Epithelial markers and differentiation in adnexal neoplasms of the skin: an immunohistochemical study including individual cytokeratins

Immunoexpression Patterns of Adhesion Molecules (E-cadherin, β-catenin, CD56) and Cytokeratins (CK19, CK20, HMWCK, CAM5.2) During Hair Development in Human Fetuses Compared With Adults

ABSTRACT

Abnormalities in the expression of cytokeratins or adhesion molecules have been associated with hair disorders. The expression patterns of these molecules in the hair follicles of developing human fetuses are not obvious. We aimed to investigate the expression patterns of some cytokeratins and adhesion molecules in the hair follicle of human fetuses and compared them with adults. Forty-eight fetuses of >16 gestational weeks and 22 adult cases with total excisions of benign nevi or cysts were enrolled. The skin samples were taken from both the scalp and back of the fetuses. The histopathologically normal skin areas were evaluated in adults. CK19, CK20, CAM5.2, high-molecular-weight cytokeratin, E-cadherin, β-catenin, and CD56 immunohistochemical stainings were performed. In the fetus group, the staining scores declined in the third trimester but elevated and reached the highest level in adults, except for CD56, which did not stain any adult samples. All stainings were mostly observed in the outer root sheath, except CD56 that stained the perifollicular dermal sheath only in fetuses. E-cadherin, β-catenin, and high-molecular-weight cytokeratin strongly and diffusely stained all adult samples. CAM5.2 and CK19 scores were correlated in fetuses (scalp scores: r s = 0.405, P = 0.004; back scores: r s = 0.422, P = 0.003) and adults (back scores: r s = 0.562, P = 0.046). CD56 negativity indicated the immune-privilege feature of adult hair follicles. As CK19, CAM5.2 may be used to find the regions of stem cells or transient amplifying cells.

TRPS1 Is Differentially Expressed in a Variety of Malignant and Benign Cutaneous Sweat Gland Neoplasms

Neoplasms of sweat glands and the breast may be morphologically and immunophenotypically similar. A recent study showed that TRPS1 staining is a highly sensitive and specific marker for breast carcinoma. In this study, we analyzed TRPS1 expression in a spectrum of cutaneous sweat gland tumors. We stained five microcystic adnexal carcinomas (MACs), three eccrine adenocarcinomas, two syringoid eccrine carcinomas, four hidradenocarcinomas, six porocarcinomas, one eccrine carcinoma-NOS, 11 hidradenomas, nine poromas, seven cylindromas, three spiradenomas, and 10 syringomas with TRPS1 antibodies. All of the MACs and syringomas were negative. Every cylindroma and two of the three spiradenomas demonstrated intense staining in cells lining the ductular spaces, with negative to relatively weak expression in surrounding cells. Of the 16 remaining malignant entities, 13 were intermediate to high positive, one was low positive, and two were negative. From the 20 hidradenomas and poromas, intermediate to high positivity was revealed in 14 cases, low positivity in three cases, and negative staining in three cases. Our study demonstrates a very high (86%) expression of TRPS1 in malignant and benign adnexal tumors that are mainly composed of islands or nodules with polygonal cells, e.g., hidradenomas. On the other hand, tumors with small ducts or strands of cells, such as MACs, appear to be completely negative. This differential staining among types of sweat gland tumors may represent either differential cells of origin or divergent differentiation and has the potential to be used as a diagnostic tool in the future.

Update of the keratin gene family: evolution, tissue-specific expression patterns, and relevance to clinical disorders

Intermediate filament (IntFil) genes arose during early metazoan evolution, to provide mechanical support for plasma membranes contacting/interacting with other cells and the extracellular matrix. Keratin genes comprise the largest subset of IntFil genes. Whereas the first keratin gene appeared in sponge, and three genes in arthropods, more rapid increases in keratin genes occurred in lungfish and amphibian genomes, concomitant with land animal-sea animal divergence (~ 440 to 410 million years ago). Human, mouse and zebrafish genomes contain 18, 17 and 24 non-keratin IntFil genes, respectively. Human has 27 of 28 type I "acidic" keratin genes clustered at chromosome (Chr) 17q21.2, and all 26 type II "basic" keratin genes clustered at Chr 12q13.13. Mouse has 27 of 28 type I keratin genes clustered on Chr 11, and all 26 type II clustered on Chr 15. Zebrafish has 18 type I keratin genes scattered on five chromosomes, and 3 type II keratin genes on two chromosomes. Types I and II keratin clusters-reflecting evolutionary blooms of keratin genes along one chromosomal segment-are found in all land animal genomes examined, but not fishes; such rapid gene expansions likely reflect sudden requirements for many novel paralogous proteins having divergent functions to enhance species survival following sea-to-land transition. Using data from the Genotype-Tissue Expression (GTEx) project, tissue-specific keratin expression throughout the human body was reconstructed. Clustering of gene expression patterns revealed similarities in tissue-specific expression patterns for previously described "keratin pairs" (i.e., KRT1/KRT10, KRT8/KRT18, KRT5/KRT14, KRT6/KRT16 and KRT6/KRT17 proteins). The ClinVar database currently lists 26 human disease-causing variants within the various domains of keratin proteins.

Differentiation of Basal Cell Carcinoma and Trichoepithelioma: An Immunohistochemical Study

ABSTRACT

Basal cell carcinoma (BCC) is the most common malignancy of the skin. It is an epithelial neoplasm with origin in the precursor cells of the interfollicular epidermis. Even though it has low metastatic potential, delay in management may lead to local destruction and morbidity. In contrast, trichoepithelioma (TE) is a benign tumor originating from the outer root sheath of the hair follicle. Similar to BCC, TE tends to affect the head and neck region. Both neoplasms may exhibit clinical and histopathological similarities, making them prone to misdiagnosis. Multiple immunomarkers have been used to distinguish among these entities, but so far, no single agent or combination of agents appear to be neither sensitive nor specific enough to differentiate between them. This study was divided into 2 parts. First, 17 cases of BCC and 14 cases of TE were stained with androgen receptor and bcl-2. Then, 27 cases of borderline/equivocal of BCC and 13 cases of borderline/equivocal TE were stained with the same protocol. Sensitivity and specificity were calculated for each individual immunomarker and for the combination of them. Androgen receptor positivity was 100% specific for BCC and borderline/equivocal BCC, whereas bcl-2 diffuse staining pattern demonstrated a sensitivity of 82.4% for BCC and 88.9% borderline/equivocal BCC. When both immunomarkers were combined, the sensitivity for BCC decreased (70.6%) but the specificity remained high (100%). Similarly, the sensitivity for borderline/equivocal BCC was 55.6%, whereas the specificity was 100%. Although moderately sensitive, combining both immunomarkers showed an excellent specificity to discriminate between BCC and TE.

The skin transcriptome in hidradenitis suppurativa uncovers an antimicrobial and sweat gland gene signature which has distinct overlap with wounded skin

Hidradenitis suppurativa (HS) is a debilitating chronic inflammatory skin disease resulting in non-healing wounds affecting body areas of high hair follicle and sweat gland density. The pathogenesis of HS is not well understood but appears to involve dysbiosis-driven aberrant activation of the innate immune system leading to excessive inflammation. Marked dysregulation of antimicrobial peptides and proteins (AMPs) in HS is observed, which may contribute to this sustained inflammation. Here, we analyzed HS skin transcriptomes from previously published studies and integrated these findings through a comparative analysis with a published wound healing data set and with immunofluorescence and qPCR analysis from new HS patient samples. Among the top differently expressed genes between lesional and non-lesional HS skin were members of the S100 family as well as dermcidin, the latter known as a sweat gland-associated AMP and one of the most downregulated genes in HS lesions. Interestingly, many genes associated with sweat gland function, such as secretoglobins and aquaporin 5, were decreased in HS lesional skin and we discovered that these genes demonstrated opposite expression profiles in healing skin. Conversely, HS lesional and wounded skin shared a common gene signature including genes encoding for S100 proteins, defensins, and genes encoding antiviral proteins. Overall, our results suggest that the pathogenesis of HS may be driven by changes in AMP expression and altered sweat gland function, and may share a similar pathology with chronic wounds.

Hierarchical Cluster Analysis of Cytokeratins and Stem Cell Expression Profiles of Canine Cutaneous Epithelial Tumors

The diagnosis of cutaneous epithelial tumors (CETs) in dogs is based on predominant histological differentiation patterns. However, the expression of a broad panel of antigens has not been comprehensively examined with immunohistochemistry. The present study aims to establish a comprehensive expression profile and identify useful diagnostic markers for each CET type. Cytokeratin (CK), stem cell, and other associated markers were immunohistochemically examined in 110 canine CETs. Among these, CK16 was useful for differentiating between basal and squamous cell carcinomas. Acantholytic squamous cell carcinomas were positive for CK8, CK18, and CK19, suggesting their close association with the apocrine duct. Unlike their benign counterparts, sebaceous carcinomas coexpressed CK5/6 and adipophilin. Smooth muscle actin (SMA) and p63 immunostaining were useful for accurately distinguishing between glandular and ductal differentiation in apocrine tumors. A case of apocrine carcinoma and malignant myoepithelioma was identified using anti-SMA antibodies. Stem cell expression profiles (CK8, CK15, CK19, and CD34) of hair follicle tumors were discrete and indicative of their anatomic origins. The effectiveness of immunohistochemistry for tumor diagnosis was further confirmed by hierarchical cluster analysis, through which selected markers were able to sort CETs into specific groups: CK5/6, CK8, CK14, CK16, CK18, CK19, p63, adipophilin, and SMA sorted tumors of epidermal, apocrine, or sebaceous origin; while CK8, CK14, CK15, CK16, CK19, CD34, and p63 sorted hair follicle tumors in agreement with their histological differentiation. In conclusion, the present study provides comprehensive immunohistochemical information, which could complement histomorphological features for the future classification of canine CETs.

Challenges in the diagnosis of cutaneous adnexal tumours

The diagnosis of cutaneous adnexal neoplasms, a heterogeneous group of entities, is often perceived by practising pathologists as challenging. A systematic approach to diagnosis is necessary for classification of these lesions, which establishes the tumour differentiation (follicular, sebaceous, sweat gland or apocrine) and evaluates histological features differentiating between benign and malignant entities. Consideration of clinical history is a necessary adjunct in evaluation of the adnexal neoplasm, as characteristic anatomical sites are described for many adnexal lesions. In some instances, immunohistochemical studies may also be employed to aid the diagnosis. The differential diagnosis between primary cutaneous adnexal neoplasms and cutaneous metastases from visceral tumours may also be difficult. Clinical, radiological, histological and immunohistochemical characteristics will be further discussed, considering that the correct diagnosis has a significant impact on the patient's management and prognosis.

Molecular pathology of skin neoplasms of the head and neck

CONTEXT

Skin neoplasms include the most common malignancies affecting humans. Many show an ultraviolet (UV)-induced pathogenesis and often affect the head and neck region.

OBJECTIVE

To review literature on cutaneous neoplasms that show a predilection for the head and neck region and that are associated with molecular alterations.

DATA SOURCES

Literature review.

CONCLUSIONS

Common nonmelanoma skin cancers, such as basal and squamous cell carcinomas, show a UV-induced pathogenesis. Basal cell carcinomas are characterized by molecular alterations of the Hedgehog pathway, affecting patched and smoothened genes. While squamous cell carcinomas show UV-induced mutations in several genes, driver mutations are only beginning to be identified. In addition, certain adnexal neoplasms also predominantly affect the head and neck region and show interesting, recently discovered molecular abnormalities, or are associated with hereditary conditions whose molecular genetic pathogenesis is well understood. Furthermore, recent advances have led to an increased understanding of the molecular pathogenesis of melanoma. Certain melanoma subtypes, such as lentigo maligna melanoma and desmoplastic melanoma, which are more often seen on the chronically sun-damaged skin of the head and neck, show differences in their molecular signature when compared to the other more common subtypes, such as superficial spreading melanoma, which are more prone to occur at sites with acute intermittent sun damage. In summary, molecular alterations in cutaneous neoplasms of the head and neck are often related to UV exposure. Their molecular footprint often reflects the histologic tumor type, and familiarity with these changes will be increasingly necessary for diagnostic and therapeutic considerations.

Neighboring look-a-likes: distinguishing between breast and dermatologic lesions

Due to the proximity of the skin, subcutis, and axilla to the breast, the possibility of a "breast mass" actually representing a dermatologic lesion should be considered, particularly if the proliferation does not look characteristically "mammary" in appearance. Even more underappreciated is the scenario of a dermatologic proliferation morphologically masquerading as a breast tumor. The pathologist can fall prey to this pitfall if he/she is led to believe that the location of the tumor is the breast proper. The aim of this review is to provide an overview of dermatologic mimickers of breast lesions and helpful ways to discern between them when possible.

Preorbital carcinoma in two Kirk's dik-diks (Madoqua kirkii)

Two Kirk's dik-diks suffered from chronic, unilateral, therapy-resistant enlargement of the preorbital gland. Computed tomographic imaging revealed a homogenous preorbital mass destroying the adjacent maxillary bone in one animal. Squamous cell carcinoma was diagnosed microscopically in both cases. Immunohistochemically, the neoplastic cells uniformly expressed cytokeratin (CK) 5/6 and CK14. Additionally, tumour cells were strongly labelled for p53 suggesting a possible role of this tumour suppressor gene in tumorigenesis. Chronic obstruction of the preorbital gland due to excessive accumulation of secretory products is considered as a likely cause of glandular and periglandular inflammation with subsequent malignant transformation.

Antigen expression of human eccrine sweat glands

BACKGROUND

The proliferating abilities of sweat glands are very limited, so researches on the repair and regeneration of sweat glands are important. First of all, we must find out reliable and specific antigen markers of sweat glands.

OBJECTIVE

To investigate the antigen expression of human eccrine sweat glands.

METHODS

The development of eccrine sweat glands was investigated by hematoxylin and eosin staining, and the antigen expression was detected by immunohistochemical techniques.

RESULTS

Human eccrine sweat glands expressed cytokeratin (CK) 7, CK8, CK14, CK18, CK19 and epithelial membrane antigen (EMA). Carcinoembryonic antigen (CEA) was only expressed in sweat glands in the adult skin. Developing and developed sweat glands all had some cells expressing Ki67 and p63 antigens. Epidermal growth factor (EGF) was mainly localized in the secretory cells and ductal cells. Some myoepithelial cells were also labeled with anti-EGF antibody. In the older fetus, positive staining for EGF was seen in the lumen of the secretory portion. EGF receptor (EGFR) was expressed in the ducts.

CONCLUSIONS

Human eccrine sweat glands express CK7, CK8, CK14, CK18, CK19, CEA, EMA, Ki67, p63, EGF and EGFR. In skin, CEA can be used as a specific immunological marker of sweat glands.

New concepts on the histogenesis of eccrine neoplasia from keratin expression in the normal eccrine gland, syringoma and poroma

BACKGROUND

Peripheral and luminal layers of eccrine sweat gland ducts are self-renewing structures. Proliferation is restricted to the lowermost luminal layer, but randomly scattered in the peripheral layer. Each layer exhibits differential expression of keratins K5/K14 and K6/K16. Keratin K1 occurs only in peripheral cells and the novel keratin K77 is specific for luminal cells.

OBJECTIVES

To investigate the expression of luminal (K77), peripheral (K1) and further discriminatory keratins in two eccrine sweat gland tumours: syringoma, thought to show differentiation towards luminal cells of intraepidermal sweat ducts and eccrine poroma, considered to arise from poroid cells, i.e. peripheral duct cells; and keratinocytes of the lower acrosyringium/sweat duct ridge differentiating towards cells of intradermal/intraepidermal duct segments.

METHODS

Paraffin-embedded sections were examined by immunohistochemistry using several keratin, smooth muscle actin and Ki-67 antibodies.

RESULTS

We confirmed the ductal nature of syringomas. Despite drastic morphological alterations in both layers, their keratin patterns remained almost undisturbed compared with normal ducts. In eccrine poroma epidermal keratins K5/K14 were ubiquitously expressed in all poroid cells. Cell islands deviating morphologically from poroid cells contained epidermal keratins K1/K10. K77 expression was limited to luminal cells of intact duct structures within the tumours.

CONCLUSIONS

Syringomas are benign tumours of luminal cells of the lowermost intraglandular sweat duct. Poroid precursor cells of poromas do not comprise peripheral duct cells nor do poromas differentiate towards peripheral or luminal duct cells. Instead, poroid cells consist only of keratinocytes of the lowermost acrosyringium and the sweat duct ridge and poromas tend to differentiate towards the cells of the upper acrosyringium.

The human keratins: biology and pathology

The keratins are the typical intermediate filament proteins of epithelia, showing an outstanding degree of molecular diversity. Heteropolymeric filaments are formed by pairing of type I and type II molecules. In humans 54 functional keratin genes exist. They are expressed in highly specific patterns related to the epithelial type and stage of cellular differentiation. About half of all keratins—including numerous keratins characterized only recently—are restricted to the various compartments of hair follicles. As part of the epithelial cytoskeleton, keratins are important for the mechanical stability and integrity of epithelial cells and tissues. Moreover, some keratins also have regulatory functions and are involved in intracellular signaling pathways, e.g. protection from stress, wound healing, and apoptosis. Applying the new consensus nomenclature, this article summarizes, for all human keratins, their cell type and tissue distribution and their functional significance in relation to transgenic mouse models and human hereditary keratin diseases. Furthermore, since keratins also exhibit characteristic expression patterns in human tumors, several of them (notably K5, K7, K8/K18, K19, and K20) have great importance in immunohistochemical tumor diagnosis of carcinomas, in particular of unclear metastases and in precise classification and subtyping. Future research might open further fields of clinical application for this remarkable protein family.

Prostate-specific antigen-positive extramammary Paget's disease--association with prostate cancer

Extramammary Paget's disease (EMPD) is a rare intraepidermal adenocarcinoma that primarily affects the anogenital region. Cases of EMPD reacting with PSA (prostate-specific antigen) have previously been associated with underlying prostate cancer. However, a recent case of EMPD in our department has led us to question the value of PSA as an indicator of underlying prostate cancer. Clinical and pathological data were obtained for 16 cases of EMPD. Formalin-fixed, paraffin-embedded tissue blocks from the primary skin lesions were investigated using PSA and other immunohistochemical markers. 5 of the 16 cases of EMPD stained positive for PSA (2 women and 3 men). However, no reactivity was seen for the prostatic marker P501S. Three of the five patients had been diagnosed with internal malignant disease-two with prostate cancer, stage 1. Immunohistochemical investigations of the tumour specimens from the prostate revealed an immunoprofile which was very different from that of the primary skin lesion. In our study, no cases of EMPD with PSA positivity seem to represent an extension of an underlying prostatic adenocarcinoma. PSA positivity can be seen in cases of EMPD without associated adenocarcinoma of the prostate.

Cylindroma of the Prostate

A sporadic prostate tumor morphologically and immunophenotypically identical to dermal cylindroma is reported for the first time. The patient was a 78-year-old man with normal prostate-specific antigen serum level. Histologically, basaloid epithelial islands with broad rims of basement membrane material and strong immunoreactivity for alpha-smooth muscle actin in peripherally sited cells were the most distinguishing features. The only obvious difference from typical dermal cylindroma was a lack of intratumoral Langerhans cells in the prostate neoplasm. Differentiation from all hitherto known variants of basal cell proliferative lesions of the prostate was straightforward. However, focal cylindromalike features have been reported in rare cases of otherwise typical basaloid proliferations of the prostate.

Facial Apocrine Fibroadenoma in Man: A Rare Finding

Apocrine fibroadenoma (AFA), considered a counterpart of fibroadenoma of breast, is a rare cutaneous apocrine neoplasm occurring almost exclusively in women. We describe a 75-year-old man who presented with a red dome-shaped papule near the nasal bridge. The tumor was composed of numerous tubular, cystic, and partially branching lumina and struts of epithelial cells oriented perpendicular to the skin surface, with which it connected through infundibula. The epithelial strands were embedded in fibrocollagenous stroma. These histopathological features are consistent with AFA. The cytokeratin profiles of our case were similar to those of apocrine or eccrine neoplasms. Progesterone and estrogen receptors (PR/ER) were not expressed. The stroma cells were stained strongly positive for vimentin, but nonreactive for alpha-smooth muscle actin, S-100 protein, or glial fibrillary acidic protein. To the best of our knowledge, this is the first report of facial AFA in man. Different from a more common anogenital AFA, this neoplasm might represent a second type of AFA with unique histopathologic and immunopathological features.

Siringomas periorbitários - excisão com tesoura de castroviejo: experiência em 38 pacientes e revisão da literatura

FUNDAMENTO: Siringoma é tumor anexial benigno do ducto sudoríparo écrino cujo tratamento é realizado por diversas modalidades cirúrgicas com resultados variáveis. OBJETIVO: 1. Relatar a experiência no tratamento cirúrgico de siringomas periorbitários mediante excisão com a tesoura oftalmológica de Castroviejo, seguida pela cicatrização por segunda intenção. 2. Apresentar revisão da literatura com enfoque no aspecto terapêutico. MATERIAL E MÉTODOS: Em 68 meses foram tratados 38 pacientes com siringomas periorbitários. Realizada a exérese cirúrgica com tesoura oftalmológica de Castroviejo seguida pela cicatrização por segunda intenção. Realizadas avaliações sete, 30 e 90 dias após a cirurgia. O seguimento variou entre três e 62 meses, com média de 33 meses. RESULTADOS: Dos 38 pacientes tratados, 63,1% tiveram resultado ótimo, 31,6% bom e 5,3% regular. A única complicação imediata observada foi edema, e as tardias foram: hipocromia (12 casos), cicatriz deprimida (um caso) e hipertrófica (um caso). Não ocorreram recidivas no período observado. CONCLUSÕES: O tratamento dos siringomas periorbitários mediante exérese cirúrgica com tesoura oftalmológica de Castroviejo, seguida pela cicatrização por segunda intenção, constitui procedimento ambulatorial de baixo custo e fácil execução. Proporciona resultados satisfatórios, sem recidivas, apesar da possibilidade de ocorrer hipocromia transitória.

Expression of cytokeratin subtypes in intraepidermal malignancies: a guide for differentiation

BACKGROUND

Among intraepidermal malignancies of epithelial origin, Bowen's disease, bowenoid actinic keratosis (BAK), intraepidermal malignant eccrine poroma (MEP), and Paget's disease may pose diagnostic difficulties.

METHODS

Histologic features and immunohistochemical profiles of 24 cases of Bowen's disease, 21 cases of BAK, 18 cases of intraepidermal MEP, and 11 cases of Paget's disease were analyzed.

RESULTS

Using multivariate logistic regression test, multinuclear giant cells and solar degeneration were found to be the only histologic parameters of diagnostic help. On the other hand, a widespread positive reaction for CK 5/8, CK 7, CK 19, and negative reaction for CK 10, was a helpful feature in the differentiation of Paget's disease from Bowen's disease and BAK. The widespread and strong expression of CK 10 was seen in almost all cases of Bowen's disease in contrast to BAK. The widespread expression of CK 5/8 and CK 7, and negative reaction for CK 10, was in favor of Paget's disease, compared to intraepidermal MEP. On the other hand, widespread expression of CK 19 was a common finding in intraepidermal MEP, in contrast to Bowen's disease.

CONCLUSION

An immunohistochemical panel may provide significant hints on the differentiation of common intraepidermal malignancies, especially in problematic cases.

K25 (K25irs1), K26 (K25irs2), K27 (K25irs3), and K28 (K25irs4) represent the type I inner root sheath keratins of the human hair follicle

The recent elucidation of the human type I keratin gene domain allowed the completion of the so far only partially characterized subcluster of type I keratin genes, KRT25-KRT28 (formerly KRT25A-KRT25D), representing the counterparts of the type II inner root sheath (IRS) keratin genes, KRT71-KRT74 (encoding proteins K71-K74, formerly K6irs1-K6irs4). Here, we describe the expression patterns of the type I IRS keratin proteins K25-K28 (formerly K25irs1-K25irs4) and their mRNAs. We found that K25 (K25irs1), K27 (K25irs3), and K28 (K25irs4) occur in the Henle layer, the Huxley layer, and in the IRS cuticle. Their expression extends from the bulb region up to the points of terminal differentiation of the three layers. In contrast, K26 (K25irs2) is restricted to the upper IRS cuticle. Apart from the three IRS layers, K25 (K25irs1), K27 (K25irs3), and K28 (K25irs4) are also present in the hair medulla. Based on previous, although controversial claims of the occurrence in the IRS of various "classical" epithelial keratins, we undertook a systematic study using antibodies against the presently described human epithelial and hair keratins and show that the type I keratins K25-K28 (K25irs1-K25irs4) and the type II keratins K71-K74 (K6irs1-K6irs4) represent the IRS keratins of the human hair follicle.

Characterization of a novel human type II epithelial keratin K1b, specifically expressed in eccrine sweat glands

In this study, we show that a novel human type II epithelial keratin, K1b, is exclusively expressed in luminal duct cells of eccrine sweat glands. Taking this luminal K1b expression as a reference, we have used antibodies against a plethora of epithelial keratins to systematically investigate their expression in the secretory globule and the two-layered sweat duct, which was divided into the intraglandular, intradermal, and intraepidermal (acrosyringium) segments, the latter being further subdivided into the sweat duct ridge and upper intraepidermal duct. We show that (i) each of the eccrine sweat gland tissue compartments expresses their own keratin patterns, (ii) the peripheral and luminal duct layers exhibit a sequential keratin expression, with both representing self-renewing cell layers, (iii) the intradermal duct and the sweat duct ridge display hitherto unknown length variations, and (iv) out of all cell layers, the luminal cell layer is the most robust layer and expresses the highest number of keratins, these being concentrated at the apical side of the cells to form the cuticle. We provide evidence that the cellular and intercellular properties of the peripheral and the luminal layers reflect adaptations to different functions.

Clinicopathologic features of epidermal cysts of the sole: comparison with traditional epidermal cysts and trichilemmal cysts

BACKGROUND

It has been described that the etiology of epidermal cysts on acral skin is different from that on non-acral skin; however, no papers have been published regarding the detailed histological differences between acral and non-acral epidermal cysts. In this study, we compared the clinicopathologic findings of epidermal cysts of the sole with those of traditional epidermal cysts and trichilemmal cysts.

METHODS

The cases studied were 12 epidermal cysts of the sole, 35 traditional (non-acral) epidermal cysts, and 12 trichilemmal cysts. The age and sex of the patients and the site, size, and microscopic findings of the lesions were evaluated. The pattern of keratinization was specifically focused on the evaluation of microscopic findings.

RESULTS

Microscopically, most of the epidermal cysts of the sole showed the presence of parakeratosis and focal lack of a granular layer at least at the upper portion of the cyst wall. The cyst content of the epidermal cysts of the sole was predominantly compact orthokeratotic material. These pathological findings could be explained by the pathogenesis of epidermal cysts of the sole, namely invagination of the surface epidermis.

CONCLUSION

Our study indicates that most cases of the epidermal cyst of the sole are considered to be a true traumatic epidermal inclusion cyst.

Human Merkel cells – aspects of cell biology, distribution and functions

Human Merkel cells were first described by Friedrich S. Merkel in 1875 and named "Tastzellen" (touch cells) assuming a sensory touch function within the skin. Only ultrastructural research revealed their characteristics such as dense-core granules, plasma membrane spines and dendrites as well as a loosely arranged cytoskeleton. Biochemical analysis identified the expression of very specific cytokeratins (most notably CK 20) allowing the immunohistochemical detection of Merkel cells. In humans, they occur within the basal epidermis, being concentrated in eccrine glandular ridges of glabrous skin and in Haarscheiben of hairy skin, within belt-like clusters of hair follicles, and in certain mucosal tissues. Within the human skin, the dense-core granules contain heterogeneously distributed neuropeptides, some of which might work as neurotransmitters through which Merkel cells and their associated nerves exert their classical function as slowly adapting mechanoreceptors type I. This is the case in the Haarscheiben, small sensory organs containing keratinocytes with a special program of differentiation that includes the expression of CK 17 and Ber-EP4. Other peptides may act as growth factors and thus might participate in growth, differentiation and homeostasis of cutaneous structures. It is not yet clear whether the Merkel cell carcinomas, aggressive skin carcinomas, indeed arise from Merkel cells. We summarize and discuss data on the distribution, function and heterogeneity of human Merkel cells in normal and diseased skin.

Cytokeratin 5/6 Immunostaining in Cutaneous Adnexal Neoplasms and Metastatic Adenocarcinoma

The differentiation of primary cutaneous adnexal neoplasms (CANs) from dermal-based metastatic lesions can be difficult. Cytokeratin 5/6 (CK 5/6) has a relatively limited expression profile, being relatively specific for mesothelium and other "pavement" type epithelium such as squamous epithelium. To date, the degree and distribution of CK 5/6 expression in cutaneous neoplasms has not been extensively studied. We speculate that since most of CANs arise from similar epithelium, they should express CK 5/6 and, therefore, CK 5/6 could potentially be helpful in distinguishing these lesions from most of metastatic neoplasms, which usually do not express this marker. Formalin-fixed, paraffin-embedded tissue sections from 228 previously classified CANs and 27 metastatic adenocarcinomas (17 breast, 4 colon, 2 prostate, 2 ovary, 1 lung, and 1 esophagus) were immunostained with anti-CK 5/6. Anti-CK 5/6 labeled 2 of 2 proliferating trichilemmal tumors, 6 of 6 poromas, 4 of 5 hydrocystomas, 10 of 10 cylindromas, 10 of 10 eccrine acrospiromas, 8 of 10 pilomatricoma, 10 of 10 nevus sebaceus, 9 of 9 desmoplastic trichoepitheliomas, 7 of 7 nevus sebaceus with basal cell carcinomas, 10 of 10 pilar cysts, 14 of 14 trichilemmomas, 10 of 10 syringomas, 6 of 7 chondroid syringomas, 10 of 10 hidradenoma papilliferum, 9 of 9 sebaceus adenomas, 3 of 3 microcystic adnexal carcinomas, 10 of 10 eccrine spiradenomas, 4 of 4 syringocystadenoma papilliferum, 3 of 5 ocular sebaceous carcinomas, 28 of 28 basal cell carcinomas, 16 of 16 trichoepitheliomas, and 33 of 33 trichoepitheliomas with basal cell features. By contrast, 9 of 27 metastatic adenocarcinomas stained positively, although only two of these stained strongly. Cumulatively, CK 5/6 was expressed by most (97%) of CANs, while only 33% of metastatic adenocarcinomas showed positive expression. The sensitivity of this marker in the malignant lesions (other than basal cell carcinoma) is 78%, while the specificity is 67%. If all lesions are considered, the sensitivity increases to 97%. Therefore, CK 5/6 may prove to be a useful adjunct marker in distinguishing CANs from metastatic lesions.

Ectopic Hamartomatous Thymoma

This report describes the clinicopathologic and immunohistochemical findings in 21 cases of a highly distinctive tumor with a strong predilection for the lower neck region of adult males. Our study group consisted of 20 males and one female. The patients were 28 to 79 years old (mean age, 47 years; median age, 40 years), and they presented with solitary, lobular or multilobular masses ranging in size from 2.0 to 19.0 cm in greatest dimension (mean size, 5.1 cm; median, 4 cm). The tumors principally involved the lower neck region, usually in close proximity to the sternoclavicular joint. The preoperative duration of the lesions ranged from 2 months to 30 years. Histologically, the tumors were typically well marginated and composed of plump spindled cells, delicate spindled cells, mature adipose tissue, and epithelial cells, including both squamous and glandular elements. Epithelial-lined cysts were a focal finding in most cases and measured up to 2 cm in greatest dimension. Mitotic counts for the tumors ranged from 0 to 7 mitotic figures per 50 high power fields (mean mitotic count, 1.1 mitotic figures per 50 HPFs). Our immunohistochemical analysis revealed a complex immunophenotype with a diverse keratin profile. The plump spindled cells had a myoepithelial phenotype, as evidenced by the coexpression of keratins (5, 5/6, and 14), alpha-smooth muscle actin, CD10, and to a lesser extent, calponin. No compelling evidence for thymic differentiation was observed. The patients were initially managed by biopsy or partial resection (n = 4), simple local excision (n = 16), or an unspecified procedure (n = 1). Clinical follow-up of > or =3 years was available for 10 patients (48%). Two patients had recurrent disease, but there were no metastases or tumor-related deaths. A derivation from sequestered branchial epithelium is likely, but evidence for a thymic component is tenuous, at best. Our data support reclassification of this distinctive process as a branchial anlage mixed tumor. The differential diagnosis includes conventional mixed tumors of skin adnexal or salivary gland origin, synovial sarcoma, a peripheral nerve sheath tumor variant, and cystic teratoma.

Milium-like syringoma: a case study on histogenesis

BACKGROUND

Milium-like syringoma is a variant of syringoma first described in 1987. Only few cases have been reported in the literature. It may be misleading clinically, and its histogenesis has not been clarified.

CASE REPORT

We present a case of periorbital milium-like syringoma, with studies on the histopathologic, histochemical, and immunohistochemical features.

RESULTS

Histology showed a large keratin-filled cyst in the upper portion of the lesion approximating the epidermis. Serial sections revealed that the cyst connected with the underlying syringomatous epithelial strands. Melanin was absent in the wall of the cyst, as demonstrated by Fontana-Masson stain. Cytokeratin 7 was expressed neither in the milia nor in the solid epithelial parts. Carcinoembryonic antigen (CEA) reactivity was seen in the luminal cells of the keratinous cysts. However, in the largest keratin-filled cyst clinically suggesting a milium, only the lower half of the cyst was positive for CEA. These results proved that the milia were part of syringoma with eccrine duct differentiation. Fusion of the upper half of the largest cyst with the epidermis may explain the absence of CEA positivity in this part, analogous with eccrine duct milia. Review of the literature indicated that this variant of syringoma occurs more often in Asians.

CONCLUSION

We present evidence, and propose the histogenesis of milium-like syringoma, that it is a variant of syringoma with a prominent cystic component showing features of eccrine duct milia. Recognition of its nature is of therapeutic significance. Further studies are required to verify its clinical characteristics as compared with ordinary syringomas.

Keratinocytes can differentiate into eccrine sweat ducts in vitro: involvement of epidermal growth factor and fetal bovine serum

BACKGROUND

in addition to formation of an epidermal sheet and dermal substitution, reconstruction of skin that possesses functionality is an important goal for dermatologists.

OBJECTIVE

we attempted to regenerate eccrine sweat glands in vitro.

METHODS

we constructed skin equivalent models with various combination of normal human keratinocytes and fibroblasts and also examined the effect of various growth factors.

RESULTS

we found that keratinocytes invaded the collagen gels and formed eccrine duct-like structures, only when (i) the culture media contained at least 15 ng/ml of epidermal growth factor (EGF) and fetal bovine serum (FBS), (ii) the keratinocytes were derived from young donors, and (iii) fibroblasts were present in the gel. Interestingly, when cultured under the same conditions eccrine gland duct cells were unable to invade the gel. Immunohistochemical analyses revealed induction of carcinoembryonic antigen by EGF at the inner part of the eccrine duct-like structures. Proliferating cell nuclear antigen was expressed mainly in basal layers of the epithelia but was not observed in the deeply invaded part. Cytokeratin profiles of the reconstructed epithelia were consistent with those of the regenerating epidermis and partly with the eccrine sweat duct.

CONCLUSIONS

although not perfect model, these results indicate that 'young' keratinocytes could differentiate into/toward eccrine sweat ducts in vitro in the presence of EGF and FBS in cooperation with dermal fibroblasts.

Vulvar Paget Disease: One Century After First Reported

OBJECTIVES.: To provide a critical assessment of the published literature on vulvar Paget disease and to allow individualized approaches to affected patients. MATERIALS AND METHODS.: A computerized search for studies published in the literature up to June 2002 was carried out using Ovid(c) and Medline databases. We excluded single case reports, letters to editors, and abstracts. RESULTS.: Historical and epidemiological aspects of vulvar Paget disease are summarized. Clinical and histopathological data support a recent proposal to classify vulvar Paget disease into two categories, primary and secondary, with significant clinical and prognostic implications. The treatment for primary vulvar Paget disease is wide and deep surgical excision. Inguinofemoral lymphadenectomy is added in the management of invasive neoplasms. In the presence of secondary Paget disease, therapy must be directed toward treatment of associated carcinoma. CONCLUSIONS.: The subclassification of vulvar Paget disease is essential for correct clinical management and treatment. Immunohistochemistry may assist in this important distinction.

An immunohistochemical and ultrastructural study of syringocystadenoma papilliferum

BACKGROUND

Syringocystadenoma papilliferum is a benign hamartomatous tumour of the skin. The histogenesis of this tumour is still controversial. There have been few reports regarding immunohistochemical investigations using only a limited range of antibodies and ultrastructural studies on this rare tumour.

OBJECTIVES

To elucidate the immunohistochemical and ultrastructural properties of this tumour.

METHODS

We investigated the immunohistological patterns of 12 different anticytokeratin (CK) antibodies and several other markers in five cases of this tumour, comparing them with the patterns in adult sweat glands. One of these cases was also evaluated ultrastructurally.

RESULTS

The luminal columnar cells of the tumour were mostly positive for CK7 and more than 70% were positive for CK19. These cells showed the heterogeneous expression of CK1/5/10/14, CK14 and CK5/8. These patterns were also observed in the luminal cells in the secretory or the ductal portion of the adult sweat glands. The basal cuboidal cells of the tumour almost constantly expressed CK1/5/10/14, CK5/8, CK14 and CK7 (except for one case), similar to the patterns of basal cells in the transitional portion and myoepithelial cells in the sweat glands. However, the basal tumour cells expressed CK19 and vimentin heterogeneously, and alpha-smooth muscle actin focally (three cases). Ultrastructurally, the constituent epithelial cells were mainly divided into three types: luminal cells, basal cells and clear cells. The luminal tumour cells bore features of the secretory or ductal luminal cells of sweat glands, although they were somewhat immature in appearance. The basal tumour cells were fundamentally basaloid in nature. The clear cells were undifferentiated or primitive in appearance, suggesting stem or progenitor cell properties. Transitional forms between the clear cells and the other two cell types were also identified.

CONCLUSIONS

The tumour epithelium was composed of several cell types demonstrating various developmental stages from the primitive clear cells to the basal cells demonstrating a tendency to differentiate toward basal cells in the apocrine transitional portion or myoepithelial lineage, or luminal cells toward the ductal or secretory epithelium. These results support the classical concept that syringocystadenoma papilliferum is a hamartomatous tumour that arises from pluripotent cells.