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

Dermatofibrosarcoma Protuberans in Children

OPINION STATEMENT

Paediatric dermatofibrosarcoma protuberans (DFSP) is a rare soft tissue malignant tumour which displays aggressive local behaviour and has low metastatic potential. The diagnosis is often delayed as DFSP is usually mistaken for other skin conditions, particularly in the early stages of disease. DFSP tends to follow an indolent course after the initial presentation with what is often described as a "rubbery lump". As the disease progresses, the lump tends to enlarge, change colour, and exhibit a more nodular consistency. In rare cases, DFSP can present as an ulcerated exophytic lesion or a depressed area of skin, making diagnosis even more challenging. A high index of suspicion is warranted for early diagnosis, and referral to a specialist unit with expertise in both oncologic resection and reconstruction. DFSP tumours arise from the dermis and grow with finger-like projections. Therefore, in cosmetically sensitive or functionally important locations, an excision and analysis technique that assesses all excision margins is the gold standard of care. Slow Mohs technique performed with en bloc excision is a well-tolerated option for oncologic resection of the tumour. Mohs technique can also be considered but can be challenging in children for reasons explained below. As an alternative, depending on the anatomical location, tumours can be excised with a wide local excision. While an excision technique that incorporates the deep fascia with a 3-cm peripheral margin is acceptable in adults, planning of the excision margin in children should involve consideration of preoperative imaging with MRI, site of the tumour, age, and physical built of the child. Patients should be offered all treatment options considering the local outcomes, available expertise, and cost. A multidisciplinary approach and good communication between team members is crucial. Close collaboration with a pathologist who is familiar with sectioning technique that allows margin control is of paramount importance. Soft tissue reconstruction should be performed immediately after oncologic clearance, although a staged approach may be required. Adjuvant radiotherapy should be avoided in children due to the long-term risk of secondary malignancies and potential for growth disruption.

A case of a large solitary fibrous tumor in the thigh, displaying NAB2ex4-STAT6ex2 gene fusion

A solitary fibrous tumor (SFT) is documented in several body sites. However, there are few reports on the radiological and corresponding histopathological, including immunohistochemical, features of SFT in the lower extremities. A 58-year-old male presented with a lump in his right thigh of 6 months duration. Plain radiograph revealed a soft tissue lesion in his right thigh, involving the adjacent mid-diaphysis and showing focal cortical thickening and calcification. Magnetic resonance imaging scans displayed two well-defined, T1-isointense and T2 heterogeneously hyperintense lesions, measuring together 15 cm in the intermuscular plane and the juxtacortical location along the mid-diaphyseal region of the right femur. Radiologically, the differential diagnoses considered were undifferentiated pleomorphic sarcoma and synovial sarcoma. Microscopic examination of the core biopsy and the resected tumor revealed a tumor composed of cells with oval to spindle-shaped nuclei in a variably collagenized stroma, including hyalinized blood vessels and focal dystrophic calcification. Mitotic figures were 4/10 high power fields. Immunohistochemically, the tumor cells were positive for CD34, BCL2, and STAT6. Diagnosis of malignant SFT was offered. The tumor displayed NAB2ex4-STAT6ex2 gene fusion on molecular testing. This constitutes a relatively uncommon case report of a large SFT in the thigh, including its radiological and pathological features, confirmed by STAT6 immunostaining. An SFT should be considered in cases of slow-growing, well-defined soft tissue tumors, which are isointense on T1 and heterogeneously hyperintense on T2-weighted sequences, and display calcification and cortical thickening of the adjacent bones. Various differential diagnoses and their treatment-related implications in such cases are discussed herewith.

Clear Cell Proliferations of the Skin: A Histopathologic Review

ABSTRACT

Cutaneous clear cell proliferations encompass a heterogenous group of several primary cutaneous neoplasms and metastatic tumors with different histogenesis. Many of these clear cell proliferations may seem strikingly similar under the microscope resulting in challenging diagnosis. In many of these clear cell lesions, the reason for the clear or pale appearance of proliferating cells is unknown, whereas in other ones, this clear cell appearance is due to intracytoplasmic accumulation of glycogen, mucin, or lipid. Artifacts of tissue processing and degenerative phenomenon may also be responsible for the clear cell appearance of proliferating cells. Awareness of the histopathologic findings as well as histochemical and immunohistochemical techniques are crucial to the accurate diagnosis. This review details the histopathologic features of clear cell cutaneous proliferations, classifying them according their type of differentiation and paying special attention to the histopathologic differential diagnosis among them.

Current Diagnosis and Treatment Options for Cutaneous Adnexal Neoplasms with Follicular Differentiation

Neoplasms derived from follicular tissue are extremely rare. Clinically, they are reported as non-symptomatic, slow-growing nodules. These lesions are mainly benign, but the malignant type can occur. Mainly middle-aged people (50-60 years of age) are affected. These carcinomas are mainly localized on the head and neck or torso. They can be locally aggressive and infiltrate surrounding tissue and metastasize to regional lymph nodes. In the minority of cases, distant metastases are diagnosed. Quick and relevant diagnosis is the basis of a treatment for all types of tumors. The patient's life expectancy depends on multiple prognostic factors, including the primary tumor size and its mitotic count. Patients should be referred to a specialized skin cancer center to receive optimal multidisciplinary treatment. This article tries to summarize all the information that is currently available about pathogenesis, diagnosis, and treatment methods of follicular tumors.

Differences and similarities between cancer and somatic stem cells: therapeutic implications

Over the last decades, the cancer survival rate has increased due to personalized therapies, the discovery of targeted therapeutics and novel biological agents, and the application of palliative treatments. Despite these advances, tumor resistance to chemotherapy and radiation and rapid progression to metastatic disease are still seen in many patients. Evidence has shown that cancer stem cells (CSCs), a sub-population of cells that share many common characteristics with somatic stem cells (SSCs), contribute to this therapeutic failure. The most critical properties of CSCs are their self-renewal ability and their capacity for differentiation into heterogeneous populations of cancer cells. Although CSCs only constitute a low percentage of the total tumor mass, these cells can regrow the tumor mass on their own. Initially identified in leukemia, CSCs have subsequently been found in cancers of the breast, the colon, the pancreas, and the brain. Common genetic and phenotypic features found in both SSCs and CSCs, including upregulated signaling pathways such as Notch, Wnt, Hedgehog, and TGF-β. These pathways play fundamental roles in the development as well as in the control of cell survival and cell fate and are relevant to therapeutic targeting of CSCs. The differences in the expression of membrane proteins and exosome-delivered microRNAs between SSCs and CSCs are also important to specifically target the stem cells of the cancer. Further research efforts should be directed toward elucidation of the fundamental differences between SSCs and CSCs to improve existing therapies and generate new clinically relevant cancer treatments.

p90RSK-MAGI1 Module Controls Endothelial Permeability by Post-translational Modifications of MAGI1 and Hippo Pathway

Previously, we reported that post-translational modifications (PTMs) of MAGI1, including S741 phosphorylation and K931 de-SUMOylation, both of which are regulated by p90RSK activation, lead to endothelial cell (EC) activation. However, roles for p90RSK and MAGI1-PTMs in regulating EC permeability remain unclear despite MAGI1 being a junctional molecule. Here, we show that thrombin (Thb)-induced EC permeability, detected by the electric cell-substrate impedance sensing (ECIS) based system, was decreased by overexpression of dominant negative p90RSK or a MAGI1-S741A phosphorylation mutant, but was accelerated by overexpression of p90RSK, siRNA-mediated knockdown of magi1, or the MAGI1-K931R SUMOylation mutant. MAGI1 depletion also increased the mRNA and protein expression of the large tumor suppressor kinases 1 and 2 (LATS1/2), which inhibited YAP/TAZ activity and increased EC permeability. Because the endothelial barrier is a critical mediator of tumor hypoxia, we also evaluated the role of p90RSK activation in tumor vessel leakiness by using a relatively low dose of the p90RSK specific inhibitor, FMK-MEA. FMK-MEA significantly inhibited tumor vessel leakiness at a dose that does not affect morphology and growth of tumor vessels in vivo. These results provide novel insights into crucial roles for p90RSK-mediated MAGI1 PTMs and the Hippo pathway in EC permeability, as well as p90RSK activation in tumor vessel leakiness.

Comparison of CD34 expression in fibrous reactive hyperplasia and healthy oral mucosa

OBJECTIVES

Fibrous reactive hyperplasia (FRH) is a common fibrous lesion in the oral cavity. The disease characteristics of FRH, including the expression patterns of CD34, which is a well-known fibroblast marker, have not been investigated in detail. Therefore, in this study, we aimed to investigate the characteristics of FRH compared to those of the healthy mucosa, based on CD34 expression profiles.

METHODS

CD34 expression was analyzed at the protein and mRNA levels using immunohistochemistry, quantitative polymerase chain reaction, and in situ hybridization (ISH).

RESULTS

CD34 was not expressed in the lamina propria of the oral mucosa, but was commonly observed in submucosal fibroblasts. CD34-positive fibroblasts were commonly observed in FRH. A total of 17 out of 19 cases (89.5%) were CD34-positive. Furthermore, we identified a significant difference in the ratio of CD34-positive cells between the healthy and FRH tissues. Quantitative polymerase chain reaction showed that CD34 mRNA was expressed in all cases of FRH, and CD34 mRNA expression in FRH samples was found to be localized to spindle-shaped fibroblasts, as determined by ISH. A positive correlation was also found between the CD34 mRNA levels and the proportion of the CD34-positive cells.

CONCLUSIONS

These findings suggest that the increase in collagen synthesis in CD34-positive fibroblasts in the submucosa leads to the development of FRH. To our knowledge, this is the first report confirming the mRNA expression patterns of CD34 in FRH.

The efficacy of Mohs micrographic surgery over the traditional wide local excision surgery in the cure of dermatofibrosarcoma protuberans

Usually most patients with dermatofibrosarcoma protuberans (DFSP) may present rather late when the tumor is in protuberant phase due to its rarity and indolent onset. It has a high propensity for local recurrence and destructive nature. Management of DFSP requires a biopsychosocial and Multidisplinary approach regardless of the clinical or immunohistochemical variant. Surgery is the Gold standard management of localized disease. DFSP rarely exhibits any lymphatic or hematogenous dissemination. It is because of its high recurrence rate associated with Wide Local Excision (WLE), the introduction of Mohs micrographic surgery (MMS) has really helped in reducing the rates of recurrence of DFSP. Thus, the aim of this meta-analysis and systemic review is to advocate for MMS over WLE for DFSP and other cutaneous malignancies using DFSP as a prototype. The objective of this study were to conduct a meta-analysis on comparative surgical methods used in the cure of DFSP with regards to WLE verses MMS, to evaluate the cure rates with relation to recurrence rates, offer a recommendation on the various treatment modalities based on the location of lesion, and use of adjuvant therapy in different clinical-medical setups. A comprehensive retrospective analysis search in EMBASE, Google Scholar and Medline (PubMed) for studies published from 2008 to 2018 containing the surgical management of DFSP with WLE verses MMS were reviewed. Five studies of moderate-quality evidence (level B) with a pooled patient load of 684 was analyzed and found for recurrence of DFSP after WLE and MMS to be 9.10% and 2.72% respectively after an average follow-up time for both groups of 5.32 years with a female predominance of 1.58. The trunk is the commonest site for the DFSP lesion which was at 52.80% then the upper and lower extremities zones and the head and neck zones at 31.75% and 15.45% respectively. The pooled adjusted odds ratio (OR) analysis indicated that there was a direct relationship with regards the reduced recurrence rate of DFSP in the MMS group compared to the WLE group (OR:0.31;95%; CI :0.17-0.56). Furthermore, there was significant association between the reduced recurrence rate with the MMS in DFSP patients with a statistical P-value of 0.0001 at 95% CI. The expected increased recurrence rate by zones was in WLE head and neck zone at 38.19% then trunk and extremities zone at 13.34%. In the MMS group it was at of 23.4% as compared to 16.0% in the head and neck zone. Mohs Micrographic Surgery (MMS) is more efficacious in the cure rate and recurrence reduction of DFSP and should be advocated for as first line therapy especially in high recurrence prone zones.

Intraoral Cutaneous Hamartomas-Clinicopathologic and Immunohistochemical Characteristics of 3 Cases

Intraoral cutaneous hamartomas (ICHs) are uncommon mucosal lesions characterized microscopically by a combination of cutaneous structures, including various stages of follicular and sebaceous elements. Due to their rarity, the clinicopathologic and immunohistochemical attributes of ICHs have not been thoroughly delineated. Three cases of ICH were identified from our records, and formalin-fixed paraffin-embedded sections were immunohistochemically stained with antibodies against androgen receptor, estrogen receptor, and progesterone receptor, p63, factor XIIIα, and CD34. All 3 ICHs involved the buccal mucosa with an M:F ratio = 2:1 and mean age = 42.3 years (age range: 27-61 years). ICHs presented as thickened, painless, white and yellow plaques or nodules of long duration, measuring 0.6-1.5 cm. No history of skin graft in the area of the lesions was reported. Histopathologically, the lesions showed aggregates of rudimentary folliculosebaceous structures. Although well-defined piloerector muscles were present in all cases of ICH, bona fide hair follicles and isolated hair shafts were identified only in 1 case. The overlying oral epithelium exhibited epidermis-like morphological features, while inflammation was generally absent. Immunohistochemically, strong and diffuse nuclear staining for androgen receptor and factor XIIIα was observed in the sebaceous glands, and estrogen receptor and p63 reactivity were confined exclusively to the peripheral basal cells, while progesterone receptor staining was negative in ICHs. CD34 diffusely decorated the lesional stroma. In conclusion, ICH is a rare lesion composed of cutaneous elements in an abnormal location. A predilection for the buccal mucosa is reported in the current study.

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

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

Congenital fibroblastic connective tissue nevi: Unusual and misleading presentations in three infantile cases

BACKGROUND

Fibroblastic connective tissue nevi (FCTN) are benign skin conditions characterized by bland spindle cells infiltrating the reticular dermis and the upper subcutis with preservation of adnexal structures. A subset of FCTN expresses CD34, which may cause difficulties in the differential diagnosis, in particular with dermatofibrosarcoma (DFSP). We aim to study clinical and histological main features of congenital FCTN to better understand their heterogeneity.

METHODS

We present 3 cases of congenital FCTN with misleading pseudo-tumoral presentations and compare them with published cases in literature. We provide a diagnostic algorithm for congenital neonatal connective tissue tumors.

RESULTS

Clinically, FCTN mostly present as well-limited and nontender plaques or nodules mainly located in the neck and face areas or in the trunk. Histologically, FCTN are composed of irregularly distributed fascicles of bland spindled cells and are defined by a list of fundamental features: (i) no atypia, pleomorphism, or mitotic activity; (ii) skin appendages entrapped but unaffected; (iii) no evidence for malignancy. In most cases CD34 is positive, but in some cases, cells can express SMA or are even CD34- and SMA-.

CONCLUSION

The initial presentation and natural history of FCTN fit better with a neoplasm than with a hamartoma. Thus, we suggest replacing the term "nevus" with tumor and considering fibroblastic connective tissue tumor (FCTT) as the right denomination of this clinico-pathological entity. FCTTs are difficult to diagnose due to their clinical heterogeneity. Clinical and histological malignant and benign differential diagnoses are discussed.

Nonepithelial Tumors and Tumor-like Lesions of the Skin and Subcutis in Children

This overview of mesenchymal tumors presenting in the skin and/or subcutis in children brings together the range of neoplasms and hamartomas which are seen in this age-group. It is not surprising from the perspective of the pediatric or general surgical pathologist that vascular anomalies, including true neoplasms and vascular malformations, are the common phenotypic category. Since there is considerable morphologic overlap among these lesions, clinicopathologic correlation may be more important than for many of the other mesenchymal tumors. The skin and subcutis are the most common sites of clinical presentation for the infantile myofibroma which is the most common of fibrous mesenchymal tumors in children. Several of the other mesenchymal tumors are more common adults-like dermatofibrosarcoma protuberans, but nonetheless have an important presence in children, even as a congenital neoplasm. A lipomatous tumor in a young child should be considered as a possible manifestation of an overgrowth syndrome.

Cyclin-dependent kinase 5 stabilizes hypoxia-inducible factor-1α: a novel approach for inhibiting angiogenesis in hepatocellular carcinoma

We recently introduced CDK5 as target in HCC, regulating DNA damage response. Based on this and on our previous knowledge about vascular effects of CDK5, we investigated the role of CDK5 in angiogenesis in HCC, one of the most vascularized tumors. We put a special focus on the transcription factor HIF-1α, a master regulator of tumor angiogenesis.

The interaction of CDK5 with HIF-1α was tested by Western blot, PCR, reporter gene assay, immunohistochemistry, kinase assay, co-immunoprecipitation, mass spectrometry, and mutation studies. In vivo, different murine HCC models, were either induced by diethylnitrosamine or subcutaneous injection of HUH7 or HepG2 cells. The correlation of vascular density and CDK5 was assessed by immunostaining of a microarray of liver tissues from HCC patients.

Inhibition of CDK5 in endothelial or HCC cells reduced HIF-1α levels in vitro and in vivo, and transcription of HIF-1α target genes (VEGFA, VEGFR1, EphrinA1). Mass spectrometry and site directed mutagenesis revealed a stabilizing phosphorylation of HIF-1α at Ser687 by CDK5. Vascular density was decreased in murine HCC models by CDK5 inhibition.

In conclusion, inhibiting CDK5 is a multi-modal systemic approach to treat HCC, hitting angiogenesis, as well as the tumor cells themselves.

Interleukin 8 serum concentration, but not lactate dehydrogenase activity, positively correlates to CD34 antigen in melanoma tumors

CD34 promotes melanoma cell motility, negative regulation of cellular response to hypoxia and positive regulation of vasculogenesis. Interleukin 8 (IL-8) is responsible for angiogenic response in endothelial cells, increases proliferation, metastasis, and survival of melanoma cells. The aim of our study was evaluation of relationship between CD34 immunoexpression and IL-8 serum concentrations in melanoma patients. The study was conducted on patients with melanoma that were divided in: Clark II (17 patients - 19.3%), Clark III (33 patients - 37.5%), Clark IV (22 patients - 25%), and Clark V (16 patients - 18.2%) levels. CD34 expression was absent for Clark II melanomas, and positive for Clark III (6.1%), Clark IV (40.9%), and Clark V (56.2%). The CD34 immune-mark was highly positive only for Clark IV and V levels. Interleukin 8 (IL-8) had high values (above 15 pg/mL) for all patients with melanoma (58.9% - Clark II; 87.8% - Clark III; 90.9% - Clark IV and 93.7% - Clark V). We have found a strong and statistically significant correlation between CD34 and IL-8 for Clark IV (r = 0.54, P < 0.05) and Clark V (r = 0.72, P < 0.05) melanomas. CD34 and IL-8 are associated with poor prognosis of melanoma, metastasis, and neoangiogenesis.

Immunohistochemistry in Dermatopathology: A Retrospective Study of the Most Frequently Used Antibodies

Immunohistochemistry (IHC) is an ancillary technique to improve diagnostic accuracy and prognosis in histopathology of both inflammatory and neoplastic cutaneous disorders. However, only a few studies address specifically the set of antibodies available for inflammatory or neoplastic skin diseases. In this study, we analyzed the IHC studies performed for inflammatory and neoplastic skin disorders in cutaneous biopsies taken in our department during 1 year. From a total of 8579 skin biopsies performed throughout the year 2011 in our department, IHC studies were performed in 283 cutaneous biopsies. The total number of different antibodies used in the IHC studies of those 283 skin biopsies was 129. These antibodies were used in 1421 studies, with a mean of 5 cases per antibody studied. The proliferative marker MIB-1 was the single antibody with the highest number of studies, with a total of 119 (8.3% of all IHC studies performed), followed by 113 of CD3 (7.9% of total IHC studies) and 108 of Melan-A (7.6% of total IHC studies). Other hematopoietic differentiation markers, such as CD20, CD4, and CD8, and other melanocytic markers, such as S-100 protein, Melan-A, and HMB-45, were all investigated with a frequency greater than 50 studies each. The 2 most frequent categories were melanocytic neoplasms, which represented 25% of all specimens studied by IHC, and the proliferations of lymphohematopoietic nature, which were 20% of all studied samples and represented by far the highest number of IHC stains per case to reach a final diagnosis. Both previous categories together accounted for 45% of all diagnoses in which IHC was performed. We compare our results with the only similar study previously published in the literature. The gold standard panel of antibodies that should be available in everyday practice in dermatopathology to arrive at a specific diagnosis in each cutaneous inflammatory disease or neoplastic process involving the skin is still a matter of discussion.

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.

Hypocellular Plaque-Like CD34-Positive Dermal Fibroma (Medallion-Like Dermal Dendrocyte Hamartoma) Presenting as a Skin-Colored Dermal Nodule

Plaque-like CD34-positive dermal fibromas, also known as medallion-like dermal dendrocyte hamartomas (MDDHs), are a recently recognized group of congenital and acquired spindle cell neoplasms that may appear histologically similar to dermatofibrosarcoma protuberans. Recognizing the clinical heterogeneity of this neoplasm and the subtle pathologic differences are crucial to making the correct diagnosis and avoiding the aggressive surgical intervention required to treat a dermatofibrosarcoma protuberans. We present the case of a 9-year-old girl with an acquired variant of a plaque-like CD34-positive dermal fibroma without clinical epidermal change. Our case expands the clinical spectrum to include an acquired variant of a plaque-like CD34-positive dermal fibroma without clinical epidermal change. Examination of more cases is needed to determine whether all clinical variants are truly subtypes of the same neoplasm or represent distinct CD34-positive spindle cell proliferations.

Oral plexiform schwannoma with unusual epithelial induction

Rare epithelial structures in benign nerve sheath tumors are almost always glandular in appearance. We describe a case of intraoral plexiform schwannoma with concurrent squamous epithelial hyperplasia. The lesion occurred as a pigmented nodule on the gingiva of a 35-year-old woman with no systemic involvement. Histologically, unencapsulated, plexiform fascicular proliferations of schwann cells could be traced from the submucosa to the lamina propria, finally making direct contact with heavily pigmented, elongated rete ridges of the overlying epithelium. Also noted was a schwannian network centered on clustered odontogenic epithelial rests of mature squamous-type, the number and size of which had markedly increased. Impressive immunoprofiles of periepithelial neural microfascicles included the complete absence of axon and perineurium and the unexpected presence of endoneurial fibroblasts. The repertoire of epithelial changes was in a confined area with no extension beyond, supporting hyperplasia induction by an underlying/surrounding schwannoma.

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.

Linear trichilemmoma following a blaschkoid pattern: a clinical dilemma

BACKGROUND

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

OBJECTIVES

We report a case of linear trichilemmoma following blaschkoid pattern.

METHODS

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

RESULTS

On histopathology, a diagnosis of trichilemmoma was made.

CONCLUSION

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

Dermatofibrosarcoma protuberans in a 10-year-old child

BACKGROUND

Dermatofibrosarcoma protuberans is a rare mesenchymal malignancy in childhood and adolescence. The tumor is characterized by dermal spindle cell proliferation with infiltration of subcutaneous tissue, expression of CD34, and a specific fusion of the platelet-derived growth factor beta with the collagen type 1alpha1 gene.

MAIN OBSERVATION

We observed a 10-year-old girl with a medaillon-like, asymptomatic plaque on the chest that was diagnosed as DSFP. The tumor was completely removed by delayed Mohs surgery. Follow-up so far has shown a complete response.

CONCLUSIONS

The prognosis of dermatofibrosarcoma protuberans in children is excellent as long as early diagnosis is followed by complete excision with Mohs surgery as a golden standard.

What makes cancer stem cell markers different?

Since the cancer stem cell concept has been widely accepted, several strategies have been proposed to attack cancer stem cells (CSC). Accordingly, stem cell markers are now preferred therapeutic targets. However, the problem of tumor specificity has not disappeared but shifted to another question: how can cancer stem cells be distinguished from normal stem cells, or more specifically, how do CSC markers differ from normal stem cell markers? A hypothesis is proposed which might help to solve this problem in at least a subgroup of stem cell markers. Glycosylation may provide the key.

CD34-positive superficial myxofibrosarcoma: a potential diagnostic pitfall

BACKGROUND

Myxofibrosarcoma (MFS) arises most commonly in the proximal extremities of the elderly, where it may involve subcutaneous and dermal tissues and masquerade as benign entities in limited biopsy samples. We encountered such a case, in which positivity for CD34 and morphologic features were initially wrongly interpreted as a 'low-fat/fat-free' spindle cell/pleomorphic lipoma. Case series have not assessed prevalence of CD34 reactivity among cutaneous examples of MFS.

METHODS

We performed a systematic review of our institution's experience, selecting from among unequivocal MFS resection specimens those superficial cases in which a limited biopsy sample might prove difficult to interpret. These cases were immunostained for CD34 and tabulated for clinicopathologic characteristics.

RESULTS

After review of all MFS diagnoses over 5 years (n = 56), we identified a study group of superficial MFS for comparison to the index case (total n = 8). Of these, the index and three additional cases (4 of 8, 50%; 2 low, 2 high grade) demonstrated positive staining for CD34, with diffuse staining of spindled cells including cellular processes. Four additional cases showed no or equivocal/rare staining.

CONCLUSIONS

CD34 positivity should be recognized as prevalent among such cases and should not be inappropriately construed as inveighing against a diagnosis of MFS in favor of benign entities.

Perineal Nodular Induration (“Biker’s Nodule”)

Perineal nodular induration (PNI) is a fibroblastic pseudotumor that presents almost exclusively in male cyclists. It develops in the soft tissues of the perineum immediately posterior to the scrotum, as a bilateral or single, central or lateralized mass. Although well known to sport medicine specialists, it is a scarcely documented entity in the pathology literature. We present 2 cases of PNI with fine-needle aspiration cytology and immunohistochemistry. They consisted of a paucicellular fibroblastic proliferation containing CD34-reactive spindle and epithelioid cells, small foci of fibrinoid degeneration, numerous blood vessels, and entrapped groups of mature fat cells. Our cases show that the histopathological features of PNI are more varied than those previously described and its immunohistochemical profile is wider. A central cystic focus and a zonal pattern are not consistent features of this entity. The lesional cells can express CD34, a hitherto unreported immunohistochemical finding.

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.

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

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

Comparison of CD34, CD31, and factor VIII-related antigen immunohistochemical expression in feline vascular neoplasms and CD34 expression in feline nonvascular neoplasms

The diagnosis of vascular neoplasms is often facilitated by the use of immunohistochemical markers such as factor VIII-related antigen, CD31, and CD34. However, the relative sensitivity and specificity of these markers have not been compared in cat vascular neoplasms. In this study, these 3 immunohistochemical markers were evaluated in 61 endothelial neoplasms (50 hemangiosarcomas and 11 hemangiomas) in 59 cats. All neoplasms were labeled by all 3 markers. CD34 had the highest average immunolabeling intensity in neoplastic endothelial cells. CD31 had the lowest average background labeling, followed by CD34 and factor VIII-related antigen, respectively. CD34 expression was also examined in 130 nonvascular neoplasms of cats; 14 of 62 epithelial neoplasms, 39 of 43 mesenchymal neoplasms, 8 of 23 leukocytic neoplasms, and 2 of 2 melanomas were positive. Given the broad expression of CD34 in mesenchymal neoplasms, this marker has limited diagnostic relevance for vascular neoplasms of cats.

Neurofibroma subungueal solitário: relato de um caso inédito no sexo masculino

Neurofibroma é uma proliferação hamartomatosa de origem neuromesenquimal. Pode ser encontrado associado à neurofibromatose ou como tumor solitário, sendo sua apresentação subungueal solitária bastante rara. É mais frequente em pacientes do sexo feminino e a cirurgia é o tratamento de escolha. Relatase um caso de um paciente masculino, com lesão tumoral subungueal no pododáctilo, cuja biópsia e imuno-histoquímica foram compatíveis com neurofibroma. Até a presente data, menos de dez casos sobre neurofibromas subungueais sem associação com doença de Von Recklinhausen foram documentados, sendo este o primeiro caso relatado no Brasil e o único no sexo masculino no mundo

Distinguishing neurofibroma from desmoplastic melanoma: the value of the CD34 fingerprint

We have observed 'fingerprint' immunopositivity in association with perineurioma and neurofibroma. A fingerprint consists of delicate, elongated areas of positive labeling that fall between collagen bundles, thereby creating a whorled configuration that is reminiscent of a human fingerprint. At present, the differential diagnosis between early desmoplastic melanoma and neurofibroma remains challenging in a subset of cases because of overlapping histopathological and immunohistochemical features. To assess whether fingerprint CD34 reactivity could be contributory in this context, we stained 50 desmoplastic melanomas and 50 neurofibromas with CD34. Fingerprint CD34 labeling was present in greater than 30% of the proliferation in 96% (n = 48) of neurofibromas and in only 4% (n = 2) of desmoplastic melanomas. Over two-thirds of the neurofibromas exhibited a CD34 fingerprint involving more than 60% of their surface area. In the two cases of desmoplastic melanoma that showed CD34 fingerprint positivity, the staining was patchy and involved less than 60% of the tumor. In partially staining neurofibromas, areas without a CD34 fingerprint tended to occur in central lobular areas. We conclude that CD34 fingerprint immunoreactivity is useful in distinguishing neurofibroma from early desmoplastic melanoma, especially if the fingerprint involves more than 60% of a tumor's cross-sectional area.

Epithelioid sarcoma and unclassified sarcoma with epithelioid features: clinicopathological variables, molecular markers, and a new experimental model

BACKGROUND

Epithelioid sarcoma (ES) and unclassified sarcoma with epithelioid features (USEF) are clinically and therapeutically unresolved. We compared ES and USEF patients' clinical behavior, treatment, outcome, and molecular marker expression. Furthermore, preclinical ES study models were developed to enable comprehensive benchside investigations.

PATIENTS AND METHODS

A database of ES and USEF patients (n = 116) treated since 1992 was created. A clinically annotated ES-USEF tissue microarray (TMA) was assayed for tumor-related markers. Newly established human and commercially available ES cell lines were characterized and tested in vivo.

RESULTS

ES and USEF patients presenting with localized disease exhibited 22% and 25% local recurrence rates, 35% and 19% nodal metastasis rates, and 41% and 53% distant metastasis rates (median follow-up, 54 months and 39 months, respectively). The 5- and 10-year disease-specific survival rates were 88% and 43% and 52% and 42% (ES and USEF, respectively). TMA immunohistochemistry identified integrase interactor (INI)-1 loss, cancer antigen 125, and p53 nuclear expression as significantly more common in ES than USEF cases. Both cell lines preserved ES morphological and biochemical characteristics in vitro and in vivo; loss of INI-1 was shown to occur in both lines.

CONCLUSIONS

Enhanced knowledge of ES and USEF clinical behavior, marker expression, and molecular determinants, extended via experimental models, will hopefully accelerate development of urgently needed effective targeted therapies for ES and USEF.

Podoplanin and CD34 in peripheral nerve sheath tumours: focus on neurofibromatosis 1-associated atypical neurofibroma

Patients suffering from neurofibromatosis type 1 and 2 (NF1 and NF2) are the main risk groups to develop peripheral nerve sheath tumours (PNSTs). In the present study, adhesion molecules CD34 and podoplanin were assessed in regard to their value for tumour classification and as indicators for tumour progression. A total of 103 NF1-, NF2- and schwannomatosis-associated neurofibromas, schwannomas and malignant peripheral nerve sheath tumours (MPNST), as well as 20 sporadic vestibular schwannomas and 9 control tissue samples, were labelled immunohistochemically for detection of podoplanin and CD34. CD34 was shown to be expressed in MPNST and all benign PNSTs except for the compact cellular parts of both, schwannomas and atypical neurofibromas. Podoplanin showed an inverse expression pattern to CD34 labelling mainly the compact parts of schwannoma and atypical neurofibroma. MPNSTs were characterized by strong podoplanin staining at the invasive front. NF1-patients who suffered from atypical neurofibromas did not develop MPNST at a higher frequency than other NF1-patients, although these tumours expressed podoplanin. Ki-67 proliferation indices did not differ significantly between neurofibromas, atypical neurofibromas and schwannomas. In accordance with other studies, CD34 was found to be of limited value for classification and grading of PNST due to its ubiquitous expression. Podoplanin expression in schwannoma and atypical neurofibroma adds to other phenotypic and genotypic similarities between these tumours, like nuclear atypia, regressive changes and euploid polyploidisation. Podoplanin expression in atypical neurofibroma was not associated with tumour progression towards MPNST.

Desmoplasia: not always a bad thing

Desmoplasia describes a histological pattern characterized by a hyalinized stroma and a minimal cellular infiltrate. In non-cutaneous neoplasms, this pattern of stromal response is classically associated with malignancy, whereas in cutaneous pathology, desmoplasia is observed in malignant as well as benign neoplasms. Given this, the obvious question is whether desmoplasia associated with a benign neoplasm is any different from that associated with malignant tumours. Is the stromal response a mere epiphenomenon, or does it actually contribute to the biological behaviour of the neoplasm? What happens at the tumour-host interface? Which molecules are involved in mediating the desmoplastic reaction pattern? This review is an attempt to answer these questions. Examples of benign and malignant cutaneous neoplasms associated with the desmoplastic reaction pattern will be included.

Plaque-like CD34-positive dermal fibroma ("medallion-like dermal dendrocyte hamartoma"): clinicopathologic, immunohistochemical, and molecular analysis of 5 cases emphasizing its distinction from superficial, plaque-like dermatofibrosarcoma protuberans

Medallion-like dermal dendrocyte hamartoma (DH) and superficial (plaque-like) dermatofibrosarcoma protuberans (DFSP) are CD34-positive dermal neoplasms with overlapping clinicopathologic features. We analyzed the clinical, histomorphologic, and molecular criteria of 5 DH and 7 DFSP to delineate diagnostically relevant differences between incipient dermal DFSP and its benign look-alike, DH. We expand the clinical and histologic spectrum of DH. As medallion-like dermal DH is neither of dermal dendrocyte lineage nor a genuine hamartoma, we propose instead the descriptive term of plaque-like CD34-positive dermal fibroma (PDF). Both PDF/DH and DFSP presented as slightly pigmented and indurated plaques on neck, trunk, and extremities. Histologically, DFSP was characterized either by horizontally oriented spindle cell fascicles or by diffusely arranged fibroblasts within a slightly myxoid stroma in the upper two-thirds of the dermis, whereas PDF/DH presented with a cellular band-like fibroblastic proliferation mostly in the papillary and adjacent upper reticular dermis. Only one congenital PDF/DH in a 9-year-old boy extended into the septa of the subcutaneous fat. Formalin-fixed paraffin-embedded archival tissue was used for detection of the COL1A1-PDGFB gene rearrangement by multiplex reverse transcription-polymerase chain reaction (RT-PCR) and by dual color fusion fluorescence in-situ hybridization (FISH). Archival blocs older than 4 years did not yield amplifiable RNA because of RNA degradation, whereas FISH analysis was feasible in all investigated cases. FISH analysis revealed COL1A1-PDGFB gene rearrangement in all DFSP cases (n=7), whereas RT-PCR could detect the COL1A1-PDGFB fusion transcript only in 1 DFSP. Two cases were negative. In 4 archival cases with storage between 4.5 and 12 years, RNA had been degraded making these cases unsuitable for RT-PCR. In PDF/DH, both RT-PCR and FISH analysis did not reveal any evidence of COL1A1-PDGFB gene rearrangement. We show that PDF/DH and superficial (plaque-like) DFSP, subtle clinicopathologic differences notwithstanding, are morphologic look-alikes that can be kept apart by molecular studies of the COL1A1-PDGFB gene fusion. For the detection of the COL1A1-PDGFB gene rearrangement in diagnostically difficult cases, RT-PCR and FISH analysis are reliable and helpful diagnostic tools. In archival formalin-fixed paraffin-embedded tissue, however, FISH analysis is more robust and exhibits a higher clinical sensitivity than RT-PCR.