D2-40, a novel immunohistochemical marker in differentiating dermatofibroma from dermatofibrosarcoma protuberans

Single-Cell and Spatial Transcriptomic Analysis of Human Skin Delineates Intercellular Communication and Pathogenic Cells

Epidermal homeostasis is governed by a balance between keratinocyte proliferation and differentiation with contributions from cell-cell interactions, but conserved or divergent mechanisms governing this equilibrium across species and how an imbalance contributes to skin disease are largely undefined. To address these questions, human skin single-cell RNA sequencing and spatial transcriptomics data were integrated and compared with mouse skin data. Human skin cell-type annotation was improved using matched spatial transcriptomics data, highlighting the importance of spatial context in cell-type identity, and spatial transcriptomics refined cellular communication inference. In cross-species analyses, we identified a human spinous keratinocyte subpopulation that exhibited proliferative capacity and a heavy metal processing signature, which was absent in mouse and may account for species differences in epidermal thickness. This human subpopulation was expanded in psoriasis and zinc-deficiency dermatitis, attesting to disease relevance and suggesting a paradigm of subpopulation dysfunction as a hallmark of the disease. To assess additional potential subpopulation drivers of skin diseases, we performed cell-of-origin enrichment analysis within genodermatoses, nominating pathogenic cell subpopulations and their communication pathways, which highlighted multiple potential therapeutic targets. This integrated dataset is encompassed in a publicly available web resource to aid mechanistic and translational studies of normal and diseased skin.

ETS-related Gene (ERG) is Differentially Expressed in Dermatofibroma (Fibrous Histiocytoma) as Compared With Dermatofibrosarcoma Protuberans and Hypertrophic Scars: A Pilot Immunohistochemical Study

Immunohistochemical staining can be of great utility in differentiating various cutaneous spindle cell neoplasms, particularly when the histomorphologic appearance of the lesions is inconclusive. Nuclear staining for ETS-related gene (ERG), a highly sensitive endothelial cell marker, has seldom been studied in the context of cutaneous spindle cell neoplasms. Little is known about its specificity for vascular differentiation. In this pilot study, immunohistochemical analysis for ERG was performed on 15 dermatofibromas (DF), 10 keloids, and 9 dermatofibrosarcoma protuberans (DFSP) tumors. Consistent nuclear expression of ERG was found in DF [100% (15/15) of the lesions demonstrated >50% labeling of tumor cells with moderate to strong intensity]. However, ERG expression was largely absent in DFSP [89% (8/9) of the lesions demonstrating <50% labeling staining, generally of mild intensity] and hypertrophic scars-keloids [80% (8/10) without expression]. On the basis of the results of this pilot study, immunohistochemical staining for ERG may prove useful in helping to differentiate DF from DFSP and hypertrophic scars in the context of partial biopsy sampling. If replicated in a larger number of samples, this finding could mitigate the use of costly sequencing panels and potentially avoid unnecessary reexcisions in certain contexts.

A novel aberration of COL1A1-PDGFB fusion as an insertion in chromosome 15 in one case of dermatofibrosarcoma protuberans involving a rare location

Dermatofibrosarcoma protuberans (DFSP) is a rare sarcoma of the skin arising from the dermis. Its location is most commonly presented on the trunk of middle-aged adults and rarely on the face. The characteristic genetic aberration in the form of a reciprocal translocation t(17;22)(q21;q13) or a ring fusing the COL1A1 and PDGFB genes is found in 90% of DFSP. We present a case of a 42-year-old man who presented with a DFSP on the left cheek with foci of myxoid-fibrosarcomatous transformation. A conventional chromosomal analysis revealed a complex karyotype without a supernumerary ring chromosome or a linear translocation t(17;22). Comparative genome hybridization and fluorescence in-situ hybridization revealed the fusion of COL1A1 and PDGFB probes inserted in chromosome 15. This is a unique case of DFSP characterized by a rare body location, unique histopathological features, and novel chromosome COL1A1-PDGFB insertion, and may help guide future diagnostic and patient care modalities.

Dermatofibrosarcoma Protuberans

Dermatofibrosarcoma protuberans (DFSP) is an uncommon dermal neoplasm that exhibits a high rate of local recurrence and infiltrative behavior, but has a low risk of metastasis. It arises as a slowly progressive, painless pink or violet plaque. Histologically, DFSP is characterized by a monomorphous spindle cell proliferation in a storiform pattern. The gold standard of treatment is surgical resection with negative margins. In cases where obtaining clear margins is not possible, radiation and systemic therapy with tyrosine kinase inhibitors, such as imatinib mesylate, has been shown to be effective.

Dermatofibrosarcoma Protuberans: An Immunomarker Study of 57 Cases That Included Putative Mesenchymal Stem Cell Markers

Dermatofibrosarcoma protuberans (DFSP) is a low-grade fibroblastic sarcoma with a superficial location that has been suggested to potentially be a type of mesenchymal stem cell tumor. We studied the expression of various immunomarkers, including putative stem cell markers, in a series of 57 DFSPs including variants, and 12 dermatofibromas (DFs). CD105, a mesenchymal stem cell marker, was weakly expressed in 24 DFSPs, whereas other stem cell markers, including CD133, ALK-1, and Oct3/4, were completely negative in all samples. The expression rates of CD105 and CD34 were significantly higher in DFSP (42% and 93%) than in DF (0% and 17%), and CD10 and D2-40 were significantly lower in DFSP (40% and 3.5%) than in DF (100% and 33%), respectively. CD99, CD117, PDGFB, and PDGFRβ expression was comparable between the groups. CD105 mesenchymal cells were not observed in non-neoplastic dermis. In summary, we did not obtain sufficient immunohistochemical evidence to support the DFSP as a cutaneous mesenchymal stem cell tumor. CD34 alone was the most consistent marker of DFSP, irrespective of its variants. Because CD34 non-neoplastic mesenchymal cells were distributed in a location similar to that of DFSP, we suggest that DFSP might have originated from CD34 mesenchymal cells in the dermis.

Cutaneous/subcutaneous mesenchymal proliferations of the breast

Cutaneous mesenchymal "spindle cell" lesions arising in the vicinity of the breast represent a complex clinical and diagnostic scenario which may overlap histopathologically and immunohistochemically with mammary spindle cell proliferations, potentially impacting management and overall prognostication. In this review, we suggest a pattern-based approach to assist in the evaluation of these lesions. A comprehensive description of each entity is accompanied by a cutaneous and mammary differential diagnosis.

Incidence and Outcomes of Dermatofibrosarcoma Protuberans in the US Pediatric Population

BACKGROUND

Dermatofibrosarcoma protuberans (DFSP) is a low-grade soft tissue sarcoma. In the pediatric population, DFSP is exceedingly rare. Aim of this study was to describe the epidemiology and clinical outcomes in a large pediatric cohort.

METHODS

Surveillance, Epidemiology, and End Results (SEER) database (1973-2010) was analyzed for all patients with dermatofibrosarcoma occurring in patients <20 years of age. Data were extracted based on age, gender, race, anatomic site, histology, stage, treatment modalities, and survival. Incidence rates were standardized to the 2000 US population.

RESULTS

A total of 451 patients were identified. Overall annual incidence was 0.10 per 100,000. Incidence was highest among black children and adolescents (ages 15 to 19 years). Trunk was most common site, followed by extremities. Head and neck region was least common site (P < 0.05). Majority (54%) of patients presented with localized disease. Overall, 95% underwent surgery. Only 2.2% were treated with perioperative radiation therapy. Overall prognosis was favorable with 5-year overall survival (OS) of 100%, 15-year OS of 98%, and 30-year OS of 97%. Median survival was 117 months. Male patients had lower 15- and 30-year OS compared with females (P < 0.05).

CONCLUSION

Pediatric DFSP has lower incidence but similar clinical characteristics to adults. Incidence is higher in black children and in the trunk region. While prognosis is favorable, male sex is associated with decreased OS.

Altered Dermal Fibroblasts in Systemic Sclerosis Display Podoplanin and CD90

Tissue injury triggers the activation and differentiation of multiple cell types to minimize damage and initiate repair processes. In systemic sclerosis, these repair processes appear to run unchecked, leading to aberrant remodeling and fibrosis of the skin and multiple internal organs, yet the fundamental pathological defect remains unknown. We describe herein a transition wherein the abundant CD34(+) dermal fibroblasts present in healthy human skin disappear in the skin of systemic sclerosis patients, and CD34(-), podoplanin(+), and CD90(+) fibroblasts appear. This transition is limited to the upper dermis in several inflammatory skin diseases, yet in systemic sclerosis, it can occur in all regions of the dermis. In vitro, primary dermal fibroblasts readily express podoplanin in response to the inflammatory stimuli tumor necrosis factor and IL-1β. Furthermore, we show that on acute skin injury in both human and murine settings, this transition occurs quickly, consistent with a response to inflammatory signaling. Transitioned fibroblasts partially resemble the cells that form the reticular networks in organized lymphoid tissues, potentially linking two areas of fibroblast research. These results allow for the visualization and quantification of a basic stage of fibroblast differentiation in inflammatory and fibrotic diseases in the skin.

Deep Penetrating Fibrous Histiocytoma: A Case Report and Implications for Surgical Management

Deep penetrating fibrous histiocytoma (DPFH) is a rare variant of fibrous histiocytoma that can arise in the subcutis and deep soft tissues with different clinical implications from dermatofibromas. Dermatofibromas are mainly cosmetic annoyances and do not require surgical management. However, the DPFH does require that negative surgical margins be achieved because of the possibility of local recurrence and distant metastasis. We describe a case of a 24-year-old man diagnosed with DPFH through histologic examination and immunohistochemistry. The lesion displayed diffuse, strong D2-40 positivity and a minority of cells were highlighted with factor XIIIa. The lesion was negative for CD34. The patient's lesion was incompletely excised and a repeat excision was required.

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.

CD99 expression in dermatofibrosarcoma protuberans and dermatofibroma

BACKGROUND

Differentiating between dermatofibrosarcoma protuberans (DFSP) and hypercellular dermatofibroma (DF) can sometimes be challenging, and a panel of immunostains is often employed. Expression of conventional markers oftentimes overlaps. We evaluated CD99 expression in DFSP and DF and its utility in distinction between these 2 entities.

METHODS

CD99 immunostaining was performed on 34 DFSPs and 24 hypercellular DFs. The intensity of staining was graded as "weak," "moderate," or "strong," and the proportion of positive cells was graded as follows: "scattered" when individual cells comprised <5% of the total cellularity of the lesion; "focal" with >5% but <25% of the cells; or "diffusely distributed" with staining of >25% of lesional spindle cells.

RESULTS

Overall, DFSPs showed positive CD99 staining in 21 (61.76%) cases. Moderate and weak patterns of staining were the most frequent, seen in 13 (38.2%) and 7 (20.6%) cases, respectively. CD99 staining in DFSPs was predominantly scattered or patchy (4 and 11 lesions respectively) with less than 25% of cells expressing CD99. In comparison, all 24 DF cases showed strong CD99 positivity in >25% of the spindle cell component (P = 0.0003). The most striking difference related to the distribution of staining. In DFSP, tumor cells in the superficial dermis, when present, were always CD99 negative. In contrast, DF cells in the superficial dermis always demonstrated strong CD99 positivity.

CONCLUSIONS

DF strongly expresses CD99 in a diffuse pattern that may serve as evidence in distinction from DFSP. As the differences in staining were most pronounced in the superficial portions of the tumor, CD99 staining may be well suited to superficial biopsy specimens, where distinction in hematoxylin and eosin sections may be most problematic.

Immunohistochemical markers in fibrohistiocytic lesions: factor XIIIa, CD34, S-100 and p75

BACKGROUND

The distinction between dermatofibroma (DF), dermatofibrosarcoma protuberans (DFSP), and other benign and malignant cutaneous spindle cell lesions frequently requires immunohistochemical staining. CD34 and factor XIIIa are the most commonly used immunostains; however, they may exhibit aberrant expression and introduce the potential for misdiagnosis. There is some data supporting that p75 and S100A6 may be additional helpful immunohistochemical markers.

METHODS

We undertook a large case series examining the use of CD34 and factor XIIIa as well as p75 and S100A6 in DF, cellular DF, DFSP, indeterminate fibrohistiocytic lesion, and scar.

RESULTS

As expected, CD34 stained DFSP, although it was usually negative in DF. Factor XIIIa was generally positive in DF and negative in DFSP. There were exceptions in both cases of DF and DFSP. S100A6 was routinely negative in all entities studied. P75 was negative in all cases except DFSP, approximately half of which showed weak and/or patchy positivity.

CONCLUSIONS

We conclude that to date, CD34 and factor XIIIa remain the most reliable immunohistochemical markers for DF and DFSP.

[Medaillon-like dermal dendrocyte hamartoma: A case report]

Medaillon-like dermal dendrocyte hamartomas are rare congenital cutaneous lesions. They are present at birth as asymptomatic, benign, round, erythematous, well-circumscribed, atrophic patches. Typically, they have characteristic pliable, wrinkled surface; subtle telangiectases may also be appreciated. They are localized on the upper trunk or the neck. They may be misdiagnosed as atrophoderma, cutis aplasia, or anetoderma. Characteristic histologic findings include epidermal atrophy and the presence of CD34-positive spindle cell proliferation in the dermis. Little is known about the pathophysiology of medaillon-like dermal dendrocyte hamartomas. The main diagnosis pitfall is atrophic congenital dermatofibrosarcoma protuberance due to clinical and histological similarities. We emphasize that molecular studies to eliminate the t(17;22)(q22;q13) translocation of dermatofibrosarcomas may provide determinant elements for diagnosis in order to avoid unnecessary mutilating surgery. We present a case of medaillon-like dermal dendrocyte hamartoma with a local recurrence.

Atypical fibrous histiocytoma of the skin with CD30 and p80/ALK1 positivity and ALK gene rearrangement

We report the case of a two patients who presented with a solitary, asymptomatic, angiomatoid nodule on the right thigh. Histopathological finding showed a poorly circumscribed lesion, located in the dermis. The morphological aspect strongly suggested the diagnosis of atypical fibrous histiocytoma (AFH), but surprisingly, the neoplastic cells were diffusely CD30+, with a membrane staining devoid of paranuclear dot. The lesions were tested for p80/ALK1 expression. Surprisingly, we found a diffuse cytoplasmic positivity. Interestingly, using break-apart fluorescent in situ hybridization (FISH), we evidenced an ALK rearrangement in nearly 50% of the neoplastic cells. The expression of CD30 and ALK1 with ALK gene rearrangement raised the possibility of three diagnoses: a primary cutaneous anaplastic large cell lymphoma (ALCL), a cutaneous inflammatory myofibroblastic tumor (IMT), an AFH of the skin associated with ALK gene rearrangement and CD30 positivity. The three hypotheses were discussed and finally, although p80/ALK1 expression and cytogenetic abnormalities in fibrous histiocytoma (FH) are not yet reported to the best of our knowledge, we favored the diagnosis of AFH.

Expression of podoplanin/D2-40 in pericryptal stromal cells in superficial colorectal epithelial neoplasia

The aim of this study is to investigate the distribution and roles of podoplanin/D2-40-positive pericryptal stromal cells in superficial colorectal epithelial neoplasia. A total of 105 superficial colorectal epithelial tumors were examined: 65 tubular/tubulovillous adenomas, 32 adenocarcinomas in situ, and 8 submucosally invasive adenocarcinomas. Immunohistochemical analysis was performed using the monoclonal antibody to podoplanin/clone D2-40, which is reactive in both lymphatic endothelial cells and activated stromal cells, but negative in vascular endothelial cells. We found 50 (78 %) of 65 tubular/tubulovillous adenomas, 30 (94 %) of 32 adenocarcinomas in situ, and all 8 (100 %) submucosally invasive adenocarcinomas had podoplanin/D2-40-positive pericryptal stromal cells, whereas all normal colorectal mucosae had no podoplanin/D2-40-positive pericryptal stromal cells. The presence of podoplanin/D2-40-positive pericryptal stromal cells is associated with epithelial tumorigenesis in the colorectum.

Dermatofibrosarcoma protuberans: Our experience of 59 cases

Dermatofibrosarcoma protuberans (DFSP) is a rare soft tissue tumor with intermediate malignancy. It is initially located on the skin from where it is able to infiltrate the deep structures and has a tendency to recur locally following inadequate excision. A t(17;22)(q22;q13) chromosome trans-location is the main cytogenetic alteration responsible for the onset of DFSP. Treatment options include complete surgical excision by performing conventional surgery with wide margins (>3 cm) or Mohs micrographic surgery. A retrospective study was conducted in our Department of Plastic and Reconstructive Surgery and all data were collected from medical records of 59 DFSP patients within this department from 1999 to 2011. A total of 13 of 59 (22%) cases were treated with conventional excision; 3 (5%) cases resulted in tumor-free margins, 8 (14%) cases required surgical revision and 2 (3%) cases lead to recurrence. A total of 46 of 59 (78%) cases were treated with wide excision; 43 (73%) cases resulted in tumor-free margins, 3 (5%) cases required surgical revision and 0 (0%) cases lead to recurrence. In conclusion, the data collected reveal the controversy surrounding the adoption of general guidelines regarding safe margins. Further studies are required to investigate the possibility of obtaining genotypically altered margins from margins that may appear phenotypically healthy.

Expression of MMP-2, MMP-9 and MMP-11 in dermatofibroma and dermatofibrosarcoma protuberans

Dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) are the spindle cell mesenchymal neoplasms of the dermis and subcutis. Their histogenesis still remains uncertain and controversial. Traditionally, CD34 and factor XIIIa or other markers have been widely used to distinguish these two diseases. However, the results of these markers reveal overlapping and they lack specificity. Formalin-fixed, paraffin-embedded blocks were collected from the biopsied cases in Kaohsiung Medical University Hospital in Taiwan between 2004 and 2006. This study included 19 cases of DF and 17 cases of DFSP. Immunohistochemical analysis using antibodies CD34, matrix metalloproteinases (MMP)-2, MMP-9, and MMP-11 was performed. We found that the expression of CD34, MMP-2 and MMP-11 shows significant statistical differences in Immunohistochemistry (IHC) study positive or negative reactivity (positive of CD34 in DFSP and positive of MMP-2 and MMP-11 in DF; p=0.03, p<0.001, and p<0.001, respectively) between DF and DFSP. The result for expression of MMP-9 reveals no differences. The results indicate that the pathogenesis of DF and DFSP are affected by different expressions of extracellular matrix proteins. Metalloproteinases may play a direct role in these two diseases. Since no single marker can completely distinguish DF from DFSP, a combination of more than two or three stains may elevate the accuracy of diagnosis.

Fibrohistiocytic tumors and related neoplasms in children and adolescents

Fibrohistiocytic tumors (FHTs) in children and adolescents range from the benign fibrous histiocytoma, or dermatofibroma, to a variety of intermediate and malignant neoplasms, such as dermatofibrosarcoma protruberans and high-grade undifferentiated pleomorphic sarcoma (malignant fibrous histiocytoma). Those tumors as a group are comprised of fibroblasts, myofibroblasts, and histiocytes-dendritic cells with a variably prominent inflammatory infiltrate consisting of lymphocytes and eosinophils. Dendritic cells are also a major constituent of another group of neoplasms that include Langerhans cell histiocytosis, follicular and interdigitating cell sarcomas, and juvenile xanthogranuloma. These latter tumors are considered in this discussion for the sake of differential diagnosis and their possible histogenetic relationship to FHTs. Recent studies have suggested that the relationship between the fibroblast and histiocyte in the FHTs may reflect the intrinsic capacity to transdifferentiate from one to the other morphologic and functional state. The so-called "facultative fibroblast," as a cell with fibroblastic and histiocytic properties, was discussed in the context of the fibrous xanthoma 50 years ago. Possibly the entire histogenetic concept of FHTs should be reconsidered in light of current studies.

EMA positivity in epithelioid fibrous histiocytoma: a potential diagnostic pitfall

BACKGROUND

Epithelioid fibrous histiocytoma (EFH) represents a morphologic variant of cutaneous fibrous histiocytoma (FH) but can lack many characteristic features. The presence of epithelioid cytomorphology may mimic other dermal neoplasms. Our anecdotal experience of epithelial membrane antigen (EMA) expression in some examples of EFH has caused diagnostic difficulty. Our aim was to examine the immunohistochemical profile and incidence of EMA expression in EFH.

METHODS

Forty-four cases of EFH were retrieved from consultation files. Clinicopathologic and immunohistochemical features were evaluated.

RESULTS

Membranous EMA positivity was found in tumor cells in 27/42 cases (64%). Focal positivity for factor XIIIa was found in 10/14 (71%) and D2-40 in 14/27 (52%). Scattered smooth muscle actin (SMA)-positive tumor cells were seen in 11/43 (25%). Focal positivity for claudin-1 was found in 3/42 (7%). CD163 staining highlighted stromal macrophages; however, in five cases it was difficult to exclude focal staining of tumor cells. Tumor cells were consistently negative for pan-keratin, AE1/AE3, S100, CD31, CD34, CD68, desmin, p63, GFAP and CD45/LCA.

CONCLUSION

Frequent EMA expression in EFH represents an unexpected finding and constitutes a potential diagnostic pitfall. Although of uncertain significance, this finding, when combined with established morphologic differences, raises the possibility that EFH is unrelated to classic FH.

Immunohistochemistry in diagnosis of soft tissue tumours

Immunohistochemistry in soft tissue tumours, and especially sarcomas, is used to identify differentiation in the neoplastic cells. In some cases, specific antigens are expressed; however, an initial panel of antibodies is often required in order to establish the broad lineage, with a subsequent, more focused, panel to allow classification. Immunohistochemical evaluation must be employed with the clinical picture, the morphology, and, when necessary, other ancillary techniques such as molecular genetics and cytogenetics. Whereas some diagnoses are evident on morphology, many soft tissue neoplasms are seen microscopically as spindle cell, epithelioid cell, small round cell or pleomorphic tumours that need to be further characterized. This article reviews selected applications of immunohistochemistry in the diagnosis of each of the principal morphological groups, concentrating on areas of most use in daily practice.