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Skin Cancer

Diagnosis and Staging

Diagnosis

Skin cancers are diagnosed based on physical exam, patient history, and a variety of diagnostic techniques. Proper diagnosis is important to not only confirm the presence of malignancy, but also to stage the cancer progression to determine a suitable treatment and prognosis (outcome) (Fecher 2012; Usatine 2011; Carillo 2012).

Biopsy. Suspected skin cancer lesions are initially biopsied (sampling of the affected tissue) using a shaving technique for raised tumors or a punch biopsy (in which a circular plug of tissue is removed) for abnormal skin. For very small tumors, complete excision of the tumor may be part of the initial diagnosis (Firnhaber 2012). Biopsied tissue is examined for malignancy by histological staining and microscopy (Al-Arashi 2007; Patil 2011).

Dermoscopy. Dermoscopy (also called dermatoscopy or skin surface microscopy) employs a handheld magnifying device (dermoscope) to improve the examination of suspect skin lesions. It allows visualization of structures below the skin surface that are not otherwise visible to the naked eye. Dermoscopy improves the accuracy in diagnosing melanoma and pigmented lesions by as much as 30% (Rao 2012).

Lymph node mapping and biopsy. Lymph nodes are small, oval-shaped organs that are distributed throughout the body (Marieb 2009; ACS 2014b). They are important organs of the immune system, and they house the lymphocytes involved in immune response. Cancers often spread to lymph nodes before invading other areas of the body. To map lymph nodes, a small amount of radioactive tracer may be injected near the skin tumor to determine the nearby lymph node(s) to which the cancer is likely to spread (sentinel lymph nodes) (Harwood 2005; Stoeckli 2001). These nodes can be biopsied to check for the presence of cancer cells.

Imaging tests. Imaging tests include the following (ACS 2013c): 

  • Computed tomography. Computed tomography (CT) is a three-dimensional X-ray imaging technique for visualizing internal structures; it is especially useful for determining the presence of metastasis to distant organs.
  • Positron emission tomography. Positron emission tomography (PET) can locate areas of malignancy by tracing the deposition of a radioactive glucose analog (given by injection). Since cancer cells have a high metabolic rate, they take up the radioactive glucose more readily than normal cells and can be identified by a PET scan.
  • Chest radiographs. Chest radiographs (“X-rays”) may be used to detect metastases to the lungs.
  • Magnetic resonance imaging. Magnetic resonance imaging (MRI), which images soft tissues using high magnetic fields, may be used to detect metastasis to the brain or spinal cord.

Novel imaging. Advances in imaging technology are improving diagnostic precision.

  • Multispectral imaging. Multispectral imagers construct images of suspected skin tumors using specific wavelengths of light to provide additional information on a lesion such as its borders, vasculature, or melanin content. This additional information can be used to strengthen a clinician’s diagnosis or determine whether a biopsy may be needed. Melafind is an imager/software system that takes images of a suspected melanoma at 10 different wavelengths of light, determining its border and collecting information on color variation, asymmetry, and changes in texture or perimeter. It compares these data to an internal database of over 9000 images of biopsied melanoma tumors and provides the clinician with a recommendation on whether the lesion should be biopsied (Ferris 2012). Melafind has been shown to increase the sensitivity of detection of melanomas when used by trained dermatologists (Wells 2012), although it has a low specificity and may over-recommend biopsy of lesions that are benign (Cukras 2013).

Blood tests. Blood chemistry analysis may be helpful in melanoma diagnosis; the enzyme lactate dehydrogenase (LDH) may be elevated in people with melanoma. A complete blood count (CBC) and liver function tests may also be part of a skin cancer workup (ACS 2013c).

Staging

Once melanoma or non-melanoma skin cancers have been identified, they are next staged. Staging is a standardized method for describing the size or extent of the original tumor and whether it has spread to other regions in the body. By understanding the severity or extent of a cancer, physicians are able to select an appropriate treatment and provide a realistic prognosis for the disease. Additionally, understanding the stage of a cancer may help identify clinical trials of emerging cancer treatments that may be available (NCI 2013).  

The standard staging system for most cancers is the American Joint Committee on Cancer (AJCC) TNM system. In the TNM system, physical examination and other diagnostic techniques are used to assess 3 categories of information about the cancer (Warner 2011; NCI 2013):

  1. T classification: tumor size, location, and penetration into other tissues
  2. N classification: spread of the cancer into nearby lymph nodes
  3. M classification: spread of the cancer to other organs (metastasis)

Depending on each of the T, N, and M classifications, the cancer is given a “stage” from 0 (pre-cancerous; best prognosis) to IV (most progressive, most difficult to treat). Each type of cancer has its own TNM system, which considers unique features of the cancer, while some cancers (brain and spinal cord, for example) use different protocols for staging (NCI 2013).

For melanoma, the clinical staging (based on physical exam and biopsy of the main melanoma) is shown in Table I.

Table I. Cutaneous Melanoma Clinical Staging System

(Balch 2009; NCI 2014b) 

Stage Description (T, N, and M values are indicated in parentheses)

0

There is a presence of abnormal or pre-cancerous cells only in the topmost layer of skin (also called melanoma in situ). There is no evidence of its spread to local lymph nodes or distant organs.

(Tis, N0, M0)

Ia

The melanoma is 1.0 mm or less in thickness and is not ulcerated (there is no breakdown of the skin over the melanoma). There is no evidence of its spread to local lymph nodes or distant organs.

(T1a, N0, M0)

Ib

The melanoma is 1.0 mm or less in thickness and ulcerated OR 1.01–2.0 mm in thickness and not ulcerated. There is no evidence of its spread to local lymph nodes or distant organs.

(T1b or T2a, N0, M0)

IIa

The melanoma is 1.01–2.0 mm in thickness and ulcerated OR 2.01–4.0 mm in thickness and not ulcerated. There is no evidence of its spread to local lymph nodes or distant organs.

(T2b or T3a, N0, M0)

IIb

The melanoma is 2.01–4.0 mm in thickness and ulcerated OR more than 4.0 mm in thickness and not ulcerated. There is no evidence of its spread to local lymph nodes or distant organs.

(T3b or T4a, N0, M0)

IIc

The melanoma is more than 4.0 mm in thickness and ulcerated. There is no evidence of its spread to local lymph nodes or distant organs.

(T4b, N0, M0)

III

The melanoma can be of any thickness and may/may not be ulcerated. There is evidence of its spread to one or more lymph nodes near the affected skin area. There is no evidence of its spread to distant organs.

(any T, N1-3, M0)

IV

The melanoma can be of any thickness and may/may not be ulcerated. It may/may not have spread to local lymph nodes. It has spread to other organs, such as distant areas of skin or lymph nodes, the lungs, or other visceral sites.

(any T, any N, M1)

Squamous cell and basal cell carcinomas share a different set of criteria for staging (Table II). For these cancers, certain “high risk features” (characteristics of tumors associated with a poor prognosis) are also considered in the staging protocol. High risk features include (ACS 2014c):

  1. Tumor is thicker than 2 mm;
  2. Tumor has invaded deeper skin layers (lower dermis or subcutis);
  3. Tumor has grown into tiny nerves in the skin (perineural invasion);
  4. Tumor started on an ear or on the lips;
  5. Tumor cells look very abnormal when seen under a microscope (poorly differentiated or undifferentiated).

Table II: Non-melanoma Staging System

Stage Description (T, N, and M values are indicated in parentheses)

0

There is a presence of abnormal or pre-cancerous cells only in the topmost layer of skin (also called carcinoma in situ). There is no evidence of its spread to local lymph nodes or distant organs.

(Tis, N0, M0)

I

The tumor is 2 cm or less across and has ≤1 high-risk feature. There is no evidence of its spread to local lymph nodes or distant organs.

(T1, N0, M0)

II

The tumor is more than 2 cm across and has 2 or more high-risk features. There is no evidence of its spread to local lymph nodes or distant organs.

(T2, N0, M0)

III

The tumor has grown into facial bones (such as the jaw or around the eye). There is no evidence of its spread to local lymph nodes or distant organs;

OR

The tumor is of any size or has grown into facial bones. It has spread to 1 nearby lymph node on the same side of the body as the main tumor and the node is 3 cm or less in size. There is no evidence of its spread to distant organs.

(T3, N0, M0) or (T1-3, N1, M0)

IV

The tumor is of any size or has grown into facial bones. It has spread to lymph nodes on the same or on the other side of the body, none of which are larger than 6 cm in diameter. There is no evidence of its spread to distant organs;

OR

The tumor is of any size. It has spread to any lymph node that is nearby and is larger than 6 cm in diameter. There is no evidence of its spread to distant organs;

OR

The tumor has grown into other bones of the body or into the skull. It may or may not have spread into the lymph nodes, but has not spread to distant organs;

OR

Any tumor that has spread to distant organs.

(T1-3, N2, M0) or (Any T, N3, M0) or (T4, any N, M0) or (any T, any N, M1)