Calcification and ossification in eccrine mixed tumors: underrecognized feature and diagnostic pitfall.
BACKGROUND
Eccrine mixed tumors of the skin are rare adnexal neoplasms, and their morphological spectrum is not well established.


OBJECTIVE
To highlight the variation of the mesenchymal component of eccrine mixed tumors.


METHODS
Among 70, 000 skin biopsies, 5 were diagnosed as eccrine mixed tumors. Cases were studied for clinical, histopathological, and immunohistochemical features (S-100, cytokeratin, epithelial membrane antigen, carcinoembryonic antigen, estrogen receptors, and herceptin receptor (HER-2)).


RESULTS
Lesions were well-circumscribed dermal or subcutaneous nodules. Epithelial elements were small round tubules, cords, and individual cell aggregations being larger at the periphery and smaller toward the center. No signs of follicular or sebaceous differentiation were seen. The stroma was mucinous and chondroid, calcification ranging from little to extensive with bone formation in 3 examples giving the impression of a chondroid or osseous neoplasm. S-100 stained epithelial and chondroid stromal cells. Cytokeratin highlighted the silhouette of epithelial elements. Estrogen receptors, EMA, carcinoembryonic antigen, and HER-2 were negative.


CONCLUSIONS
Eccrine mixed tumors are distinctive tumors that should not be lumped together with their apocrine counterparts. Extensive ossification and calcification may be present and may eclipse by far the epithelial elements.
Tirumalae
Rajalakshmi
R
Department of Pathology, St. John's Medical College, Bangalore, India.
Böer
Almut
A
D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D002114:Calcinosis; D004439:Eccrine Glands / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D018294:Neoplasms, Adnexal and Skin Appendage / Q000378:metabolism / Q000473:pathology*; D018193:Neoplasms, Complex and Mixed / Q000378:metabolism / Q000473:pathology*
D014408:Biomarkers, Tumor