perifollicular fibroma

PERIFOLLICULAR FIBROMA

A TYPE OF MATURE FIBROEPITHELIAL FOLLICULOSEBACEOUS HAMARTOMA

Solitary lesion from the left side of the neck of a 29 year old female.

The fibrous follicular sheath as well as the epithelial components of the folliculosebaceous unit participate in the formation of a class of tumors best categorized as hamartomas. Such tumors may be solitary or multiple in a given patient. Reed discusses this group of tumors more extensively.

Although the term perifollicular fibroma implies pure follicular differentiation, common usage allows for a sebaceous component. A sebaceous component is present in Fig. 33-19 on page 871 in Lever's text^{ref 1}.

An architectural variant, the fibrofolliculoma , has sweeping, arcuate, delicate strands of epithelium that may interconnect, and such strands of epithelium are reminiscent of the mantle component of a follicle.

A variant that is dominated by sebaceous differentiation associated with a central cystic area has been described as folliculosebaceous cystic hamartoma .

The stroma in these various hamartomas can be composed of dense collagen, as in this case, or it can be myxoid of the type prototypically found in trichodiscomas.

Scan power view. The arrows mark planes delimiting the lesion. The connective tissue component is an integral part of the tumor. This is only a slight suggestion of arcuate hyperplasia of the epithelium in the upper right side of the tumor.

Medium power view. The lesion is to the left of the arrow. Compare the connective tissue on each side of the apparent cleavage plane. Normal reticular dermis is to the right of the arrow, and the hyperplastic follicular sheath connective tissue is to the left.

High power view. Note the character of the connective tissue. The collagen fibers are coarse but smaller than reticular dermis collagen bundles. Some of the fibers in this field are perpendicular to the epithelium thereby resembling the pattern found in some fibrous papules of the nose .

Reference:
1. Elder et al; editors: Lever's Histopathology of the Skin, 8^thedition. Philadelphia- NewYork, Lippincott-Raven 1997.

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	Scan power view. The arrows mark planes delimiting the lesion. The connective tissue component is an integral part of the tumor. This is only a slight suggestion of arcuate hyperplasia of the epithelium in the upper right side of the tumor.
	Medium power view. The lesion is to the left of the arrow. Compare the connective tissue on each side of the apparent cleavage plane. Normal reticular dermis is to the right of the arrow, and the hyperplastic follicular sheath connective tissue is to the left.
	High power view. Note the character of the connective tissue. The collagen fibers are coarse but smaller than reticular dermis collagen bundles. Some of the fibers in this field are perpendicular to the epithelium thereby resembling the pattern found in some fibrous papules of the nose .