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

External auditory canal sebaceous carcinoma

The incidence of sebaceous carcinoma (SC) in the outer one-third of the external auditory canal is considered extremely rare, and only eight case reports have been published. We present a case of a male patient in his late 70s known case of hypertension on indapamide. His medical history included a postspinal tumour that had been treated with surgery and radiation more than 40 years ago and current complaints of right ear pain and purulent discharge. A right ear soft granular tissue mass was found. Complete debulking of the right ear mass was done in conjunction with middle ear exploration, moderately differentiated SC diagnosis was made based on the histopathological analysis. The patient was free of recurrence but then died of an unrelated pulmonary infection. SC should be suspected in elderly patients who present with long-term complaints of a mass with or without otalgia, and these patients should be examined for the presence of such tumours especially if they report a history of radiation. Additionally, more research is warranted to investigate the association of diuretics with SC.

Cytokeratin 6 identifies basal-like subtypes of pancreatic ductal adenocarcinoma with decreased survival

PURPOSE

Rising incidence of pancreatic ductal adenocarcinoma (PDAC) bind with insufficient therapy options showcases a great medical challenge. Further biomarkers are required to identify patients, who will benefit from more aggressive therapy.

METHODS

320 patients were included by the PANCALYZE study group. Cytokeratin 6 (CK6) immunohistochemical staining as a putative marker for the basal-like subtype of PDAC was performed. The correlation between CK6 expression patterns and survival data, as well as various markers of the (inflammatory) tumor microenvironment, were analyzed.

RESULTS

We divided the study population based on the expression pattern of CK6. Patients with a high CK6 tumor expression had a significantly shorter survival (p = 0.013), confirmed in a multivariate cox regression model. CK6-expression is an independent marker for a decreased overall survival (HR = 1.655, 95% CI 1.158-2.365, p = 0.006). In addition, the CK6-positive tumors showed significantly less plasma cell infiltration and more cancer-associated fibroblasts (CAFs) expressing Periostin and SMA.

CONCLUSIONS

CK6 could be considered as an independent biomarker for a shorter overall survival. CK6 is a clinically easily accessible biomarker for the identification of the basal-like subtype of PDAC. Therefore, it could be taken into consideration in deciding for the more aggressive therapy regimes. Prospectively, studies addressing the chemosensitive characteristics of this subtype are required.

Pagetoid Spread in Basal Cell Carcinoma: Potential for Misdiagnosis

ABSTRACT

Basal cell carcinomas are one of the most common cutaneous carcinomas and show classical histologic features of basaloid nests with peripheral palisading. Pagetoid and intraepidermal spread has not been described in basal cell carcinoma to the best of our knowledge. We report 5 cases of basal cell carcinoma with classic histologic patterns and overlying basaloid nests and single intraepidermal tumor cells. A panel of immunostains were performed that included CK7, MOC31, CEA-m, EMA, androgen receptor, and Bcl2. Most of our cases were positive for both MOC31 and CK7, and all cases were negative for CEA-m and EMA excluding extramammary Paget disease, one of the most common differential diagnoses. These cases expand the spectrum of findings that can be seen in basal cell carcinoma and can help prevent misdiagnoses of basal cell carcinomas as more aggressive tumors.

Double knock-in pig models with elements of binary Tet-On and phiC31 integrase systems for controllable and switchable gene expression

Inducible expression systems are indispensable for precise regulation and in-depth analysis of biological process. Binary Tet-On system has been widely employed to regulate transgenic expression by doxycycline. Previous pig models with tetracycline regulatory elements were generated through random integration. This process often resulted in uncertain expression and unpredictable phenotypes, thus hindering their applications. Here, by precise knock-in of binary Tet-On 3G elements into Rosa26 and Hipp11 locus, respectively, a double knock-in reporter pig model was generated. We characterized excellent properties of this system for controllable transgenic expression both in vitro and in vivo. Two attP sites were arranged to flank the tdTomato to switch reporter gene. Single or multiple gene replacement was efficiently and faithfully achieved in fetal fibroblasts and nuclear transfer embryos. To display the flexible application of this system, we generated a pig strain with Dox-inducing hKRAS^G12D expression through phiC31 integrase-mediated cassette exchange. After eight months of Dox administration, squamous cell carcinoma developed in the nose, mouth, and scrotum, which indicated this pig strain could serve as an ideal large animal model to study tumorigenesis. Overall, the established pig models with controllable and switchable transgene expression system will provide a facilitating platform for transgenic and biomedical research.

Evidence-Based Clinical Practice Guidelines for Microcystic Adnexal Carcinoma: Informed by a Systematic Review

IMPORTANCE

Microcystic adnexal carcinoma (MAC) occurs primarily in older adults of white race/ethnicity on sun-exposed skin of the head and neck. There are no formal guiding principles based on expert review of the evidence to assist clinicians in providing the highest-quality care for patients.

OBJECTIVE

To develop recommendations for the care of adults with MAC.

EVIDENCE REVIEW

A systematic review of the literature (1990 to June 2018) was performed using MEDLINE, Embase, Web of Science, and the Cochrane Library. The keywords searched were microcystic adnexal carcinoma, sclerosing sweat gland carcinoma, sclerosing sweat duct carcinoma, syringomatous carcinoma, malignant syringoma, sweat gland carcinoma with syringomatous features, locally aggressive adnexal carcinoma, and combined adnexal tumor. A multidisciplinary expert committee critically evaluated the literature to create recommendations for clinical practice. Statistical analysis was used to estimate optimal surgical margins.

FINDINGS

In total, 55 studies met our inclusion criteria. The mean age of 1968 patients across the studies was 61.8 years; 54.1% were women. Recommendations were generated for diagnosis, treatment, and follow-up of MAC. There are 5 key findings of the expert committee based on the available evidence: (1) A suspect skin lesion requires a deep biopsy that includes subcutis. (2) MAC confined to the skin is best treated by surgery that examines the surrounding and deep edges of the tissue removed (Mohs micrographic surgery or complete circumferential peripheral and deep margin assessment). (3) Radiotherapy can be considered as an adjuvant for MAC at high risk for recurrence, surgically unresectable tumors, or patients who cannot have surgery for medical reasons. (4) Patients should be seen by a physician familiar with MAC every 6 to 12 months for the first 5 years after treatment. Patient education on photoprotection, periodic skin self-examination, postoperative healing, and the possible normal changes in local sensation (eg, initial hyperalgesia) should be considered. (5) There is limited evidence to guide the treatment of metastasis in MAC due to its rarity. Limitations of our findings are that the medical literature on MAC comprises only retrospective reviews and descriptions of individual patients and there are no controlled studies to guide management.

CONCLUSIONS AND RELEVANCE

The presented clinical practice guidelines provide an outline for the diagnosis and management of MAC. Future efforts using multi-institutional registries may improve our understanding of the natural history of the disease in patients with lymph node or nerve involvement, the role of radiotherapy, and the treatment of metastatic MAC with drug therapy.

The Study for Diagnostic Value of β-Catenin Immunohistochemistry Marker in Distinction of Aggressive and Non-Aggressive Basal Cell Carcinoma

BACKGROUND & OBJECTIVE

Basal cell carcinoma (BCC) is a common skin cancer arising from the basal layer of the epidermis and its appendages. They are locally invasive, aggressive, and destructive of skin and the surrounding struc- tures. β-Catenin is a multifunctional protein located to the intracellular side of the cytoplasmic membrane coded by the CTNNB1 gene, which maps to chromosome 3p22.1. It has a critical role in cell-to-cell adhesion by linking cadherins to the actin cytoskeleton and has a central role in transcriptional regulation in the Wnt signaling pathway. We evaluated the diagnostic value of the Beta catenin immunohistochemistry marker in distinction of aggressive and non-aggressive Basal cell carcinoma.

METHODS

This cross sectional and descriptive-analytical study was done on archived formalin fixed, paraffin embed- ded tissue blocks in pathology library of Al-Zahra hospital in Isfahan city. We used immunochemistry to determinate the role of β-Catenin in aggressiveness in BCC with higher rate of relapse.

RESULTS

A total of 76 samples were evaluated in two groups (aggressive &none aggressive). The mean percentage of cytoplasmic β-Catenin staining in aggressive group was more significant than the other group (sensitivity: 86.8% specificity: 81.6%, PPV: 81.5% and NPV: 86.1%) and the mean percentage of membranous β-Catenin staining in non- aggressive group were significant more than the aggressive group. Intensity of membranous staining in both groups significant less than normal epithelium.

CONCLUSION

Cytoplasmic β-Catenin staining in aggressive BCC is more significant than non-aggressive subtypes, so this indicates that the use of β-Catenin IHC marker maybe helpful in the diagnosis of aggressive BCC.

Polymorphous Sweat Gland Carcinoma: An Immunohistochemical and Molecular Study

Polymorphous sweat gland carcinoma is an uncommon low-grade malignant adnexal tumor with a marked predilection for the distal extremities. Histologically, the lesions are characterized by a cellular proliferation showing a combination of growth patterns, including trabecular, solid, tubular, cribriform, or adenoid cystic and pseudopapillary. The immunohistochemical and molecular profile of these tumors has not yet been properly addressed. We have studied 3 cases of polymorphous sweat gland carcinoma using a broad panel of immunohistochemical markers including cytokeratin AE1/AE3, CK5/6, MOC31, p40, p63, p16, chromogranin, synaptophysin, CD56, MIB-1, estrogen receptor, progesterone receptor, androgen receptor, BER-EP4, smooth muscle actin, epithelial membrane antigen, carcinoembryonic antigen, CD117, S100 protein, HBME-1, DOG1, vimentin, and mammaglobin. We also examined for the MYB-NFIB fusion by fluorescent in situ hybridization (ISH) and for human papilloma virus by ISH. Our studies show that cytokeratin AE1/AE3, CK5/6, p40, p63, p16, chromogranin, and CD56 stains were positive in all 3 cases. All 3 cases were negative for MYB-NFIB fusion by fluorescent ISH which rules out adenoid cystic carcinoma. DNA ISH studies for high-risk human papilloma virus were negative in all cases. MIB-1 proliferation index was very high (30%-70% nuclear positivity), supporting a malignant phenotype. The positivity for chromogranin and CD56 suggests partial neuroendocrine differentiation. The differential diagnosis includes metastases from internal malignancies, basal cell carcinoma, and other benign and malignant adnexal neoplasms such as adenoid cystic carcinoma, ductal eccrine carcinoma, and microcystic carcinoma. Positivity for p16 in combination with chromogranin and CD56 may be potentially good markers for differentiating this tumor from other adnexal tumors.

Metastatic adnexal cancer in a man

Primary cutaneous adnexal neoplasms are mostly benign in nature; however, there have been reports of malignant adnexal tumors with distant metastasis to lymph nodes. Adnexal cutaneous malignancy with metastasis to the gastrointestinal tract has never been reported. Here, we present a rare case of a man with primary adnexal cutaneous adenocarcinoma who presented with symptomatic anemia secondary to occult gastrointestinal bleeding, found to be from gastrointestinal metastasis of the adnexal malignancy.

Topics in histopathology of sweat gland and sebaceous neoplasms

This article reviews several topics regarding sweat gland and sebaceous neoplasms. First, the clinicopathological characteristics of poroid neoplasms are summarized. It was recently reported that one-fourth of poroid neoplasms are composite tumors and one-fourth are apocrine type lesions. Recent progress in the immunohistochemical diagnosis of sweat gland neoplasms is also reviewed. CD117 can help to distinguish sweat gland or sebaceous tumors from other non-Merkel cell epithelial tumors of the skin. For immunohistochemical differential diagnosis between sweat gland carcinoma (SGC) other than primary cutanesous apocrine carcinoma and skin metastasis of breast carcinoma (SMBC), a panel of antibodies may be useful, including p63 (SGC⁺ , SMBC^- ), CK5/6 (SGC⁺ , SMBC^- ), podoplanin (SGC⁺ , SMBC^- ) and mammaglobin (SGC^- , SMBC⁺ ). Comparison of antibodies used for immunohistochemical diagnosis of sebaceous carcinoma (SC) suggests that adipophilin has the highest sensitivity and specificity. Some authors have found that immunostaining for survivin, androgen receptor and ZEB2/SIP1 has prognostic value for ocular SC, but not extraocular SC. In situ SC is rare, especially extraocular SC, but there have been several recent reports that actinic keratosis and Bowen's disease are the source of invasive SC. Finally, based on recent reports, classification of sebaceous neoplasms into three categories is proposed, which are sebaceoma (a benign neoplasm with well-defined architecture and no atypia), borderline sebaceous neoplasm (low-grade SC; an intermediate tumor with well-defined architecture and nuclear atypia) and SC (a malignant tumor with invasive growth and evident nuclear atypia).

Primary Cutaneous Mammary Analog Secretory Carcinoma With ETV6-NTRK3 Translocation

Mammary analog secretory carcinoma (MASC) is a recently described tumor of the salivary glands named for its morphological and molecular similarity to secretory carcinoma of the breast. Many primary carcinomas arising from the adnexal glands also share similar morphology to those arising from the breast. Brandt et al first described primary cutaneous MASC in 2009 and since then only 2 other cases have been reported. Herein, we describe a long-standing mass on the arm of an otherwise healthy 40-year-old female. Histologic examination revealed a circumscribed but unencapsulated, nodular tumor composed of bland epithelial cells arranged in solid and microcystic growth patterns. The cells showed vacuolated cytoplasm and round to oval nuclei with vesicular chromatin. Intraluminal homogenous eosinophilic secretions were present. Mitotic figures were not identified. The tumor cells stained positive for CK8/18, CK7, and S100 but were negative for other markers performed, including estrogen receptor, progesterone receptor, HER2/neu, paired box 8 (PAX8), and thyroid transcription factor 1 (TTF1). As the patient clinically had no other masses or known carcinomas, a diagnosis of primary cutaneous MASC was rendered. The ETV6-NTRK3 fusion transcript was subsequently detected by reverse transcriptase polymerase chain reaction amplification, further supporting the diagnosis. We present this case to review the histologic features of MASC and highlight the importance of recognizing this lesion not only as a possible cutaneous metastasis but also as a primary cutaneous tumor.

[Therapy of basal cell carcinoma]

Basal cell carcinoma (BCC) represents the most common malignant skin tumour in fair-skinned people. Despite low metastatic potential, BCC can cause decisive tissue destruction and disfigurement by invasive growth. In addition to clinical and histologic diagnosis modern imaging techniques as optical coherence tomography and confocal laser microscopy have been introduced. BCCs with aggressive growth pattern and/or increased risk of relapse are preferentially treated surgically. For superficial BCCs various topical treatments and photodynamic therapy are available. Inhibitors of the sonic hedgehog pathway have been approved for symptomatic treatment of metastatic BCC and locally advanced BCC inappropriate for surgery or radiotherapy. Detailed knowledge of the clinical spectrum of BCC and an appropriate choice of therapy are mandatory for the successful treatment of BCC.

[Basal cell carcinoma and rare form variants]

Basal cell carcinomas are the most common primary cutaneous malignant neoplasms. The diagnosis of basal cell carcinoma represents a common and routine task for pathologists and dermatopathologists. The aim of this review is the clinical and histopathological presentation of the most common subtypes of basal cell carcinoma. Furthermore, the rare variants of basal cell carcinoma and their differential diagnoses are also discussed.

Immunohistochemistry in dermatopathology

CONTEXT

Immunohistochemistry is not a diagnostic test but a highly valuable tool that requires interpretation within a context.

OBJECTIVE

To review the current status and limitations of immunohistochemistry in dermatopathology.

DATA SOURCES

English-language literature published between 1980 and 2014.

CONCLUSIONS

Although immunohistochemistry is rarely completely specific or sensitive, it is an important adjunctive technique in dermatopathology and can be helpful in a series of diagnostic dilemmas.

Diagnostic Immunohistochemistry in Cutaneous Neoplasia: An Update

Immunohistochemistry (IHC) is an important adjunct in the diagnosis of neoplastic skin diseases. In addition to the many established IHC markers currently in use, new markers continue to emerge, although their general acceptance and routine application requires robust validation. Here, we summarize the most well-established and commonly used biomarkers along with an array of newer ones reported in the past several decades that either demonstrate or hold high clinical promise in the field of cutaneous pathology. We also highlight recent applications of novel IHC markers in melanoma diagnosis including genetic mutation status markers [e.g. BRAF (v-raf murine sarcoma viral oncogene homolog B) and NRAS (neuroblastoma RAS viral oncogene homolog)] and an epigenetic alteration marker (e.g. 5-hydroxymethylcytosine). We specifically focus on the role of IHC in the differential diagnosis of cutaneous lesions that fall under the following categories: melanoma, epidermal tumors with an intraepidermal epitheliomatous pattern, spindle cell lesions of the dermis, small round blue cell tumors of the dermis, and cutaneous adnexal tumors. While IHC is a valuable tool in diagnostic dermatopathology, marker selection and interpretation must be highly informed by clinical context and the histologic differential diagnosis. With rapid progress in our understanding of the genetic and epigenetic mechanisms of tumorigenesis, new IHC markers will continue to emerge in the field of diagnostic dermatopathology.

Immunohistochemical distinction of primary sweat gland carcinoma and metastatic breast carcinoma: can it always be accomplished reliably?

OBJECTIVES

Even with adequate history, the distinction of cutaneous metastatic breast carcinoma from primary sweat gland carcinoma can be difficult. Although previous studies have attempted to separate these tumors with various immunohistochemical panels, those series have been limited by small numbers of patients as well as the inclusion of benign sweat gland tumors.

METHODS

In this analysis, stains for p63, CK5/6, and D2-40 were included, as well as GATA3 and mammaglobin, in an evaluation of 21 primary sweat gland carcinomas and 33 examples of cutaneous metastatic breast carcinoma.

RESULTS

Immunoreactivity for p63, CK5/6, D2-40, GATA3, and mammaglobin was respectively observed in 81%, 71%, 52%, 71%, and 5% of sweat gland carcinomas compared with 6%, 6%, 6%, 91%, and 45% of metastatic breast carcinomas. These differences were statistically significant for p63, CK5/6, and D2-40. For the diagnosis of metastatic breast carcinoma, GATA3 was the most sensitive marker (91%), but its sensitivity was substantially lower. Mammaglobin was 95% specific for breast carcinoma but again suffered from limited sensitivity (45%) in this context.

CONCLUSIONS

These data suggest that p63 and CK5/6 are specific determinants for sweat gland carcinoma in the stated setting. In the absence of those analytes, metastatic breast carcinoma cannot always be identified to the exclusion of a primary tumor. This diagnostic scenario continues to require the procurement of a detailed clinical history regarding the number and duration of skin lesions in any given case.

Cutaneous and mammary apocrine carcinomas have different immunoprofiles

Often the distinction of cutaneous apocrine carcinoma from metastatic mammary apocrine carcinoma to the skin can be a diagnostic dilemma because both tumors share similar histologic features and have overlapping immunohistochemical profile. We compared the expression of adipophilin, cytokeratin 5/6, p63, GATA3, mammaglobin, androgen receptor, estrogen receptor, progesterone receptor, and HER2 by immunohistochemistry in 14 cutaneous apocrine carcinomas (11 primary tumors, 3 metastases) and 26 primary apocrine carcinomas of the breast. Whereas focal adipophilin staining was seen in 36% (5/14) of cutaneous apocrine carcinoma, strong and diffuse adipophilin staining was seen in 88% (22/25) of mammary apocrine carcinoma (P = .0013). Differences in estrogen receptor and progesterone receptor expression were also statistically significant (P = .018 and .043). Androgen receptor was strongly positive in all cutaneous and mammary cases. Although there was no significant difference in the frequency of expression of cytokeratin 5/6, p63, HER2, GATA3, and mammaglobin in cutaneous apocrine carcinoma versus mammary apocrine carcinoma, strong and diffuse cytokeratin 5/6 and/or mammaglobin expression were seen only in cutaneous apocrine carcinoma. In conclusion, cutaneous apocrine carcinoma is likely adipophilin- ER+ PR+/- HER2- and can exhibit strong and diffuse cytokeratin 5/6 and/or mammaglobin expression. On the contrary, a mammary apocrine carcinoma is likely adipophilin+ ER- PR- and often exhibit 3+ HER2 with corresponding HER2 gene amplification. A panel of adipophilin, ER, PR, HER2, cytokeratin 5/6, and mammaglobin may be helpful in distinguishing cutaneous apocrine carcinoma from mammary apocrine carcinoma.

Eccrine carcinoma : a rare cutaneous neoplasm

Eccrine carcinoma is an extremely rare malignancy of the skin with few well documented cases reported in the literature. It is frequently found on the lower extremities, and it equally affects both sexes in the sixth and seventh decade.

In our case, we present a 46- year-old female with a recurring exophytic tumor on the right lower extremity, without local extension.

The initial tumor was biopsied, excised and diagnosed as an eccrine carcinoma.

Role of immunohistochemistry in diagnosing tumors of cutaneous appendages

In recent years, there has been significant progress in immunohistochemistry as an ancillary tool in diagnostic dermatopathology. In most instances, the histologic diagnosis can be rendered with the routine histologic sections; however, immunohistochemistry can help to narrow the differential in diagnosing neoplasms of cutaneous appendages in some settings including adnexal versus epidermal origin, benign versus malignant adnexal neoplasms, and primary adnexal carcinoma versus cutaneous metastases as outlined in this review.

An Immunohistochemical Panel to Differentiate Metastatic Breast Carcinoma to Skin From Primary Sweat Gland Carcinomas With a Review of the Literature

Context.—Approximately 25% of patients with breast cancer develop cutaneous metastases. Sweat gland carcinomas (SGCs) account for about 0.05% of all cutaneous neoplasms. Cutaneous metastases of breast carcinoma (CMBCs) (especially the ductal type) can be difficult to distinguish from SGCs. Treatment and prognoses for these 2 types of tumors differ radically, making accurate histologic diagnosis crucial. Although a few studies attempt to differentiate these entities employing immunohistochemical (IHC) studies (some of which we review here), to date, no panel of IHC stains exists, to our knowledge, to distinguish these entities.

Objective.—To devise a panel of IHC stains to distinguish CMBC from SGC.

Design.—Twelve cases of ductal CMBCs (11 not otherwise specified type, and 1 basal phenotype), 11 cases of SGCs (5 eccrine carcinomas, 3 porocarcinomas, and 3 microcystic adnexal carcinomas), 2 benign sweat gland neoplasm cases, and 2 primary breast cancer cases were retrieved and analyzed with the following IHC panel: mammaglobin, gross cystic disease fluid protein (GCDFP) 15, p63, basal cytokeratins (CK5, CK14, and CK17), androgen receptor, and PAX5.

Results.—The p63 was only weakly expressed in 1 of 12 CMBC cases (8.3%), whereas it was strongly expressed in 10 of 11 SGC cases (90.9%) (P < .001). Basal cytokeratins demonstrated a similar immunoprofile in the SGC group, with 10 of 11 cases (90.9%) expressing all 3 markers, and a variable immunoprofile in the CMBC group with 0% (CK14) (P < .001) to 16.7% (2 of 12 cases; CK5 and CK17) (P < .001) expression. Mammaglobin was expressed in 8 of 12 cases (66.7%) of CMBC.

Conclusions.—Together, these 5 IHC stains were combined to make a panel that was 100% sensitive and 91% specific in distinguishing between CMBC and SGC.

Malignant proliferating trichilemmal tumour presenting early in life: an uncommon feature

Malignant proliferating trichilemmal tumour is a rare cutaneous malignant neoplasm usually occurring in elderly women. We present a case of malignant trichilemmal tumour in a young lady of 26 years of age with a previous history of proliferating trichilemmal tumour at the same site.

Lesions of anogenital mammary-like glands: an update

Long considered to be ectopic breast tissue representing the caudal remnants of the milk ridges, anogenital mammary-like glands are nowadays thought to represent a normal constituent of the anogenital area. Lesions involving these glands, benign or malignant, epithelial or stromal manifest a striking similarity to their mammary counterparts. This review addresses the recent literature on lesions of anogenital mammary-like glands and our personal experience with various lesions related to these structures. Discussed are the normal anatomy and histology of these glands as well as the clinical presentation, histopathological and immunohistochemical features, molecular biological aspects, and differential diagnosis of various lesions involving anogenital mammary-like glands, including lactating adenoma, hidradenoma papilliferum, hidradenocarcinoma papilliferum, fibroadenomas, phyllodes tumor, pseudoangiomatous stromal hyperplasia, extramammary Paget disease, and other carcinomas. In addition, "nonspecific" epithelial or stromal changes some of which can be likened to similar changes occurring in a range of benign breast disease, including sclerosing adenosis, columnar cell lesions, ductal lesions and various metaplastic changes affecting epithelium and myoepithelium are discussed. Although lesions of anogenital mammary-like glands are often discussed in many dermatopathology textbooks in the context of cutaneous adnexal neoplasms we advocate that the best approach to the diagnosis of these lesions is to relate them to analogous well recognized lesions occurring in the breast, that is, through the eyes of a breast pathologist. This will enable their recognition, precise classification and should introduce greater uniformity in how they are reported in the literature so that more meaningful clinicopathological comparisons and correlations may be made.

Update on immunohistochemical methods relevant to dermatopathology

CONTEXT

Dermatopathology covers a large variety of entities, some having very similar histologic appearances. Immunohistochemistry is an incredibly helpful tool that is useful in diagnosis as well as prognosis of selected skin tumors.

OBJECTIVE

To provide a comprehensive review of recent trends and immunohistochemical stains used by dermatopathologists. Emphasis is placed on new stains as well as novel uses of existing stains.

DATA SOURCES

All data were gathered from published journal articles available through the National Center for Biotechnology Information PubMed database.

CONCLUSIONS

New immunohistochemical targets are continually being found, contributing to more accurate diagnosis and classification of skin tumors. The presence of specific markers can be used to determine the aggressiveness of malignancies and design treatment strategies. In addition, application of existing stains can help determine intravascular spread of malignancy in primary cutaneous lesions. And use of rapid immunohistochemical staining techniques on frozen sections can assist in more complete excision of tumor margins. Immunohistochemistry is a highly versatile and growing tool of dermatopathologists.

Review of the hair follicle origin hypothesis for basal cell carcinoma

BACKGROUND

Basal cell carcinoma (BCC) is the most common type of skin cancer treated by the dermatologic surgeon. The discovery that patients with the nevoid BCC syndrome had mutations in the human homologue of the Drosophila patched gene led to a rapid increase in our understanding of the pathogenesis of BCC. It is theorized that altered regulation at multiple steps in the patched signal transduction pathway may contribute to the development of BCC. This pathway also plays an essential role in embryonic hair follicle development and during the hair cycle. Taken together, a considerable body of evidence suggests that at least some BCC may be derived from deregulated patched signaling in hair follicle stem cells.

OBJECTIVE

To review evidence of a follicular derivation of BCC and to highlight emerging therapeutic strategies to block deregulated patched signaling in BCC.

CONCLUSION

Deregulation of the patched signal transduction pathway is present in the vast majority of human BCCs. Pharmacologic inhibitors of this pathway may offer a therapeutic strategy to block tumor growth. The author has indicated no significant interest with commercial supporters.

Skin adnexal neoplasms--part 2: an approach to tumours of cutaneous sweat glands

Tumours of cutaneous sweat glands are uncommon, with a wide histological spectrum, complex classification and many different terms often used to describe the same tumour. Furthermore, many eccrine/apocrine lesions coexist within hamartomas or within lesions with composite/mixed differentiation. In addition to the eccrine and apocrine glands, two other skin sweat glands have recently been described: the apoeccrine and the mammary-like glands of the anogenital area. In this review (the second of two articles on skin adnexal neoplasms), common as well as important benign and malignant lesions of cutaneous sweat glands are described, and a summary for differentiating primary adnexal neoplasms from metastatic carcinoma is outlined, striving to maintain a common and acceptable terminology in this complex subject. Composite/mixed adnexal tumours are also discussed briefly.

CD10 Expression in Cutaneous Adnexal Neoplasms and a Potential Role for Differentiating Cutaneous Metastatic Renal Cell Carcinoma

Context.—Recent investigations have demonstrated the utility of CD10 as a marker for renal cell carcinoma (RCC). Cutaneous metastases occur in up to 11% of patients with RCC and may be the presenting sign of widespread disease. The differential diagnosis in histopathologic evaluation of these cases includes cutaneous adnexal neoplasms, and describing the expression of CD10 in these tumors may be helpful in delineating the differential diagnosis.

Objective.—To determine CD10 expression in a variety of adnexal lesions and to determine the diagnostic utility of CD10 in an immunohistochemical panel differentiating metastatic cutaneous renal cell carcinoma from cutaneous adnexal neoplasms.

Design.—We studied 57 primary adnexal neoplasms of eccrine (n = 31), apocrine (n = 16), and sebaceous (n = 10) differentiation as well as normal skin (n = 3) and RCC metastatic to the skin (n = 4). A CD10 monoclonal antibody was applied to formalin-fixed, paraffin-embedded tissue. Specimens were randomized and categorized as immunopositive or immunonegative by a pathologist with expertise in immunohistochemistry who was blinded to the diagnoses.

Results.—Two (6.5%) of 31 eccrine, 1 (6%) of 16 apocrine, and 4 (40%) of 10 sebaceous neoplasms demonstrated CD10 immunopositivity. Four (100%) of 4 RCC were CD10 immunopositive. CD10 expression was significant for eccrine and apocrine neoplasms (P < .001) compared to metastatic RCC, but not for sebaceous neoplasms (P = .08).

Conclusion.—Based on these results, CD10 is a useful additional immunostain for the discrimination of RCC metastatic to the skin and cutaneous adnexal neoplasms with eccrine and apocrine differentiation, but not with sebaceous differentiation.

Basal cell carcinoma: biology, morphology and clinical implications

Basal cell carcinoma (BCC) is the most common malignant neoplasm of humans. Rising dramatically in incidence in North America, as likely reflects changing habits of the population and a move from more northerly climes to the sunbelt of the Southern and Southwestern United States, the incidence is surely to rise even higher in the future. The last decade has seen significant advances in our understanding of BCC biology and novel approaches to therapy, which hinge upon accurate diagnosis and subclassification by pathologists. The purpose of this review article is to summate the research advances in our understanding of BCC biology and to acquaint pathologists and clinicians to the practical issues in BCC diagnosis and subclassification which flow there from.

Malignant adnexal neoplasms

Malignant cutaneous adnexal neoplasms are one of the most challenging areas of dermatopathology. Tumors of the pilosebaceous apparatus can occur as single-lineage neoplasms or may manifest as complex proliferations with multilineal differentiation patterns including not only the germinative component of the hair bulb, the inner or outer root sheath epithelium and the sebaceous gland and duct, but also the sweat duct components that relate to the apocrine secretory apparatus which empties into the follicle near the follicular bulge. Eccrine and apocrine neoplasms present a bewildering array of morphologies, which often defy precise classification. The purpose of this review is to discuss in detail the malignant neoplasms of the cutaneous adnexae and their benign and prognostically indeterminate mimics.