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Skin Cancer-Staging And Risk Stratification

Skin cancer staging systems are used to describe the severity of cancer, based on the size, extent of invasion, and the spread of disease to different body parts. Staging helps to determine disease prognosis and treatment strategy.

Since different skin cancers behave differently and have variable tendency to invade nearby tissue or to spread to distant body parts, they are staged differently.


BASAL CELL CARCINOMA (BCC)

BCC rarely spreads to distant body parts. Fortunately, most of the cases of BCC are cured before they can spread to distant body parts. Thus, assessment of tumor spread and staging of BCC is not required. However, several prognostic factors have been described for BCC that can predict poor prognosis of the disease.

Following is the list of such high-risk factors: Anatomic site and tumor size (mask area of face, genitalia, hands, and feet with any tumor size; cheeks, forehead, scalp, neck, and pretibial region with tumor size >/=1 cm; and Trunk/remaining extremities areas with tumor size >/=2 cm), tumor invading deeper skin layers, poorly defined borders, perineural invasion, extranodal extension, extension to bony structures, nodal disease, site of prior radiotherapy, immunosuppression, advanced disease/aggressive growth pattern, recurrent disease, poor overall health, comorbidity, and tobacco use.

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SQUAMOUS CELL CARCINOMA

TNM is the most commonly used system for staging squamous cell carcinoma. “T” stands for “Tumor Size”, “N” for “Lymph Nodes”, and “M” for “Metastasis”. Numbers and/or letters after T (is, 1, 2, 3, 4, 4a, and 4b), N (0, 1, 2, 2a, 2b, 2c, 3, 3a, and 3b), and M (0 and 1) provide more details about each of these factors.

Once T, N, and M categories of a skin cancer are determined through different diagnostic techniques, this information is combined to assign an overall stage (from 0 to IV) to the disease.

Following table describe the characteristics of different pathological stages assigned to the SCC of the Head and Neck region:

STAGE TNM DESCRIPTION
0 Tis N0 M0 Carcinoma in situ or non-invasive pre-cancerous lesion confined to the superficial skin layer.
I T1 N0 M0 A primary tumor is <2 cm in size. No spread to nearby lymph nodes or distant body parts.
II T2 N0 M0 A primary tumor size may range from >/=2 cm to <4 cm. No spread to nearby lymph nodes or distant body parts.
III T3 N0 M0 A primary tumor is >/=4 cm in size with minor bone, perineural, or deeper skin layer involvement. No spread to nearby lymph nodes or distant body parts.
T1-3 N1 M0 A primary tumor size may range from <2 cm to >/=4 cm with minor bone, perineural, or deeper skin layer involvement. The disease has spread to a single ipsilateral lymph node measuring </=3 cm without any sign of extranodal extension. No spread to distant body parts.
IV T1-3 N2 M0 A primary tumor size may range from <2 cm to >/=4 cm with minor bone, perineural, or deeper skin layer involvement. The disease has spread to a single ipsilateral lymph node measuring </=3 cm with extranodal involvement; or measuring >3 cm but <6 cm without extranodal involvement; or involvement of multiple ipsilateral/ bilateral/ contralateral lymph nodes, all measuring <6 cm without extranodal involvement. No spread to distant body parts.
Any T N3 M0 A primary tumor of any size with or without invasion to nearby tissues/structures. The disease has spread to a single lymph node measuring >6 cm without extranodal involvement or involvement of single/multiple lymph nodes with extranodal involvement. No spread to distant body parts.
T4 Any N M0 A primary tumor of any size with gross cortical bone/marrow, skull base invasion and/or skull base foramen invasion. The disease might or might not have spread to nearby lymph nodes. No spread to distant body parts.
Any T Any N M1 A primary tumor of any size with or without invasion to nearby tissues/structures. The disease might or might not have spread to nearby lymph nodes. The disease has spread to distant body parts, such as the lungs, liver, etc.

Similar to BCC, several prognostic factors have been described for SCC that can predict poor prognosis of the disease.

Following is the list of such high-risk prognostic factors: Anatomic site and tumor size combinations (mask area of face, genitalia, hands, and feet with any tumor size; cheeks, forehead, scalp, neck, and pretibial region with tumor size >/=1 cm; and Trunk/remaining extremities areas with tumor size >/=2 cm), tumor invading deeper skin layers or tumors with greater thickness, poorly defined borders, perineural invasion, extranodal extension, extension to bony structures, vascular involvement, lymphatic involvement, site of prior radiotherapy, immunosuppression, advanced disease/aggressive subtype/poorly differentiated cells, recurrent disease, poor overall health, comorbidities, and patients with certain genetic disorders such as albinism or xeroderma pigmentosum.

MELANOMA

TNM is the most commonly used system for staging melanoma. “T” stands for “Tumor Thickness”, “N” for “Lymph Nodes”, and “M” for “Metastasis”. Instead of tumor size, tumor thickness or Breslow measurement is used for assessing melanoma stage, because vertical tumor thickness is considered a better indicator of the disease prognosis and the tendency of disease spread to distant body parts.

Also, ulceration status of the melanoma lesion is important and can affect disease prognosis. Numbers and/or letters after T (is, 1, 1a, 1b, 2, 2a, 2b, 3, 3a, 3b, 4a, and 4b), N (0, 1, 1a, 1b, 1c, 2a, 2b, 2c, 3, 3a, 3b, and 3c), and M (0 and 1) provide more details about each of these factors. Once T, N, and M categories of melanoma are determined, this information is combined to assign an overall stage (from 0 to IV) to the disease.

Following table describes the characteristics of different pathological stages assigned to melanoma:

STAGE TNM DESCRIPTION
0 Tis N0 M0 Carcinoma/Melanoma in situ or non-invasive pre-cancerous lesion confined to the superficial skin layer.
IA T1 N0 M0 A primary tumor </=1 mm in thickness without ulceration. No spread to nearby lymph nodes or distant body parts.
IB T2a N0 M0 A primary tumor >1 mm but </=2 mm in thickness without ulceration. No spread to nearby lymph nodes or distant body parts.
IIA T2b/3a N0 M0 A primary tumor >1 mm but </=2 mm in thickness with ulceration or >2 mm but </=4 mm in thickness without ulceration. No spread to nearby lymph nodes or distant body parts.
IIB T3b/4a N0 M0 A primary tumor >2 mm but </=4 mm in thickness with ulceration or >4 mm in thickness without ulceration. No spread to nearby lymph nodes or distant body parts.
IIC T4b N0 M0 A primary tumor >4 mm in thickness with ulceration. No spread to nearby lymph nodes or distant body parts.
IIIA T1/2a N1a/2a M0 A primary tumor </=1 mm in thickness without ulceration or >1 mm but </=2 mm in thickness without ulceration. A microscopic disease spread to 1–3 nearby lymph nodes. No spread to distant body parts.
IIIB T0 N1b/1c M0 A primary tumor is not present, but the microscopic disease has been detected in a nearby lymph node or in lymphatic channels around the tumor or presence of satellite tumors (nearby microscopic skin involvement). No spread to distant body parts.
T1/2a N1b/1c/2b M0 A primary tumor </=1 mm in thickness without ulceration or >1 mm but </=2 mm in thickness without ulceration. A microscopic disease has been detected in a nearby lymph node or in lymphatic channels around the tumor or the presence of satellite tumors or a spread of disease to 1–3 nearby lymph nodes. No spread to distant body parts.
T2b/3a N1a‑2b M0 A primary tumor >1 mm but </=2 mm in thickness with ulceration or >2 mm but </=4 mm in thickness without ulceration. A microscopic disease has been detected in a nearby lymph node or in lymphatic channels around the tumor or the presence of satellite tumors or a spread of disease to 1–3 nearby lymph nodes. No spread to distant body parts.
IIIC T0 N2b/2c/3b/3c M0 A primary tumor is not present, but the disease has detected in 1 or more nearby lymph nodes with or without the presence of satellite tumors. No spread to distant body parts.
T1/2/3a N2c/3 M0 A primary tumor >1 mm to </=4 mm in thickness with or without ulceration. The disease has spread to 1 or more nearby lymph nodes with or without the presence of satellite tumors. No spread to distant body parts.
T3b/4a N>1 M0 A primary tumor >2 mm but </=4 mm in thickness with ulceration or >4 mm in thickness without ulceration. The disease has spread to 1 or more nearby lymph nodes with or without the presence of satellite tumors. No spread to distant body parts.
T4b N1-2 M0 A primary tumor >4 mm in thickness with ulceration. A microscopic disease has been detected in a nearby lymph node or in lymphatic channels around the tumor or the presence of satellite tumors or a spread of disease to 1–3 nearby lymph nodes. No spread to distant body parts.
IIID T4b N3 M0 A primary tumor >4 mm in thickness with ulceration. The disease has spread to 4 or more nearby lymph nodes with or without the presence of satellite tumors. No spread to distant body parts.
IV Any T Any N M1 A primary tumor of any thickness with or without ulceration. The disease might or might not have spread to nearby lymph nodes with or without the presence of satellite tumors. The disease has spread to distant body parts, for example, the skin, soft tissue including muscles, distant lymph nodes, or visceral organs, such as the lungs, liver, or brain.
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