This is one of the two eccrine sweat unit tumors where solid areas dominate over tubular areas and the cells, for the most part, do not have discernable cytoplasmic outlines. The other tumor having these characteristics is the spiradenoma. The spiradenoma is composed of relatively large, round tumor masses, and the cylindroma is composed of smaller, somewhat angulated subunits. The subunits of cylindromas are separated by glassy basement membrane material that is PAS positive. Globs of similar material may be found within the subunits in cylindromas and in spiradenomas. Two cell variants (light and dark cells) may be found in the solid areas of both tumors. These cells are often intermingled in spiradenomas. The darker cells tend to be found around the periphery of the small tumor nests in cylindromas. Foci of follicular differentiation are sometimes found in cylindromas.
 

	Scan power view. The tumor masses are fairly well-circumscribed. In this example. The tumor masses may be broken up in other examples and have infiltrating characteristics. Tumors having the infiltrating pattern may recur.
	Medium power view. Small subunits are separated by glassy, eosinophilic basement membrane material. Some of the subunits have angulated outlines. The darker cells tend to be found around the periphery of the subunits.
	High power view. Note the focus of tubular differentiation. Tubules are usually few in number or absent..

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