Skin nonmelanocytic tumor

• All primary cutaneous neuroendocrine carcinomas are covered by this staging system
• Metastatic extracutaneous neuroendocrine carcinomas are not covered

• pTX: primary tumor cannot be assessed (e.g. curetted)
• pT0: no evidence of primary tumor
• pTis: in situ primary tumor
• pT1: maximum clinical tumor diameter ≤ 2 cm
• pT2: maximum clinical tumor diameter > 2 cm but ≤ 5 cm
• pT3: maximum clinical tumor diameter > 5 cm
• pT4: primary tumor invades fascia, muscle, cartilage or bone

Notes:

• Tumor diameter: measured as the largest diameter of the primary tumor; this is a clinical measurement
• Gross or microscopic measurement should only be used when the clinical measurement is unavailable since tumor shrinkage during formalin fixation will result in underestimation of diameter

• pNX: cannot be assessed (staging procedure not performed or previously removed)
• pN0: no regional metastasis detected on pathological evaluation
• pN1a(sn): microscopic lymph node metastasis detected by sentinel node biopsy, clinically occult
• pN1a: microscopic regional lymph node metastasis following dissection, clinically occult
• pN1b: microscopic confirmation of clinically detected regional lymph node metastasis
• pN2: in transit metastasis without lymph node metastasis
• pN3: in transit metastasis with lymph node metastases

Notes:

• Regional lymph nodes / sentinel lymph nodes: sentinel node(s) receive direct lymphatic drainage from the primary tumor site
• Clinically occult: nodal metastasis detectable only by microscopic evaluation
• Clinically detected: lymph node enlarged or abnormal by physical or radiologic examination
• Isolated tumor cells: counted as metastases whether identified on H&E or by IHC
• In transit metastasis: intralymphatic tumor deposits discontinuous from the primary lesion and located either between the primary lesion and the draining regional lymph nodes or distal to the primary lesion

Stage group 0:	Tis	N0	M0
Stage group I:	T1	N0	M0
Stage group IIA:	T2 - T3	N0	M0
Stage group IIB:	T4	N0	M0
Stage group IIIA:	T1 - T4	N1a(sn) or N1a	M0
	T0	N1b	M0
Stage group IIIB:	T1 - T4	N1b - N3	M0
Stage group IV:	T0 - 4	N0 - N3	M1

Notes:

• Unknown primary tumor: patients presenting with metastatic Merkel cell carcinoma to a lymph node in the absence of a primary tumor have a significantly more favorable prognosis than patients with a primary tumor and a clinically detected nodal metastasis
• Survival rates are similar to those of patients with a primary tumor and occult nodal metastases detected by sentinel lymph node biopsy (J Am Acad Dermatol 2013;68:433, Am J Surg 2013;206:752, J Am Acad Dermatol 2012;67:395)

• Largest tumor diameter (clinical measurement in millimeters)
• Regional node status (clinically detected, pathologically detected or neither)
• Unknown primary status (yes or no)
• Tumor thickness (reported in millimeters)
• Excision margin status (tumor base transected or not transected)
• Profound immunosuppression (no conditions, HIV / AIDS, solid organ transplant recipient, CLL / SLL, other non-Hodgkin lymphoma, multiple conditions or condition NOS)
• Lymphovascular invasion (present or absent)
• Merkel cell polyomavirus positive staining by IHC (yes, no or not applicable)
• p63 positive staining by IHC (yes or no)
• Tumor infiltrating lymphocytes in primary tumor (not present, present nonbrisk or brisk)
• Growth pattern of primary tumor (circumscribed, nodular or infiltrative)
• Extranodal extension in regional lymph nodes (yes or no)
• Tumor nest size in regional lymph nodes (greatest dimension of largest aggregate in millimeters)
• Isolated tumor cells in regional lymph node (yes or no)
• Eyelid tumor (no, yes upper lid, yes lower lid or yes involving both lids)
• Eyelid tumor involving eyelid margin, defined as the juncture of eyelid skin and tarsal plate at the lash line (no, yes non full thickness or yes full thickness)

Notes:

• Tumor thickness: measure from the surface of the epidermal granular layer to the point of maximum tumor thickness at a right angle to adjacent epidermis
• Tumor infiltrating lymphocytes: considered brisk when the inflammation diffusely infiltrates the tumor or is present around the entire base of the tumor

Which of the following Merkel cell carcinoma is associated with the worst prognosis?


1. Primary tumor involves dermis and there are clinically detected regional lymph node metastases
2. Primary tumor involves fat and there are no regional lymph node metastases
3. Primary tumor involves muscle and there are no regional lymph node metastases
4. Metastatic Merkel cell carcinoma is present in a lymph node but no primary tumor is identified

A. The presence of nodal metastases upstages the carcinoma regardless of primary tumor attributes. Patients with clinically detected nodal metastases in the absence of an identifiable primary Merkel cell carcinoma (Stage IIIA) fare significantly better than patients with a known primary tumor and clinically detected regional node metastases (Stage IIIB).

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Reference: Pathologic TNM staging of Merkel cell carcinoma (AJCC 8th edition)

In the AJCC 8th edition, the most important parameters determining the pT category for Merkel cell carcinoma is which of the following?

1. Lymphovascular invasion and p16 expression
2. Maximum clinical tumor diameter and extent of anatomic invasion
3. Tumor infiltrating lymphocytes and necrosis
4. Tumor thickness and mitotic rate
5. Ulceration and regression

B. Maximum clinical tumor diameter and extent of anatomic invasion

pT categories for primary cutaneous Merkel cell carcinoma (AJCC 8th edition) are as follows:
pTis: in situ primary tumor
pT1: maximum clinical tumor diameter ≤ 2 cm
pT2: maximum clinical tumor diameter > 2 cm but ≤ 5 cm
pT3: maximum clinical tumor diameter > 5 cm
pT4: primary tumor invades fascia, muscle, cartilage or bone

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Reference: Pathologic TNM staging of Merkel cell carcinoma (AJCC 8th edition)