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Merkel Cell Carcinoma Treatment (PDQ®)

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Stage Information for Merkel Cell Carcinoma

Definitions of TNM

Previously, five competing staging systems have been used to describe Merkel cell carcinoma (MCC) in most publications.

Table 2. Five Previously Used Competing Merkel Cell Carcinoma Staging Systems
First Author Publication Date  Institution(s) No. of Patients in Case Series Dates of Cases 
Yiengpruksawan et al.[2]1991MSKCCa771969–1989
Allen et al.[3]1999MSKCCa1021969–1996
Allen et al.[4]2005MSKCCa2501970–2002
American Joint Committee on Cancer[5]2002N/AN/A
Clark et al.[6]2007Westmead Hospital, Sydney, Australia110
Princess Margaret Hospital/University Health Network, Toronto, Canada
Sydney Head and Neck Cancer Institute/Royal Prince Alfred Hospital, Sydney, Australia

MSKCC = Memorial Sloan Kettering Cancer Center; N/A = Not applicable.
aThe MSKCC system has evolved over time. MSKCC authors have published one additional case series with 256 patients.[1]

These staging systems are highly inconsistent with each other. Indeed, stage III disease can mean anything from advanced local disease to nodal disease to distant metastatic disease. Furthermore, all MCC staging systems in use have been based on fewer than 300 patients.

Definitions of TNM

To address these concerns, a new MCC-specific consensus staging system was developed by the American Joint Committee on Cancer (AJCC) to define Merkel cell carcinoma, as shown in tables 3, 4, 5, and 6.[7] Prior to the publication of this new system, the AJCC advocated using the nonmelanoma staging system.

Table 3. Primary Tumor (T)a
aReprinted with permission from AJCC: Merkel cell carcinoma. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 315-23.
TXPrimary tumor cannot be assessed.
T0No evidence of primary tumor (e.g., nodal/metastatic presentation without associated primary).
TisIn situ primary tumor.
T1≤2 cm maximum tumor dimension.
T2>2 cm but ≤5 cm maximum tumor dimension.
T3>5 cm maximum tumor dimension.
T4Primary tumor invades bone, muscle, fascia, or cartilage.

Table 4. Regional Lymph Nodes (N)a
NXRegional lymph nodes cannot be assessed.
N0No regional lymph nodes metastasis.
cN0Nodes negative by clinical examb (no pathologic node exam performed).
pN0Nodes negative by pathologic exam.
N1Metastases in regional lymph node(s).
N1aMicrometastasis.c
N1bMacrometastasis.d
N2In transit metastasis.e

aReprinted with permission from AJCC: Merkel cell carcinoma. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 315-23.
bClinical detection of nodal disease may be via inspection, palpation, and/or imaging.
cMicrometastases are diagnosed after sentinel or elective lymphadenectomy.
dMacrometastases are defined as clinically detectable nodal metastases confirmed by therapeutic lymphadenectomy or needle biopsy.
eIn transit metastasis: a tumor distinct from the primary lesion and located either (1) between the primary lesion and the draining regional lymph nodes or (2) distal to the primary lesion.

Table 5. Distant Metastasis (M)a
aReprinted with permission from AJCC: Merkel cell carcinoma. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 315-23.
M0No distant metastasis.
M1Metastases beyond regional lymph nodes.
M1aMetastases to skin, subcutaneous tissues, or distant lymph nodes.
M1bMetastasis to lung.
M1cMetastases to all other visceral sites.

Table 6. Anatomic Stage/Prognostic Groupsa
Stage T N M 
aReprinted with permission from AJCC: Merkel cell carcinoma. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 315-23.
0TisN0M0
IAT1pN0M0
IBT1cN0M0
IIAT2/T3pN0M0
IIBT2/T3cN0M0
IICT4N0M0
IIIAAny TN1aM0
IIIBAny TN1b/N2M0
IVAny TAny NM1

Before the new AJCC consensus staging system was published, the most recent MSKCC four-stage system was favored because it was based on the largest number of patients and was the best validated.[1] The stages in the MSKCC system included:

  • Stage I: local disease <2 cm.
  • Stage II: local disease ≥2 cm.
  • Stage III: regional nodal disease.
  • Stage IV: distant metastatic disease.

One group has suggested a list of 12 elements that should be described in pathology reports of resected primary lesions and nine elements to be described in pathology reports of sentinel lymph nodes. The prognostic significance of these elements has not been validated prospectively.[8] The 2009 AJCC staging manual also specifies a variety of factors which should be collected prospectively on pathology reports.

References
  1. Andea AA, Coit DG, Amin B, et al.: Merkel cell carcinoma: histologic features and prognosis. Cancer 113 (9): 2549-58, 2008.  [PUBMED Abstract]

  2. Yiengpruksawan A, Coit DG, Thaler HT, et al.: Merkel cell carcinoma. Prognosis and management. Arch Surg 126 (12): 1514-9, 1991.  [PUBMED Abstract]

  3. Allen PJ, Zhang ZF, Coit DG: Surgical management of Merkel cell carcinoma. Ann Surg 229 (1): 97-105, 1999.  [PUBMED Abstract]

  4. Allen PJ, Bowne WB, Jaques DP, et al.: Merkel cell carcinoma: prognosis and treatment of patients from a single institution. J Clin Oncol 23 (10): 2300-9, 2005.  [PUBMED Abstract]

  5. American Joint Committee on Cancer.: AJCC Cancer Staging Manual. 6th ed. New York, NY: Springer, 2002. 

  6. Clark JR, Veness MJ, Gilbert R, et al.: Merkel cell carcinoma of the head and neck: is adjuvant radiotherapy necessary? Head Neck 29 (3): 249-57, 2007.  [PUBMED Abstract]

  7. Merkel cell carcinoma. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 315-23. 

  8. Bichakjian CK, Lowe L, Lao CD, et al.: Merkel cell carcinoma: critical review with guidelines for multidisciplinary management. Cancer 110 (1): 1-12, 2007.  [PUBMED Abstract]