Two Different Cell Populations Is an Important Clue for Diagnosis of Primary Cutaneous Adenoid Cystic Carcinoma: Immunohistochemical Study

Table 2

Differential diagnosis of primary cutaneous adenoid cystic carcinoma.

Main differential diagnosis	Morphologic clues	Immunohistochemistry	Other
Adenoid basal cell carcinoma	(i) Peripheral palisading; (ii) Retraction artifact; (iii) Continuing with epidermis or hair follicle; (iv) Lack of two cell populations	(i) CEA, EMA negative; (ii) CD117, CK7 usually negative	Although the staining pattern is not the same, Ber-Ep4 may not be very helpful, with positivity in both lesions.
Primary cutaneous cribriform carcinoma	(i) Epithelial attenuation; (ii) No perineural invasion; (iii) Micropapilla formation; (iv) Lack of two cell populations	(i) Myoepithelial markers (p63, calponin, and SMA) usually negative	CD117 is not helpful, with positivity in both lesions.
Metastatic ACC	(i) Similar morphology	(i) Similar immunohistochemical findings	Differential diagnosis should be done on clinical grounds.
Cribriform patterns in spiradenomas	(i) Focal cribriform areas with typical spiradenoma morphology; (ii) Two cell populations may be found but may be more irregular	N/A	ACC-like areas show myoepithelial differentiation and may be positive with p63 and SMA.
Metastatic breast carcinoma	(i) Lack of two cell populations; (ii) Cancer cells in lymphovascular spaces	(i) Myoepithelial markers (p63, calponin, and SMA) usually negative	Strong ER and PR may point out metastatic breast carcinoma, but adnexal neoplasms may also be positive.

This table is established by using [1–3, 13, 16, 25–33]. ACC: adenoid cystic carcinoma.