation, smoking, drugs etc. Once Squamous cell carcinoma (SCC) develops on the skin it grows slowly. If neglected and once it reaches the size of 2 cm and more it is three times more likely to spread to other areas than the smaller lesions. Usual size ranges from 1 cm to 5 cm. It is the mechanical interference of this fungiform exophytic lesion that brings it to the notice of the patient or the clinician. When treated early squamous cell carcinoma is completely curable by 95% - 98%. This lesion has a cure rate of 95% - 98%. But once the lesion spreads to other regions beyond skin, like lymph nodes and internal organs less than half of the patients live five years. A sub set of SCC carries the risk of local recurrence, nodal or distant metastasis (usually to the lungs) and eventually death. A biopsy is the gold standard test for the diagnosis of squamous cell carcinoma of the skin.  Diagnosis is established by biopsy and histopathological confirmation. Complete excision is curative in the vast majority of cases. Occasionally squamous cell carcinoma will invade along the perineural layer of peripheral nerves and will extend well beyond the clinically apparent mass. Local recurrence is more common in these instances and when present on the head, direct intracranial extension may occur. Metastases to draining lymph nodes occurs in a minority of cases and disseminated disease is the cause of most squamous cell carcinoma-related deaths. Higher rates of metastasis (~15%) are observed with primary lesions of the lips or ears (Rowe et al., 1992). Radiation therapy is helpful in some cases of locally recurrent disease in which complete resection is difficult to achieve and in cases of limited metastatic disease. There are no CT scan findings associated with squamous cell carcinoma of the skin. However, a CT scan may be helpful in the detection of disease extent, assessment of metastasis, and perineural invasion of the tumor. Magnetic Resonance Imaging (MRI) has implications similar to that of a CT scan. It has many advantages compared to a CT scan including increased sensitive than a CT scan in identifying the extent of a lesion and its use in the evaluation of a tumor for its invasion of perineural tissue. Medical therapy for squamous cell carcinoma includes chemotherapy with cisplatin, topical fluorouracil, capecitabine, methotrexate, cetuximab, bleomycin and doxorubicin. Other treatment modalities include cryotherapy, radiation therapy and photodynamic therapy. Surgery is the mainstay of therapy for squamous cell carcinoma of the skin. Most cases of squamous cell carcinoma are the result of exposure to sunlight and other forms of ultraviolet radiation. Primary prevention focuses primarily on protecting our self from these forms of radiation. Secondary prevention aims at taking care of early symptoms and preclude the development of possible irreparable disease conditions.

# Historical Perspective
Reports of non-melanoma cancer date back to biblical times. Percival Pott was the first person to report the malignant nature of squamous cell carcinoma in adolescent British chimney sweeps. This was the first described occupational and exposure-related risk factor for squamous cell carcinoma. Later, other occupational and exposure associations were reported when there were reported incidences of squamous cell carcinoma in mule spinners, and it was therefore called mule spinner's disease. French surgeon Jean-Nicholas Marjolin, in 1828, first described this carcinoma arising in traumatic scars, and subsequently any squamous cell carcinoma associated with burns was termed Marjolin's ulcer.

# Classification
Squamous cell carcinoma of the skin is a slow growing invasive non-melanoma skin tumour, which is caused mainly by prolonged exposure to sunlight and other forms of UV radiation. Patients undergo staging as a routine part of their diagnosis and treatment. Staging of the lesion assists the physician to choose which form of treatment strategy suits the patient.

# Pathophysiology
Squamous cell carcinoma (SCC) is type of non-melanoma skin cancer. The cancer arises as a result of uncontrolled growth of the squamous cells in the epidermis of the skin. Unlike it's counter part, the basal cell carcinoma which also belongs to the group of non-melanoma cancer, squamous cell carcinoma is rapid growing and invasive. SCCs may occur on all areas of the body including the mucous membranes and genitals, but are most common in areas frequently exposed to the sun, such as the rim of the ear, lower lip, face, bald scalp, neck, hands, arms and legs. Wrinkling, changes in pigmentation, and loss of elasticity of the skin are often the telltale signs of sun damage

# Causes
Squamous cell carcinoma is most commonly caused by long term exposure to sunlight and other forms of UV radiation. Male sex, fair skinned people, smokers, the elderly, and people who have previous history of a skin cancer are particularly prone to the development of this non-melanomatous skin cancer.

# Differential Diagnosis
Squamous cell carcinoma should be differentiated from melanoma and basal cell carcinoma. It accounts for 20% of all non-melanomatous tumors, and is fairly invasive  contrary to its counterpart, basal cell carcinoma. Squamous cell carcinoma typically presents as a non-healing ulcer or growth on a sun exposed area of the skin.

# Epidemiology and Demographics
Squamous cell carcinoma (SCC) is one of the most common subtypes of skin cancer. Its main risk factors include prolonged exposure to sunlight and/or UV radiation. Most of the affected individuals are elderly.

# Risk factors
The risk factors for the Squamous cell carcinoma (SCC) include prolonged sunlight exposure, UV radiation, smoking, drugs etc.

# Screening
Since Squamous cell carcinoma is almost always cured without specified screening no studies have shown that such screening will improve the already high cure rates for this type of skin carcinoma.

# Natural history, Complications and Prognosis
Once Squamous cell carcinoma (SCC) develops on the skin it grows slowly. If neglected and once it reaches the size of 2 cm and more it is three times more likely to spread to other areas than the smaller lesions. Usual size ranges from 1 cm to 5 cm. It is the mechanical interference of this fungiform exophytic lesion that brings it to the notice of the patient or the clinician. When treated early squamous cell carcinoma is completely curable by 95% - 98%. This lesion has a cure rate of 95% - 98%. But once the lesion spreads to other regions beyond skin, like lymph nodes and internal organs less than half of the patients live five years. A sub set of SCC carries the risk of local recurrence, nodal or distant metastasis (usually to the lungs) and eventually death.

# Diagnosis

## Diagnostic Study of Choice
A biopsy is the gold standard test for the diagnosis of squamous cell carcinoma of the skin.

## History and Symptoms
Most Squamous cell carcinomas (SCC) arise on the sun-exposed skin of the head and neck, with fewer lesions arising on the extremities and occasional tumors occurring on the trunk. Early lesions frequently present as a red, scaly spots. Later lesions may form nodules or firm plaques, either of which can ulcerate ( ). Diagnosis is established by biopsy and histopathological confirmation. Complete excision is curative in the vast majority of cases. Occasionally squamous cell carcinoma will invade along the perineural layer of peripheral nerves and will extend well beyond the clinically apparent mass. Local recurrence is more common in these instances and when present on the head, direct intracranial extension may occur. Metastases to draining lymph nodes occurs in a minority of cases and disseminated disease is the cause of most squamous cell carcinoma-related deaths. Higher rates of metastasis (~15%) are observed with primary lesions of the lips or ears (Rowe et al., 1992). Radiation therapy is helpful in some cases of locally recurrent disease in which complete resection is difficult to achieve and in cases of limited metastatic disease

## Physical examination
The findings of physical exam helps us in diagnosis and provides information about the prognosis of the disease. Many times physical exam done for some other reason may give us a hint for this.

## Laboratory findings
Squamous cell carcinoma of the skin is most often caused by long term exposure to the sun, and other certain risk factors. No specific laboratory tests are indicated for the diagnosis, as physical exam and biopsy are the primary means of diagnosis. Histopathological evaluation of the biopsy specimen stands out to be the most important diagnostic test.

## Electrocardiogram
There are no ECG findings associated with squamous cell carcinoma of the skin.

## Chest Xray
There are no x-ray findings associated with squamous cell carcinoma of the skin. However, a chest x-ray may be helpful in the diagnosis of lung metastases.

## Ultrasound
Ultrasonography is not the routine test performed for the diagnosis of SCC. It is useful in certain cases when it is difficult to delineate the border of the lesion. It can be used in addition to a physical exam for better overview of the lesion

## CT Scan
There are no CT scan findings associated with squamous cell carcinoma of the skin. However, a CT scan may be helpful in the detection of disease extent, assessment of metastasis, and perineural invasion of the tumor.

## MRI
Magnetic Resonance Imaging (MRI) has implications similar to that of a CT scan. It has many advantages compared to a CT scan including increased sensitive than a CT scan in identifying the extent of a lesion and its use in the evaluation of a tumor for its invasion of perineural tissue.

## Other diagnostic studies
There are few modalities used for diagnosis and follow up.
- Fourier Transform Infrared Imaging (FTIR)
- Immunohistochemistry

# Medical Therapy
Medical therapy for squamous cell carcinoma includes chemotherapy with cisplatin, topical fluorouracil, capecitabine, methotrexate, cetuximab, bleomycin and doxorubicin. Other treatment modalities include cryotherapy, radiation therapy and photodynamic therapy.

# Surgery
Surgery is the mainstay of therapy for squamous cell carcinoma of the skin.

# Primary Prevention
Most cases of squamous cell carcinoma are the result of exposure to sunlight and other forms of ultraviolet radiation. Primary prevention focuses primarily on protecting our self from these forms of radiation.

# Secondary prevention
Secondary prevention aims at taking care of early symptoms and preclude the development of possible irreparable disease conditions.