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The basics: diagnostic terms, skin anatomy, and stains

Epithelial membrane antigen (EMA) Highlights normal sebaceous and sweat

glands Positive in sebaceous carcinoma, Pagets, and

extramammary Pagets Positive in squamous cell carcinoma but

negative in basal cell carcinoma

Carcinoembryonic antigen (CEA) Sweat glands are immunoreactive Positive in sweat gland neoplasms,

Pagets, extramammary Pagets, and most adenocarcinomas

Ber-EP4 Marks most epithelial cells, but not those

undergoing squamous differentiation Positive in basal cell carcinoma and negative

in squamous cell carcinoma

Mesenchymal markersDesmin Positive staining in skeletal and most smooth

muscle Generally negative in vascular smooth muscle

(including glomus cells)

Smooth-muscle actin (SMA) Positive in smooth muscle, including vascular

smooth muscle Examples: glomus tumor, leiomyosarcoma

Figure 1-87 CEA-positive pagetoid cells of Pagets disease

Figure 1-88 Infiltrating basal cell carcinoma with Ber-EP4

Figure 1-89 Desmin-positive piloleiomyoma

Figure 1-90 Piloleiomyoma with SMA. Note positive staining of normal surrounding vascular smooth muscle in contrast to the absence of reactivity with desmin in Figure 1-89.

Figure 1-86 EMA positivity in sebaceous epithelioma