Hybrid cysts: A clinicopathological study of seven cases

Abstract

Hybrid cysts develop from more than two components of the pilosebaceous unit. The pathogenesis of this unusual disease has not yet been elucidated. The aim of this study was to assess the clinical and histopathological features of hybrid cysts. Histological sections of seven cases indexed as hybrid cysts were reviewed from 1996-2009 at the Department of Dermatology, Eulji Medical Center, Seoul, Korea. Hospital charts and slides were retrospectively evaluated. All cases had a combination of an epidermal cyst and a pilomatricoma with sharp transitional zones. The epidermal cyst lining was composed of thickened stratified squamous epithelium with a granular layer. Basophilic cells, shadow cells and the contents of the pilomatricoma were present in all lesions. There were no differences in the clinical features between patients with hybrid cysts and others with single cystic lesions. There were five women and two men, ranging in age from 11 to 50 years (mean 27 years). The most common sites were the upper extremities. None of the patients had any sign of Gardner's syndrome. Hybrid cysts are an interesting pathological phenomenon. Further study is needed to analyze hybrid cysts to improve our understanding of their pathogenesis and development from tumours of the pilosebaceous unit.

SkIndia Quiz 9: Solitary cystic nodule with a horn on the thigh of elderly male

“…[1] In a series reported by Kim et al ., all cases had combination of epidermoid cyst and pilomatricoma. [3] In our case also, combination of epidermoid cyst and pilomatricoma was seen with clear areas of transition in the cyst wall.…”

“…It has been reported that pilomatricoma-like changes may be a feature of the epidermal cysts associated with Gardner's syndrome. However, in our case and also in series of Kim et al .,[3] there was no any evidence of Gardner's syndrome.…”

“…[3] An epidermal cyst originates from the follicular infundibulum and contains stratified squamous epithelium with granular layer and lamellar keratinized material. A trichilemmal cyst shows keratinization similar to the isthmus of the outer root sheath of the hair follicle.…”

“…[3] Lower extremity appears a rare site for follicular hybrid cysts (FHC). According to a review of 15 cases of FHC in Japan, the most frequent histological type was the combination of an epidermal cyst with a trichilemmal cyst.…”

Follicular hybrid cyst with rare juxtaposition of epidermal cyst and steatocystoma

“…[ 3 ] Contradictorily, Kim et al . [ 5 ] reported seven FHCs of epidermal cysts combining with pilomatrixomas. Rarely, cysts featuring trichilemmal with pilomatrical, pilomatrical with steatocystoma, epidermal with apocrine, and vellus hair cyst with steatocystoma or epidermal or trichilemmal derivatives have also been described.…”