A Rare Hybrid Skin Cyst of the Scalp With Pilar and Apocrine Features.

Benign epithelial skin cysts containing multiple components of the folliculo-sebaceous apocrine unit are only rarely reported in the literature. Here, we describe a 12-year-old girl who presented with a cystic mass on the vertex of her scalp. Upon resection, it showed a hybrid benign skin cyst with interesting histological features of both pilar and apocrine differentiation. The clinicopathological and imaging findings of this unusual skin cyst, successfully managed by a plastic surgeon and neurosurgeon, are described. Pathologists and clinicians should be aware of this type of skin cyst rarely encountered in their clinical practice.

Follicular Hybrid Cyst with Rare Juxtaposition of Epidermal Cyst and Steatocystoma.

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.

In situ carcinoma in a hybrid cyst: a case report.

Follicular hybrid cysts including two or more components of the epithelial skin adnexa are very rare. The epithelial lining of hybrid cysts varies, and either contains epidermis, and trichilemmal squamous epithelium, or other epithelia of the skin adnexa. Hybrid cysts may also be associated with neoplasia, such as in situ carcinoma, Bowen's disease and squamous cell carcinoma. A 37-year-old female was complaining of a cyst on her scalp. The unilocular cystic lesion was lined with markedly atypical squamous cells with trichilemmal differentiation. Marked nuclear and cytological atypia, pleomorphism, numerous mitotic figures and atypical mitosis was detected in the squamous epithelium. The epithelium of the cyst was also composed of ductal structures lined with cuboidal epithelium. Immunohistochemical staining was positive for cytokeratin 7 (CK7) in both squamous and glandular epithelium. Luminal staining was shown by carcinoembryonic antigen (CEA), although gross cystic disease fluid protein-15 (GCDFP-15) was negative in the glandular epithelium. In addition, p16 tumor suppressor gene was strongly positive in both the squamous and glandular epithelium. Overall, the unique cystic lesion reported contained pilar squamous epithelium with in situ carcinoma and eccrine ductal structures, which was interpreted as a hybrid cyst composed of in situ trichilemmal carcinoma and a ductal eccrine component.

Cutaneous Epithelial Lesions Induced by N-Methyl-N-nitrosourea in Male Sprague-Dawley Rats: A Possible Animal Model for Human Keratoacanthoma.

A single intraperitoneal injection of 50 or 75 mg/kg N-methyl-N-nitrosourea in male Sprague-Dawley rats at 4 weeks of age, dose-dependently resulted in cutaneous epithelial cysts and tumors of pilosebaceous origin. Cysts were composed of epidermal cysts or mixed epidermal and inner root sheath hybrid cysts. The majority of induced tumors were keratoacanthomas. A few tumors were trichofolliculomas, trichoblastomas, pilomatricomas, or sebaceous adenomas. All tumors were benign pilosebaceous tumors. Keratoacanthomas were crater-shaped tumors with thick infoldings of epithelium containing keratohyalin granules (epidermal lip) that abruptly changed to epithelium containing trichohyalin granules. The morphological similarity and resemblance of keratin 1, 10, and 14 profiles, and p63 and ß-catenin expression between mixed epidermal and inner root sheath hybrid cysts and keratoacanthomas suggests that hybrid cysts progressed to keratoacanthomas, and the cells from infundibular cells to inner root sheath cells of the pilar segment seem to be the origin of rat keratoacanthomas. Immunohistochemical localization of keratins 1, 10 and 14, p63, and ß-catenin in trichofolliculoma, trichoblastoma, and pilomatricoma, as well as keratoacanthoma, may indicate tumor histogenesis.

Classification of cysts with follicular germinative differentiation.

BACKGROUND: Cysts are very common in the routine of dermatopathology but follicular germinative (trichoblastic) differentiation in cysts is seen rarely. The presence of follicular germinative differentiation in a cyst alerts to consider the possibility of a basal cell carcinoma (BCC) arising in a cyst. METHODS: Five cystic lesions with zones of follicular germinative differentiation were collected. Hematoxylin and eosin sections were reassessed for architecture, types of follicular differentiation and stromal characteristics; immunohistochemical studies with Ber-EP4 were analyzed. Articles about follicular germinative differentiation in cystic lesions were reviewed. RESULTS: Cystic lesions with follicular germinative differentiation have been described in the literature under various names including trichoblastic infundibular cyst, cystic trichoblastoma, cystic panfolliculoma (CPF), dermoid cyst with basaloid proliferations, folliculosebaceous cystic hamartoma and BCC occurring in infundibular cysts. The lesions presented by us could be classified as three cystic trichoblastomas, one CPF and one cystic hamartoma with follicular germinative differentiation. CONCLUSIONS: Histopathologically, cystic trichoblastomas can be separated from CPFs. Some lesions defy classification and may be regarded as cystic follicular hamartomas. The presence of follicular papillae and bulb-like structures, advanced follicular differentiation like that of inner and outer root sheath exclude the differential diagnosis of BCC arising in a cyst.

Follicular hybrid cyst: a combination of bullous pilomatricoma and epidermoid cyst.

The follicular hybrid is composed of more than two components of pilosebaceous unit. There are several studies of hybrid cyst, combination of trichilemmal and epidermoid cyst was the most frequently reported. In this paper, we reported one case of hybrid cyst composed of bullous pilomatricoma and epidermoid cyst. A 14-year-old girl was complaint of a solitary flesh-colored to erythematous nodule with flaccid appearance sized 3.2 × 1.8 cm in diameter on her right upper back for one year. The histologic findings showed there were edema and proliferation of capillaries in the superficial dermis, a cyst in the middle to deep dermis. There were laminated keratins in the cystic space. The cyst wall was composed of two different components, one was composed of epithelial cells containing of granular layer, and another consisted of basophilic cells, transient cells and shadow cells. The cyst not related with Gardner's syndrome. Hybrid cyst such as trichilemmal cyst, epidermoid and pilomatricoma cysts maybe have same clinical features or mimicking each others, but we can distinguish them from histopathology evaluation.

Cutaneous hybrid cyst in a sprague-dawley rat.

This report describes a spontaneous hybrid cyst in a Sprague-Dawley (SD) rat. A 52-week-old, male SD rat had a cutaneous cyst on the left mystacial pad. Histologically, the cyst wall showed infundibular differentiation with keratohyalin granules in the granular layer and matrical differentiation comprising basaloid epithelial cells with trichohyalin granules. The cyst cavity was filled with lamellar, flaky keratin and aggregates of shadow cells. Immunohistochemically, the infundibular-type epithelium was positive for cytokeratin (CK) AE1/AE3, CK KL1 and CK14 but negative for CK15, whereas the matrical-type epithelium was negative for all four CK isoforms examined. These immunohistochemical properties of the infundibular- and matrical-type epithelia were similar to those of the infundibulum and inferior segment of normal hair follicles, respectively. Based on these findings, the cyst was diagnosed as a hybrid cyst, comprising more than one type of cyst arising from various parts of the pilosebaceous unit.

Coexistence of Pilomatricoma and Epidermal Cyst (Hybrid Cyst) / 대한피부과학회지

Pilomatricoma is a benign tumor derived from the hair matrix. Pilomatricoma-like changes have been described in epidermal cysts in Gardner's syndrome. Apart from this association, a cyst can arise from various portions of a hair follicle, and combine to form a hybrid cyst. Follicular hybrid cyst is an interesting pathologic phenomenon, and needs to be explained for their pathogenesis. We present a case in which a pilomatricoma was situated in the immediate vicinity of an epidermal cyst. Histopathologic findings showed that one part of the cyst had a feature of an epidermal cyst, and the other part had a feature of a pilomatricoma.

A Case of a Follicular Hybrid Cyst

Various cutaneous cysts such as epidermal cysts, trichilemmal cysts, vellus hair cysts, steatocystoma, or pilomatricoma can arise from a different part of the pilosebaceous unit, namely the infundibulum, isthmus, sebaceous ducts, and bulbar or inferior portion. Rarely, a hybrid cyst that includes two or more components of a cystic lesion arising from the pilosebaceous unit can develop. The pathogenesis of this unusual disease is not yet known. We report a case of a follicular hybrid cyst which showed combined histologic features of both an epidermal cyst and pilomatricoma, and discuss the possible pathomechanism of the development of this hybrid cyst with a review of the literature.

A Case of a Hybrid Cyst Composed of an Epidermal Cyst and a Pilomatricoma / 대한피부과학회지

It is known that different parts of a pilosebaceous unit, namely the infundibulum, isthmus, sebaceous ducts, and bulbar or inferior portion, can give rise to a variety of cutaneous cysts, such as epidermal, trichilemmal, steatocystoma, or pilomatricoma. In rare instances, a cyst can arise from various portions of a hair follicle and combine to form a hybrid cyst. The pathogenesis of this lesion is uncertain. Studying the clinicopathological features of hybrid cysts helps us to understand the pathogenesis of disease which can arise from pilosebaceous units. Epidermal cysts and pilomatricoma are recognised to be clinically similar but histologically distinct entities. We present a case of a patient with a solitary nodule on the posterior neck, showing combined histologic features of both an epidermal cyst and pilomatricoma.

A Case of a Follicular Hybrid Cyst (Epidermal Cyst and Pilomatricoma)

No abstract available.

A Case of Hybrid Cyst: A Combined Epidermal and Trichilemmal Cyst

No abstract available.

A Case of Hybrid Cyst showing Composite Features of an Eruptive Vellus Hair Cyst and Steatocystoma Multiplex / 대한피부과학회지

Both eruptive vellus hair cyst and steatocystoma multiplex are uncommon conditions. There are clinical similarities between these two entities, but histological features are distinctive. We describe a patient with multiple subcutaneous nodules on the chest and both axilla, showing combined histological features of both an eruptive vellus hair cyst and steatocystoma multiplex. This case suggests that eruptive vellus hair cyst and steatocystoma multiplex are variants of one disorder which originate in the pilosebaceous duct.