Folliculosebaceous-apocrine Unit Research Articles

Primitive follicular induction in molluscum contagiosum.

Molluscum contagiosum (MC) is the commonest human poxvirus infection. Follicular induction has rarely been observed in the epidermis surrounding lesions of MC. A virus-induced localized proliferation of germinative/stem cells of the folliculosebaceous-apocrine unit has been suggested as the underlying cause, however few reports of this peculiar phenomenon exist in the literature and the mechanisms involved in this proliferation require further study. We prospectively collected MC cases showing multifocal areas of primitive follicular induction involving the adjacent undersurface epidermis. Immunohistochemical expression of BerEP4, PHLDA1 and cytokeratin 20 (CK20) was evaluated in the basaloid germs surrounding the lesions. For PHLDA1, we used epidermal melanocytes as a positive internal control. For BerEP4, we employed a basal cell carcinoma (BCC) and for CK20, colon as positive external controls. An incubation without the primary antibody functioned as an external negative control. All the cases studied showed an intense positive staining of the basaloid buds with BerEP4 and weaker stain for PHLDA1. CK20 showed the presence of scattered Merkel cells within the induced epidermal basaloid proliferations favoring their reactive origin. The pathogenetic mechanisms behind the development of these microscopic features and the link between follicular induction and poxvirus infection are explored. Awareness of this unusual phenomenon by dermatopathologists will be helpful in avoiding a misdiagnosis of a superficial BCC in such cases. BerEP4 and PHLDA1 were consistently expressed in the areas of primitive follicular induction surrounding lesions of MC. CK 20 stained the Merkel cells present in the basaloid buds. All these findings support the reactive origin of this phenomenon, which we believe is most probably viral-induced.

Unusual sites for poromas are not very unusual: a survey of 101 cases

Poromas are benign adnexal tumours generally believed to be of eccrine origin, which usually develop on palmoplantar sites. However, it is thought that a percentage of poromas develop on non-palmoplantar or 'unusual' sites. To review cases of poromas with reference to their clinicoepidemiological characteristics, paying particular attention to the those located on sites other than the palms and soles. All histologically confirmed poromas seen at our department between 1994 to 2012 were reviewed. The clinicoepidemiological data recorded included age at diagnosis, gender, location, size, colour, and preoperative and pathological diagnoses. In total, 101 poromas were reviewed, corresponding to 0.0058% of all the epithelial skin tumours biopsied in our department. The mean age was 65.05 years (range 30-100 years), and the male to female ratio was 1.52. All the lesions were solitary and asymptomatic, with no sign of bleeding. The most common presentation was a red or reddish lesion, particularly at palmoplantar sites, where 33 (32.7%) of the 101 poromas were located, Poromas found at other affected sites were more usually skin-coloured, and these lesions included 7 neoplasms located in the armpits and 18 on the head and neck. The correct preoperative diagnosis was made in 12 cases of 33 detected poromas (36%), all of which were localized to the palmoplantar surfaces. Based on our experience, we consider that there are no 'unusual' sites for poromas, and palmoplantar poromas were in fact in the minority. Furthermore, some localizations suggest derivation of these palmoplantar poromas from the folliculosebaceous apocrine unit.

Development of Six Tumors in a Sebaceus Nevus of Jadassohn: Report of a Case

Nevus sebaceus of Jadassohn is a congenital cutaneous hamartoma comprised of multiple skin structures. It has the potential to develop into variety of neoplasms of various epidermal adnexal origins. While multiple tumors may occasionally arise, it is unusual for more than four tumors to arise simultaneously within a single sebaceus nevus. Here in, we report a case of a 70-year-old woman with six neoplastic proliferations including a syringocystadenoma papilliferum, pigmented trichoblastoma, tubular apocrine adenoma, sebaceoma, tumors of follicular infundibulum and superficial epithelioma with sebaceus differentiation arising in a long standing nevus sebaceus on the scalp. Our case is extraordinary because a single nevus sebaceus contained six neoplastic proliferations with differentiation toward the folliculosebaceous-apocrine unit.

Porocarcinoma in situ showing follicular differentiation: A case report

Abstract Poroid neoplasm is a skin appendage tumor that has both benign and malignant counterparts. It has traditionally been regarded as of eccrine origin and has four types: intraepidermal poroma (hidroacanthoma simplex), poroma, dermal duct tumor, and poroid hidradenoma. Here we describe the case of a 64-year-old woman who had a verrucous, erythematous to brownish tumor on her left buttock for many years. Histopathology revealed an intra-epidermal poroid tumor with both benign and malignant parts. The benign part had intra-epidermal nests of poroid cells, which were smaller, monomorphic and sharply marginated from adjacent keratinocytes. The malignant part showed similar cell types, but had a higher nuclear/cytoplasmic ratio, pleomorphism, and prominent mitoses. Ductal structures were noted in neoplastic cells and an epithelial membrane antigen stain was strongly positive. Interestingly, peripheral palisading and primitive follicular germ formation were also observed in the neoplasm, which suggests follicular differentiation. We made a final diagnosis of porocarcinoma in situ with follicular differentiation, which may support the folliculosebaceous–apocrine unit theory, but a tumor with such a combination has not been described before.

Recurrent CYLD Nonsense Mutation Associated With a Severe, Disfiguring Phenotype in an African American Family With Multiple Familial Trichoepithelioma

To the Editor:Recently, Kazakov et al1 performed a clinicopathologic and genotypic analysis on a series of 16 patients suffering from multiple (familial) trichoepitheliomas (MFT: MIM 601606) and found mutations in the CYLD gene in 46%. Based on the frequent presence of CYLD mutations in MFT, it, alo

Expression of Stem-Cell Markers (Cytokeratin 15 and Nestin) in Primary Adnexal Neoplasms-Clues to Etiopathogenesis

The overlap in histopathologic features and immunoprofile of eccrine and apocrine neoplasms confounds basic issues relating to lineage of these entities. We evaluated expression of follicular stem-cell markers, cytokeratin (CK) 15 and nestin, in 78 benign and 23 malignant adnexal neoplasms. CK15 and nestin expression were noted in 39 of 78 (50%) and 36 of 78 (46%) cases in the benign group, respectively (8 cutaneous mixed tumor, 10 hidradenoma papilliferum, 9 apocrine cystadenoma, 11 cylindroma and/or spiradenoma, and 9 poroma/dermal duct tumor). CK15 and nestin expression were noted in 11 of 23 (48%) and 7 of 23 (30%) cases in the malignant group, respectively (6 microcystic adnexal carcinoma, 7 porocarcinoma, and 9 eccrine carcinoma). Except 1, both markers were negative in 4 syringocystadenoma papilliferum, 10 hidradenoma, 1 syringofibroadenoma, 10 syringoma, 1 eccrine adenoma, 8 poroma/dermal duct tumor, 5 eccrine hidrocystoma, and 1 apocrine carcinoma. Given that follicular germinative cells give rise to the folliculosebaceous apocrine unit, expression of CK15 and nestin in the majority of cutaneous mixed tumor, hidradenoma papilliferum, apocrine cystadenoma, and cylindroma/spiradenoma is suggestive of an apocrine origin/differentiation of these neoplasms. Reinforcing this and a novel finding of our study is the preferential expression of nestin in myoepithelial cells of these lesions.

Mantle Structures in the Uterine Cervix

To the Editor: Ectopic skin-type adnexal structures, including sebaceous glands and hair follicles, are rare in the lower female genital tract, namely in the vagina and uterine cervix (1–6). The presence and histogenesis of these elements, derivatives of the ectoderm, in müllerian organs are unclear and intriguing. It has been speculated that they may be the result of congenital misplacement or may represent an acquired metaplastic change (1–6). In our report on a case of ectopic sebaceous gland in the vagina, we commented that in that case an entire sebaceous unit, that is, sebaceous gland and sebaceous duct, was present and there was a canal connecting sebocytes to the surface resembling that of an infundibulum and an isthmus (6). It is known that in a human embryo future sebaceous glands develop together with future hair follicle and apocrine glands, as a folliculosebaceous-apocrine unit (7). Thus, the association of ectopic elements with follicular structures (infundibulum as in the above mentioned case) would strongly argue against the metaplastic theory. Recently, Ackerman and Böer (8) reconsidered the normal histology of a hair follicle and suggested that the infundibulum is part of the epidermis, and not of a hair follicle. While reviewing the original histologic slides of a case of a 6-week-old girl with hair follicles in the endocervix published in 1972 by our colleague, Professor Linhartova (9), we noted a feature that was not addressed by the author, namely the presence of mantle structures around some follicles (Fig. 1). Professor Linhartova was not aware of this feature at the time of writing, as the concept of the mantle was fully elaborated years after her publication. Although described by Pinkus in 1987 as a rudimentary sebaceous gland termed “Mantlehaare” (German: hair cloaks), only recently was a mantle shown to represent a distinctive sebaceous structure related to the cycle of the sebaceous gland, different from that seen in hair follicles (7). Microscopically, a mantle appears on longitudinal sections of the skin sections as cords of epithelial cells emanating from both sides of a hair follicle at the junction between the infundibulum and the isthmus and then descending parallel with the follicle for a longer distance. In transversal sections, the cords encircle the hair follicle. These cords may display occasional sebocytes. Such an appearance of the mantle is seen before puberty and after menarche/andarche and is thought to result from a decreased level of androgens. At puberty, a mantle transforms to conventionally appearing sebaceous lobules with numerous mature sebocytes with vacuolated cytoplasm and scalloped nuclei (7). Thus, the presence of mantle structures in the case under discussion lends strong support to the theory of congenital misplacement, which is also sustained in that particular case by the presence of other congenital abnormalities, including uterus bicornis unicollis. Of special interest is the fact that in this 6-week-girl only mantle structures were present, without mature sebaceous elements, which mirrors the situation in the skin wherein large fully developed sebaceous lobules seen after birth of a child wither progressively within the ensuing weeks to become a mantle due to a decrease in the level of maternal androgens.FIG 1 UTERINE.: cervix (A) with several hair follicles, one of which (B, C) display a mantle structure.Dmitry V. Kazakov, MD, PhD* Petr Mukensnabl, MD* Denisa Kacerovska, MD, PhD* Michal Michal, MD* † *Sikl's Department of Pathology, Charles University, Medical Faculty Hospital †Bioptical Laboratory, Pilsen, Czech Republic

Spiradenocylindrocarcinoma. Report of a Case With a Low-Grade Component of Spiradenocarcinoma and an Immunohistochemical Study

Spiradenocylindrocarcinoma is a very rare malignant cutaneous neoplasm of the folliculosebaceous-apocrine unit. We report a case of this hybrid tumor in a 42-year-old woman. The tumor consisted of 2 circumscribed nodules with areas of cylindrocarcinoma and low-grade spiradenocarcinoma. In the overlapping areas, both spiradenomatous and cylindromatous features were observed. Expansion of the tumor beyond the fibrous pseudocapsule into the adjacent tissue was present. Furthermore, tumor cells were demonstrating mild to moderate pleomorphism and an increased mitotic index. p53 and ki-67 were among the positive immunohistochemical markers. A relatively small number of tumor cells expressed estrogen receptors. The aim of this study was to investigate the nature of this rare tumor of the skin appendages.

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.

Clinicopathologic analysis of 21 cases of nevus sebaceus: A retrospective study

Nevus sebaceus (NS), otherwise designated as 'organoid nevus', involves proliferative changes of the sebaceous glands, sweat glands, and the hair follicles. It displays a range of appearances, depending on the lesion's age. To study the histopathological features of NS and correlate these with clinical findings. All skin biopsy specimens over a 12-year period from 1995 to 2007 which had a diagnosis of NS were included. Clinical data with follow-up notes and histopathology were reviewed. Half of the cases had a verrucous clinical appearance, while the rest presented as papules, plaques, or patches. All the cases showed immature hair follicles, and 24% of cases showed immature sebaceous glands. Normal terminal hair follicles were characteristically absent in the lesion. Nineteen percent of the cases showed dilated apocrine glands, and 14% showed hyperplasia of eccrine glands. Epidermal changes in the form of acanthosis, papillomatosis, and hyperkeratosis were seen in 86% of cases. Dilated keratin-filled infundibula were observed in 24% of cases. One case was associated with a squamous cell carcinoma. Nevus sebaceus is a cutaneous hamartoma, consisting of various elements indigenous to the organ. Normal terminal hair follicles are characteristically absent in the lesion although the same may be seen in rest of the epidermis, a feature of diagnostic importance, not usually highlighted in literature. The divergent differentiation observed in NS is consistent with the common embryologic origin of the folliculosebaceous-apocrine unit and should not mislead the pathologist.

A Novel Missense Mutation in the CYLD Gene in a Spanish Family With Multiple Familial Trichoepithelioma

Brooke-Spiegler syndrome (BSS) includes the combination of spiradenomas, cylindromas, and trichoepitheliomas. It has been postulated that BSS results from defects in the regulation of putative stem cells of the folliculosebaceous-apocrine unit. This follicular dysregulation may give rise to 3 different genodermatoses: familial cylindromatosis (FC), multiple familial trichoepithelioma (MFT), or the classic triad of BSS.

Apocrine mixed tumor of the skin (“mixed tumor of the folliculosebaceous-apocrine complex”): Spectrum of differentiations and metaplastic changes in the epithelial, myoepithelial, and stromal components based on a histopathologic study of 244 cases

A systematic analysis of the entire spectrum of various forms of differentiation and metaplastic epiphenomena in cutaneous apocrine mixed tumor (AMT) has never been performed. The purpose of our study was to study a large number of cutaneous mixed tumors so as to fully characterize the entire spectrum of differentiations and metaplastic changes that may occur in the epithelial, myoepithelial, and stromal components of AMT. This article reports a light-microscopic study of 244 cases of cutaneous AMT, complemented by a literature review. All types of differentiation along the lines of the folliculosebaceous-apocrine unit can be seen in AMT. The spectrum of metaplastic changes in the epithelial components includes squamous metaplasia, mucinous metaplasia, oxyphilic metaplasia, clear cell change, columnar metaplasia, hobnail metaplasia, and cytoplasmic vacuolization. The following changes in the myoepithelial component were documented: clear cell change, hyaline cells, plasmacytoid cells, spindling, and collagenous spherulosis. Stromal alterations included chondroid metaplasia, osseous metaplasia, and adipose metaplasia. This study utilizes tissue specimens that mainly came as consultations; therefore some inherent selection bias exists. AMT displays a wide range of differentiation and metaplastic changes in its epithelial, myoepithelial, and stromal components. These phenomena are not mutually exclusive. When unduly prominent, they may present diagnostic pitfalls. Our findings corroborate those of previous publications, stressing the remarkable diversity of differentiation and metaplasias that may be found in cutaneous AMT. We propose that the most appropriate name for these lesions is "mixed tumor of the folliculosebaceous-apocrine complex."

Cutaneous Sebaceous Neoplasms With a Focal Glandular Pattern (Seboapocrine Lesions): A Clinicopathological Study of Three Cases

Presented here are three cutaneous sebaceous tumors (one carcinoma and two sebaceomas), each demonstrating a focal glandular pattern representing apocrine differentiation. The patients, two males and one female, each clinically presented with a small solitary nodule or tumor on the scalp. None of the patients had features of Muir-Torre syndrome. Surgical removal of the lesions was performed in all cases. None of the patients developed recurrence or metastasis after surgery (follow-up ranged from 18 to 24 months). The glandular areas represented a minor but significant component of the lesions and appeared as glands of various complexity, mostly as simple round or elongated tubular structures lined by a row of cuboidal to columnar cells with eosinophilic cytoplasm and round nuclei, with or without a distinct nucleolus. Decapitation secretion was evident but not prominent. In both sebaceomas, at least a portion of the glands had a peripheral small-cell layer that appeared similar to the basal/myoepithelial cells of normal eccrine and apocrine ducts. In some glands, the basal/myoepithelial cells seemed to have undergone hyperplasia, resulting in two or more rows of cells that even formed small islands, with an overall appearance reminiscent of basal cell hyperplasia in the prostate, arising in the basal layer of the prostatic glands. The descriptive terms seboapocrine carcinoma or seboapocrine sebaceoma are proposed for such lesions. These tumors may be viewed as rare histopathological variants of sebaceous carcinoma and sebaceoma, with a second type of differentiation along the lines of the folliculosebaceous-apocrine unit.

Low-grade Adnexal Carcinoma of the Skin With Multidirectional (Glandular, Trichoblastomatous, Spiradenocylindromatous) Differentiation

The conjoint occurrence of follicular, sebaceous, or apocrine differentiations in a cutaneous adnexal neoplasm is a known event, more often encountered in benign neoplasms, whereas reports of cutaneous malignant adnexal tumors with bilineage or trilineage differentiation are few. A new case of a cutaneous malignant adnexal neoplasm with multidirectional differentiation is reported here. A 57-year-old woman presented with a long-standing, slowly growing, asymptomatic solitary tumor the size of a large nut in the coccygeal area, which was surgically excised. Ten years after the surgery, there was no evidence of recurrence or metastasis. Microscopically, the neoplasm was located in the dermis with focal extension into the subcutis. It was asymmetric, horizontally oriented, and mostly composed of small nodules that varied in shape from round and oval aggregations to elongated strands and irregular islands; the nodules were either clustered, formed a jigsaw puzzle-like pattern or were dispersed. The nodules were composed of small basaloid cells sometimes intermixed with larger cells with ample cytoplasm forming glandular structures. Rare nodules resembled elements seen in a spiradenoma by containing scattered lymphocytes and globules of hyalinized eosinophilic basal membrane material. The stroma was paucicellular, but focally it resembled that seen in perifollicular mesenchyme. Mitotic figures, including abnormal ones, were infrequent, but mild nuclear pleomorphism, nuclear crowding, and individual cell necrosis were easily appreciable in both small basaloid cells and cells with clear cytoplasm. Perineural invasion was apparent. We classified this tumor as a well-differentiated adnexal carcinoma demonstrating combined follicular and apocrine differentiation. It differs from previously published cases of malignant adnexal tumors with multidirectional differentiation and further exemplifies the spectrum of diversity encountered in malignant proliferations with differentiation toward the folliculosebaceous-apocrine unit.

An unusual hamartoma of the folliculosebaceous‐apocrine unit: a case report

Hamartoma is a neoplasm-like lesion composed of an abnormal mixture of tissues native to the area. We report on an unusual example of a hamartomatous lesion that showed an abnormal mixture of elements of the folliculosebaceous-apocrine unit and arrector pili muscle. A 13-year-old female presented with two nodules situated 2 cm apart on the lower leg that were present since birth. The patient reported some enlargement and slight pain of the otherwise asymptomatic lesions during 2 years, before they were surgically removed. The patient obviously had no skin problems afterwards; her 12-year follow-up was significant for leucopenia and nephrolithiasis. The biopsies from both lesions looked identical. Each lesion was biphasic, i.e. composed of a predominant mesenchymal component and epithelial elements. The mesenchymal part resembled a leiomyoma, or in minor areas, the constituting cells had a myofibroblastic appearance. Encased within the mesenchymal component were large infundibulocystic structures and plentiful grouped and scattered roundish solid epithelial nodules, duct-like, glandular, and tubular elements. Some of the epithelial structures were reminiscent of those seen in tubular apocrine adenoma; others resembled syringomatous elements. We interpreted this unusual lesion as a hamartoma of the folliculosebaceous-apocrine unit.

Carcinosarcoma Arising in a Patient with Multiple Cylindromas

Familial cylindromatosis (Brooke-Spiegler syndrome) is a rare autosomal dominant inherited disease characterized by the development of adnexal tumors, mostly cylindromas, but also trichoepitheliomas and spiradenomas. Malignant tumors may occur, usually with the features of a cylindrocarcinoma. The authors describe the case of a 75-year-old woman with the Brooke-Spiegler syndrome who presented with multiple nodules of the scalp, face, and trunk. In 1997 she underwent surgical excision of the entire forehead and scalp with skin grafting. Histologic examination revealed multiple cylindromas, some with areas of spiradenoma and one with an extensive adenomatous component; some trichoepitheliomas were also evident. In 2002, a nodule of the trunk suddenly increased in size and became painful. The lesion was excised and histologic and immunohistochemical evaluation revealed a malignant cutaneous biphasic tumor extending into the subcutis, consisting of a major portion with the features of an adnexal carcinoma and of a minor one of atypical spindle cells. Biphasic malignant skin tumors are rare and only a limited number have been described, none in association with the Brooke-Spiegler syndrome. The authors discuss the morphogenesis of the folliculosebaceous-apocrine unit from which the tumors in this syndrome derive, and the pivotal role of mesenchymal cells in determining the process. Since the Brooke-Spiegler syndrome is characterized by a germline mutation in the CYLD oncosuppressor gene, a biphasic tumor in this setting may represent a true carcinosarcoma.

Brooke-Spiegler Syndrome

Brooke-Spiegler syndrome is an autosomal dominantly inherited disease with predisposition to cutaneous adnexal neoplasms, most commonly cylindromas and trichoepitheliomas. We report a patient in whom 11 lesions were removed from the scalp and face for various reasons over a period of 3 years. The histopathological survey revealed a plethora of benign adnexal neoplasms showing apocrine, follicular, and sebaceous differentiation occurring independently and conjointly. The histopathological spectrum in our patient included cylindromas, spiradenomas, trichoepitheliomas, small nodular trichoblastomas, and lymphadenomas. Many lesions had hybrid features of two or more neoplasms. By far the most common composite tumor was spiradenocylindroma. Some spiradenocylindromas demonstrated prominent sebaceous or trichoblastomatous differentiation or both. We suggest the terms "sebaceous spiradenocylindroma" and "trichospiradenocylindroma" for these lesions. The occurrence of sebaceous and trichoblastic differentiation in spiradenocylindromas is a further proof that spiradenoma and cylindroma are not eccrine tumors but neoplasms of the folliculosebaceousapocrine unit.

Expression of CD10 in Basal Cell Carcinoma

We investigated the expression of CD10 by an immunohistochemical method in 51 basal cell carcinomas (BCCs), eight pilomatricomas, five trichoblastomas, two trichofolliculomas, three sebaceomas, five sebaceous carcinomas, ten syringomas, two spiradenomas, ten poromas, four porocarcinomas, one eccrine duct carcinoma (not otherwise specified, NOS), six mixed tumors of apocrine origin, and nine squamous cell carcinomas (SCCs). We detected strong expression of CD10 in tumor cells of BCC (86%), and found that the smaller the number of positive tumor cells, the larger the number of positive stromal cells, in particular in sclerosing BCCs. Spearman's rank correlation test revealed a significant negative correlation in BCCs between the expression of CD10 in tumor cells and that in stromal cells (P = 0.001). In all pilomatricomas (100%) and in four trichoblastomas (80%), strong expression was also detected in tumor cells. There was no detectable expression in trichofolliculomas. One sebaceoma (33%) and two sebaceous carcinomas (40%) expressed CD10 in a similar fashion to BCCs. All tumors of eccrine gland origin, including syringoma, spiradenoma, poroma, porocarcinoma, and eccrine duct carcinoma (NOS), did not express CD10. Five mixed tumors (83%) were immunopositive. In SCC, CD10 was overexpressed only in the stromal cells. These findings support the hypothesis that BCC is derived from the folliculo-sebaceous apocrine unit, especially having the same origin as trichoblastoma and pilomatricoma. CD10 might be an indicator of tumor invasiveness if it is expressed in stromal cells, while it might be a marker of follicular differentiation if it is expressed in the actual tumor cells of cutaneous epithelial neoplasms.

Immunohistochemical and ultrastructural observations of desmoplastic trichoepithelioma with a special reference to a morphological comparison with normal apocrine acrosyringeum

Desmoplastic trichoepithelioma is a benign neoplasm considered to have follicular differentiation. Its sweat gland- or sebaceous-lines of differentiation have been also reported. There have been, however, only a few reports regarding extensive immunohistochemical and ultrastructural investigations of this neoplasm. Histopathological and immunohistochemical studies were performed on three cases of desmoplastic trichoepithelioma, comparing it with normal skin. One of these cases was ultrastructurally investigated. The cord-like basaloid nests were reacted with the anti-cytokeratin (CK)1/5/10/14, -CK5/8, -CK14 and -CK15 antibodies, but not with the anti-CK6 antibody. Similar findings were observed in the outer layers of the normal follicular outer root sheath. Basaloid cell nests in one case, which showed ductal structures in the nests, also expressed CK7, CK8/18 and CK19. These keratins were also detected in the normal sweat glands. In addition, CK8/18 and CK19 were expressed in the basal cells of the outer root sheath. Keratinous cysts had inner reactions with the anti-CK10/11 and -CK6 antibodies, and outer reactions with anti-CK5/8 and -CK14 antibodies. Ultrastructurally, the cells in the cord-like nests were basically immature and basaloid in appearance. A few cells contained Odland bodies, which were also observed in the normal apocrine acrosyringeum. The ductal structure was lined by the cells which bore numerous microvilli in the luminal surface. The cells in desmoplastic trichoepithelioma are suggested to be in close association with the basal cells in the outer root sheath, which can differentiate into various parts of the folliculosebaceous apocrine unit.

An immunohistochemical study of the apocrine type of cutaneous mixed tumors with special reference to their follicular and sebaceous differentiation.

An immunohistochemical analysis of 8 cases of the apocrine type of cutaneous mixed tumor is reported. Histologically, 7 cases of the tumor were suggested to have follicular and/or sebaceous differentiation. Carcinoembryonic antigen (CEA), epithelial membrane antigen and gross cystic disease fluid protein-15 were present in the inner surface and/or in the luminal cell bodies of the tubular structures. CEA and non-specific cross-reacting antigen were also detected in the keratinous cysts. Positive reactions for S-100 protein and vimentin were observed in the solid nests, the outer layer of the tubular structures and some stromal cells. However, smooth muscle actin was only focally expressed in the outer cells of the tubular nests in one case. Involucrin was positive in the inner layers of the keratinous cysts. Various staining patterns were observed in the keratin immunohistochemistry. The solid nests showed heterogeneous expressions of CK1/5/10/14, CK7, CK10/11, CK14, CK8/18 and CK19. The inner cells of the tubular structures were constantly positive for CK7, CK8/18 and CK19, and heterogeneously for CK1/5/10/14, CK10/11 and CK14. The outer cells were heterogeneously positive for CK1/5/10/14 and CK14. The keratinous cysts showed positive reactions for CK1/5/10/14 throughout the whole cell layers, and for CK14 in the basal layer. The inner layers in some keratinous cysts expressed CK6, CK10/11 and CK17, but only CK10 in others. CK13 was positively stained in the transitional portion between the matricial structure and the column of shadow cells in the cyst wall in only one case. When compared with the immunohistochemistry of the normal skin, the apocrine type of cutaneous mixed tumor can show various immunophenotypical patterns similar to those of entire structures of hair follicles, sebaceous glands and all components of apocrine glands, that is to say, the folliculosebaceous-apocrine unit.