Table 1. Main differences between EMPD, Bowen disease and melanoma-in-situ. Immunohistochemical markers in bold are part of recommended panel for the characterization of these lesions.

	Common sites	Dermoscopy findings	Histopathological features	Immunohistochemical stains
Extra-mammary Pagets disease	Apocrine-rich areas of perineum, groin, genitalia and axillae.	Equivocal pigmentation [32], but may have features of MIS	Mucin-rich clear plump cells in the epidermis, may have signet ring appearance, and some may be in clusters, glandular or tubular differentiation. Rarely Paget cells may contain melanin pigment.	CK7, CK20, CAM5.2, CEA, EMA
Squamous cell carcinoma-in-situ	Sun-exposed sites of the face, extremities, also frequently in groin and genitalia	Linear brown/grey dots Coiled vessels [33]	Full-thickness atypia of epidermis with loss of polarity, with possible extension along follicular and adnexal structures, occasionally may also contain melanin pigment	p63, high molecular weight cytokeratin eg. 34βE12
Melanoma-in-situ (MIS)	Typically in sun exposed sites	Irregular pigment network, blue-white veil and blue-grey areas	Pigmented atypical melanocytes with Pagetoid spread, fine melanin granules and pleomorphic naevus cells in basal layer of epidermis	S100, HMB45