Cystic trichoblastoma (so-called trichoblastic infundibular cyst): a report of three new cases

Three cases of so-called trichoblastic infundibular cyst are reported. The lesions showed a configuration similar to infundibular cysts, including basophilic orthokeratotic corneocytes arranged in basket-weave pattern and intermingled with eosinophilic sebum. The cyst wall was mainly composed of stratified squamous epithelium showing infundibular keratinization throughout a granular layer. However, in some areas, epithelial cords, buds and reticulated proliferations of follicular germinative cells surrounded by a densely cellular stroma emanated radially from the cyst wall. In one case, in addition to the presence of follicular germinative cells, there were also aggregations of matrical cells with evidences of inner sheath and matrical differentiation. In our opinion, these findings support a neoplastic rather than a cystic nature for this lesion. We discuss the histopathologic differential diagnosis with other follicular cystic lesions showing similar keratinization.     

Trichoblastic infundibular cyst should be renamed infundibular cyst with unique papillary projections

Trichoblastic infundibular cyst (TBIC) was previously reported as a unique keratinous cystic lesion, which was characterized by the papillary projections of follicular germinative-like cells emanating from the cyst wall. Here, we report three additional cases of this cyst and discuss the pathogenesis of this unique entity. In all cases, a unilocular cyst contained keratin, and the cyst wall was composed of squamous epithelium. A number of cords and papillary projections emanated from the basal layer of the cyst wall. They were composed of cells with large nuclei and scant cytoplasm arranged in a peripheral palisade. Immunohistochemically, anti-cytokeratin 15, anti-cytokeratin 20, and anti-epithelial cell adhesion molecule antibodies were negative. Thus, these cells resembled follicular germinative cells or sebaceous mantle morphologically, but we failed to prove the differentiation immunohistochemically. The cyst was surrounded by fibrotic stroma and inflammatory cells, suggesting previous rupture of the cyst. We speculate that the cells of the projections possibly differentiate into the mantle rather than follicular germinative cells, even though we could not provide sufficient immunohistochemical evidence. We also suggest that they may be induced by special reaction to fibrohistiocytic stroma surrounding the infundibular cyst. Therefore, TBIC should be renamed infundibular cyst with unique papillary projections.     

Apocrine mixed tumor of the skin with a prominent pilomatricomal component

Pilomatrical differentiation within an apocrine mixed tumor (AMT) when present is only focal and has not been reported to be extensive. We herein report an AMT with prominent pilomatrical differentiation. A 47-year-old male presented with a 0.7 cm lesion on the right eyebrow. Histologic sections revealed, underneath a neurofibroma, a well-circumscribed tumor composed of nodules of branching epithelial elements and occasional keratinous cysts within a myxoid and lipomatous stroma. The ductal structures appeared to be composed of two layers of basophilic cuboidal cells and exhibited decapitation secretion. In approximately 50% of the tumor, eosinophilic ghost/shadow cells associated with a foreign body giant cell reaction formed a nodule resembling a pilomatricoma. Focally, columns of matrical cells were seen giving rise to shadow cells. Cytokeratin (CK) 5/6 and CK14 labeled the epithelial component. CK7, CK19 and Ber-EP4 labeled the ductal structures. Carcinoembryonic antigen and epithelial membrane antigen highlighted the luminal surface. S100 stained the stromal cells within the myxoid matrix, adipocytes and spindle cells within the overlying neurofibroma. CK10 highlighted the corneocytes within the keratinous cysts. CK17 labeled the epithelial lining of the keratinous cyst. The presence of follicular and apocrine differentiation within our tumor reinforces the common embryologic derivation of these elements.     

Congenital panfollicular nevus: report of a new entity

The various forms of non-melanocytic nevi (hamartomas) are usually encountered in pediatric patients, and nevus sebaceous of Jadassohn is the most common to have undifferentiated pilosebaceous units. We report a unique congenital follicular nevus that fails to meet the criteria of any previously described follicular neoplasm, despite the plethora of alternatives. Clinically considered a syringocystadenoma papilliferum, the excised lesion contained multiple dermal nodules that exhibited nearly all stages of follicular differentiation. The periodicity of the follicular proliferations was akin to normal terminal hair, and a prominent perifollicular sheath surrounded each. This benign lesion of abortive hair follicles was unassociated with any established genodermatous syndrome or other adnexal neoplasm.     

Follicular hybrid cysts. An expanded spectrum.

Currently it is well established that each of the three parts of the hair follicle (infundibulum, isthmus, and the inferior portion) originates different types of cutaneous cysts. Thus, follicular cysts include infundibular, trichilemmal, and matricial cysts. Brownstein in 1983 described a mixed type of cutaneous cyst combining epidermoid, infundibular, and trichilemmal types of keratinization. We review and illustrate the different combinations of follicular hybrid cysts reported to date: infundibular and trichilemmal cyst, infundibular and pilomatricoma cyst, trichilemmal and pilomatricoma cyst, eruptive vellus hair cyst and steatocystoma, and eruptive vellus hair cyst and trichilemmal cyst. Therefore, the concept of hybrid cyst should not be restricted to those composed of infundibular and trichilemmal cysts, because any cyst arising from the various parts of the pilosebaceous unit can combine with others to form a large series of follicular hybrid cysts.     

Folliculo-sebaceous cystic hamartoma is a trichofolliculoma at its very late stage

Folliculo-sebaceous cystic hamartoma (FCH) was described as an entity recently and was defined as an adnexal hamartoma, showing above all an infundibular cystic structure linked to many sebaceous lobules. Differentiation toward the inferior segment of the hair follicle also occurs, although to a markedly lesser degree. Signs of regression and rest corresponding to the normal follicular cycle are often apparent in these follicular proliferations. Therefore so-called FCH has much in common with the newly described late stage of trichofolliculoma, which also exhibits an infundibular cyst and sebaceous and follicular differentiation with various signs of catagen and telogen. Comparing our 8 cases of FCH and 31 cases of trichofolliculoma, we came to the conclusion that FCH is the very late stage of trichofolliculoma. This stage could be characterized by a nearly complete regression of the transient follicular epithelium, whereas concurrent growth and maturation of sebaceous elements appear.     

Follicular hybrid cyst (trichilemmal cyst and pilomatricoma) arising within a nevus sebaceus

We report a case of follicular hybrid cyst arising in a nevus sebaceus. Histopathologic findings showed one part with the features of a trichilemmal cyst and the other part with those of a pilomatricoma. To our knowledge, this is the first case of follicular hybrid cyst associated with nevus sebaceus. We consider that the cyst in our case is derived from the hair matrix and from the follicular isthmus.     

Signet ring cell melanocytic nevus: report of a case over trichilemmal cyst and review of the literature

Different melanocytic nevi have been reported as being associated with dermal cysts. Signet ring cell melanocytic nevus is a rare variant of melanocytic nevus characterized by cells with signet ring morphology within a common melanocytic nevus. This article describes an exceptional case of melanocytic nevus composed exclusively of signet ring cells over a trichilemmal cyst. Histologically, above the cyst, there was a small, symmetrical and sharply demarcated lesion showing a compound proliferation of small, round, monomorphous cells with signet ring morphology. Immunohistochemically, signet ring cells were negative for cytokeratin AE1/3, leukocyte common antigen, HMB-45, and CD34. Occasionally, isolated signet ring cells were positive for S-100 and melan A. Melanocytic nevus composed of signet ring cells should raise the differential diagnosis with other cutaneous tumors exhibiting signet ring cells. Previous cases of this entity reported in the literature are also reviewed.     

The sebaceous nevus as part of the Schimmelpenning-Feuerstein-Mims Syndrome--an obvious phacomatosis first documented in 1927

The sebaceous nevus is a common nevus and can be easily diagnosed because of its typical rough fatty surface due to its amount of sebaceous glands. In some rare cases, the sebaceous nevus is part of a genetic disorder, the Schimmelpenning-Feuerstein-Mims (SFM) syndrome. If the SFM syndrome is suspected, further investigation is necessary, because multiple organ involvement is highly likely. We suggest that diagnosis of the SFM syndrome is simple, considering the special linear arrangement of sebaceous nevi in cases of SFM syndrome.     

Melanoma associated with a dysplastic nevus: report of two cases with unusual sebocyte-like melanocytes in the nevus part of the lesion

We present two cases of melanoma arising in a dysplastic nevus that contained intradermal sebocyte-like melanocytes characterized by a scalloped dark-staining nucleus surrounded by the pale multivacuolated cytoplasm imitating sebaceous differentiation. Both patients were women, aged 49 and 55 years. Location included the back and temporal area. Microscopically, both cases had the following features in common: the melanoma in situ, which was of the superficially spreading type, was associated with a dysplastic compound nevus, in which the sebocyte-like cells were identified in the intradermal nevus part of the lesion. The sebocyte-like cells comprised a minor component but were immediately recognizable and appeared as cells with multivacuolated neoplasm and scalloped nuclei arranged in nests. Some contained melanin in the cytoplasm. They stained positively for S-100 protein and melan A but were EMA and HMB-45 negative. The conventional part of the nevi demonstrated the same phenotype, with the exception of the melanocytic nests located at the dermoepidermal junction that were HMB-45 positive. The cases are discussed in the context of the pertinent literature.     

Apocrine type of cutaneous mixed tumor with follicular and sebaceous differentiation.

Eight cases of apocrine (tubular branching lumina) type cutaneous mixed tumors with follicular and sebaceous differentiation are presented. All eight tumors arose on facial skin; six patients were male and two were female. The lesions showed a cystic or nodular clinical appearance and were surgically excised. Histopathological examination confirmed the diagnosis of apocrine type of cutaneous mixed tumor in each case. Follicular differentiation consisted of (a) keratinous cysts with infundibular keratinization (infundibular differentiation); (b) hair bulbs with papillary mesenchyma, matricial differentiation with basophilic, transitional, and shadow cells, trichohyaline granules, vellous hair shafts, and clear cells of the outer root sheath (anagen differentiation); and (c) epithelial columns composed of inner cells with plump oval nuclei and scant cytoplasm, and similar cells at the periphery that were arranged in a palisade, resembling the inferior segment of a normal hair follicle in telogen. Sebaceous differentiation was represented by mature sebaceous cells, either as single cells or as small islands, within epithelial tracts of the tumor. The proportion of the areas showing these different types of differentiation varied among lesions, but some follicular differentiation was always present, whereas three cases lacked sebaceous differentiation. Immunohistochemical analysis in three cases with respect to their eccrine or apocrine differentiation showed contradictory results as in a previously reported series of cutaneous mixed tumors. The presence of follicular and sebaceous differentiation in the apocrine (tubular branching lumina) type of cutaneous mixed tumor is a confirmation of the apocrine nature of this neoplasm as well as an expression of the common embryologic derivation of all elements of the folliculosebaceous-apocrine unit.     

Syringocystadenoma papilliferum with sebaceous differentiation in an intradermal tubular apocrine component. Report of a case

Syringocystadenoma papilliferum is a benign tumor most commonly located on the scalp or face, and it often arises within a nevus sebaceus of Jadassohn. We describe a 61-year-old man with syringocystadenoma papilliferum developing within a nevus sebaceus with sebaceous differentiation in an intradermal tubular apocrine component of the syringocystadenoma papilliferum. Although some adnexal neoplasms that develop in association with a nevus sebaceus may exhibit conjoint sebaceous, follicular, or apocrine differentiation, reflecting close embryological relations of the folliculosebaceous-apocrine unit, the feature we report on has not previously been described to the best of our knowledge.     

The Spectrum of Epidermal Nevi: A Case of Verrucous Epidermal Nevus Contiguous with Nevus Sebaceus

During the normal development of skin, pluripotential cells give rise to keratinocytes, sebaceous glands, hair follicles, apocrine glands, and eccrine glands. In epidermal nevi, these components emerge in an abnormal mixture within a circumscribed site. Many authors have categorized epidermal nevi based on their predominant component; however, there is often notable overlap that occurs within a single area or within contiguous areas. We report a verrucous epidermal nevus contiguous to a nevus sebaceus of Jadassohn. The categories of epidermal nevi are somewhat artificial. Our case supports the view that epidermal nevi have a spectrum of manifestations, including verrucous epidermal nevi and nevus sebaceus of Jadassohn.     

Trichoblastic infundibular cyst

We report 4 cases of an infundibular cyst that histopathologically showed small papillary projections of follicular germinative cells emanating from the basal layer of the cyst wall. Some of these projections branched and formed a reticulated pattern. This cystic lesion is histopathologically distinctive. We propose to designate it as a trichoblastic infundibular cyst because its lining resembles that of an infundibular cyst, yet it has cells that resemble those of the follicular germ in its wall.     

Multiple pigmented follicular cysts: a subtype of multiple pilosebaceous cysts

Summary Pigmented follicular cyst is a rare disorder which typically presents as a pigmented papule on the head or neck and which, histologically, exhibits terminally differentiated, pigmented hair shafts in an epidermoid cyst. We report a 22-year-old man with the multiple variant of this disorder. Clinically he had numerous brown-blue to flesh-coloured, domed-shaped papules, on the anterior chest and abdomen, of 10 years duration. Histologically, hybrid cysts exhibiting trichilemmal and epidermoid keratinization were seen. The cysts contained numerous pigmented. Terminally differentiated hair shafts and embedded in the wall of one cyst, was a sebaceous gland. The condition of multiple pigmented follicular cysts, is thought to represent a distinct subtype within the spectrum of multiple pilosebaceous cystic disorders.     

Extensive cerebriform nevus sebaceus: an unusual presentation

Nevus sebaceus is an epidermal nevi composed of sebaceous glands, which usually presents as single yellowish plaque over the head and neck. A rare morphological variant, namely cerebriform nevus sebaceus was first reported in 1998. As with other nevi, the occurrence of nevus sebaceous is related to genetic mosaicism and the shape and distribution of the nevus is determined by the stage at which mosaicism has arisen. We report a patient with cerebriform nevus sebaceus having an unusually widespread distribution over the head, face, and trunk, but without any other organ system involvement.     

Immunohistochemical study of calretinin in normal hair follicles and tumors with follicular differentiation

BackgroundSelective immunostaining for calretinin labels the innermost layer of the outer root sheath of normal hair follicles, which is difficult to distinguish with hematoxylin-eosin staining.ObjectiveThe aim of this study was to determine whether immunohistochemistry for calretinin allows identification of cutaneous adnexal tumors with follicular differentiation towards cells of the outer root sheath.Material and methodsWe analyzed the staining pattern for calretinin by immunohistochemistry in 49 biopsies of cutaneous adnexal tumors with follicular differentiation.ResultsFifteen biopsies corresponded to trichilemmomas/inverted follicular keratosis and had staining for calretinin in the epithelium of the most superficial areas of the lesions and in squamous eddies. Ten were trichilemmal cysts, which displayed staining of the cyst wall. Three were basal cell carcinomas with variable staining according to the type of follicular differentiation in each variant. One was a panfolliculoma that had focal staining. Two were folliculosebaceous cystic hamartomas with staining of the excretory duct of the sebaceous glands. Two pilomatricomas and 3 proliferative trichilemmal tumors had positive staining in the cellular layers close to the lumen of the cystic structures. Nine trichoblastomas/trichoepitheliomas, 2 infundibular cysts, 1 dilated pore of Winer, and 2 acanthomas of the follicular sheath were negative for calretinin.ConclusionImmunohistochemistry for calretinin allows identification of cutaneous adnexal tumors of the hair follicle or a component of the follicle with differentiation towards cells of the outer root sheath.     

Trichostasis spinulosa within an intradermal melanocytic nevus

A thirty-six-year-old man presented with a melanocytic nevus on his left shoulder. The lesion was excised and histopathologic examination showed an intradermal nevus with several infundibular cysts among the nevus cells. These cysts showed a cyst wall with epidermoid keratinization and a lumen filled by many cross-sectioned hair shafts. These findings were consistent with a diagnosis of trichostasis spinulosa within an intradermal melanocytic nevus. We note the relationship between these two disorders in the same lesion.     

Spitz nevi arising in speckled lentiginous nevus: clinical, histologic, and molecular evaluation of two cases

Spitz nevi are small dome-shaped nodules that sometimes arise in areas of preexisting hyperpigmentation, such as a speckled lentiginous nevus (nevus spilus), where they present a diagnostic dilemma. We report clinical, histopathological, and molecular findings of two cases of multiple Spitz nevi arising in a speckled lentiginous nevus. We used immunohistochemistry to assess expression of Ki-67, epidermal growth factor receptor, vascular endothelial growth factor, and RelA in two cases of Spitz nevi arising in a speckled lentiginous nevus. We observed rare staining for the proliferative marker Ki-67, but positive staining for the growth and antiapoptotic factors epidermal growth factor receptor, vascular endothelial growth factor, and RelA. Characterization of the molecular phenotype of Spitz nevi arising in speckled lentiginous nevi may provide a useful adjunct to long-term monitoring in this rare but difficult clinical presentation.     

Trichoadenoma associated with an intradermal melanocytic nevus: a combined malformation

Melanocytic nevi have been associated with epidermal hyperplasia, adnexal hyperplasia with follicular and sebaceous differentiation, cysts, and tumors of epidermal or adnexal origin. We report a combined cutaneous hamartoma in a 29-year-old woman that comprised a trichoadenoma within an intradermal melanocytic nevus. Clinical diagnosis was a malignant transformation of a melanocytic nevus. Histopathologically, multiple keratinous cysts together with solid islands or masses of eosinophilic epithelial cells were closely intermingled with the nevus cells. Occasional nests of basaloid cells were present. Although to our knowledge this association has not been previously reported, it is worth considering that trichoadenoma and desmoplastic trichoepithelioma are the two ends of a spectrum of lesions. This combined hamartoma reported herein is important because growth of these lesions could be clinically misinterpreted as malignant transformation of a preexisting lesion. Histologic study will reveal the correct diagnosis in such cases.