cylindroma/spiradenoma hybrid, dispersed and nodular

CYLINDROMA/SPIRADENOMA HYBRID WITH NODULAR AND DISPERSED (MICRONODULAR) PATTERNS

Cylindromas of skin have been variously interpreted as being of eccrine, apocrine, or follicular origin. The dominant line of differentiation in most examples appears to be eccrine. Though most are found in the dermis, subcutaneous involvement may be extensive as in this case.

The cells that form cylindromas resemble those found in eccrine spiradenomas in that they are small, light and dark, and they do not have visible cytoplasmic junctions except in foci of ductal differentiation. Eosinohilic blobs can be found within tumor nests of cylindromas and spiradenomas.

Cylindromas are composed of small subunits of tumor that often have angulated outlines, and these subunits are surrounded by a thick layer of eosinophilic material having the characteristics of basement membrane material. The darker cells, when present, are found in the periphery of the subunits. The subunits are often grouped in a jigsaw puzzle pattern to form a larger nodular aggregate. Some cylindromas, however, are composed of dispersed, micronodular subunits, and this pattern resembles infiltration. Rare examples appear to be truly infiltrating and cannot be distinguished from carcinomas by pattern.

Spiradenomas, in contrast with cylindromas, are composed of large subunits that have gently rounded peripheral borders. The light and dark cells are intermingled. Therefore the differences between cylindromas and spiradenomas is largely architectural rather than cellular.

Tumors having combined features of cylindroma and spiradenoma are not as rare as textbooks would lead one to believe.

Solitary nodule from a 67 year old female:

Very low power view (direct scan). Several nodular tumor aggregates are seen in addition to more dispersed patterns.

Medium power view of the area in the red rectangle above. Small subunits are surrounded by a thick,glassy layer of basement membrane material. Darker cells are seen around the periphery of some subunits.

Low power view of the area in the black rectangle in the top picture. Small subunits of cylindroma are in the upper left side of the picture. Part of a large nodule characteristic of a spiradenoma is in the rest of the picture.

High power view of above. There is a random mixture of lightly and darkly staining cells in the spiradenoma type of nodule. Eosinophilic blobs are found centrally.

A scanning power view of a section taken from another area of the same specimen. The cylindromatous subunits are found in a dispersed pattern.

A medium power view of above. Each subunit is surrounded by a thick layer of glassy basement membrane material. Darker cells are around the periphery of most of the subunits.

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	Very low power view (direct scan). Several nodular tumor aggregates are seen in addition to more dispersed patterns.
	Medium power view of the area in the red rectangle above. Small subunits are surrounded by a thick,glassy layer of basement membrane material. Darker cells are seen around the periphery of some subunits.
	Low power view of the area in the black rectangle in the top picture. Small subunits of cylindroma are in the upper left side of the picture. Part of a large nodule characteristic of a spiradenoma is in the rest of the picture.
	High power view of above. There is a random mixture of lightly and darkly staining cells in the spiradenoma type of nodule. Eosinophilic blobs are found centrally.
	A scanning power view of a section taken from another area of the same specimen. The cylindromatous subunits are found in a dispersed pattern.
	A medium power view of above. Each subunit is surrounded by a thick layer of glassy basement membrane material. Darker cells are around the periphery of most of the subunits.