Immunohistochemical differentiation of four benign eccrine tumors

Background:  The histogenesis and differentiation of eccrine tumors, including cylindroma, poroma, spiradenoma and syringoma, remains controversial. This controversy may be because of sporadic and incomplete studies of these neoplasms.
Methods:  Ten examples each of normal eccrine structures and of four benign eccrine tumors are analyzed with antibodies to cytokeratin (CK) 7, CD34, CK6, CK10, smooth muscle actin (SMA) and CD10. These markers represent two different immunohistochemical stains for each part of the eccrine structure; CK7 and CD34 stain the secretory coil, CK6 and CK10 stain the straight duct and SMA and CD10 stain the myoepithelial cells. This redundancy in staining is performed on four benign eccrine tumors to better interpret the existing literature.
Results:  We find that CK7 is a sensitive marker for the secretory coil; both cylindromas and spiradenomas express CK7. We also find that CK6 is a marker for the inner ductal cells, while CK10 is a marker for the middle ductal cells; syringomas express both these markers. SMA appears to be a more specific marker for myoepithelial cells surrounding normal eccrine coils, and none of the studied tumors express SMA or CD10.
Conclusions:  Our studies suggest that syringomas are tumors of the eccrine duct, while cylindromas and spiradenomas are tumors of the secretory coil.