Extramammary Paget’s Disease (EMPD)

Intraepithelial adenocarcinoma of apocrine gland, histologically and morphologically similar to Paget’s disease of the nipple; however, EMPD typically targets genital and perianal skin; can be primary cutaneous adenocarcinoma or can result from spread of in situ or invasive malignancy (secondary EMPD), latter in up to 25% of cases
Often presents as unilateral, well-demarcated erythematous plaque resembling chronic eczematous dermatitis in perianal or genital area; ensuing pruritus often results in excoriations and lichenification
Histology: diffuse infiltration of large vacuolated cells with bluish cytoplasm in epidermis (Paget cells) often in lower epidermis, CK20 + (immunohistochemical stains needed to differentiation between pagetoid melanoma)
Treatment: thorough search for possible concurrent underlying malignancy, surgical excision

Table 5-1 Melanoma Staging
	Stage	TNM	Criteria
	0	Tis N0M0	Melanoma in situ
	IA	T1a N0M0	≤ 1.0 mm without ulceration and mitotic rate <1/mm²
	IB	T1b N0M0 T2a N0M0	≤ 1.0 mm with ulceration or mitotic rate >1/mm² 1.01–2.0 mm without ulceration
	IIA	T2b N0M0 T3a N0M0	1.01–2.0 mm with ulceration 2.01–4.0 mm without ulceration
	IIB	T3b N0M0 T4a N0M0	2.01–4.0 mm with ulceration >4 mm without ulceration
	IIC	T4b N0M0	>4 mm with ulceration
	IIIA	T1-4a N1a M0 T1-4a N2a M0	Nonulcerated tumor with single regional nodal micrometastasis Nonulcerated tumor with 2–3 nodal micrometastasis
	IIIB	T1-4b N1a M0 T1-4b N2a M0 T1-4a N1b M0 T1-4a N2b M0 T1-4a/b N2c M0	Ulcerated tumor with single regional nodal micrometastasis Ulcerated tumor with 2–3 nodal micrometastasis Nonulcerated tumor with single regional nodal macrometastasis Nonulcerated tumor with 2–3 nodal macrometastasis In-transit met(s) and/or satellite lesion(s) without metastatic LNs
	IIIC	T1-4b N2a M0 T1-4b N2b M0 T1-4a/b N3M0	Ulcerated tumor with macrometastasis of one lymph node Ulcerated tumor with macrometastasis in 2–3 lymph nodes Tumor with four or more metastatic nodes, matted nodes or in transit mets/satellite lesion(s) with metastatic nodes
	IV	Any T, any N, M1a Any T, any N, M1b Any T, any N, M1c	Distant skin, subcutaneous, or lymph node metastasis Lung metastasis Visceral or any distant metastasis + elevated LDH