A 45-year-old man presented with a long-standing subcentimeter nodule on the right inferior central malar cheek.
A shave biopsy showed an extensive tumefactive atypical glandular proliferation primarily involving the dermis throughout its depth. In addition, there were discrete foci of epidermotropism. The dermal component had some element of circumscription; however, the borders of the tumor assumed a focally infiltrative growth pattern including single-cell infiltration of deep-seated skeletal muscle. The dominant architectural growth pattern consisted of tubules containing basophilic mucin; however, there were also foci of striking cribriform formation with nodular foci composed of closely juxtaposed rounded tubules exhibiting abundant mucin. No significant areas of solid growth were seen. Hyaline globules were also noted within some of the glands. Focal perineural invasion was identified.
The cells ranged from being small cuboidal to vacuolated to cells exhibiting more voluminous eosinophilic cytoplasms reminiscent of apocrine differentiation. Some of the cells had a signet ring appearance. The nuclear chromatin in general was fine and nucleoli were inconspicuous. However, there were cells that assumed some degree of atypia while maintaining a well-differentiated appearance. These atypical features included nuclear size and shape heterogeneity, notched nuclear contours, more conspicuous nucleolation, and irregular nuclear membranes. Areas of chondroid or truly hyalinized stromal change were not seen, although there were small collections of mucin in the stroma.
There were areas of direct continuity with the epidermis and the acrosyringium, whereby singly disposed and mucin containing tubules assumed a vertical orientation in the epidermis following and essentially replacing the acrosyringium. In addition, there were areas of focal periacrosyringial somewhat infiltrative basilar and parabasilar epidermal infiltration. The intraepidermal acrosyringeal foci also extended into the subjacent eccrine ducts.
Immunohistochemical and special stains have been performed. The hyaline globules were positive for periodic acid–Schiff with and without diastase. An alcian blue preparation highlighted the intra and interglandular mucin deposition. The luminal cells were diffusely positive for CAM 5.2, cytokeratin (CK) 7, and CK19. A majority of these cells also stained with epithelial membrane antigen. An androgen receptor preparation was focally positive. The myoepithelial component of the tumor was highlighted by S100. A CK15 preparation was negative (Figures 1 and 2).
Figure 1. A-C Low power examination shows a well-differentiated infiltrative glandular process characterized by tubule and cribriform formation. These glands are focally in direct continuity with the supervening epidermis and acrosyringium. D. Under higher magnification, the direct involvement of the epidermis can be appreciated, with basilar and suprabasilar spread of glands noted. E. A CK19 preparation highlights the luminal cells. F. A S100 stain highlights the myoepithelial component. G. An alcian blue preparation highlights the intraglandular and interglandular mucin. H. The infiltration of the supervening epidermis is highlighted by CK19 (Figures A-D: hematoxylin-eosin stained, E: CK19, F: S100, G: alcian blue, H: CK19).
Figure 2. A. Perineural invasion is seen. B. Mitotic figures are readily identified (arrows). C. Hyaline globules are seen in many of the glands. D. Focal infiltration of skeletal muscle by single cells is seen.
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