Diagnostic utility of immunohistochemistry in distinguishing trichoepithelioma and basal cell carcinoma: evaluation using tissue microarray samples

Expression of Early Growth Response 3 in Skin Cancers

OBJECTIVE

To assess the expression of early growth response 3 (EGR3) in normal skin and different types of skin tumors: cutaneous squamous cell carcinoma (cSCC), basal cell carcinoma (BCC), melanoma (MM), and cutaneous adnexal tumors containing sebaceous carcinoma (SC), trichoepithelioma (TE) and clear cell hidradenoma (CCH).

BACKGROUND

EGR3, expressed in multiple organs, including skin, plays an important role in cell differentiation and tumor growth. Previous studies have shown that EGR3 suppresses tumor growth and is downregulated in various malignancies. However, its distribution in normal skin and its expression especially in skin tumors have not been studied.

MATERIALS AND METHODS

Samples of normal cases (n = 4), cSCC (n = 12), BCC (n = 12), MM (n = 12), SC (n = 4), TE (n = 4), and CCH (n = 4) were collected from patients treated in our department between 2018 and 2023. Immunohistochemistry was used to investigate the expression of EGR3. The results were analyzed with the description of the staining pattern and the histochemical score.

RESULTS

Immunohistochemical staining showed that EGR3 was uniquely expressed in normal skin in the granular layer and upper part of the stratum spinosum, as well as in sebaceous glands and hair follicles, but not in sweat glands. In skin cancers, BCC, SC, and TE showed positive EGR3 staining, whereas cSCC, MM, and CCH were negative.

CONCLUSIONS

EGR3 has a specific expression pattern in normal skin and in skin tumors, which is important for the differential diagnosis of skin tumors, in particular for cSCC and sebaceous gland carcinoma.

Gorlin-Like Phenotype in a Young Girl With a De Novo PTCH2 Variant Mutation of Uncertain Significance

ABSTRACT

Gorlin syndrome, also known as basal cell nevus syndrome, is an autosomal dominant genetic disorder that predisposes humans to tumors. In most cases, this syndrome results from inactivating mutations in the patched homologue 1 gene. Basal cell carcinomas are one of the main characteristics of this syndrome and serve as a major diagnostic criterion. Gorlin syndrome shows a variable phenotype, and recently, other less common mutations in the suppressor of fused homologue or patched homologue 2 genes have been documented in individuals with this syndrome. We present the case of a patient with early-onset basal cell carcinomas and a mild Gorlin syndrome phenotype, attributed to a de novo patched homologue 2 variant of uncertain significance, which has not been previously reported in the literature.

TRPS1: A Marker of Follicular Differentiation

The trichorhinophalangeal syndrome type 1 (TRPS1) immunohistochemical (IHC) stain has increased in use in recent years as a marker for breast carcinomas. The TRPS1 gene is involved in various tissues, including the growth and differentiation of hair follicles. This article seeks to evaluate the IHC expression of TRPS1 in cutaneous neoplasms with follicular differentiation, such as trichoblastoma (TB), trichoepithelioma (TE), and basal cell carcinoma (BCC). IHC studies were performed on 13 TBs, 15 TEs, and 15 BCCs with an antibody against TRPS1. The study found a variable staining expression of TRPS1 in the tumor nests of TB, TE, and BCC. BCCs were distinct in that none of the BCCs demonstrated intermediate or high positivity, while TBs and TEs showed intermediate-to-high positivity in 5/13 (38%) and 3/15 (20%) of cases, respectively. We observed a distinct staining pattern among the mesenchymal cells of TB and TE. We found that TRPS1 highlighted perifollicular mesenchymal cells adjacent to the nests of TB and TE tumor cells. This staining pattern was absent in BCCs, where only scattered stromal cells were positive for TRPS1. Papillary mesenchymal bodies were also highlighted by TRPS1 in TB and TE. TRPS1 stained various parts of the normal hair follicle, including the nuclei of cells in the germinal matrix, outer root sheaths, and hair papillae. TRPS1 may be a useful IHC marker for follicular differentiation.

Enemy in disguise: A case report of solitary trichoepithelioma initially diagnosed as BCC

INTRODUCTION

Solitary trichoepitheliomas (TE) are benign tumors that are strikingly similar to their malignant counterpart, basal cell carcinoma (BCC).

PRESENTATION OF CASE

An 83-year-old man presented with a 10-year history of a right lower lid skin mass initially diagnosed as BCC. Intraoperatively, an excisional biopsy was performed with primary reconstruction of the skin defect and the specimen was submitted for histopathology processing. Eventually, histopathology findings suggested the diagnosis of benign hair follicle tumor. The postoperative results were aesthetically pleasing and the integrity of the lower lid was preserved.

DISCUSSION

Despite being rare, benign solitary TE are frequently misdiagnosed as malignant BCC, and vice versa. Oculoplastic surgeons face considerable difficulty distinguishing the two pathologies due to their similar clinical and histological pictures. Hence, excisional biopsy should be considered whenever such discrepancy is confronted to avoid the possibility of recurrence or malignant transformation. Furthermore, immunohistochemical staining could increase the accuracy of diagnosis in such unequivocal findings.

CONCLUSION

Correlation of clinical, dermoscopic and histopathological findings are essential to establish an accurate diagnosis and select the appropriate management. In-depth understanding of eyelid reconstruction principles is mandatory to achieve desirable goals.

Immunohistochemical Evaluation of S100, Alpha-Smooth Muscle Actin, Podoplanin, Matrix Metalloproteinase 13, and Human Epidermal Growth Factor Receptor 2neu Markers in Basal Cell Carcinoma Variants

Background Variants of basal cell carcinoma (BCC) appear to behave biologically differently. Several histological patterns impact the concept of low-risk (indolent) and high-risk (aggressive) types in the head and neck. This study aims to assess the biological behavior of BCC variants by immunohistochemical expression of S100, alpha-smooth muscle actin (α-SMA), podoplanin, matrix metalloproteinase 13 (MMP-13), and human epidermal growth factor receptor 2 (HER2)neu biomarkers. Methodology A total of 65 paraffin-embedded tissue blocks of BCC of the head and neck were retrieved from the collections of the Histopathology Department of the Medical City Teaching Complex and the Ghazi Al-Harerri Hospital at the University of Baghdad's College of Dentistry, spanning the years 2015 through 2021. S100, α-SMA, podoplanin, MMP-13, and HER2neu biomarkers were used to perform immunohistochemical analysis (Abcam). Results This study noticed different expressions of S100, α-SMA, podoplanin, MMP-13, and HER2neu between different variants. There was no immunohistochemical expression in perineural invasion with all cases of BCC variants. The highest expression was seen in HER2neu, MMP-13, and α-SMA with aggressive histological patterns. There was no podoplanin lymphatic vessel density immunoexpressing in all variants, while tumoral podoplanin showed a significant difference in all variants. HER2neu was correlated with all other biomarkers. Conclusions HER2neu, MMP-13, and α-SMA biomarkers can be used as diagnostic markers to predict the aggressive biological behavior of BCC tumors.

CD133, but Not CD44, May Serve as a Novel Biomarker for Differential Diagnosis Between Basal Cell Carcinoma and Trichoblastomas

Purpose

To investigate the clinical value of CD133 and CD44 as putative cancer stem cell markers in distinguishing between basal cell carcinoma (BCC) and trichoblastomas (TB).

Patients and Methods

Tumor samples from 24 BCC and 23 TB patients were retrospectively retrieved for immunohistochemical staining of CD133 and CD44. The results were interpreted using a semiquantitative scoring system (H score). A receiver operating characteristic (ROC) curve was developed to identify an optimal cutoff value for differentiating between BCC and TB.

Results

Expression of CD133 was significantly higher in BCC patients than in TB patients (median H score: 30 [IQR: 12.5–56.3] vs 0 [IQR: 0–2], P < 0.001). However, there was no significant difference in CD44 expression between the two groups (median H score: 105 [IQR: 63.8–155.0] vs 60 [IQR: 30–120], P = 0.095). The ROC analysis of CD133 immunostaining yielded an area under the curve (AUC) of 0.881 (95% CI: 0.756–1.000) for differentiating between BCC and TB by using a H score of 7 as the cut-off value (98.5% sensitivity and 87.0% specificity). By contrast, immunostaining of CD44 showed a lower diagnostic value, with an AUC of 0.642 (95% CI: 0.476–0.808) at the optimal cut-off value of 85 (62.5% sensitivity and 73.9% specificity). The positive and negative predictive values were 88.5% and 95.2% for CD133 and 71.4% and 65.4% for CD44, respectively. Additionally, CD133 expression was significantly associated with mitotic activity in BCC patients (r = 0.549, P = 0.005).

Conclusion

Our study expanded upon previous studies of CD133 and CD44 expressions in skin tumors, suggesting that CD133, but not CD44, may serve as a novel biomarker for differential diagnosis of BCC, although future studies using a larger number of patients are needed to justify it further.

Cd34+ Stromal Cells/Telocytes in Normal and Pathological Skin

We studied CD34+ stromal cells/telocytes (CD34+SCs/TCs) in pathologic skin, after briefly examining them in normal conditions. We confirm previous studies by other authors in the normal dermis regarding CD34+SC/TC characteristics and distribution around vessels, nerves and cutaneous annexes, highlighting their practical absence in the papillary dermis and presence in the bulge region of perifollicular groups of very small CD34+ stromal cells. In non-tumoral skin pathology, we studied examples of the principal histologic patterns in which CD34+SCs/TCs have (1) a fundamental pathophysiological role, including (a) fibrosing/sclerosing diseases, such as systemic sclerosis, with loss of CD34+SCs/TCs and presence of stromal cells co-expressing CD34 and αSMA, and (b) metabolic degenerative processes, including basophilic degeneration of collagen, with stromal cells/telocytes in close association with degenerative fibrils, and cutaneous myxoid cysts with spindle-shaped, stellate and bulky vacuolated CD34+ stromal cells, and (2) a secondary reactive role, encompassing dermatitis—e.g., interface (erythema multiforme), acantholytic (pemphigus, Hailey–Hailey disease), lichenoid (lichen planus), subepidermal vesicular (bullous pemphigoid), psoriasiform (psoriasis), granulomatous (granuloma annulare)—vasculitis (leukocytoclastic and lymphocytic vasculitis), folliculitis, perifolliculitis and inflammation of the sweat and sebaceous glands (perifolliculitis and rosacea) and infectious dermatitis (verruca vulgaris). In skin tumor and tumor-like conditions, we studied examples of those in which CD34+ stromal cells are (1) the neoplastic component (dermatofibrosarcoma protuberans, sclerotic fibroma and solitary fibrous tumor), (2) a neoplastic component with varying presentation (fibroepithelial polyp and superficial myxofibrosarcoma) and (3) a reactive component in other tumor/tumor-like cell lines, such as those deriving from vessel periendothelial cells (myopericytoma), epithelial cells (trichoepithelioma, nevus sebaceous of Jadassohn and seborrheic keratosis), Merkel cells (Merkel cell carcinoma), melanocytes (dermal melanocytic nevi) and Schwann cells (neurofibroma and granular cell tumor).

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.

A Low-Grade Trichoblastic Carcinoma Treated with Mohs Micrographic Surgery

Trichoblastomas are rare dermal neoplasms usually found on the scalp and face. Histology shows a proliferation of small basaloid cells arranged in cords or fields surrounded by cellular stroma. Trichoblastomas are usually not aggressive, but trichoblastic carcinomas arising from preexisting trichoblastomas have been described and have been linked to basal cell carcinoma. We found a tumor with features of trichoblastoma with presence of Merkel cells, but with a deeply infiltrative growth pattern into the fat and muscle tissue, without significant architectural or cellular atypia. Tumors with similar growth patterns were previously described as deeply invasive trichoblastic neoplasms. It appears to be a new entity that has been described before but has not been fully characterized: low-grade trichoblastic carcinoma. This malignancy seems to show only locally aggressive growth. Radical excision was accomplished with Mohs micrographic surgery.

Clinical, Histopathological, and Management Challenges of Multiple Familial Trichoepithelioma: A Case Report of a Patient Presenting with Multiple Facial Papules

Trichoepitheliomas (TE) are benign skin tumours of the pilosebaceous apocrine unit with follicular differentiation. Multiple familial trichoepithelioma (MFT) is a considerably rare condition inherited in an autosomal dominant pattern. We present a case of a 15-year-old male who presented with multiple papulo-nodular lesions in the central face and a family history of a similar type of lesions from his mother. Significance of consideration of various clinical differential diagnoses with serious pathological outcomes, strategies followed in the diagnosis including histopathological evaluation aided by immunohistochemical investigations, and subsequent challenges that may be faced in the management of MFT in light of the presentation with multiple facial papules are documented in this case report.

Basal Cell Carcinoma Arising within a Trichoepithelioma: An Immunohistochemical Study

Background: Trichoepithelioma (TE) and basal cell carcinoma (BCC) of skin represent distinct tumor entities but they have a close histogenetic and phenotypic relationship.

Objective: A unique case of a BCC arising within a TE is described with an emphasis on the analysis of different and for each tumor type typical immunophenotype.

Material and Methods: A 71-year-old man presented with a subcutaneous solid tumor in the lumbar region. The resected tumor specimen was studied by immunohistochemistry.

Results: Histology revealed a coexistence of classic TE and nodular BCC. Both tumors were strongly positive for BerEP4 and negative for EMA. Neoplastic epithelium of the BCC showed a diffuse staining for Bcl-2, while the TE expressed Bcl-2 almost exclusively in the peripheral cells of tumor islands. In the BCC, neoplastic nodules exhibited a focal staining for CD10, while the peritumorous stroma did not. In contrast, the TE showed a focal immunoreactivity for CD10 in the stromal cells around the neoplastic islands which were completely negative. The TE contained intratumorous CK20-labeled Merkel cells but they were not detected in the BCC. A stromal immunore-activity for CD34 was found in both tumors. Proliferative activity (Ki-67) was slightly higher in the BCC than in the TE.

Conclusion: Although a concomitant presence of TE and BCC in the same skin lesion is a unique finding, it may be sometimes encountered in a biopsy practice. Pathologists should provide a careful histologic examination of the whole TE lesion with precise section sampling to unveil such possible association.

High-Risk Recurrence Basal Cell Carcinoma: Focus on Hedgehog Pathway Inhibitors and Review of the Literature

Basal cell carcinoma is the most common skin tumour, with the majority of the cases occurring on the head and neck district, where cosmetic and functional results are crucial. It can be locally destructive if not diagnosed early and treated appropriately. Surgery is the treatment of choice for most lesions, but aggressive, recurrent, or unresectable tumours can be challenging to manage. Advanced basal cell carcinoma includes high recurrence risk subtypes, in which standard therapies demonstrate lack of efficacy. This led to a need for investigating more deeply the pathogenesis of the disease and to the discovery of the implication of the hedgehog pathway. The development of systemic inhibitors of this pathway provides new treatment options for patients with advanced disease, resulting in survival improvement. Food and Drug Administration, before, and European Medicines Agency later approved 2 Hedgehog pathway inhibitors for the treatment of advanced basal cell carcinomas, vismodegib and sonidegib. Here, we present a review of the current English language literature trying to analyze differences in the 2 drugs as a head-to-head comparison between them has not already been documented in a randomized controlled clinical trial. Although vismodegib and sonidegib showed similar efficacy and safety profiles, in an indirect comparison scenario, sonidegib has shown slightly better outcomes in locally advanced basal cell carcinoma than vismodegib. They present different molecular structures, as they bind different residues on their targets and develop resistance for different mutations. In a future scenario, clinical trials comparing the 2 drugs are needed, as well as expanding data on discontinuation of therapy and/or consequential administration of them, with the aim to improve our clinical practise.

Slicing Spheroids in Microfluidic Devices for Morphological and Immunohistochemical Analysis

Microfluidic devices utilizing spheroids play important roles in in vitro experimental systems to closely simulate morphological and biochemical characteristics of the in vivo tumor microenvironment. For the observation and analysis of the inner structure of spheroids, sectioning is an efficient approach. However, conventional microfluidic devices are difficult for sectioning, and therefore, spheroids inside the microfluidic channels have not been sliced well. We proposed a microfluidic device created from embedding resin for sectioning. Spheroids were cultured, embedded by resin, and sectioned in the microfluidic device. Slices of the sectioned spheroids yielded clear images at the cellular level. According to morphological and immunohistochemical analyses of the slices of the spheroid, specific protein distribution was observed.

Multiple Nonfamilial Unilateral Trichoepitheliomas: Report of a Case-Mini Review of the Literature

Trichoepitheliomas are benign skin tumors with follicular differentiation that present most commonly as solitary lesions. They can also present as multiple centrofacial papules due to several mutations in the CYLD gene. Multiple unilateral trichoepitheliomas in a linear or dermatomal distribution may rarely be seen. Herein, we report a case of multiple unilateral trichoepitheliomas on the face of a healthy 34-year-old woman of Caucasian origin.

CD10, TDAG51, CK20, AR, INSM1, and Nestin Expression in the Differential Diagnosis of Trichoblastoma and Basal Cell Carcinoma

BACKGROUND

Trichoblastoma (TB) and basal cell carcinoma (BCC) are 2 different neoplasms composed of basaloid cells and have overlapping histopathological features. We compared the immunoexpression of CD10, T-cell death-associated gene 51 (TDAG51), cytokeratin 20 (CK20), androgen receptor (AR), insulinoma-associated protein 1 (INSM1), and nestin for the differential diagnosis of these tumors.

MATERIALS AND METHODS

We assessed a total of 27 BCC and 27 TB cases, including 4 TB lesions in nevus sebaceous and 3 malignant TB lesions for CD10, TDAG51, CK20, AR, INSM1, and nestin expression.

RESULTS

Staining for CK20, TDAG51, INSM1, and stromal CD10 was significantly more common in TB cases than in BCC cases ( P < .001). Epithelial CD10 and AR staining was significantly more common in BCC cases than in TB cases ( P < .001). The difference between the groups for nestin staining was not significant ( P > .05). Stromal CD10 staining was the most sensitive marker (96.3%) and INSM1 the least sensitive (55.6%) marker for TB. TDAG51 showed 100% specificity for TB. A larger number of CK20 positive cells was found in the cases associated with nevus sebaceous than in the other TBs.

CONCLUSION

All the selected markers except nestin were useful for the differential diagnosis between TB and BCC. CD10 and TDAG51 were more useful than the other markers. The use of CK20 could be preferred in nevus sebaceous lesions. INSM1 was less effective in highlighting Merkel cells within the lesion than CK20.

Histologic Mimics of Basal Cell Carcinoma

CONTEXT

- Basal cell carcinoma (BCC) is the most common human malignant neoplasm and is a frequently encountered diagnosis in dermatopathology. Although BCC may be locally destructive, it rarely metastasizes. Many diagnostic entities display morphologic and immunophenotypic overlap with BCC, including nonneoplastic processes, such as follicular induction over dermatofibroma; benign follicular tumors, such as trichoblastoma, trichoepithelioma, or basaloid follicular hamartoma; and malignant tumors, such as sebaceous carcinoma or Merkel cell carcinoma. Thus, misdiagnosis has significant potential to result in overtreatment or undertreatment.

OBJECTIVE

- To review key features distinguishing BCC from histologic mimics, including current evidence regarding immunohistochemical markers useful for that distinction.

DATA SOURCES

- Review of pertinent literature on BCC immunohistochemistry and differential diagnosis.

CONCLUSIONS

- In most cases, BCC can be reliably diagnosed by histopathologic features. Immunohistochemistry may provide useful ancillary data in certain cases. Awareness of potential mimics is critical to avoid misdiagnosis and resulting inappropriate management.

Induction of Desmoplastic Trichoepithelioma in a Dermatofibroma

Induction of follicular germinative structures above a dermatofibroma (DF) is a common finding. Rarely, induction of a trichoblastoma in a DF has been observed. Here, we report the case of a desmoplastic trichoepithelioma induced by a DF. The lesion with clinical and histological appearance of a DF situated on the left dorsal foot showed an associated adnexal proliferation that fulfilled histopathological criteria of desmoplastic trichoepithelioma. Immunohistochemistry (Ber-EP4, Bcl-2, CK17, CK20, CK7, EMA, and Ki67) helped to confirm the diagnosis and to exclude possible differential diagnoses.

p40 in Conjunction With CK20 and E-Cadherin Distinguishes Primary Adnexal Neoplasms of the Skin

Although basal cell carcinomas (BCC) show typical histomorphologic features, they sometimes remain difficult in distinction from benign adnexal skin tumors of follicular origin like trichoepithelioma (TE) or trichoblastoma (TB). Consequently, an immunohistochemical marker panel separating described entities would be helpful in clinical routine. Thus, we stained 22 skin lesions (BCC, TE, and TB) against β-catenin, CK20, E-cadherin, p40, and p63. The staining pattern was described and quantified using an immunohistochemical score. Although p40 and p63 revealed a strong staining intensity of all skin lesions without distinction between BCC and benign lesions (P=1.000), established Merkel cell marker CK20 illustrated a loss of staining in BCC compared with TE and TB (P=0.007). In contrast, BCC exhibited an increased expression of E-cadherin in relation to TE and TB (P=0.009). Single application of CK20 or E-cadherin could predict diagnosis of BCC in 81.8% or 72.7%, respectively. Combining consecutive staining of E-cadherin and CK20 could even enhance specificity toward diagnosis of TE or TB. Hence, findings of our study imply that sequential staining of CK20 and E-cadherin prevents false-positive classification of BCC. Furthermore, our study demonstrated that p40 exhibits the same staining pattern in BCC, TE, and TB. Therefore, p40 might replace p63 equivalently establishing diagnosis of primary adnexal neoplasms of the skin in the form of BCC as well as benign adnexal tumors. As a result, the depicted immunohistochemical marker panel may be applied for adnexal skin neoplasms as a diagnostic adjunct especially in surgically challenging body regions.

GREM1 is expressed in the cancer-associated myofibroblasts of basal cell carcinomas

Cancer-associated fibroblasts (CAFs) play important roles in cancer progression through their complex interactions with cancer cells. The secreted bone morphogenetic protein antagonist, gremlin1 (GREM1) is expressed by the CAFs of basal cell carcinomas (BCCs), and promotes the growth of cancer cells. In this study, we investigated the expression of GREM1 mRNAs in various benign and malignant skin tumors, including various BCC subtypes. Analysis by RNA in situ hybridization (ISH) revealed that fibroblasts in the scar tissue expressed GREM1 and α-smooth muscle actin (α-SMA), whereas resident fibroblasts in the dermis of the normal skin did not express GREM1. Real-time polymerase chain reaction analysis showed significantly higher GREM1 expression in skin cancers and pilomatricomas (PMCs) than in other benign skin tumors. Tissue microarrays analyzed by RNA ISH for GREM1 expression also demonstrated that 23% of BCCs, 42% of squamous cell carcinomas, 20% of melanomas, and 90% of PMCs were positive for GREM1 expression, whereas trichoepitheliomas, eccrine poromas, hidradenomas, and spiradenomas were negative for GREM1 expression. Most BCCs that were GREM1 expression positive were of desmoplastic or mixed subtypes, and GREM1 expression was localized to activated myofibroblasts at the tumoral-stromal interface. Interestingly, most PMCs harbored GREM1-expressing fibroblasts, probably because of the inflammatory responses caused by foreign body reactions to keratin. Additionally, in BCCs, stromal GREM1 expression had a strong correlation with CD10 expression. In conclusion, GREM1 is frequently expressed by myofibroblasts in scars or in the stroma of basal cell carcinomas, suggesting that GREM1 expression can be a marker for activated myofibroblasts in the cancer stroma or in scar tissue.

Trichoepithelioma Arising in an Ovarian Mature Cystic Teratoma

Here, we report an extremely rare case of trichoepithelioma (TE)-a benign epithelial tumor originating from the outer root sheath of a hair follicle-arising in an ovarian mature cystic teratoma (MCT) with fluorodeoxyglucose-positron emission tomography (FDG-PET) findings. A 48-year-old Japanese woman presented to our hospital for her annual follow-up of adenomyosis. Ultrasonography and magnetic resonance imaging revealed a left ovarian tumor with irregular-shaped septum, which was suspicious of malignancy. However, tumor marker levels were within normal range. On FDG-PET, the maximum standardized uptake value (SUVmax) of the tumor was 2.9. Laparotomy with left salpingooophorectomy was performed. Pathologic examination revealed the probability of TE, rather than basal cell carcinoma (BCC), arising in an ovarian MCT. After five years of follow-up, the patient had no sign of recurrence. The FDG-PET SUVmax was low in TE, as with other benign tumor. However, future investigation is needed to evaluate the findings of FDG-PET imaging in TE cases.

Fibroepithelioma of Pinkus Revisited

Background

Fibroepithelioma of Pinkus (FeP) is considered a variant of basal cell carcinoma (BCC); however, in the past 20 years, some researchers have argued for its classification as a trichoblastoma. Recently, use of a new immunostaining marker and further dermoscopic characterization of FeP have advanced the debate about its proper classification.

Purpose

A review of the evidence for and against classification of FeP as BCC or trichoblastoma is presented.

Methods

Using PubMed, the term FeP was searched and relevant citations were assessed. Additional relevant articles were identified from references of key papers.

Results

FeP shares characteristics of both trichoblastoma and BCC.

Conclusion

Derived from the same cell type, BCC and trichoblastoma may be best considered as representing opposite ends of a spectrum of differentiation, with FeP deserving an intermediate classification.

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.

Diagnostic value of CD10 and Bcl2 expression in distinguishing cutaneous basal cell carcinoma from squamous cell carcinoma and seborrheic keratosis

The distinction between cutaneous basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and seborrheic keratosis (SK), which are common entities in clinical practice, can be difficult clinically and histologically. CD10 and Bcl2 antigens are important factors in tumor growth, survival and spread. The aim of the present study is to define the frequency of CD10 and Bcl2 expression in such cutaneous tumors and its relation to the clinicopathological characteristics as well as their possible diagnostic utility. CD10 and Bcl2 immunohistochemistry was performed on 30 BCC, 20 SCC and 15 SK. 93.3% of SK cases and 53.3% of BCC cases showed significant expression of CD10 in tumor cells when compared either with each other or with SCC cases (100% negative). Stromal CD10 expression was positive in 50% of BCC cases and 75% of SCC cases. Stromal CD10 expression was significantly higher in high risk BCC and BCC with infiltrating deep margins; furthermore, it showed a significant positive correlation with grade of SCC. A significant inverse correlation between CD10 expression in stromal and tumor cells of BCC was present. Bcl2 was significantly expressed in 93.3% of SK cases and 80% of BCC cases when compared with SCC cases (100% negative). It was found that for distinguishing BCC from SK, only CD10 expression in tumor cells provided a high diagnostic value with positive likelihood ratio (PLR) was 7.00. In addition, CD10 and Bcl2 expression in tumor cells could give convincing diagnostic value to distinguish SCC from SK (PLR=15.00 for each marker). Moreover, for differentiating BCC from SCC, only Bcl2 in the tumor cells could provide a high diagnostic value (PLR=5.5). In conclusion, CD10 and Bcl2 can help in differentiating cutaneous BCC from SK and SCC. The overexpression of CD10 in the stromal cells of SCC and some variants of BCC suggests the invasive properties of such tumors.

Desmoplastic Trichoepithelioma: An Infrequent Entity not to be Missed: Report of Two Cases

Desmoplastic trichoepitheliomas are rare benign tumors with follicular differentiation. They have rarely been described in children. We report two children with this uncommon condition.

Coordinate expression of cytokeratins 7 and 14, vimentin, and Bcl-2 in canine cutaneous epithelial tumors and cysts

Forty-seven canine cutaneous epithelial tumors and cysts were examined to determine coordinate expression of cytokeratins 7 (CK7) and 14 (CK14), vimentin, and Bcl-2 using commercially available antibodies. Within non-affected normal skin adjacent to tumors or cysts, CK7 expression was observed in luminal cells in apocrine glands; CK14 expression was observed in the stratum basale, stratum spinosum, stratum granulosum, basal layer of outer root sheath, sebaceous glands, and myoepithelial cells of apocrine glands; vimentin expression was observed in dermal papilla and scattered non-epithelial cells within the epidermis; and Bcl-2 expression was observed in scattered non-epithelial cells in the epidermis and some apocrine glands. The pattern of expression of CK7 and CK14 in cases of adenocarcinoma of the apocrine gland of the anal sac (CK7+/CK14-) and hepatoid gland tumors (CK7-/CK14+) may prove useful for diagnostic purposes. Loss of expression of CK14 and vimentin, identifying myoepithelial cells, was observed in apocrine and ceruminous adenocarcinomas. Differences in patterns of expression of Bcl-2 were observed between infundibular keratinizing acanthomas compared to trichoepitheliomas.

Multiple Familial Trichoepithelioma with an Adjacent Basal Cell Carcinoma, Transformation or Collision - A Case Report and Review of Literature

Trichoepithelioma is a benign tumor of follicular origin that presents as small, skin-colored papules predominantly on the face. When more than one family member is affected, the disease is known as multiple familial trichoepithelioma (MFT). It is a rare autosomal dominant skin disease. Malignant transformation is very rare. We describe here a case that developed malignant neoplasm in a setting of multiple trichoepithelioma.

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.

Keratins in health and disease

The cytoprotective keratins (K) compose the intermediate filaments of epithelial cells and their inherited and spontaneous mutations give rise to keratinopathies. For example, mutations in K1/K5/K10/K14 cause epidermal skin diseases whereas simple epithelial K8/K18/K19 variants predispose to development of several liver disorders. Due to their abundance, tissue- and context-specific expression, keratins constitute excellent diagnostic markers of both neoplastic and non-neoplastic diseases. During injury and in disease, keratin expression levels, cellular localization or posttranslational modifications are altered. Accumulating evidence suggests that these changes modulate multiple processes including cell migration, tumor growth/metastasis and development of infections. Therefore, our understanding of keratins is shifting from diagnostic markers to active disease modifiers.

Vulvar Adnexal Lesions: A 32-Year, Single-Institution Review From Massachusetts General Hospital

Context.—Because the skin and modified mucosal surfaces of the vulvar region contain dense apocrine glands and anogenital mammary-like glands, in addition to eccrine glands and folliculosebaceous units, benign as well as malignant lesions derived from these adnexal structures are, not surprisingly, found in the vulva. However, their incidence occurring in the vulva has not been reported, to our knowledge.

Objective.—To determine the incidence of various vulvar adnexal lesions.

Design.—We performed a retrospective review (1978–2010) of the cases at our institution.

Results.—A total of 189 vulvar adnexal lesions were identified. Most of these lesions were benign (133 of 189; 70%), with hidradenoma papilliferum being the most common, followed by syringoma and various types of cysts. Rare cases of tubular adenoma, poroma, spiradenoma, hidradenoma, cylindroma, sebaceoma, and trichoepithelioma were identified. Malignant adnexal neoplasms comprised the remaining 30% (56 of 189) of the cases. Extramammary Paget disease was the most common (49 of 56), and 29% (14 of 49) demonstrated an invasive component. Rare cases of basal cell carcinoma, sebaceous carcinoma, apocrine carcinoma, adenoid cystic carcinoma, and spiradenocarcinoma were identified.

Conclusions.—In this retrospective review, we identified several benign entities that have not been previously reported on the vulva, namely pilomatricoma, poroma, spiradenoma, and sebaceoma. Hidradenoma papilliferum and extramammary Paget disease were the most common benign and malignant adnexal neoplasms, respectively. The spectrum of various vulvar adnexal lesions appears to reflect the frequency of the underlying glandular elements.