Follicular Hybrid Cyst with Rare Juxtaposition of Epidermal Cyst and Steatocystoma

Abstract

Any cutaneous cyst differentiating toward two or more pilosebaceous components is known as follicular hybrid cyst (FHC). A combination of epidermal and trichilemmal cyst is its most frequent example. Other combinations of pilosebaceous derivatives occur uncommonly as well. The histogenesis of this condition has been controversial. In this latest report, we describe an unusual FHC from the earlobe of a 19-year-old male, which expressed the cohabitation of epidermal cyst and steatocystoma. A sharp transition was noted between the two kinds of epithelial components.

Keywords: Earlobe; epidermal cyst; follicular hybrid cyst; pilosebaceous follicle; steatocystoma.

Figure 1

Clinically, skin-colored nodule at the lower pole of pinna with a tiny (arrow) surface punctum

Figure 2

Histopathologically, hybrid cyst comprising steatocystoma (right half) and epidermal cyst (left half) with an abrupt transition (arrow) in between. Note the intermittent presence of stratified squamous cells over the sebaceous epithelium (a) (H and E stain, ×40). Steatocystoma component characterized by multilayered sebaceous epithelium (b) with occasional presence of multinucleate giant cells (c) (H and E stain, ×400). Epidermal cyst featuring stratified squamous epithelium with intermediate stratum granulosum and laminated keratinization (d) (H and E stain, ×400)