QBEND/10 (anti-CD34 antibody) in external root sheath cells and follicular tumors

Gelatin-Chitosan Hydrogel Biological, Antimicrobial and Mechanical Properties for Dental Applications

Chitosan, a natural polysaccharide sourced from crustaceans and insects, is often used with hydrogels in wound care. Evaluating its cytotoxicity and antimicrobial properties is crucial for its potential use in dentistry.

OBJECTIVE

To investigate the mechanical properties of gelatin hydrogels based on decaethylated chitosan and antimicrobial activity against Streptococcus mutans and their biological effects with stem cells from apical papilla (SCAPs).

MATERIAL AND METHODS

Gelatin-chitosan hydrogels were synthesized at concentrations of 0%, 0.2% and 0.5%. Enzymatic and hydrolytic degradation, along with swelling capacity, was assessed. Fourier transform infrared spectroscopy (FTIR) analysis was employed to characterize the hydrogels. The interaction between hydrogels and SCAPs was examined through initial adhesion and cell proliferation at 24 and 48 h, using the Thiazolyl Blue Tetrazolium Bromide (MTT assay). The antimicrobial effect was evaluated using agar diffusion and a microdilution test against S. mutans. Uniaxial tensile strength (UTS) was also measured to assess the mechanical properties of the hydrogels.

RESULTS

The hydrogels underwent hydrolytic and enzymatic degradation at 30, 220, 300 min and 15, 25, 30 min, respectively. Significantly, (p < 0.01) swelling capacity occurred at 20, 40, 30 min, respectively. Gelatin-chitosan hydrogels' functional groups were confirmed using vibrational pattern analysis. SCAPs proliferation corresponded to 24 h = 73 ± 2%, 82 ± 2%, 61 ± 6% and 48 h = 83 ± 11%, 86 ± 2%, 44 ± 2%, respectively. The bacterial survival of hydrogel interaction was found to be 96 ± 1%, 17 ± 1.5% (p < 0.01) and 1 ± 0.5% (p < 0.01), respectively. UTS showed enhanced (p < 0.05) mechanical properties with chitosan presence.

CONCLUSION

Gelatin-chitosan hydrogels displayed favorable degradation, swelling capacity, mild dose-dependent cytotoxicity, significant proliferation with stem cells from apical papilla (SCAPs), substantial antimicrobial effects against S. mutans and enhanced mechanical properties. These findings highlight their potential applications as postoperative care dressings.

A Contemporary View on Felix Pinkus' Concept of the Vitreous Membrane

Introduction

Felix Pinkus' concept of the vitreous membrane (VM) published in 1927 describes circular folds protruding into the outer root sheath (ORS), which, in his opinion, serve as interdigitations between the outer root sheath (ORS) and the VM. This concept currently seems to have fallen into oblivion.

Objective

To determine the origin and possible function of the VM in the proliferation and vascularization of the hair follicle (HF).

Methods

Serial investigation of healthy skin probes with histological (hematoxylin & eosin and periodic acid-Schiff) and immunohistochemical examination (Ki67, CD56, CD8, and collagen IV) were performed.

Results

Morphological variations of the VM in various HFs such as protrusions and folds, the latter unilateral, bilateral or circular, some acute-angled, were found. Similarly, protrusions of the VM into the ORS were observed, that consisted of capillary tissue together with perifollicular tissue and VM mimicking minimal variants of the dermal papilla.

Conclusions

Pinkus' concept of the VM is revisited, reproduced and possible functions are proposed. Since these structures are found in a HF region with a high metabolic dynamism, they may be involved in differentiation or nutrition, or else be formed as a result of pressure arising from outgrowing hair shafts.

CD34 and BerEP4 Are Helpful to Distinguish Basaloid Tricholemmoma From Basal Cell Carcinoma

Tricholemmoma, a benign follicular neoplasm with outer root sheath differentiation, typically comprises clear or pale cells, and when multiple is pathognomic of Cowden's syndrome. The tumor is probably underrecognized and in basaloid examples can be difficult to distinguish from basal cell carcinoma (BCC). We studied 55 tricholemmomas (including 15 basaloid cases) and compared immunohistochemical profile with nodular BCC from our archives. Basaloid and non-basaloid tricholemmomas had similar staining characteristics. BerEP4 was focally positive (range 10%-20%) in only 3/39 (7.7%) tricholemmomas compared with widespread positivity in BCC (90.8%, 139 of 151 cases with ≥50% tumor area stained). CD34 was expressed, usually focally (median 20%, range 10%-90%), in 52/53 (98.1%) tricholemmomas and was negative in all 21 BCCs stained. EMA staining lacked sensitivity or specificity in differentiating tricholemmoma from BCC. Five or more Merkel cells were found in 7/17 (40.1%) tricholemmomas and 1/23 (4.3%) nodular BCCs studied. In summary, immunohistochemistry is helpful in distinction between tricholemmoma, including difficult basaloid examples (BerEP4 negative or focal, CD34 positive) compared with BCC (BerEP4 widespread in most cases, CD34 negative). The presence of 5 or more Merkel cells is a relatively specific but not a particularly sensitive discriminator.

Plaque-Like Pilar Sheath Acanthoma: Histopathologic and Immunohistochemical Study of 3 Unusual Cases

Pilar sheath acanthoma is an uncommon, benign follicular neoplasm that frequently presents as a solitary lesion. This neoplasm usually appears on the skin around the upper lip of elderly patients. Histopathologically, the neoplasm usually shows a cystic configuration with epithelial lobules resembling to those of the outer root sheath of the hair follicle at the level of the isthmus emanating radially from the cyst wall. We present 3 peculiar cases of a pilar sheath acanthoma showing a plaque-like architecture because the lesions exhibited a horizontal configuration. To our knowledge, there are no previously reported examples of plaque-like pilar sheath acanthoma.

Cellular mechanisms of skin repair in humans and other mammals

The increased incidence of non-healing skin wounds in developed societies has prompted tremendous research efforts on the complex process known as "wound healing". Unfortunately, the weak relevance of modern wound healing research to human health continues to be a matter of concern. This review summarizes the current knowledge of the cellular mechanisms that mediate wound closure in the skin of humans and laboratory animals. The author highlights the anatomical singularities of human skin vs. the skin of other mammals commonly used for wound healing research (i.e. as mice, rats, rabbits, and pigs), and discusses the roles of stem cells, myofibroblasts, and the matrix environment in the repair process. The majority of this review focuses on reepithelialization and wound closure. Other aspects of wound healing (e.g. inflammation, fibrous healing) are referred to when relevant to the main topic. This review aims at providing the reader with a clear understanding of the similarities and differences that have been reported over the past 100 years between the healing of human wounds and that of other mammals.

A Rare Cutaneous Adnexal Tumor: Malignant Proliferating Trichilemmal Tumor

Proliferating trichilemmal tumors (PTTs) are neoplasms derived from the outer root sheath of the hair follicle. These tumors, which commonly affect the scalp of elderly women, rarely demonstrate malignant transformation. Although invasion of the tumors into neighboring tissues and being accompanied with anaplasia and necrosis are accepted as findings of malignancy, histological features may not always be sufficient to identify these tumors. The clinical behavior of the tumor may be incompatible with its histological characteristics. Squamous-cell carcinoma should certainly be considered in differential diagnosis because of its similarity in morphological appearance with PTT. Immunostaining for CD34, P53, and Ki-67 is a useful adjuvant diagnostic method that can be used in differential diagnosis aside from morphological findings. In this study, we aimed to present the case of a 52-year-old female patient with clinicopathological features. We reported a low-grade malignant proliferating trichilemmal tumor in this patient and detected no relapse or metastasis in a 24-month period of follow-up.

Linear trichilemmoma following a blaschkoid pattern: a clinical dilemma

BACKGROUND

Trichilemmoma are benign adnexal neoplasm with follicular outer sheath differentiation. It usually appears as single or multiple papules that resembles colour of the surrounding skin. They are most commonly seen on the face particularly on the nose and cheek.

OBJECTIVES

We report a case of linear trichilemmoma following blaschkoid pattern.

METHODS

A 13 year old boy presenting with asymptomatic plaque on the right side of the nose was fully evaluated for possible cause.

RESULTS

On histopathology, a diagnosis of trichilemmoma was made.

CONCLUSION

This is the first case report where linear trichilemmoma following a blaschkoid pattern is seen.

Human Hair Follicle Cells with the Cell Surface Marker CD34 Can Regenerate New Mouse Hair Follicles and Located in the Outer Root Sheath of Immunodeficient Nude Mice

BACKGROUND AND OBJECTIVES

The bulge region of hair follicle has been reported as a putative reservoir of hair follicle stem cells. The purpose of this study was to compare hair follice CD34 negative (CD34-) cell with CD34 positive (CD34+) cell and to evaluate the ability to regenerate new hair of immunodeficient nude mouse.

METHODS AND RESULTS

In this report, we isolated the cells with CD34, known as bulge-negative cell surface marker from cultured human hair follicle cells using by magnetic cell sorting (MACS), injected the cells to immunodeficient nude mouse. To determine immunological characterization, human hair follicle CD34+ cells and CD34- cells were assessed by flow cytometry. The localization of injected-CD34+ cells was assessed on formalin-fixed, paraffin-embedded mouse skin samples by in situ hybridization technique. Our findings show that the human hair follicle cells with cell surface marker CD34 were located in the outer root sheath of nude mouse after transplantation and the cells were able to regenerate new hair follicle in immunodeficient nude mouse. CD34- cells also were able to regenerate follicles in the mouse, however, CD34+ cells were able to regenerate much more hair follicle than CD34- cells.

CONCLUSIONS

Therefore, the results of this study add new insight into the investigation of CD34 stem cell-related molecule in human hair follicles and suggest that not all human hair follicle stem cells reside in bulge region, but in a lager niche.

The changes in the expression levels of follicular markers in keratoacanthoma depend on the stage: keratoacanthoma is a follicular neoplasm exhibiting infundibular/isthmic differentiation without expression of CK15

BACKGROUND

Although the precise etiology of keratoacanthoma (KA) is unknown, KA is generally assumed to differentiate toward hair follicles based on previous studies of experimental carcinogenesis.

METHODS

We performed a comprehensive immunohistochemical study of various follicular markers in all stages of KA. A total of 67 tumors, including 16 early or proliferative stage lesions, 43 well-developed stage lesions, five regressing stage lesions and three regressed stage lesions, were subjected to the analysis.

RESULTS

CK15 (clone C8/144B), CK19 and CD34 were not expressed at any stage. CK1, CK10, CK16, CK17, CK15 (clone LHK15) and calretinin showed dynamic changes in their expression in KA depending on the stage.

CONCLUSIONS

KA is a follicular neoplasm with infundibular/isthmic (upper segmental region of hair follicles) differentiation. It is considered that early or proliferative stage tumors show keratin-filled invaginations with infundibular differentiation and gradual isthmic differentiation. Well-developed examples of KA generally show isthmic differentiation in the whole lesions. The regressed stage KAs lose the features of this type of follicular differentiation and show epidermal characteristics. No expression of CK15 (clone C8/144B) was observed in KAs, although this finding is insufficient to completely rule out the correlation between the regression of KA and the hair follicle cycle.

Immunohistochemistry of soft tissue tumours - review with emphasis on 10 markers

Immunohistochemistry is an integral component in the proper analysis of soft tissue tumours, and a simple panel of six markers is useful in practical triage: CD34, desmin, epithelial membrane antigen (EMA), keratin cocktail AE1/AE3, S100 protein and alpha smooth muscle actin (SMA). These markers frequently assist in the differential diagnosis of fibroblastic, myoid, nerve sheath and perineurial cell tumours, synovial and epithelioid sarcoma and others. However, they all are multispecific, so that one has to be cognizant of their distribution in normal and neoplastic tissues. Four additional useful markers for specific tumour types are discussed here: CD31 and ERG for vascular endothelial tumours, and KIT and DOG1/Ano-1 for gastrointestinal stromal tumours (GISTs). However, hardly any marker is totally monospecific for any one type of tumour. Furthermore, variably lineage-specific markers do not usually distinguish between benign and malignant proliferations, so that this distinction has to be made on histological grounds. Immunohistochemical evaluation is most useful, efficient and cost-effective when used in the context of careful histological evaluation by an experienced pathologist, aware of all diagnostic entities and their histological spectra. Additional diagnostic steps that must be considered in difficult cases include clinicoradiological correlation and additional sampling of remaining wet tissue, if possible.

Tricholemmoma and clear cell squamous cell carcinoma (associated with Bowen's disease): immunohistochemical profile in comparison to normal hair follicles

There have been only a few reported comparative immunohistochemical studies of normal hair follicles and tricholemmomas. Clear cell squamous cell carcinomas (SCCs), which are derived from Bowen's disease, histopathologically mimic or are difficult to distinguish from tricholemmal carcinoma. The purpose of and methods used in the present study are as follows: (1) evaluation of whether the immunohistochemical profile (cytokeratin (CK)1, CK10, CK17, CD34, and D2-40) in normal hair follicles is retained in tricholemmomas (11 lesions); and (2) a study of the immunohistochemical profile of in situ or superficially invasive clear cell SCCs (associated with Bowen's disease) (10 lesions) to investigate the presence or absence of tricholemmal differentiation markers in these lesions. The present study demonstrated that (1) the immunohistochemical profile of the normal outer root sheath cells was generally retained in tricholemmomas; (2) in contrast to the D2-40 expression in tricholemmomas (only a peripheral pattern, which is similar to that in the normal outer root sheath), the CD34 expression in tricholemmomas represented in a diffuse pattern, a peripheral pattern, and a combined diffuse and peripheral pattern; (3) tricholemmomas are benign neoplasms with outer root sheath (below the isthmus) differentiation, which characteristically show upregulation of CD34 expression with some functionally similar conditions to the terminal hair follicles in the anagen phase; and (4) there is no clear immunohistochemical evidence of tricholemmal differentiation in clear cell SCC (associated with Bowen's disease).

Trichilemmoma arising in the nasal vestibule: report of three cases with special emphasis on the differential diagnosis

Trichilemmoma is a benign cutaneous epithelial tumor with differentiation towards cells of the outer hair root sheath and usually presents as a small papule on the face of middle-aged or older adults. We herein report three cases of trichilemmoma located in the nasal vestibule, including two of the conventional type and one of the desmoplastic variant. To our knowledge, only one case of trichilemmoma arising in the nasal vestibule has been previously reported. Trichilemmoma must be included in the differential diagnosis of epithelial lesions arising in this location. This is particularly important in the case of the desmoplastic trichilemmoma, a tumor that resembles invasive carcinoma such as desmoplastic squamous cell carcinoma, sclerosing basal cell carcinoma, and trichilemmal carcinoma. The circumscription of the lesion, the architectural pattern of epithelial cell cords and small nests merging with a desmoplastic stroma in the central area of the tumor, the expression of CD34, and the lack of an obvious squamous differentiation or basaloid foci favor the diagnosis of desmoplastic trichilemmoma. All these features help to rule out the diagnosis of carcinoma with significant clinical implications.

Production of embryonic and fetal-like red blood cells from human induced pluripotent stem cells

We have previously shown that human embryonic stem cells can be differentiated into embryonic and fetal type of red blood cells that sequentially express three types of hemoglobins recapitulating early human erythropoiesis. We report here that we have produced iPS from three somatic cell types: adult skin fibroblasts as well as embryonic and fetal mesenchymal stem cells. We show that regardless of the age of the donor cells, the iPS produced are fully reprogrammed into a pluripotent state that is undistinguishable from that of hESCs by low and high-throughput expression and detailed analysis of globin expression patterns by HPLC. This suggests that reprogramming with the four original Yamanaka pluripotency factors leads to complete erasure of all functionally important epigenetic marks associated with erythroid differentiation regardless of the age or the tissue type of the donor cells, at least as detected in these assays. The ability to produce large number of erythroid cells with embryonic and fetal-like characteristics is likely to have many translational applications.

Basal cell carcinoma: cell of origin, cancer stem cell hypothesis and stem cell markers

Cancer stem cells have recently been described in several high-grade neoplasms. It is still unclear if they also occur in cutaneous malignancies. Cancer stem cells are not identical with somatic stem cells. The presence of tumour stem cells in a neoplasm does not in itself equal that the tumour derives from a somatic stem cell. A cell originally lacking stem cell characteristics could also acquire those features during the course of carcinogenesis and then becomes the clonal founder cell of a tumour. Basal cell carcinoma (BCC) is the most common cutaneous malignancy. A plethora of various stem cell markers has been applied to study its cellular origin. Intriguingly, the anatomical origin of BCC is still uncertain. This review will discuss the various stem cell markers used in BCC and the cellular origin of this tumour, and touches briefly on the possibility of cancer stem cells in BCC. If BCC or other skin cancers harbour tumour stem cells, these cells could be specifically targeted, making use of specific cell surface molecules such as receptor proteins. Novel drugs directed against those receptor proteins could replace currently available shotgun approaches including imiquimod.

Acclimatized induction reveals the multipotency of adult human undifferentiated keratinocytes

It has been demonstrated that several types of somatic stem cells have the remarkable capacity to differentiate into other types of tissues. However, the promise of keratinocyte stem cells seems slim for generating nonepidermal tissues. Using our recently developed acclimatization induction strategy, we demonstrate the multipotency of adult human undifferentiated keratinocytes (UKs). The UKs were isolated from the basal layer of adult human foreskin and cultured in Epilife medium, which allows for the growth of only keratin-positive keratinocytes, promotes high proliferation of UKs, and prevents their differentiation. Induction of the UKs by either serum or lineage-committed medium only produce differentiated epidermal cells. Hence, serum or lineage-committed medium was added to Epilife to acclimate UKs to differentiate to other cell types. Unexpectedly, serum acclimatization can induce UKs to produce a large number of smooth muscle cells and fewer of adipocytes and neurocytes within 3 weeks. In contrast, except for the terminally differentiated epidermal cells, committed acclimatization can induce UKs to differentiate exclusively into the adipocytic, myogenic, or neurogenic lineages. These data indicate that human UKs represent a novel multipotent adult stem cell, and suggest that they may provide an accessible, therapeutically promising cell source for regenerative medicine.

Trichilemmal carcinoma of the upper eyelid: a case report

We report a very rare case of trichilemmal carcinoma (TLC) involving the upper eyelid. To the best of our knowledge, this is the first report of trichilemmal carcinoma of the upper eyelid in Korea. A 51-year-old man presented to our hospital complaining of a bloody discharge from his left upper eyelid. He had a soft and lobulated mass on the palpebral conjunctiva. An incisional biopsy revealed trabecular growth of tumor cells with clear cytoplasm, prominent nucleoli, frequent mitoses, and foci of trichilemmal keratinization. Immunohistochemically, the lesion was positive for p53 and negative for CD 34. A diagnosis of TLC was made, and total excision of the mass and reconstruction of the eyelid were performed. Trichilemmal carcinoma is a rare malignant tumor, though it appears to be an indolent neoplasm with no metastatic potential. The treatment of choice for trichilemmal carcinoma of the eyelid is complete excision with tumor-free margins due to the locally invasive nature of the lesion.

Hedgehog signaling maintains hair follicle stem cell phenotype in young and aged human skin

Skin hair follicles (HF) contain bulge stem cells (SC) that regenerate HFs during hair cycles, and repair skin epithelia following injury. As natural aging is associated with decreased skin repair capacity in humans, we have investigated the impact of age on human scalp HF bulge cell number and function. Here, we isolated human bulge cells, characterized as CD200+/KRT15+/KRT19+ cells of the HF, by dissection-combined CD200 selection in young and aged human skin. Targeted transcriptional profiling indicates that KRT15, KRT19, Dkk3, Dkk4, Tcf3, S100A4, Gas1, EGFR and CTGF/CCN2 are also preferentially expressed by human bulge cells, compared to differentiated HF keratinocytes (KC). Our results demonstrate that aging does not alter expression or localization of these HF SC markers. In addition, we could not detect significant differences in HF density or bulge cell number between young and aged human scalp skin. Interestingly, hedgehog (Hh) signaling is activated in human bulge cells in vivo, and down-regulated in differentiated HF KCs, both in young and aged skin. In addition, activation of Hh signaling by lentivirus-mediated overexpression of transcription factor Gli1 induces transcription of HF SC markers KRT15, KRT19, and Gas1, in cultured KCs. Together with previously reported knock-out mouse results, these data suggest a role for Hh signaling in maintaining bulge cell phenotype in young and aged human skin.

Differential expression of stem-cell-associated markers in human hair follicle epithelial cells

Several putative biomarkers have been suggested for identifying murine follicular stem cells; however, human hair follicles have a different pattern of biomarker expression, and follicular stem cell isolation methods have not been established. To isolate a stem cell population applicable to clinical settings, we conducted a comprehensive survey of the expression of stem-cell-associated (K15, CD200, CD34, and CD271) and other biomarkers (K1, K14, CD29, and CD49f) in immunohistological sections of the human epidermis and follicular outer root sheath (ORS). We also examined freshly isolated and cultured epidermal or follicular cells with single- and multicolor flow cytometry or immunocytochemistry. After sorting cells by CD200, CD34, and forward scatter (FSC) values (cell size), colony-forming assays were performed. We found that biomarkers were differentially expressed in the epidermis and ORS. Basal bulge cells were mainly K15+CD200+CD34(-)CD271(-), and suprabasal cells were K15(-)CD200+CD34(-)CD271(-). We categorized follicular cells into nine subpopulations according to biomarker expression profiles. The CD200+CD34(-) bulge cells had much higher colony-forming abilities than the CD34+ population, and were divided into two subpopulations: a CD200+CD34(-)FSC(high) (K15-rich, basal) and a CD200+CD34(-)FSC(low) (K15-poor, suprabasal) population. The former formed fewer but larger-sized colonies than the latter. Follicular epithelial cell cultivation resulted in loss of K15, CD200, CD34, and CD271 expression, but maintenance of K14, CD29, and CD49f expression. We found that the bulge contained two populations with different localizations, cell sizes, and colony-forming abilities. We showed that K15, CD200, CD34, and CD271 were useful biomarkers for characterizing freshly isolated human follicular epithelial cells in diverse stages of differentiation.

CD34-reactive tumors of the skin. An updated review of an ever-growing list of lesions

Over the past few years, a growing number of cutaneous tumors expressing CD34 is being reported. The list contains benign and malignant neoplasms as well as reactive and hamartomatous lesions of diverse lineages of differentiation, including fibroblastic, myofibroblastic, fibrohistiocytic, vascular, neural, adipocytic, smooth muscle, hematopoietic, melanocytic and epithelial. The more frequent diagnostic difficulties are found in spindle cell proliferations, mainly in those of the fibrocytic lineage. In part, this is because of the fact that in this area are, aside to well-defined entities, histologically and clinically diverse, recently reported cutaneous CD34-reactive lesions, whose definitions, limits and relationships are not completely established. The CD34 expression plays a key role in the differential diagnosis of some tumors, such as dermatofibrosarcoma protuberans, epithelioid sarcoma or pleomorphic hyalinizing angiectatic tumor of soft parts, with important therapeutic consequences. In others, as in desmoplastic trichilemmoma, it can help to resolve diagnostic problems in concrete cases. Finally, in many of the CD34-positive lesions, the diagnosis with the hematoxylin and eosin stain is straightforward. However, in all of them, the knowledge of the immunohistochemical profile contributes to our understanding of the cutaneous pathology.

Squamous cell carcinoma with clear cells: how often is there evidence of tricholemmal differentiation?

Clear-cell carcinoma of the skin was described by Kuo in 1980 as a cutaneous tumor composed of clear cells that lacked cytoplasmic glycogen or evidence of tricholemmal keratinization. Tricholemmal carcinoma (TC) is conventionally considered to be a neoplasm derived from adnexal keratinocytes with glycogenated clear cells and evidence of outer root sheath or tricholemmal differentiation. The existence of TC has been questioned as it has been argued that without clear immunohistochemical evidence of outer root sheath differentiation, TC cannot be distinguished from clear-cell carcinoma of the skin. Our laboratory has not routinely stained the cases that appear to be carcinomas with clear keratinocytes to determine if glycogen is present and has not made the diagnosis of TC. We sought to test whether the presence of glycogen, light microscopic features said to be typical of TC, or immunohistochemical findings would delineate a group of "true" TC among the cases that we have been recording as squamous cell carcinomas with clear cells (SCC-C). 40 cases of SCC-C were evaluated for 7 histologic and histochemical criteria (a lobular arrangement, peripheral palisading, tricholemmal keratinization, folliculocentricity, evidence of a preexisting tricholemmoma, the presence of intracytoplasmic glycogen, and a thickened basement membrane) said to characterize TC. Selected cases were then stained for immunohistochemical markers (CD34, CK17, and NGFR/p75) that have been used as evidence for tricholemmal differentiation in some studies. Of the 40 cases, 38 (95%) SCC-C showed intracytoplasmic glycogen (periodic Schiff positivity abolished by diastase) and 55% of cases showed foci of tricholemmal keratinization. Overall, the carcinomas showed a spectrum of the above aggregated criteria ranging from 0 to 5. None possessed all the criteria expected in an ideal TC. In addition, the majority of the selected SCC-C in this study were negative (85%) for antigens typically found in the outer root sheath epithelium of the hair follicle. The glycogen-free clear-cell carcinoma described by Kuo seems uncommon in our patient population. Rare cases of SCC-C met the majority of Headington's criteria for TC or showed immunohistochemical evidence of tricholemmal differentiation. Thus, we also conclude that well-differentiated TC is rare and its description in the literature may overstate the case that it is a well-characterized cutaneous neoplasm.

Immunophenotyping of the human bulge region: the quest to define useful in situ markers for human epithelial hair follicle stem cells and their niche

Since the discovery of epithelial hair follicle stem cells (eHFSCs) in the bulge of human hair follicles (HFs) an important quest has started: to define useful markers. In the current study, we contribute to this by critically evaluating corresponding published immunoreactivity (IR) patterns, and by attempting to identify markers for the in situ identification of human eHFSCs and their niche. For this, human scalp skin cryosections of at least five different individuals were examined, employing standard immunohistology as well as increased sensitivity methods. Defined reference areas were compared by quantitative immunohistochemistry for the relative intensity of their specific IR. According to our experience, the most useful positive markers for human bulge cells turned out to be cytokeratin 15, cytokeratin 19 and CD200, but were not exclusive, while beta1 integrin and Lhx2 IR were not upregulated by human bulge keratinocytes. Absent IR for CD34, connexin43 and nestin on human bulge cells may be exploited as negative markers. alpha6 integrin, fibronectin, nidogen, fibrillin-1 and latent transforming growth factor (TGF)-beta-binding protein-1 were expressed throughout the connective tissue sheath of human HFs. On the other hand, tenascin-C was upregulated in the bulge and may thus constitute a component of the bulge stem cell niche of human HFs. These immunophenotyping results shed further light on the in situ expression patterns of claimed follicular 'stem cell markers' and suggest that not a single marker alone but only the use of a limited corresponding panel of positive and negative markers may offer a reasonable and pragmatic compromise for identifying human bulge stem cells in situ.

CD10 and CD34 in fetal and adult human hair follicles: dynamic changes in their immunohistochemical expression during embryogenesis and hair cycling

BACKGROUND

CD10 and CD34 have been detected in both epithelial and mesenchymal components of anagen human hair follicles.

OBJECTIVES

To analyse the expression of CD10 and CD34 in human hair follicle development as well as in different phases of the hair cycle.

METHODS

Fetal and adult hair follicles at different stages of the hair cycle were examined by immunohistochemistry for CD10 and CD34.

RESULTS

In fetal follicles, CD10 is expressed by the cells of the placodes, and CD34 by the mesenchymal cells of the dermal condensate. As the follicle matures, CD10 can be seen in the matrix cells, inner root sheath and dermal sheath. In adult follicles, the expression of CD10 in the follicular epithelium is present in anagen follicles, but tends to disappear in catagen, and is not detected in telogen. The CD10 positivity of the dermal sheath is more intense in catagen than in anagen follicles. CD34 immunostaining of the external root sheath was seen in adult anagen follicles but not in fetal follicles. This staining of the anagen outer sheath tends to disappear in catagen and is not detected in telogen.

CONCLUSIONS

CD10 and CD34 are not proteins constantly present in a specific cell type of the hair follicle, but are proteins that can be expressed by both epithelial and mesenchymal cells depending on the stage of development and hair cycle. The distribution of the immunoreactivity to CD10 in the placode and CD34 in the dermal condensate suggests a role of these proteins in initial stages of hair formation.

CD34 expression by hair follicle stem cells is required for skin tumor development in mice

The cell surface marker CD34 marks mouse hair follicle bulge cells, which have attributes of stem cells, including quiescence and multipotency. Using a CD34 knockout (KO) mouse, we tested the hypothesis that CD34 may participate in tumor development in mice because hair follicle stem cells are thought to be a major target of carcinogens in the two-stage model of mouse skin carcinogenesis. Following initiation with 200 nmol 7,12-dimethylbenz(a)anthracene (DMBA), mice were promoted with 12-O-tetradecanoylphorbol-13-acetate (TPA) for 20 weeks. Under these conditions, CD34KO mice failed to develop papillomas. Increasing the initiating dose of DMBA to 400 nmol resulted in tumor development in the CD34KO mice, albeit with an increased latency and lower tumor yield compared with the wild-type (WT) strain. DNA adduct analysis of keratinocytes from DMBA-initiated CD34KO mice revealed that DMBA was metabolically activated into carcinogenic diol epoxides at both 200 and 400 nmol. Chronic exposure to TPA revealed that CD34KO skin developed and sustained epidermal hyperplasia. However, CD34KO hair follicles typically remained in telogen rather than transitioning into anagen growth, confirmed by retention of bromodeoxyuridine-labeled bulge stem cells within the hair follicle. Unique localization of the hair follicle progenitor cell marker MTS24 was found in interfollicular basal cells in TPA-treated WT mice, whereas staining remained restricted to the hair follicles of CD34KO mice, suggesting that progenitor cells migrate into epidermis differently between strains. These data show that CD34 is required for TPA-induced hair follicle stem cell activation and tumor formation in mice.

CD34 glycoprotein identifies putative stem cells located in the isthmic region of canine hair follicles

It is widely documented that a pool of multipotent stem cells located in humans and mice hair follicle outer root sheath (bulge region) is involved in the restoration of the whole follicular unit during each anagen phase. To the authors' knowledge, data regarding the location and characterization of hair follicle stem compartment in dogs have not been reported in the recent relevant literature. In this study, we investigated the haematopoietic stem and progenitor cell antigen CD34 as a marker of putative stem cells located in a bulge-like region of canine hair follicles. The presence of CD34 mRNA and glycoprotein was assessed on formalin-fixed, paraffin-embedded canine skin samples by in situ hybridization technique and by standard immunohistochemistry, respectively. A strong expression of CD34 mRNA and glycoprotein was observed in a well-defined area of the hair follicle isthmic region and appeared uniformly concentrated at the level of the basal layer of the outer root sheath. These findings provide compelling support to the hypothesis that in dogs, a subpopulation of basal keratinocytes located in the hair follicle isthmic region and characterized by the selective expression of CD34 is potentially associated with the stem cell compartment of this skin appendage.

The immunohistochemical expression of CD34 in human hair follicles: a comparative study with the bulge marker CK15

BACKGROUND

Anti-CD34 antibodies label the bulge region of mouse hair follicles. However, in human hair follicles, CD34 immunoreactivity is found in the outer root sheath below the bulge zone. The immunohistochemical staining of CD34 in catagen and telogen follicles has not been evaluated.

AIMS

To characterize the expression of CD34 immunoreactivity at different stages of the hair cycle in human terminal hair follicles, and to compare the immunostaining pattern of CD34 with that of CK15, used here as a marker of the bulge region.

METHOD

Serial vertical sections of human hair follicles in anagen, catagen and telogen phases were immunostained with anti-CD34 (QBEnd 10) and anti-CK15 (LHK15 and C8/144B) antibodies. Double-labelling immunofluorescence was also performed.

RESULTS

The catagen and telogen follicles studied did not show CD34 immunoreactivity in the outer root sheath. The location of CD34 and CK15 immunoreactivity in anagen follicles reveals a different staining pattern: CD34-positive cells are located in the outer root sheath below the attachment zone of the arrector pili muscle, whereas CK15-positive cells are located in the outer root sheath above the attachment zone of the arrector pili muscle.

CONCLUSIONS

Only anagen human hair follicles show CD34 immunoreactivity. CD34 and CK15 recognize different types of cells or cells at different stages of differentiation.

Characterization and isolation of stem cell-enriched human hair follicle bulge cells

The human hair follicle bulge is an important niche for keratinocyte stem cells (KSCs). Elucidation of human bulge cell biology could be facilitated by analysis of global gene expression profiles and identification of unique cell-surface markers. The lack of distinctive bulge morphology in human hair follicles has hampered studies of bulge cells and KSCs. In this study, we determined the distribution of label-retaining cells to define the human anagen bulge. Using navigated laser capture microdissection, bulge cells and outer root sheath cells from other follicle regions were obtained and analyzed with cDNA microarrays. Gene transcripts encoding inhibitors of WNT and activin/bone morphogenic protein signaling were overrepresented in the bulge, while genes responsible for cell proliferation were underrepresented, consistent with the existence of quiescent noncycling KSCs in anagen follicles. Positive markers for bulge cells included CD200, PHLDA1, follistatin, and frizzled homolog 1, while CD24, CD34, CD71, and CD146 were preferentially expressed by non-bulge keratinocytes. Importantly, CD200+ cells (CD200hiCD24loCD34loCD71loCD146lo) obtained from hair follicle suspensions demonstrated high colony-forming efficiency in clonogenic assays, indicating successful enrichment of living human bulge stem cells. The stem cell behavior of enriched bulge cells and their utility for gene therapy and hair regeneration will need to be assessed in in vivo assays.

Proliferating trichilemmal cyst: report of two cases, one benign and the other malignant

Proliferating trichilemmal cyst (PTC) is a rare but morphologically distinct tumor that usually arises on the scalp of elderly women. We report two cases of PTC, one benign and the other malignant. PTCs are well circumscribed, subepidermal lesions and demonstrate a uniform histologic pattern with varying degrees of cytological atypia. Malignant proliferating trichilemmal cyst (MPTC) has features in common with benign proliferating trichilemmal cyst (BPTC), including a central area of abrupt keratinization and hyperplastic squamous epithelium forming solid areas. The diagnosis of MPTC is essentially based on histological features. The presence of a high mitotic rate, atypical mitosis, severe nuclear pleomorphism, and tumor invasion of the adjacent tissues are the essential histological features of malignancy in these unusual tumors. The therapeutic approach in malignant cases is the same as that in the treatment of BPTC: surgical removal with a wide clear margin. However, even with adequate resection, both tumors tend to recur locally.

Proliferating trichilemmal tumour: p53 immunoreactivity in association with p27Kip1 over-expression indicates a low-grade carcinoma profile

AIMS

Alterations of cell-cycle regulatory molecules in tumorigenesis may predict the biological behaviour of neoplasms and greatly contribute to their proper classification. Since the behaviour of proliferating trichilemmal tumour (PTT) is controversial, we decided to explore the possible significance of altered p53 and p27Kip1 immunohistochemical expression patterns in PTT.

METHODS AND RESULTS

We evaluated the percentage and distribution of positive tumour cells and compared the results with those obtained from usual trichilemmal cysts (TC) and squamous cell carcinomas with trichilemmal differentiation (SCCT). PTT showed p53 immunoreactivity (50.4 +/- 29.6, mean +/- standard deviation) that was not statistically different from that seen in SCCT (75.2 +/- 36.3). On the other hand, p53 immunostaining was virtually absent in TC cases (positivity for p53 was observed in only one instance in < 1% of cells). As for p27Kip1, the mean percentage of positive cells in PTT (82.7 +/- 9.9) was slightly lower than in TC (90.6 +/- 4.6) but significantly higher than in SCCT (53.4 +/- 30).

CONCLUSIONS

The similar p53 immunoreactivity in both PTT and SCCT favour the interpretation of the former as carcinoma, albeit one whose behaviour would be tempered by the well-known regulatory effect exerted by p27Kip1 on the cell cycle.

Malignant proliferating trichilemmal tumours: an histopathological and immunohistochemical study of three cases with DNA ploidy and morphometric evaluation

AIMS

Malignant proliferating trichilemmal tumours (MPTT) are rare neoplasms capable of tissue invasion and metastasis, the diagnosis of which is based essentially on histological features. In difficult cases, however, evaluation of additional parameters may be needed to diagnose malignancy.

METHODS AND RESULTS

We report three cases of MPTT in which, in addition to the histological features, we have determined the DNA ploidy, nuclear area and proliferative fraction. CD34 immunoreactivity has also been tested. Two cases were aneuploid, and one diploid with increased proliferating index. PCNA immunostaining labelled 40% and 80% of tumour cells in aneuploid tumours and 30% of the diploid neoplasm. In all cases, nuclear area was consistent with large pleomorphic tumour cells. No CD34 immunostaining was detected.

CONCLUSIONS

Aneuploidy is common in MPTT, particularly in tumours with a high proliferative fraction. Loss of CD34 immunoreactivity is an additional feature of potential, though limited, value. Therefore, evaluation of the DNA content, proliferation markers and CD34 immunostaining may be helpful in the diagnosis of MPTT.

The use of immunostaining for bcl-2 and CD34 and the lectin peanut agglutinin in differentiating between basal cell carcinomas and trichoepitheliomas

Fifteen unequivocal basal cell carcinomas (BCC) and ten unequivocal trichoepitheliomas (TE) were studied using the lectin peanut agglutinin (PNA), and the monoclonal antibodies Q bend 10 and bcl-2 oncoprotein directed against the antigens CD34 and bcl-2, respectively, to see whether these markers could be used to differentiate between the two tumors. Ten percent of TE demonstrated a continuous band-like peritumorous staining with PNA and 80% demonstrated a discontinuous band-like peritumorous staining with PNA, with the comparable figures for BCC being 40% and 20%, respectively. In addition, 40% of BCC showed focal areas of pemphigus-like staining in contrast with only 10% of TE. Using the antibody directed against bcl-2, TE demonstrated weak staining mainly confined to the basal layer of tumor cells in 20% of cases and staining of the cells throughout the tumor in 30% of cases. Similarly, BCC also showed staining of the basal layer of tumor cells in 7% of specimens and staining of cells throughout the tumor mass in 40% of specimens studied. Finally, with the antibody Q bend 10 directed against CD34, staining of the immediate peritumoral spindle-shaped cells was observed in 20% of TE compared with 7% of BCC. Despite reports in the literature, we found that none of these three markers can be reliably used to differentiate between TE and BCC.

Diagnostic value of CD34 immunostaining in desmoplastic trichilemmoma

Desmoplastic trichilemmoma (DT) is a variant of trichilemmoma, characterized by a central prominent desmoplastic component which may simulate invasive carcinoma. We have studied the morphologic and immunohistochemical features of seven cases of DT. Immunohistochemistry was performed on paraffin sections using monoclonal antibodies to CD34 (QBEND/10), vimentin and GCDFP-15. CD34 was also tested in seven cases of basal cell carcinoma (BCC), three with outer root sheath differentiation and four with morphea-form features, and five squamous cell carcinomas. Histologically, features of conventional trichilemmoma were seen at the periphery of the seven lesions. In contrast, at the center, the epithelial cells tended to cluster in narrow irregular cords and nests entrapped in a dense collagenous stroma. One case of DT coexisted with a BCC. In all cases of DT, epithelial tumor cells showed CD34 immunostaining. All cases of BCC, including the one contiguous to a DT, were CD34 negative. CD34 immunodetection in the epithelial cells of the pseudoinvasive component of DT may be of great value in the differential diagnosis with other desmoplastic tumors of the skin, and particularly with BCC.

Trichilemmal horn: case presentation and literature review

A trichilemmal horn is a histologically unique, uncommonly reported lesion, characterized by a plate-like nodule that extends from the epithelium into the dermis and has a prominent basement membrane. At the periphery of the nodule, there is palisading of basal cells. Trichilemmal keratinization is present in the overlying horn and is composed of orthokeratosis with focal parakeratosis. We describe a 22-year-old white women with a trichilemmal horn on her left elbow and review the literature. With the addition of our patient, trichilemmal horns have been described in 28 patients. They have been observed more often in women (15) than in men (11). The patients ranged in age from 16 to 78 years; more than 60% were 50 years of age or older. Trichilemmal horns were most common on the extremities (12 cases) and the head (11 cases). The diagnosis of a trichilemmal horn should be considered when a cutaneous horn shows trichilemmal keratinization in the absence of dermal inflammation.

Immunohistologic differential diagnosis of basal cell carcinoma, squamous cell carcinoma, and trichoepithelioma in small cutaneous biopsy specimens

The distinction between squamoid basal cell carcinoma and basaloid squamous cell carcinoma (or between BCC and trichoepithelioma variants) is usually made readily on the basis of defined histological criteria. However, these differential diagnoses occasionally can pose difficult morphological problems. The stated distinctions are clinically important because the risk of progressive disease is significantly higher with squamous carcinoma of the skin than with basal cell carcinoma (BCC), and a trichoepithelioma misinterpreted as BCC burdens the patient with an inaccurate diagnosis that may result in inappropriate surgery. Recent reports have suggested that reactivity with the monoclonal antibody Ber-EP4 is capable of separating histologically similar basal cell and squamous carcinomas, and that the expression of bcl-2 or CD34 antigen is able to distinguish BCC from trichoepithelioma. However, corroborative studies of these contentions are few in number. In order to investigate the usefulness of the stated immunostains in the above-cited differential diagnoses, the authors analyzed 45 basal cell carcinomas and 22 squamous carcinomas, as well as 36 trichoepitheliomas. The monoclonal antibodies Ber-EP4, My10 (CD34), and anti-bcl-2 were applied to formalin-fixed paraffin sections in all cases, using a standard avidin-biotin-peroxidase complex method. Most BCCs demonstrated strong, diffuse cytoplasmic labeling with Ber-EP4 and anti-bcl-2. In contrast, the squamous carcinomas were uniformly negative for the former marker and only focally reactive for the latter in four examples. 'Peripheral' bcl-2 staining of trichoepitheliomas was noted in 24 of 33 of the immunoreactive tumors, but the remainder were marked diffusely and similarly to most BCCs. Among the latter, immature trichoepitheliomas were diffusely reactive for this marker in 6 of 8 cases. Labeling of epithelium for CD34 failed to discriminate between any of the tumor types under evaluation, whereas staining of peritumoral stroma was characteristic of the majority of trichoepitheliomas and more than one-third of metatypical basal cell carcinomas. These data support the suggestion that Ber-EP4 and bcl-2 are useful in the separation of BCC from squamous carcinomas. Nevertheless, they also serve to caution against reliance upon bcl-2 and CD34 immunostains in attempting to distinguish BCC from trichoepithelioma in histologically enigmatic cases. There is currently no certain method other than conventional microscopy that can be applied successfully to the latter problem.

Basal cell carcinoma with thickened basement membrane: a variant that resembles some benign adnexal neoplasms

Because cutaneous basal cell carcinoma (BCC) is such a common malignancy, its unusual histologic manifestations are important. We identified a variant of BCC in which thickened basement membranes surround aggregations of neoplastic epithelial cells. Thickened basement membranes of similar appearance have previously been observed in benign cutaneous adnexal neoplasms, in basaloid monomorphic adenomas of the salivary gland and in other benign conditions, such as folliculocentric basaloid proliferation. We identified nine BCCs that otherwise met standard criteria, but which also had thick basement membranes surrounding some of the aggregations, and examined them by routine and histochemical staining. The cases included BCC with nodular, micronodular, and infiltrating patterns. Two neoplasms were composed largely of clear cells, suggesting, together with the thickened membranes, outer root sheath differentiation. CD34, which labels keratinocytes of the outer root sheath, marked only the epithelial cells of one of these cases. The thickened membranes were stained by periodic-acid Schiff with and without diastase (PAS-D) and by antibodies to type IV collagen and laminin, with slightly different staining patterns. Intraepithelial droplets within aggregations stained with PAS-D and type IV collagen antibodies. Thickened basement membranes therefore can occur in most of the common growth patterns of BCC. The absence of CD34 staining of epithelial cells in most cases makes it problematic at this time to prove that the thickened membranes indicate trichilemmal differentiation. BCC with thick basement membranes can closely mimic benign neoplasms, such as cylindroma and trichilemmoma, from which they can be distinguished in routinely stained sections. The presence of a continuous thick basement membrane around aggregates of epithelial cells does not in and of itself distinguish between benign and malignant cutaneous epithelial neoplasms.