Immunohistochemical study of CD34-positive dendritic cells of human dermis

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.

The capsule of human Meissner corpuscles: immunohistochemical evidence

Meissner corpuscles are cutaneous mechanoreceptors that are usually located in the dermal papillae of human glabrous skin. Structurally, these sensory corpuscles consist of a mechanoreceptive sensory neuron surrounded by non-myelinating lamellar Schwann-like cells. Some authors have described a partially developed fibroblastic capsule of endoneurial or perineurial origin around Meissner corpuscles; however, others have noted that these structures are non-encapsulated. As there is continuity between the periaxonic cells forming the sensory corpuscles and the cells of the nerve trunks, we used immunohistochemistry to examine the expression of endoneurial (CD34 antigen) or perineurial [Glucose transporter 1 (Glut1)] markers in human cutaneous Meissner corpuscles. We also investigated the immunohistochemical patterns of nestin and vimentin (the main intermediate filaments of the cytoskeleton of endoneurial and perineurial cells, respectively) in Meissner corpuscles. The most important finding from this study was that CD34-positive cells formed a partial/complete capsule of endoneurial origin around most Meissner corpuscles, without signs of other perineurial Glut1-positive elements. However, the cytoskeletal proteins of the capsular CD34-positive cells did not include either nestin or vimentin, so the cytoskeletal composition of these cells remains to be established. Finally, the intensity of the immunoreactivity for CD34 in the capsule decreased with ageing, sometimes becoming completely absent in the oldest individuals. In conclusion, we report the first immunohistochemical evidence of the capsule of Meissner corpuscles in humans and demonstrate the endoneurial origin of the capsule.

Hypertrophic and keloid scars fail to progress from the CD34- /α-smooth muscle actin (α-SMA)+ immature scar phenotype and show gradient differences in α-SMA and p16 expression

BACKGROUND

Our understanding of the pathogenesis underlying keloid scar formation is still very limited, and the morphological distinction between hypertrophic and keloid scars remains difficult.

OBJECTIVES

To test whether hypertrophic and keloid scars may reflect an inability to progress from immaturity to the desired mature normotrophic scar phenotype.

METHODS

Using whole-biopsy imaging and an objectively quantifiable way to analyse immunoreactivity, we have compared the immunohistopathological profiles of young immature scars with mature normotrophic scars, hypertrophic scars, and keloids with their surrounding-normal-skin.

RESULTS

Abnormal scars (hypertrophic scars and keloids) maintain the immature scar phenotype, characterized by a CD34^- (tumour biomarker) and α-smooth muscle actin (α-SMA)⁺ (myofibroblast) dermal region. This is in contrast to normal skin, surrounding-normal-skin and mature normotrophic scars that were CD34⁺ / α-SMA^- . Immature, hypertrophic and keloid scars showed abnormal epidermal differentiation (involucrin), but only hypertrophic scars and keloids showed increased epidermal thickness. Immature scars did show increased epidermal and dermal proliferation (Ki67), which was absent from abnormal scars, where mesenchymal hypercellularity (vimentin) and senescence (p16) were predominant. Keloidal collagen and α-SMA were previously considered to distinguish between hypertrophic scars and keloids. However, α-SMA staining was present in both abnormal scar types, while keloidal collagen was present mostly in keloids. There were no obvious signs of heterogeneity within keloid scars, and the surrounding-normal-skin resembled normal skin.

CONCLUSIONS

Both abnormal scar types showed a unique CD34^- /α-SMA⁺ /p16⁺ scar phenotype, but the differences between hypertrophic scars and keloids observed in this study were of a gradient rather than absolute nature. This suggests that scar progression to the mature normal scar phenotype is, for as yet unknown reasons, hindered in hypertrophic and keloid scars. What's already known about this topic? Hypertrophic and keloid scars both have sustained epidermal barrier dysfunction, suggesting the persistence of an immature scar phenotype. Morphological distinction between hypertrophic and keloid scars remains a topic of debate, although α-smooth muscle actin (α-SMA) and keloidal collagen have been considered distinguishing features of hypertrophic and keloid scars, respectively. It has been suggested that keloids are not simply homogeneous growths, as heterogeneity within keloid scars and possible involvement of the surrounding-normal-skin have been reported. What does this study add? An extensive whole-biopsy imaging and quantifiable immunohistochemical assessment of immature, mature normal, hypertrophic and keloid scars, including normal skin surrounding keloids. Hypertrophic and keloid scars maintain dermal characteristics of immature scars, rather than transitioning into the normal mature phenotype. Differences between hypertrophic and keloid scars were of a gradient rather than absolute nature, with keloids showing the more extreme phenotype. There was no obvious heterogeneity within keloids, and the normal skin surrounding keloids resembled normal skin. What is the translational message? Keloids remain primarily a clinical diagnosis. A raised scar with the CD34^- /α-SMA⁺ /p16⁺ phenotype with strong immunoreactivity for p16 and significant amounts of keloidal collagen, together with a thickened and strongly abnormal involucrin-stained epidermis, would sway the diagnosis towards keloid scars. A hypertrophic scar seems more likely when the CD34^- /α-SMA⁺ /p16⁺ phenotype shows very strong presence of α-SMA⁺ in large dermal nodules, with lesser p16 staining and absent or negligible keloidal collagen.

Hypocellular medallion-like dermal dendrocyte hamartoma on the abdomen of a 25 year old male

Medallion-like dermal dendrocyte hamartoma is a rare congenital lesion that is more commonly seen in females. It often presents at birth on the neck or upper trunk as a well-circumscribed, atrophic patch with wrinkling of the overlying skin. Clinically, the differential diagnosis includes atrophoderma, anetoderma, and congenital atrophic dermatofibrosarcoma protuberans. Histologic findings show epidermal atrophy and dermal spindle cell proliferation that is CD34 positive, along with Factor XIIIa in the original reports. Due to this CD34 positivity, another name for the lesion is plaque-like CD34+ dermal fibroma. We present a unique patient case as he is male and the lesion is located on his abdomen. Further reports and studies need to be done for thorough understanding of this neoplasm.

Polypoid Dermal Dendrocytic Hamartoma in a Giant Congenital Melanocytic Nevus

Giant congenital melanocytic nevus (CMN) might be complicated by the development of several tumor types, mainly melanoma and rhabdomyosarcoma, but also poorly differentiated neoplasms. Striking polypoid exophytic masses occasionally result from neuroectodermal and neuromesenchymal hamartomatous overgrowths, which lends support to the concept of pluripotential melanoblastomatous and neurocristic origin of these lesions. The present report describes what appears to be a unique example of dermal hamartomatous polypoid CD34+ fibrogenic proliferation devoid of melanin, namely a dendrocytoma, surrounded by the melanocytes from the nevus, located in the skin of the scrotum against a background of giant CMN. The differential diagnosis included dermatofibrosarcoma protuberans, giant-cell fibroblastoma, angiofibroma, Bednar tumor, other types of dermal dendrocytic hamartoma, and neurocristic cutaneous hamartoma. This case lends support to the proposed neurocristic origin of dermal fibrogenic cells.

CD34+ dermal dendritic cells and mucin deposition in dermatomyositis

Dermal mucinosis is often associated with collagen diseases such as rheumatoid arthritis, lupus erythematosus, and dermatomyositis, in addition to autoimmune thyroiditis. We report eight cases of dermal mucin deposition secondary to typical dermatomyositis with cutaneous lesions known as heliotrope rash and Gottron’s papules. Striking mucin deposition was observed in both the papillary dermis and reticular dermis of all biopsy specimens. Immunohistochemical analysis showed that CD34+ dermal dendritic cells (DDCs) in the perilesional area in combination with vimentin+ cells within the mucinous lesion might be important in giving rise to abnormal deposition of dermal mucin. On the other hand, numbers of factor XIIIa+ DDCs and tryptase+ mast cells were reduced within and surrounding the mucin deposition, as compared with those in the dermis of normal controls. A pathogenic mechanism of dermal mucin deposition is proposed.

Dermal dendritic cell population and blood vessels are diminished in the skin of systemic sclerosis patients: relationship with fibrosis degree and disease duration

Recent studies have suggested that the number of dermal dendritic cells is altered in the skin of patients with scleroderma and that these cells may have an important role in the pathogenesis of this disease. There is also a belief that insufficient blood flow to the affected organs may also be responsible for the disease. Our aim was to quantify CD34+ cells, factor XIIIa cells, and blood vessels in the skin of patients with systemic sclerosis and to correlate these data with fibrosis degree and duration of disease. Paraffin-embedded skin sections from patients with systemic sclerosis and from healthy subjects were immunolabelled with antibodies against CD34+ and factor XIIIa. Cells and blood vessels were quantified in the papillary and reticular dermis. Both, the number of CD34+ cells and factor XIIIa cells in the skin of patients with systemic sclerosis were reduced. The reduction of these cell types preceded the appearance of intense fibrosis, suggesting that fibrosis is not responsible of this phenomenon. Blood vessel volume and surface density were also reduced in the skin of systemic sclerosis patients. This reduction was also noted early in the evolution of the disease. Our results suggest that CD34+ cells and factor XIIIa cells may contribute to normal regulation of extracellular matrix assembly. We confirmed the observation that capillary density is diminished in scleroderma skin.

Expression and significance of α-SMA and PCNA in the vascular adventitia of balloon-injured rat aorta

The aim of this study was to investigate changes in the expression of α-smooth muscle actin (α-SMA) and proliferating cell nuclear antigen (PCNA) in the vascular adventitia of balloon-injured rat aortas in the second and sixth postoperative weeks. A total of 32 rats were divided into a control group and a balloon-injured group. The rats underwent vascular morphometric analysis and adventitial cell counting, as well as immunohistochemical staining of α-SMA and PCNA in postoperative weeks 2 and 6 for observation of the expression of each immune parameter in the vascular adventitia and calculation of the number of PCNA-positive nuclei and the PCNA labeling index (PCNALI) in the vascular adventitia. The area and thickness of the adventitia, the number of nuclei and the PCNALI of the vascular adventitia were significantly increased in the injured group compared with the control group (P<0.05), while the external elastic lamina area (EELA), internal elastic lamina area (IELA) and lumen area (LA) were significantly decreased (P<0.05) in the second week. The area and thickness of the adventitia, the number of nuclei and the PCNALI of the vascular adventitia were significantly increased in the injured group compared with the control group (P<0.05), while the EELA, IELA and LA were significantly reduced (P<0.05) in the sixth week, and were significantly lower than those in the injured group in the second week (P<0.05). The positive expression levels of α-SMA and PCNA in the vascular adventitia were significantly reduced compared with those in the second week after injury. The vascular adventitial cells underwent proliferation and phenotypic switching and participated in vascular remodeling and vascular restenosis following balloon-induced injury. The vascular contractile remodeling in the injured group was more evident in the sixth week than in the second week, followed by a more aggravated vascular stenosis. Consequently, the vascular remodeling was one of the causes of vascular restenosis.

Nephrogenic systemic fibrosis: evidence for oxidative stress and bone marrow-derived fibrocytes in skin, liver, and heart lesions using a 5/6 nephrectomy rodent model

Nephrogenic systemic fibrosis (NSF) is associated with gadolinium-based magnetic resonance imaging (MRI) contrast exposure in the setting of acute or chronic renal compromise. It has been proposed that circulating fibrocytes mediate the disease. A study was conducted to determine whether bone marrow-derived fibroblast precursors are involved in contributing to organ fibrosis in MRI contrast-treated rodents with renal insufficiency. Rats status post 5/6 nephrectomy underwent bone marrow transplant from human placental alkaline phosphatase (hPAP)-expressing donors. After engraftment, animals were treated with gadolinium-based MRI contrast (2.5 mmol/kg IP), during weekdays for 4 weeks, or an equivalent volume of normal saline. Dermal cellularity in the contrast-treated group was fourfold that of control. Skin cells from the contrast-treated group demonstrated greater hPAP expression with co-expression of pro-collagen I and α-smooth muscle actin-positive stress fibers. Donor and host cells expressed CD34. Dihydroethidium staining of skin was greater in the contrast-treated animals, indicating oxidative stress. This was abrogated when the animals were co-administered the superoxide dismutase mimetic tempol. In conclusion, a bone marrow-derived cell population is increased in the dermis of MRI contrast-treated rodents. The cell markers are consistent with fibrocytes mediating the disease. These changes correlate with oxidative stress and expression of Nox4, suggestive of a novel therapeutic target. Elucidation of the mechanisms of MRI contrast-induced fibrosis may aid in discovering therapies to this devastating disease.

Telocytes in human skin--are they involved in skin regeneration?

Telocytes (TCs), a particular interstitial cell type, have been recently described in a wide variety of mammalian organs (www.telocytes.com). The TCs are identified morphologically by a small cell body and extremely long (tens to hundreds of μm), thin prolongations (less than 100 nm in diameter, below the resolving power of light microscopy) called telopodes. Here, we demonstrated with electron microscopy and immunofluorescence that TCs were present in human dermis. In particular, TCs were found in the reticular dermis, around blood vessels, in the perifollicular sheath, outside the glassy membrane and surrounding sebaceous glands, arrector pili muscles and both the secretory and excretory portions of eccrine sweat glands. Immunofluorescence screening and laser scanning confocal microscopy showed two subpopulations of dermal TCs; one expressed c-kit/CD117 and the other was positive for CD34. Both subpopulations were also positive for vimentin. The TCs were connected to each other by homocellular junctions, and they formed an interstitial 3D network. We also found TCs adjoined to stem cells in the bulge region of hair follicles. Moreover, TCs established atypical heterocellular junctions with stem cells (clusters of undifferentiated cells). Given the frequency of allergic skin pathologies, we would like to emphasize the finding that close, planar junctions were frequently observed between TCs and mast cells. In conclusion, based on TC distribution and intercellular connections, our results suggested that TCs might be involved in skin homeostasis, skin remodelling, skin regeneration and skin repair.

Dendritic cells: novel players in fibrosis and scleroderma

Dendritic cells are professional antigen-presenting cells that are most studied for their function in mediating T-cell tolerance and T-cell activation. In addition, recent evidence indicates that dendritic cells can regulate the vasculature and function of fibroblast-type cells. The potential contribution of dendritic cells to scleroderma and fibrosis is not well-understood. In this article, we review recent studies as well as describe our own ongoing work that points toward a role for dendritic cells in scleroderma and fibrosis.

Application of a partial-thickness human ex vivo skin culture model in cutaneous wound healing study

A number of in vivo and ex vivo skin models have been applied to human wound healing studies. A reliable skin model, which recapitulates the features of human wound repair, is essential for the clinical and mechanical investigation of human cutaneous wound healing. Full-skin ex vivo culture systems have been used in wound healing studies. However, important structures of the skin, such as the differentiation of keratinocytes and epidermis-dermis junction, are poorly characterized in this model. This study aims to develop an optimized partial-thickness human ex vivo skin culture (HESC) model to maintain human skin characteristics in vitro. During our culture, the basal layer, suprabasal layer, and stratum granulosum layer of epidermis were preserved until day 8. Analyses of hemidesmosome proteins, bullous pemphigoid antigen 1 (BP180) and 2 (BP230), showed that the integrity of the basement membrane of the epidermis was well preserved in the HESC model. In contrast, an organotypic culture with human keratinocytes and fibroblasts failed to show an integrated basement membrane. Maintenance of skin structure by histological analysis and proliferation of epidermal keratinocytes by Ki67 staining were observed in our model for 12 days. Complete re-epithelialization of the wounding area was observed at day 6 post wounding when a superficial incisional wound was created. The expression of Ki-67 and keratin 6, indicators of activated keratinocytes in epidermis, was significantly upregulated and new collagen synthesis was found in the dermis during the wound healing process. As control, we also used organotypic culture in studying the differentiation of the keratinocyte layers and incisional wound repair. It turned out that our model has advantage in these study fields. The results suggest that our HESC model retains important elements of in vivo skin and has significant advantages for the wound healing studies in vitro.

Symplastic trichodiscoma: a spindle-cell predominant variant of trichodiscoma with pseudosarcomatous/ancient features

Trichodiscomas are hamartomatous lesions of the follicular unit and of its surrounding stroma composed of epithelial and mesenchymal tissue elements. The dominating tissue element in trichodiscoma is the central fibrous stroma, encircled by prominent clusters of sebaceous lobules that resemble mitts. Rare variants of trichodiscomas with CD34-positive spindle cell-pedominant stroma have been described. We report a case of spindle cell-predominant trichodiscoma with prominent pseudosarcomatous/ancient features consisting in numerous large atypical spindle cells with frequent multinucleation, with no mitotic activity. The cytological changes were similar to those described in ancient schwannoma and symplastic hemangioma. We propose to call this lesion symplastic trichodiscoma. Only 1 previous case of fibrofolliculoma with pseudosarcomatous/ancient changes has already been reported. Although such lesions can appear worrisome at first glance, their benign evolution, the absence of mitosis, and the phenotypic studies excluding malignant differential diagnoses like atypical fibroxanthoma are reassuring. The precise pathogenesis of the symplastic features in schwannoma as in trichodiscoma/fibrofolliculoma is not known yet.

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.

Quantification of mast cells and blood vessels in the skin of patients with cutaneous mucinosis

Recent studies have suggested that mast cell numbers are increased in the skin of patients with cutaneous mucinosis and that these cells may have an important role in angiogenesis and production of mucin. Then, skin biopsies from 30 patients with cutaneous mucinosis (papular mucinosis, focal mucinosis, and mucinosis associated with lupus erythematosus) and from 10 healthy subjects were analyzed. Mast cells and blood vessels were immunolabeled with anti-tryptase and anti-CD34 antibodies, respectively, and then quantified stereologically. Counting was performed in papillary and reticular dermis. An increase in the number of mast cells was observed in the skin of patients with cutaneous mucinosis compared with the control group. Only minimal differences were observed in vessel stereology. There was no correlation between the increase in the number of mast cells and the number of blood vessels in the patients studied. There was no significant difference in the numbers of mast cells or blood vessels between the 3 subgroups of cutaneous mucinosis. Although many clinical forms of mucinosis have been described, neither mast cell number nor vessel distribution seems to distinguish the 3 different forms studied here.

Fibrofolliculoma with ancient/pseudosarcomatous features

Fibrofolliculoma is a benign skin lesion that, when multiple, can be part of the Birt-Hogg-Dube syndrome. We report on a case of solitary fibrofolliculoma arisen on the nose of a 63-year-old woman, with peculiar histological and immunohistochemical features. The lesion was characterized by the presence of bizarre multinucleated perifollicular stromal cells, positive for factor XIIIa, in a background of CD34-positive cells, and by a peripheral population of CD34-positive spindle cells organized in fascicles haphazardly infiltrating the deep dermis, and surrounded by scattered factor XIIIa-positive dendrocytes. We consider the bizarre perifollicular cellular component as an 'ancient' feature of fibrofolliculoma, hypothesis corroborated by the co-expression of CD34 and factor XIIIa, whereas the peripheral spindle cell fascicles represent a pseudosarcomatous proliferation of CD34-positive cells, normally surrounding adnexal structures, stimulated by factor XIIIa-positive dendrocytes.

An Ultrastructural and Immunohistochemical Study of Elastofibroma: CD 34, MEF-2, prominin 2 (CD133), and Factor XIIIa-positive Proliferating Fibroblastic Stromal Cells Connected by Cx43-type Gap Junctions

Elastofibromas have been described as ill-defined tumors, composed of fibroblastic stromal cells and a dense collagenous stroma. A total of 5 elastofibromas from 4 Japanese patients were examined by ultrastructural and immunohistochemical methods. The proliferating fibroblastic stromal cells in the lesion showed Cx43-type gap junctions, isolated cilia, prominent nuclear fibrous laminae, and primitive cellular junctions with incomplete laminae. The active proliferating fibroblastic cells showed positive staining for vimentin, CD34, factor XIIIa, prominin 2 (CD133), and MEF 2. Conspicuous cell-to-matrix interactions were observed with abnormally unique elastins, collagens (type I, III, and IV), laminin, fibronectin, and amorphous extracellular matrix (GAGs; glycosaminoglycans). As for the origin of elastofibromas, the tumors in the present study were suggested to arise from subscapular or periosteal connective tissue, but further revealed some similarities to other tissues, such as human skin dermal tissue, as exemplified by the presence of an abundance of type I and III collagen, CD34/factor XIIIa-expressing stromal fibroblast-like cells, amorphous extracellular matrix, and a unique abnormal elastin. The elastofibromas might have arisen from stromal stem cell candidate populations of stromal fibroblastic cells (CD34(+), MEF2(+), prominin 2(CD133)(+), and factor XIIIa(+)).

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

Over the past few years, a growing number of cutaneous tumors expressing CD34 is being reported. The list contains benign and malignant neoplasms as well as reactive and hamartomatous lesions of diverse lineages of differentiation, including fibroblastic, myofibroblastic, fibrohistiocytic, vascular, neural, adipocytic, smooth muscle, hematopoietic, melanocytic and epithelial. The more frequent diagnostic difficulties are found in spindle cell proliferations, mainly in those of the fibrocytic lineage. In part, this is because of the fact that in this area are, aside to well-defined entities, histologically and clinically diverse, recently reported cutaneous CD34-reactive lesions, whose definitions, limits and relationships are not completely established. The CD34 expression plays a key role in the differential diagnosis of some tumors, such as dermatofibrosarcoma protuberans, epithelioid sarcoma or pleomorphic hyalinizing angiectatic tumor of soft parts, with important therapeutic consequences. In others, as in desmoplastic trichilemmoma, it can help to resolve diagnostic problems in concrete cases. Finally, in many of the CD34-positive lesions, the diagnosis with the hematoxylin and eosin stain is straightforward. However, in all of them, the knowledge of the immunohistochemical profile contributes to our understanding of the cutaneous pathology.

CD34(+) fibrocytes in melanocytic nevi and malignant melanomas of the skin

CD34(+) fibrocytes are constitutive elements of the human connective tissue. The stroma associated with invasive carcinomas is characterized by a stereotypic loss of CD34(+) fibrocytes and a phenotype change towards CD34(-) alpha-Smooth muscle actin (SMA)(+) myofibroblasts. Secreted protein acidic and rich in cysteine (SPARC) is an important mediator of tumor-associated stromal remodeling. Melanocytic lesions of the skin have not been investigated as to this aspect up to now. Thus, we investigated a total of 20 malignant melanomas and 29 melanocytic nevi. The normal dermis and benign melanocytic nevi showed numerous CD34(+) fibrocytes, whereas malignant melanomas were devoid of this cell type. alpha-SMA-positive myofibroblasts were absent from the normal dermis, melanocytic nevi, and malignant melanomas. SPARC was positive in malignant melanoma cells and negative in their associated stroma, while all melanocytic nevi were completely negative. The stromal phenotype of malignant melanomas (CD34(-) alpha-SMA(-)) differs from that of invasive carcinomas (CD34(-) alpha-SMA(+)) suggesting different pathogenic mechanisms involved in tumor-associated stromal remodeling. SPARC expression appears to be closely related to malignancy in melanocytic lesions.

A case of Birt-Hogg-Dubé syndrome

Birt-Hogg-Dubé syndrome (BHDS) is an autosomal dominant genodermatosis characterized by cutaneous hair follicle tumors (fibrofolliculoma or trichodiscoma), pulmonary cysts, and increased risk of renal neoplasia. The genetic alteration for BHDS has been mapped to chromosome 17p12q11, and the gene in this region has been cloned and believed to be responsible for the BHDS. Mutations in the BHD gene (also known as FLCN) have been described in the patients with BHDS. We present a case of a 30-yr-old Korean woman with multiple mildly pruritic papules on her face and neck area. The patient had several firm, flesh-colored, dome-shaped, papular lesions measuring between 2 to 5 mm. Except for a history of pneumothorax her medical records were not remarkable. Mutation analysis of the BHD gene was performed, and a novel deletion mutation (p.F519LfsX17 [c.1557delT]) causing truncation of the gene product, folliculin, was found in the exon 14. The actual incidence of BHDS is unknown, but it is most likely underdiagnosed. So it is imperative that doctors recognize the skin lesions of BHDS and institute proper screening to detect other manifestations of the disease. Here, we report a case of BHDS with a novel mutation, which is the first report in Korea.

A novel population of repair cells identified in the stroma of the human cornea

The transmembrane protein CD133 is expressed on somatic stem cells of various adult human tissues. To investigate whether human corneal stroma also contains CD133-expressing cells and to analyze their functional features, stromal cells were isolated by collagenase digestion, immunophenotyped, and transferred to different culture systems to determine their stem cell properties as well as their differentiation potentials. For comparison, the embryonic keratocyte cell line EK1.Br, the dermal stromal cell line NHDF, and stromal cells of diseased corneas were studied. On average, 5.3% of the normal stromal cells expressed the stem cell marker CD133 and 3.6% co-expressed CD34. Expression of CD133 but not CD34 was also demonstrated for EK1.Br cells, whereas NHDF cells were negative for both markers. Further analysis of CD133(+) normal corneal cells revealed that a significant proportion displayed a monocytic phenotype with co-expression of CD45 and CD14. In diseased corneas, up to 26.8% of the stromal cells showed expression of CD133, and virtually all CD133(+) cells co-expressed CD14 but not CD45. Moreover, using a standard clonogenic assay, normal stromal cells had the capacity to form colonies of the macrophage lineage. These colonies could be further differentiated into lumican-expressing keratocytes. Our data suggest that the human corneal stroma harbors CD133(+) monocytic progenitor cells, which possess the potential to differentiate into the fibrocytic lineage. Thus, CD133(+) /CD45(+) /CD14(+) cells might represent stromal repair cells that differentiate into keratocytes via a CD133(+)/CD45()/CD14(+) intermediate stage. The findings from our study may shed new light on regenerative processes of the human corneal stroma.

Radiologic findings in a patient with frontal parafalcine dendritic cell histiocytoma

We report the case history and radiologic findings of a patient with a biopsy-proven dendritic cell histiocytoma presenting as a single intracranial extra-axial mass and no systemic disease. Even though this entity is relatively rare, it should nevertheless be considered in the differential diagnosis of dural-based space-occupying central nervous system lesions.

Medallion-like dermal dendrocyte hamartoma

Medallion-like dermal dendrocyte hamartomas are rare congenital cutaneous lesions, with only three occurrences reported in the English language literature. They present at birth as asymptomatic circular, oval, or triangular well-circumscribed, atrophic patches. Typically, they have an erythematous or yellow-brown hue and a characteristic pliable, wrinkled surface; subtle telangiectases may also be appreciated. They may be misdiagnosed as atrophoderma, cutis aplasia, or anetoderma. All reported patients have been female. Characteristic histologic findings include epidermal atrophy and the presence of a CD34-positive spindle cell proliferation in the dermis. This spindle cell proliferation represents a population of dermal dendrocytes, which are bone marrow-derived cells that are believed to function as antigen-presenting cells that contribute to the function of the skin immune system. Little is known about the pathophysiology of medallion-like dermal dendrocyte hamartomas. We present a patient with this entity and review similar presentations reported in the literature.

Transdifferentiation of peripheral blood mononuclear cells into epithelial-like cells

Bone marrow-derived stem cells have the potential to transdifferentiate into unexpected peripheral cells. We hypothesize that circulating bone marrow-derived stem cells might have the capacity to transdifferentiate into epithelial-like cells and release matrix metalloproteinase-1-modulating factors such as 14-3-3varsigma for dermal fibroblasts. We have characterized a subset of peripheral blood mononuclear cells (PBMCs) that develops an epithelial-like profile. Our findings show that these cells develop epithelial-like morphology and express 14-3-3varsigma and keratin-5, -8 as early as day 7 and day 21, respectively. When compared with control, conditioned media collected from PBMCs in advanced epithelial-like differentiation (cultures on days 28, 35, and 42) increased the matrix metalloproteinase-1 expression in dermal fibroblasts (P </= 0.01). The depletion of 14-3-3varsigma from these conditioned media by immunoprecipitation reduced the effect by 39.5% (P value, 0.05). Therefore, the releasable 14-3-3varsigma from PBMC-derived epithelial-like cells is involved in this process. Our findings provide new insights into the PBMC transdifferentiation to generate epithelial-like cells and subsequently release of 14-3-3varsigma that will disclose new therapeutic alternatives for different dermal clinical settings.

CD34 glycoprotein identifies putative stem cells located in the isthmic region of canine hair follicles

It is widely documented that a pool of multipotent stem cells located in humans and mice hair follicle outer root sheath (bulge region) is involved in the restoration of the whole follicular unit during each anagen phase. To the authors' knowledge, data regarding the location and characterization of hair follicle stem compartment in dogs have not been reported in the recent relevant literature. In this study, we investigated the haematopoietic stem and progenitor cell antigen CD34 as a marker of putative stem cells located in a bulge-like region of canine hair follicles. The presence of CD34 mRNA and glycoprotein was assessed on formalin-fixed, paraffin-embedded canine skin samples by in situ hybridization technique and by standard immunohistochemistry, respectively. A strong expression of CD34 mRNA and glycoprotein was observed in a well-defined area of the hair follicle isthmic region and appeared uniformly concentrated at the level of the basal layer of the outer root sheath. These findings provide compelling support to the hypothesis that in dogs, a subpopulation of basal keratinocytes located in the hair follicle isthmic region and characterized by the selective expression of CD34 is potentially associated with the stem cell compartment of this skin appendage.

Spindle cell predominant trichodiscoma: a fibrofolliculoma/trichodiscoma variant considered formerly to be a neurofollicular hamartoma: a clinicopathological and immunohistochemical analysis of 17 cases

Seventeen solitary nasal tumors that fulfilled all diagnostic criteria of so-called neurofollicular hamartoma, apart from distinct S100-positivity, were compared histopathologically and immunohistochemically with seven typical trichodiscomas from a similar clinical setting. Both the S100-negative neurofollicular hamartoma-like tumors and the trichodiscomas expressed an identical CD13-positive/CD34-positive fibrocytic immunophenotype without co-expression of neural/perineural (S100, neurofilament, epithelial membrane antigen), myogenic (desmin, calponin, muscle-specific actin, and alpha-smooth muscle actin), or melanocytic (S100, HMB45, NKI/C3, MelanA) epitopes. Histopathologically, there was striking morphologic overlap between trichodiscoma and S100-negative neurofollicular hamartoma-like tumor, apart from a highly characteristic fascicularly organized cellular fibrocytic stroma in the latter. We conclude that fibrofolliculoma/trichodiscoma and neurofollicular hamartoma-like tumor are morphologic variants of a single hamartomatous entity in which neurofollicular hamartoma-like tumor occupies the cellular pole of the morphologic spectrum. The entity formerly known as neurofollicular hamartoma appears to be nothing but a particularly cellular trichodiscoma with a distinctively organized stroma composed of CD34-positive fibrocytes. We therefore propose the new term spindle cell predominant trichodiscoma (SCPT) for this particular variant of the morphologic fibrofolliculoma/trichodiscoma spectrum.

Expression of CD163 in dermatofibroma, cellular fibrous histiocytoma, and dermatofibrosarcoma protuberans: comparison with CD68, CD34, and Factor XIIIa

BACKGROUND

Distinction between cellular fibrous histiocytomas (FHs) with a deep component and dermatofibrosarcoma protuberans (DFSPs) can pose diagnostic problems. While CD68, CD34, and Factor XIIIa are helpful in distinguishing between these entities, none are diagnostically absolute. Recent work with CD163, a hemoglobin scavenger receptor, has demonstrated that this marker has high specificity for monocytes, macrophages, and histiocytes. Our goal is to evaluate the utility of CD163 in the diagnosis of dermatofibromas (DFs), cellular FHs, and DFSPs.

METHODS

Sixty cases including 19 DFs, 23 cellular FHs with a deep component, and 18 DFSPs were tested with antibodies against CD163, CD68, CD34, and Factor XIIIa.

RESULTS

CD163 was expressed in 17/19 (89%) DFs, 23/23 (100%) cellular FHs, and 3/18 (17%) DFSPs. CD68 was positive in 8/19 (42%) DFs, 19/23 (83%) cellular FHs, and 1/16 (6%) DFSPs. CD34 was expressed in 1/19 (5%) DFs, 5/23 (22%) cellular FHs, and 100% of DFSPs. Factor XIIIa labeled 4/19 (21%) DFs, 11/23 (48%) cellular FHs, and 0/17 cases of DFSPs.

CONCLUSIONS

CD163 expression is helpful in distinguishing between cellular FHs and DFSPs and will be useful in a panel of antibodies when these entities are in the differential diagnosis. Sachdev R, Sundram U. Expression of CD163 in dermatofibroma, cellular fibrous histiocytoma, and dermatofibrosarcoma protuberans: comparison with CD68, CD34, and Factor XIIIa.

Two sporadic cases of adult-onset progressive mucinous histiocytosis

Progressive mucinous histiocytosis is a rare, benign, non-Langerhans' cell histiocytosis limited to the skin. Ten cases--all women--in four families and one sporadic case have been described in the literature. The disorder usually begins in childhood and progresses slowly. We report two sporadic cases of adult-onset progressive mucinous histiocytosis in unrelated African-American women, aged 48 and 55 years, respectively, who developed red-brown and flesh-coloured, asymptomatic papules on the face, the arms and the legs without truncal, mucosal or visceral involvement. The lesions showed no spontaneous regression. Both patients lacked associated systemic symptoms, including polyuria, polydipsia or seizures. There was no underlying hyperlipidaemia, paraproteinaemia or lymphoproliferative disease. No family history of similar lesions could be identified. Light microscopy revealed dermal proliferation of spindle-shaped histiocytes with abundant mucin deposition. Electron microscopy demonstrated a high number of myelin figures or zebra bodies in the cytoplasm of histiocytes. On immunohistochemistry, positive staining with macrophage markers--CD68, HAM56 and lysozyme--and factor XIIIa, a transglutaminase present in dermal dendrocytes, and negative staining with Langerhans' cell markers--CD1a and S100--and CD34, a marker present in dermal dendritic cells derived from uncommitted mesenchymal cells, were observed.

Immunohistochemical characterization of fibroblast subpopulations in normal peritoneal tissue and in peritoneal dialysis-induced fibrosis

Peritoneal fibrosis is one of the most common morphological changes observed in continuous ambulatory peritoneal dialysis (CAPD) patients. Both resident fibroblasts and new fibroblast-like cells derived from the mesothelium by epithelial-to-mesenchymal transition are the main cells involved fibrogenesis. In order to establish markers of peritoneal impairment and pathogenic clues to explain the fibrogenic process, we conducted an immunohistochemical study focused on peritoneal fibroblasts. Parietal peritoneal biopsies were collected from four patient groups: normal controls ( n = 15), non-CAPD uremic patients ( n = 17), uremic patients on CAPD ( n = 27) and non-renal patients with inguinal hernia ( n = 12). To study myofibroblastic conversion of mesothelial cells, alpha-smooth muscle actin (SMA), desmin, cytokeratins and E-cadherin were analyzed. The expression of CD34 by fibroblasts was also analyzed. Fibroblasts from controls and non-CAPD uremic patients showed expression of CD34, but no myofibroblastic or mesothelial markers. The opposite pattern was present during CAPD-related fibrosis. Expression of cytokeratins and E-cadherin by fibroblast-like cells and alpha-SMA by mesothelial and stromal cells supports that mesothelial-to-myofibroblast transition occurs during CAPD. Loss of CD34 expression correlated with the degree of peritoneal fibrosis. The immunophenotype of fibroblasts varies during the progression of fibrosis. Myofibroblasts seem to derive from both activation of resident fibroblasts and local conversion of mesothelial cells.

Are CD34+ cells found in renal interstitial fibrosis?

BACKGROUND

The CD34 antigen is a marker of precursor myeloid cells and endothelial cells, but also of a subset of spindle cells.

METHODS

To establish the possible role of CD34+ cells in the progression of glomerulonephritis, 30 renal biopsies were investigated. Immunohistochemistry for CD34 and smooth muscle actin (SMA) were performed by standard methods. The results were assessed semiquantitatively. The relative interstitial volume (RIV) was evaluated by the point counting method. Clinical data such as sex, age, serum creatinine and urea levels were taken into account.

RESULTS

CD34+ spindle cells and SMA+ myofibroblasts were present in the renal interstitium in all but one case. In membranous, membranoproliferative and segmental-proliferative glomerulonephritis, CD34+ cells were seen in clusters, while in IgA nephropathy and in segmental and focal glomerulosclerosis, single, scattered cells were seen. The density of CD34+ cells showed a positive correlation with the myofibroblast density and the RIV. Serum creatinine and urea levels were associated with the RIV of the kidney and to a smaller degree with the number of myofibroblasts and CD34+ cells.

CONCLUSION

These results show that in glomerulonephritis, CD34+ spindle cells appear in the interstitium. At present, their possible role can only be speculated.

Epithelioid cell histiocytoma--histogenetic and kinetics analysis of dermal microvascular unit dendritic cell subpopulations

BACKGROUND

Epithelioid cell histiocytoma (ECH), also known as epithelioid fibrous histiocytoma, is a peculiar dermal tumor, which can mimic melanocytic, vascular, epithelial, or other histiocytic lesions. Thought to arise from dermal dendrocytes, most ECH contain approximately 50% FXIIIa+ histiocytic dendrocytes, but not all lesional cells express FXIIIa. A putative fibroblastic component has not been characterized.

METHODS

We analyzed the differentiation and cell kinetics of dermal microvascular unit cells in 12 previously reported ECH using antibodies to FXIIIa, CD68 (KP1), CD34, CD117, CD31, smooth muscle actin, collagen type 1 aminopropeptide, and MIB-1, using single and double immunostains.

RESULTS

In ECH, many variably sized CD34/CD31+ tumor vessels with actin+ myopericytes were surrounded by epithelioid-to-dendritic cells of three types. About 5-80% were dendritic histiocytes that expressed FXIIIa but not CD31 or KP1. Fibroblasts, in some cases showing mild nuclear pleomorphism, were usually collagen type 1+, but CD34 and actin- in 11/12 cases. One 'early' ECH had 40% CD34+ epithelioid cells, admixed with 50% FXIIIa+ histiocytes. Most ECH had about 2-20% KP1+, CD117+ mast cells. Mast cell numbers increased with FXIIIa+ histiocyte numbers and the intensity of FXIIIa expression. MIB-1/FXIIIa double-labeling showed only rare cycling histiocytes, with numerous cycling fibroblasts and endothelial cells.

CONCLUSIONS

Our findings support the impression that ECH is a vascular fibrous histiocytoma. The constituent cells appear to arise from the activation of resident microvascular CD34+ dermal fibroblasts and the accumulation of FXIIIa+ dendritic stromal assembly histiocytes. The CD34+ cells appear to differentiate toward collagenous fibrocytes in association with histiocytes and mast cells in forming collagenous stroma and vessels. ECH is a tumor composed of all requisite cell types consistent with the origin from the dermal microvascular unit.

Dendritic cells and pattern of cytokines in paracoccidioidomycosis skin lesions

We demonstrated and quantified by immunohistochemistry epidermal Langerhans cells, CD34+ dermal dendrocytes (DDs), and cells expressing TNFalpha, interferon-gamma (IFNgamma), IL-5, and IL-10 in skin lesions of paracoccidioidomycosis (PCM). Sixty-one biopsies were classified in three groups according to the pattern of tissue response: Group 1, well-organized granuloma; Group 2, poorly organized granuloma; and Group 3, both kinds of granuloma. Langerhans cells had short and irregular dendrites in all groups and were decreased in number in Groups 1 and 2. CD34+ DDs did not differ in number from the control group. Group 1 was characterized by many cells expressing IFNgamma. Groups 2 and 3 exhibited large numbers of cells expressing IL-5 and IL-10. The data obtained suggest that well-organized granulomas reflect a better cellular immune response, and the large number of cells expressing IL-5 and IL-10 in Group 2 indicate an ineffective response in PCM skin lesions. Both kinds of granuloma in the same cutaneous lesion probably represent an intermediate response between the anergic and hyperergic poles. Group 3 also showed higher numbers of cells expressing TNFalpha when compared with the control group. Some cells expressing TNFalpha were dendritic and localized around the granuloma similar to the factor XIIIa+ DD localization that we previously described.

Histomorphologic and immunophenotypic analysis of fibrofolliculomas and trichodiscomas in Birt-Hogg-Dube syndrome and sporadic disease

BACKGROUND

Fibrofolliculomas and trichodiscomas are benign dermal neoplasms that likely derive from the mantle of the hair follicle and can occur sporadically or in association with Birt-Hogg-Dube syndrome (BHDS). Little is known about the pathogenesis and immunophenotypic properties of these entities.

METHODS

We investigated the histomorphologic and immnophenotypic properties of 15 fibrofolliculomas and trichodiscomas in two patients with BHDS and eight with sporadic disease.

RESULTS

We found the following: (1) fibrofolliculomas and trichodiscomas occurring in the setting of BHDS show microscopically contiguous histomorphologic features as compared to those occurring sporadically; (2) the immunophenotypic characteristics of syndromic-associated and sporadic types are identical and consist of (3) perifollicular vimentin (+), CD34 (+) and Factor XIII (-) spindle cells.

CONCLUSIONS

Despite subtle histomorphologic differences, trichodiscomas and fibrofolliculomas are immunophenotypically similar, and are thus likely derived from a similar histogenic precursor. Given the previously reported CD34 (+) immunophenotype of the hair mantle, our findings would support an origin of these lesions from the mantle of the hair follicle. The proliferation of CD34 (+) spindle cells seen in conjunction with these lesions should not be confused with other CD34 (+) dermal entities.

CD34 positive stromal cells in gastric adenocarcinomas

AIMS

To investigate the role of CD34 positive stromal cells, namely dendritic interstitial cells, in gastric carcinomas, the distribution of CD34 positive stromal cells in gastric adenocarcinomas (GCs), with special reference to two histological types (diffuse (D-type) and intestinal (I-type)), was examined.

METHODS

In total, 55 surgically resected GCs (15 D-type and 40 I-type) and their normal tissues were examined. To distinguish CD34 positive stromal cells from vascular endothelial cells and to recognise the tumour border, immunostaining for CD34, CD31, and low molecular weight cytokeratins was performed.

RESULTS

In the 15 D-type GCs, eight of the nine D-type GCs invading the muscularis propria and subserosa had a large number of CD34 positive stromal cells in the tumour stroma, whereas all six D-type GCs confined to the submucosa had no CD34 positive stromal cells in the tumour stroma. All of the 40 I-type GCs had no CD34 positive stromal cells, regardless of tumour depth.

CONCLUSIONS

These results suggest that CD34 expression in stromal cells is associated with progression of D-type GCs, and that absence of expression is also seen in I-type GCs that are progressing.

S100 expression in cutaneous scars: a potential diagnostic pitfall in the diagnosis of desmoplastic melanoma

AIMS

The histological distinction of desmoplastic melanoma from cutaneous scar tissue, particularly in the context of re-excision specimens or possible recurrence, may be very difficult. Immunostaining for S100 protein is often used to discriminate although there are little data on S100 expression in scar tissue. The aim of this study was to assess whether S100-positive cells are present in dermal scars and, if so, their extent, distribution and nature.

METHODS AND RESULTS

Twenty-two re-excision specimens of previously biopsied nonmelanocytic skin lesions were reviewed. Formalin-fixed paraffin-embedded sections containing dermal scars were stained by a standard ABC immunoperoxidase technique for S100 protein, CD1a and neurofilaments. The distribution and morphology of positive cells within the dermal scar tissue were documented. Cells expressing S100 protein were identified within the scars of 21 of the 22 cases. The number of S100-positive cells varied between cases but in four specimens was substantial. They displayed a variety of morphological appearances but the majority were spindle-shaped. A few showed mild cytological atypia. It is suggested that the majority represent Schwann cells with a minority of Langerhans cells and cells of uncertain lineage.

CONCLUSION

S100-positive cells, including spindle cells showing mild atypia, are found in cutaneous scars. S100 staining of re-excision specimens or putative recurrences of desmoplastic melanoma should be interpreted with caution.

Analysis of dendritic cell populations using a revised histological staging of morphoea

BACKGROUND

Recent studies have suggested that dermal dendritic cells (DDCs) may play a part in maintaining the structure of the dermis and in dermal immune modulation. Alteration in the population of DDCs has been noted in localized and systemic scleroderma, particularly a decline in the number of CD34+ DDCs. Objectives To define the alteration of the DDC populations with respect to the histological stage of morphoea.

METHODS

We examined 33 biopsies of morphoea, categorized into four histological stages, and examined the DDC population (CD34+ DDCs and factor XIIIa+ DDCs), the lymphocytic infiltrate, and tenascin (extracellular matrix glycoprotein) and transforming growth factor (TGF)-beta1 expression in each biopsy.

RESULTS

As the dermis became less inflammatory and more sclerotic, there was a significant decline in the number of CD34+ DDCs and an increase in the number of factor XIIIa+ DDCs. The pan-T-cell infiltrate (UCHL-1/CD45RO) and tenascin deposition exhibited a similar pattern, with elevated expression in inflammatory stages and a decrease in expression as the dermis became sclerotic. TGF-beta1 was significantly elevated in three of the four histological stages of morphoea, in both the inflammatory and sclerotic stages. The proposed four-stage histological analysis of morphoea biopsies was a useful basis for studying dendritic cells and mediators in cutaneous sclerosis.

CONCLUSIONS

Our study indicates that there is a reciprocal relationship between CD34+ DDCs and factor XIIIa+ DDCs in morphoea that correlates with the relative degrees of inflammation and sclerosis.

Infiltrative glomus tumor arising from a benign glomus tumor: a distinctive immunohistochemical pattern in the infiltrative component

Malignant glomus tumors (MGT) are rare. Although metastatic MGT has been reported, most MGT have only been locally aggressive, some with multiple local recurrences. We report an additional case of an infiltrative glomus tumor. In addition to the pattern of immunohistochemical staining for alpha-smooth muscle actin (SM-actin) previously described, we performed immunohistochemical stains for Ki-67 and CD34. The infiltrative component of the glomus tumor showed variably decreased staining with SM-actin and occasional tumor cells showed nuclear staining with Ki-67. CD34 staining occurred in stromal cells forming the pseudocapsule in the benign component of this tumor and in other benign glomus tumors. The infiltrative component showed increased CD34 stromal cells. Although Ki-67 staining showed only an occasional proliferative cell, the immunohistochemical staining pattern of CD34 and SM-actin raise the possibility that the infiltrative component of this tumor may have differences in the degree of differentiation from the circumscribed part and that local factors could support its spread from a conventional benign glomus tumor.

Congenital CD34-positive granular cell dendrocytosis

Granular cell tumors involving the skin are mostly acquired lesions. The Schwann cell origin of these lesions is supported by positive immunostaining for S-100 protein and myelin basic protein. S-100- granular cell lesions rarely have been described in association with fibrous papules or dermatofibromas. The congenital variety of S-100- granular cell tumors occurs almost exclusively in the gingiva. The cell origin of these lesions is not well delineated. We report a hitherto undescribed case of a congenital cutaneous lesion which is histologically characterized by diffuse dermal infiltrates of S-100- but CD34+ granular dermal dendrocytes. The granular appearance of these CD34+ dendrocytes is attributed to an abundance of phagolysosomes. The pathogenetic mechanism of this unusual lesion remains to be elucidated.

Diagnostic value of CD34 immunostaining in desmoplastic trichilemmoma

Desmoplastic trichilemmoma (DT) is a variant of trichilemmoma, characterized by a central prominent desmoplastic component which may simulate invasive carcinoma. We have studied the morphologic and immunohistochemical features of seven cases of DT. Immunohistochemistry was performed on paraffin sections using monoclonal antibodies to CD34 (QBEND/10), vimentin and GCDFP-15. CD34 was also tested in seven cases of basal cell carcinoma (BCC), three with outer root sheath differentiation and four with morphea-form features, and five squamous cell carcinomas. Histologically, features of conventional trichilemmoma were seen at the periphery of the seven lesions. In contrast, at the center, the epithelial cells tended to cluster in narrow irregular cords and nests entrapped in a dense collagenous stroma. One case of DT coexisted with a BCC. In all cases of DT, epithelial tumor cells showed CD34 immunostaining. All cases of BCC, including the one contiguous to a DT, were CD34 negative. CD34 immunodetection in the epithelial cells of the pseudoinvasive component of DT may be of great value in the differential diagnosis with other desmoplastic tumors of the skin, and particularly with BCC.