Primary cutaneous adenosquamous carcinoma of the penis: the first characterization of HPV status in this rare and diagnostically challenging entity with review of glandular carcinomas of the penis

Glandular and pseudoglandular tumors of the penile skin are extremely uncommon and can present diagnostic challenges. Primary adenosquamous carcinoma of the penis is an extremely rare tumor, composed of distinct areas of malignant squamous and glandular cells, making it a diagnostically challenging entity. The World Health Organization (WHO) recognizes several subtypes of squamous cell carcinoma (SCC), each with its own distinctive pathologic appearance, clinical associations and prognosis. Among these variants is the exceedingly uncommon adenosquamous carcinoma (ASC), representing 1%-2% of all SCC of the penis. Recent large studies have interrogated the presence of human papillomavirus (HPV) in malignant penile tumors and have shown specific morphologic patterns and clinical presentations to associate with HPV status. However, given the rarity of the adenosquamous variant of SCC, it has largely been excluded from these studies. The glandular components of these lesions can present a confusing appearance, particularly when a large tumor is represented on a small biopsy. Here we describe a difficult histologic presentation of this rare tumor, with the first published characterization of the HPV status of this subtype. This case represents a distinctly unusual case of metastatic HPV-positive primary cutaneous adenosquamous carcinoma of the penis.

Recurrent missense mutations in the hair keratin gene hHb6 in monilethrix

Monilethrix is an autosomal dominant hair disorder characterized by a beaded appearance of the hair resulting from periodic thinning of the shaft (MIM 158000). The phenotype shows variable penetrance and results in hair fragility and patchy dystrophic alopecia. Mutations of the helix-encoded region in two hair-specific keratins (hHb1 and hHb6) have been identified as responsible for this disorder. We investigated two unrelated families from Russia and Colombia with monilethrix and found two missense mutations in hHb6. In the Russian family, we found a G to A transition at the first base of codon 402, resulting in a lysine substitution (GAG to AAG), designated E402K. In the Colombian family, affected patients carried a missense mutation of codon 413, involving a transition from G to A causing a lysine substitution (GAG to AAG), designated E413K. These two mutations have been identified in other monilethrix families from Europe. Our findings extend the body of evidence implicating recurrent hHb6 and hHb1 mutations in monilethrix families from around the world.

Mastocytosis

Mastocytosis represents a heterogeneous group of clinical disorders resulting from the infiltration of mast cells in the skin and other organs. Although mastocytosis was first described over 130 years ago, the pathophysiologic mechanisms responsible for this disease have been identified only recently. This article discusses the salient clinical features of the disease, the mechanisms responsible for its development, and provides treatment approaches that have proven useful for managing patients with this disorder.

Diagnostic criteria and classification of mastocytosis: a consensus proposal

The term 'mastocytosis' denotes a heterogeneous group of disorders characterized by abnormal growth and accumulation of mast cells (MC) in one or more organ systems. Over the last 20 years, there has been an evolution in accepted classification systems for this disease. In light of such developments and novel useful markers, it seems appropriate now to re-evaluate and update the classification of mastocytosis. Here, we propose criteria to delineate categories of mastocytosis together with an updated consensus classification system. In this proposal, the diagnosis cutaneous mastocytosis (CM) is based on typical clinical and histological skin lesions and absence of definitive signs (criteria) of systemic involvement. Most patients with CM are children and present with maculopapular cutaneous mastocytosis (=urticaria pigmentosa, UP). Other less frequent forms of CM are diffuse cutaneous mastocytosis (DCM) and mastocytoma of skin. Systemic mastocytosis (SM) is commonly seen in adults and defined by multifocal histological lesions in the bone marrow (affected almost invariably) or other extracutaneous organs (major criteria) together with cytological and biochemical signs (minor criteria) of systemic disease (SM-criteria). SM is further divided into the following categories: indolent systemic mastocytosis (ISM), SM with an associated clonal hematologic non-mast cell lineage disease (AHNMD), aggressive systemic mastocytosis (ASM), and mast cell leukemia (MCL). Patients with ISM usually have maculopapular skin lesions and a good prognosis. In the group with associated hematologic disease, the AHNMD should be classified according to FAB/WHO criteria. ASM is characterized by impaired organ-function due to infiltration of the bone marrow, liver, spleen, GI-tract, or skeletal system, by pathologic MC. MCL is a 'high-grade' leukemic disease defined by increased numbers of MC in bone marrow smears (>or=20%) and peripheral blood, absence of skin lesions, multiorgan failure, and a short survival. In typical cases, circulating MC amount to >or=10% of leukocytes (classical form of MCL). Mast cell sarcoma is a unifocal tumor that consists of atypical MC and shows a destructive growth without (primary) systemic involvement. This high-grade malignant MC disease has to be distinguished from a localized benign mastocytoma in either extracutaneous organs (=extracutaneous mastocytoma) or skin. Depending on the clinical course of mastocytosis and development of an AHNMD, patients can shift from one category of MC disease into another. In all categories, mediator-related symptoms may occur and may represent a serious clinical problem. All categories of mastocytosis should be distinctively separated from reactive MC hyperplasia, MC activation syndromes, and a more or less pronounced increase in MC in myelogenous malignancies other than mastocytosis. Criteria proposed in this article should be helpful in this regard.

Classes of c-KIT activating mutations: proposed mechanisms of action and implications for disease classification and therapy

Mutations causing constitutive activation of KIT have been shown to be causative in some forms of mastocytosis, and several types of mutations have been associated with myeloproliferative disorders (MPDs), acute myelogenous leukemia (AML), sinonasal lymphomas, and gastrointestinal stromal tumors (GIST). We divide these activating mutation into two types - 'regulatory type' mutations, which affect regulation of the kinase molecule, and 'enzymatic pocket type' mutations, which alter the amino acid sequence directly forming the enzymatic site. KIT inhibitors have been suggested as therapeutic drugs for these conditions, but different types of activating mutations respond differentially to KIT inhibitors, so classification of individuals on the basis of specific mutations is necessary to guide therapy.

Kwashiorkor in patients with AIDS

Kwashiorkor, a form of severe protein-energy malnutrition that entails loss of lean body weight, occurs endemically among children in many parts of the world but also has been documented in adults. We report a case of kwashiorkor in an HIV-positive adult male. Cutaneous findings are striking, and skin, hair, and nails are affected. Although kwashiorkor occurs in patients with HIV-AIDS, the skin manifestations have not been emphasized in the dermatologic literature. Indeed, dermatologists may play a vital role in diagnosing this treatable condition.

SCF/c-kit signaling is required for cyclic regeneration of the hair pigmentation unit

Hair graying, an age-associated process of unknown etiology, is characterized by a reduced number and activity of hair follicle (HF) melanocytes. Stem cell factor (SCF) and its receptor c-kit are important for melanocyte survival during development, and mutations in these genes result in unpigmented hairs. Here we show that during cyclic HF regeneration in C57BL/6 mice, proliferating, differentiating, and melanin-producing melanocytes express c-kit, whereas presumptive melanocyte precursors do not. SCF overexpression in HF epithelium significantly increases the number and proliferative activity of melanocytes. During the induced hair cycle in C57BL/6 mice, administration of anti-c-kit antibody dose-dependently decreases hair pigmentation and leads to partially depigmented (gray) or fully depigmented (white) hairs, associated with significant decreases in melanocyte proliferation and differentiation, as determined by immunostaining and confocal microscopy. However, in the next hair cycle, the previously treated animals grow fully pigmented hairs with the normal number and distribution of melanocytes. This suggests that melanocyte stem cells are not dependent on SCF/c-kit and when appropriately stimulated can generate melanogenically active melanocytes. Therefore, the blockade of c-kit signaling offers a fully reversible model for hair depigmentation, which might be used for the studies of hair pigmentation disorders.

P-glycoprotein expression and multidrug resistance in cutaneous T-cell lymphoma

Advanced-stage cutaneous T-cell lymphoma (CTCL) is generally resistant to standard chemotherapy. Because P-glycoprotein (P-gp) has been detected in other types of resistant solid tumors, leukemias, and lymphomas, we analyzed P-gp expression in CTCL. Twenty-seven patients with CTCL and circulating Sezary cells in the peripheral blood as observed on a peripheral smear treated at the Yale Photopheresis Center between 1987 and 1993 were identified. Twenty-five of these patients had skin biopsies evaluated for expression of P-gp using JSB-1 (Accurate Chemical), MRK-16 (gift of T. Tsuruo), and UIC-2 (gift of E. Metchner). P-gp expression was considered present if immunoreactivity was noted with two of the three antibodies. Eighteen of 25 patients (72%) evaluated exhibited expression. The patients were treated with various combinations of drugs consisting of topical and systemic steroids electron beam therapy, psoralens in combination with UV light A (PUVA), systemic chemotherapy, and photopheresis before testing the tissue for P-gp expression. Treatment with systemic chemotherapy in P-gp-positive patients produced responses in 3 and no responses in 11 patients (4 were lost to follow-up). Seven patients did not express P-gp: One patient responded to treatment, five did not respond, and one patient was lost to follow-up. These results demonstrate that P-gp is frequently expressed in CTCL. P-gp expression in our study was not a useful predictor of drug resistance.

Genital variant of folliculosebaceous cystic hamartoma

BACKGROUND

Clinically, folliculosebaceous cystic hamartomas (FSCH) present as skin-colored papulonodules of the face, especially the nose. This is in contrast to sebaceous trichofolliculomas which often present as depressed ostia containing terminal or vellus hairs.

OBSERVATION

A 34-year-old female had a skin-colored multinodular plaque of the labia majora that demonstrated the histologic findings of an FSCH. These included an irregularly shaped central cystic structure surrounded by multiple sebaceous lobules as well as a fibrous stroma. The epithelial-lined cyst contained no hair shafts.

CONCLUSION

A single case report of a scrotal lesion with a similar clinical appearance and histologic findings has previously been described as a genital variant of sebaceous trichofolliculoma. However, the report predated the initial description of FSCH. In our opinion, both cases represent examples of the genital variant of FSCH.

New approaches to therapy for mastocytosis. A case for treatment with kit kinase inhibitors

Some forms of mastocytosis are caused by c-kit mutations which cause constitutive activation of kit kinase. Compounds that inhibit kit kinase, such as indolinones, are therefore attractive as potential therapeutic agents. A hierarchy exists in the ability of compounds to inhibit kit kinase effectively. Some compounds can inhibit ligand-induced activation of wild-type receptor but are ineffective against constitutively activated mutants. Other compounds can inhibit ligand-induced activation of wild-type kit and ligand-independent activation by juxtamembrane domain mutations but not activation by activation loop mutations. Still others effectively inhibit wild-type kit and constitutively activated kit bearing either juxtamembrane or kinase domain mutations and kill the neoplastic mast cells expressing these mutants. No therapy currently exists that specifically targets a cause of mastocytosis, but there are good reasons to believe that kit kinase inhibitors may fulfill that role someday.

Fusarium fingernail infection responsive to fluconazole intermittent therapy

A case of fingernail infection by Fusarium is presented. This nondermatophytic mold is an infrequent cause of onychomycosis, more typically involving the great toenail. Characteristic histologic features including the presence of hyphae and chlamydoconia are helpful in rapid diagnosis and selection of appropriate antifungal therapy. Although Fusarium has shown resistance to most antifungal medications in vitro, intermittent therapy with fluconazole led to improvement in this patient.

A proposed classification of mastocytosis incorporating molecular genetics

As an understanding of the molecular genetic causes of different forms of mastocytosis is developed, the therapy of choice may depend on the specific genetic abnormalities expressed by a patient's neoplastic mast cells. The authors propose a new classification system for mastocytosis that incorporates both molecular-genetic and clinical data. This system provides a theoretic framework for mast cell researchers and helps practicing physicians in estimating prognosis and determining therapeutic options for individual patients.

Indolinone derivatives inhibit constitutively activated KIT mutants and kill neoplastic mast cells

Mastocytosis is a neoplastic disease caused at least in part by somatic mutations of the c-KIT proto-oncogene resulting in constitutive activation of its protein product, KIT, the receptor tyrosine kinase for stem cell factor. KIT stimulates mast cell proliferation and prevents apoptosis of neoplastic mast cells. To develop potential therapies for mastocytosis we used indolinones, small molecules that inhibit tyrosine kinases. Four indolinone derivatives (SU4984, SU6663, SU6577, and SU5614) inhibited wild-type KIT, but variably inhibited constitutively activated KIT mutants. SU4984, SU6577, and SU5614 were effective against KIT with juxtamembrane activating mutations, whereas only SU6577 could suppress KIT containing either juxtamembrane or kinase domain activating mutations. Furthermore, SU4984, SU6577, and SU5614 killed neoplastic mast cells expressing a juxtamembrane-mutated KIT, whereas SU4984 and SU6577 killed neoplastic mast cells expressing KIT bearing a kinase domain mutation. These data show a direct correlation between inhibition of constitutively activated KIT and the death of neoplastic mast cells, and point to specific tyrosine kinase inhibitors as a potential therapy aimed directly at a cause of mastocytosis.

Eruptive paraneoplastic keloids

We present a 66-year-old woman who developed eruptive keloids in association with endometrial carcinoma in the absence of trauma, surgery, inflammation, or other known preludes to keloid formation. Keloid formation and endometrial carcinoma are both associated with similar cytokine abnormalities and as such, we hypothesize that this is a previously unreported paraneoplastic phenomenon.

Cutaneous cryoanesthesia does not affect histopathology of biopsy specimens

Localized freezing of skin lesions in situ is widely used by dermatologists to provide anesthesia prior to excision or curettage. To determine whether this technique adversely affects the interpretation of biopsy specimens, we compared the histopathologic features of frozen and unfrozen portions of nine skin lesions, eight seborrheic keratoses, and one basal cell carcinoma. We detected no differences in the histopathologic features between the frozen and unfrozen portions of the lesions. We conclude that the technique of cutaneous cryoanesthesia does not adversely affect the histopathologic evaluation of skin lesions.

What dermatologists need to know about mast cell disease: a dermatopathologist's view

Mast cell disease involves a group of conditions characterized by the infiltration of mast cells in the tissues and organs. Mast cell disease predominantly affects the skin, presenting in the form of urticaria pigmentosa. This concise review article defines mast cell disease. This paper presents a dermatopathologist's perspective on the diagnosis, management, and treatment of mast cell disease.

Inhibition of spontaneous receptor phosphorylation by residues in a putative alpha-helix in the KIT intracellular juxtamembrane region

KIT receptor kinase activity is repressed, prior to stem cell factor binding, by unknown structural constraints. Using site-directed mutagenesis, we examined the role of KIT intracellular juxtamembrane residues Met-552 through Ile-563 in controlling receptor autophosphorylation. Alanine substitution for Tyr-553, Trp-557, Val-559, or Val-560, all sitting along the hydrophobic side of an amphipathic alpha-helix (Tyr-553-Ile-563) predicted by the Chou-Fasman algorithm, resulted in substantially increased spontaneous receptor phosphorylation, revealing inhibitory roles for these residues. Alanine substitution for other residues, most of which are on the hydrophilic side of the helix, caused no or slightly increased basal receptor phosphorylation. Converting Tyr-553 or Trp-557 to phenylalanine generated slight or no elevation, respectively, in basal KIT phosphorylation, indicating that the phenyl ring of Tyr-553 and the hydrophobicity of Trp-557 are critical for the inhibition. Although alanine substitution for Lys-558 had no effect on receptor phosphorylation, its substitution with proline produced high spontaneous receptor phosphorylation, suggesting that the predicted alpha-helical conformation is involved in the inhibition. A synthetic peptide comprising Tyr-553 through Ile-563 showed circular dichroism spectra characteristic of alpha-helix, supporting the structural prediction. Thus, the KIT intracellular juxtamembrane region contains important residues which, in a putative alpha-helical conformation, exert inhibitory control on the kinase activity of ligand-unoccupied receptor.

Activating and dominant inactivating c-KIT catalytic domain mutations in distinct clinical forms of human mastocytosis

Human mastocytosis is characterized by increased mast cells. It usually occurs as a sporadic disease that is often transient and limited in children and persistent or progressive in adults. The c-KIT protooncogene encodes KIT, a tyrosine kinase that is the receptor for mast cell growth factor. Because mutated KIT can transform cells, we examined c-KIT in skin lesions of 22 patients with sporadic mastocytosis and 3 patients with familial mastocytosis. All patients with adult sporadic mastocytosis had somatic c-KIT mutations in codon 816 causing substitution of valine for aspartate and spontaneous activation of mast cell growth factor receptor (P = 0.0001). A subset of four pediatric onset cases with clinically unusual disease also had codon 816 activating mutations substituting valine, tyrosine, or phenylalanine for aspartate. Typical pediatric patients lacked 816 mutations, but limited sequencing showed three of six had a novel dominant inactivating mutation substituting lysine for glutamic acid in position 839, the site of a potential salt bridge that is highly conserved in receptor tyrosine kinases. No c-KIT mutations were found in the entire coding region of three patients with familial mastocytosis. We conclude that c-KIT somatic mutations substituting valine in position 816 of KIT are characteristic of sporadic adult mastocytosis and may cause this disease. Similar mutations causing activation of the mast cell growth factor receptor are found in children apparently at risk for extensive or persistent disease. In contrast, typical pediatric mastocytosis patients lack these mutations and may express inactivating c-KIT mutations. Familial mastocytosis, however, may occur in the absence of c-KIT coding mutations.

Clustering of activating mutations in c-KIT's juxtamembrane coding region in canine mast cell neoplasms

The proto-oncogene c-KIT encodes a growth factor receptor, KIT, with ligand-dependent tyrosine kinase activity that is expressed by several cell types including mast cells. c-KIT juxtamembrane coding region mutations causing constitutive activation of KIT are capable of transforming cell lines and have been identified in a human mast cell line and in situ in human gastrointestinal stromal tumors, but have not been demonstrated in situ in neoplastic mast cells from any species. To determine whether c-KIT juxtamembrane mutations occur in the development of mast cell neoplasms, we examined canine mastocytomas, which are among the most common tumors of dogs and which often behave in a malignant fashion, unlike human solitary mastocytomas. Sequencing of c-KIT cDNA generated from tumor tissues removed from seven dogs revealed that three of the tumors contained a total of four mutations in an intracellular juxtamembrane coding region that is completely conserved among vertebrates. In addition, two mutations were found in three mast cell lines derived from two additional dogs. One mutation from one line matched that found in situ in one of the tumors. The second was found in two lines derived from one dog at different times, indicating that the mutation was present in situ in the animal. All five mutations cause high spontaneous tyrosine phosphorylation of KIT. Our study provides in situ evidence that activating c-KIT juxtamembrane mutations are present in, and may therefore contribute to, the pathogenesis of mast cell neoplasia. Our data also suggest an inhibitory role for the KIT juxtamembrane region in controlling the receptor kinase activity.

c-kit mutation and osteopetrosis-like osteopathy in a patient with systemic mast cell disease

We describe the case of a 69-year-old man with systemic mastocytosis and severe osteopetrosis who carries a somatic activating mutation in the c-kit proto-oncogene. The patient initially presented with urticaria pigmentosa, progressing to systemic mast cell disease with severe anemia due to bone marrow involvement, chronic diarrhea, and hepatosplenomegaly. Direct sequencing using amplimers from reverse transcriptase-polymerase chain reactions (RT-PCR) from skin mast cell-derived RNA revealed a point mutation in the c-kit proto-oncogene at position 2468, introducing a new recognition site for the restriction endonuclease HinfI. Treatment with interferon-alpha 2a, prednisone, and erythropoietin was initiated. Subsequently, clinical symptoms improved significantly and hemoglobin levels are now stable at 13 g/dl.

Murine cutaneous mastocytosis and epidermal melanocytosis induced by keratinocyte expression of transgenic stem cell factor

The growth and differentiation of mast cells and melanocytes require stem cell factor (SCF), the ligand for the kit receptor tyrosine kinase. SCF may exist as a membrane-bound or soluble molecule. Abnormalities of the SCF-kit signaling pathway, with increased local concentrations of soluble SCF, have been implicated in the pathogenesis of the human disease cutaneous mastocytosis, but have not yet been shown to play a causal role. To investigate both the potential of SCF to cause mastocytosis and its role in epidermal melanocyte homeostasis, we targeted the expression of SCF to epidermal keratinocytes in mice with two different transgenes controlled by the human keratin 14 promoter. The transgenes contained cDNAs that either produced SCF, which can exist in both membrane-bound and soluble forms, or SCF, which remains essentially membrane bound. Murine epidermal keratinocyte expression of membrane-bound/ soluble SCF reproduced the phenotype of human cutaneous mastocytosis, with dermal mast cell infiltrates and epidermal hyperpigmentation, and caused the maintenance of a population of melanocytes in the interadnexal epidermis, an area where melanocytes and melanin are found in human skin but where they are not typically found in murine skin. Expression of membrane-bound SCF alone resulted in epidermal melanocytosis and melanin production, but did not by itself cause mastocytosis. We conclude, first, that a phenotype matching that of human mastocytosis can be produced in mice by keratinocyte overproduction of soluble SCF, suggesting a potential cause of this disease. Second, we conclude that keratinocyte expression of membrane-bound SCF results in the postnatal maintenance of epidermal melanocytes in mice. Since the resulting animals have skin that more closely approximates human skin than do normal mice, their study may be more relevant to human melanocyte biology than the study of skin of normal mice.

Tumor-specific peptides in cutaneous T-cell lymphoma: association with class I major histocompatibility complex and possible derivation from the clonotypic T-cell receptor

We wished to identify and characterize tumor-associated class I peptides which could potentially serve as immunogens for an immunoprotective CD8 response in cutaneous T-cell lymphoma (CTCL). Candidate idiotypic peptides were identified from the third complementarity determining region (CDR3) of the clonotypic T-cell receptor (TCR) expressed on malignant T cells and native class I peptides were identified from CTCL cells. Idiotypic peptides were designed by sequencing of patients' CDR3 and identifying 9 amino acid peptides that could be accommodated in the peptide-binding motif of the class I alleles. Three candidate idiotypic peptides were synthesized and tested by measuring release of tumor necrosis factor-alpha (TNF-alpha) from autologous CD8 cells. Native peptides were acid-eluted from class I molecules on CTCL lymphocytes, fractionated, tested in the TNF-alpha assay and sequenced. Two unique idiotypic peptides were specifically recognized by autologous CD8 cells from CTCL patients. In addition, a native peptide eluted from class I molecules of CTCL tumor cells was identified, in the protein data base, as a novel molecule with partial sequence homology to the conserved portion of the patient's TCR. This homology was used to construct an extended native peptide sequence that was immunogenic for CD8 cells from both CTCL patients. Our results demonstrate that peptides derived from the TCR can be used as tumor-specific immunogens that are recognized by CD8 cells. Moreover, novel class I peptides isolated from the tumor cell also serve as immunogens. These peptides might form the basis of an anti-tumor vaccine for immunotherapy of CTCL.

Chymase cleavage of stem cell factor yields a bioactive, soluble product

Stem cell factor (SCF) is produced by stromal cells as a membrane-bound molecule, which may be proteolytically cleaved at a site close to the membrane to produce a soluble bioactive form. The proteases producing this cleavage are unknown. In this study, we demonstrate that human mast cell chymase, a chymotrypsin-like protease, cleaves SCF at a novel site. Cleavage is at the peptide bond between Phe-158 and Met-159, which are encoded by exon 6 of the SCF gene. This cleavage results in a soluble bioactive product that is 7 amino acids shorter at the C terminus than previously identified soluble SCF. This research shows the identification of a physiologically relevant enzyme that specifically cleaves SCF. Because mast cells express the KIT protein, the receptor for SCF, and respond to SCF by proliferation and degranulation, this observation identifies a possible feedback loop in which chymase released from mast cell secretory granules may solubilize SCF bound to the membrane of surrounding stromal cells. The liberated soluble SCF may in turn stimulate mast cell proliferation and differentiated functions; this loop could contribute to abnormal accumulations of mast cells in the skin and hyperpigmentation at sites of chronic cutaneous inflammation.

Human skin/SCID mouse chimeras as an in vivo model for human cutaneous mast cell hyperplasia

Human skin xenografted to mice with severe combined immunodeficiency syndrome (SCID) was evaluated to determine the integrity and fate of human dermal mast cells. There was an approximately 3-fold increase in number of dermal mast cells by 3 mo after engraftment (p < 0.05). These cells were responsive to conventional mast cell secretagogues and were confirmed to be of human origin by ultrastructural characterization of granule substructure and by reactivity for the human mast cell proteinase, chymase. CD1a+ Langerhans cells, also bone marrow-derived cells, failed to show evidence of concomitant hyperplasia, and increased mast cell number was not associated with alterations in number of dermal vascular profiles identified immunohistochemically for human CD31. RT-PCR analysis demonstrated human but not murine stem cell factor (SCF; also termed mast cell growth factor, c-kit ligand) mRNA in xenografts. Epidermal reactivity for stem cell factor protein shifted from a cytoplasmic pattern to an intercellular pattern by 3 mo after engraftment, suggesting a secretory phenotype, as previously documented for human cutaneous mastocytosis. The majority (>90%) of mast cells demonstrated membrane reactivity for human SCF at the time points of peak hyperplasia. These data establish SCID mouse recipients of human skin xenografts as a potential in vivo model for cutaneous mast cell hyperplasia.

Role of CD4+ T cells in pathogenesis associated with Leishmania amazonensis infection

Most inbred strains of mice are susceptible to Leishmania amazonensis infection. We have examined the mechanism(s) underlying this generalized susceptibility using mice deficient in T cell development or in the expression of either MHC class I or class II. In contrast to wild-type C57BL/6 (B6) mice that uniformly developed large ulcerating lesions, mice lacking functional CD4+ T cells (due to targeted disruption of genes for either MHC class II trans-activator or I-A beta) showed no signs of lesion development for up to 12 to 14 wk postinfection and contained significantly lower numbers of parasites in lesions. Similarly, both B6 nude and RAG2 -/- mice failed to develop lesions. However, RAG2 -/- mice reconstituted with naive wild-type CD4+ T cells and beta2m -/- mice did develop lesions. Lesions of MHC class II -/- mice contained minimal numbers of CD8+ T cells, a marked reduction of monocytes/macrophages, and evident extracellular parasites. The inability to mount an inflammatory response in MHC class II -/- mice correlated with the failure to produce lymphokines that lead to the recruitment of monocytes/granulocytes. These results demonstrate that CD4+ T cells are the primary lymphocyte subset that mediates cellular infiltration, lesion pathology, and therefore, susceptibility to L. amazonensis infection. The disease-promoting CD4+ T cells in L. amazonensis-infected mice have the characteristics of Th1 cells. The striking differences in the course of infection between MHC class II -/- mice infected with L. amazonensis and Leishmania major suggest that these parasites may have adapted different strategies regarding the CD4-dependent immune response.

Role of CD4+ T cells in pathogenesis associated with Leishmania amazonensis infection

Most inbred strains of mice are susceptible to Leishmania amazonensis infection. We have examined the mechanism(s) underlying this generalized susceptibility using mice deficient in T cell development or in the expression of either MHC class I or class II. In contrast to wild-type C57BL/6 (B6) mice that uniformly developed large ulcerating lesions, mice lacking functional CD4+ T cells (due to targeted disruption of genes for either MHC class II trans-activator or I-A beta) showed no signs of lesion development for up to 12 to 14 wk postinfection and contained significantly lower numbers of parasites in lesions. Similarly, both B6 nude and RAG2 -/- mice failed to develop lesions. However, RAG2 -/- mice reconstituted with naive wild-type CD4+ T cells and beta2m -/- mice did develop lesions. Lesions of MHC class II -/- mice contained minimal numbers of CD8+ T cells, a marked reduction of monocytes/macrophages, and evident extracellular parasites. The inability to mount an inflammatory response in MHC class II -/- mice correlated with the failure to produce lymphokines that lead to the recruitment of monocytes/granulocytes. These results demonstrate that CD4+ T cells are the primary lymphocyte subset that mediates cellular infiltration, lesion pathology, and therefore, susceptibility to L. amazonensis infection. The disease-promoting CD4+ T cells in L. amazonensis-infected mice have the characteristics of Th1 cells. The striking differences in the course of infection between MHC class II -/- mice infected with L. amazonensis and Leishmania major suggest that these parasites may have adapted different strategies regarding the CD4-dependent immune response.

Chronically KIT-stimulated clonally-derived human mast cells show heterogeneity in different tissue microenvironments

Human mast cell precursors arise in the bone marrow and circulate to different tissue microenvironments, where they develop distinct phenotypes that may be characterized by differential expression of the serine protease, chymase. The growth and development of mast cells is stimulated by mast cell growth factor, which is also known as kit ligand because its obligate receptor is KIT, the protein product of the c-KIT proto-oncogene. The in vivo influence of the KIT-kit ligand axis on the phenotype of human mast cells has not been determined. We used immunohistochemistry to detect in situ expression of tryptase and chymase by mast cells of a patient with urticaria pigmentosa and aggressive systemic mastocytosis, whose pathologic mast cells are clonally derived and chronically stimulated by KIT because they all contain the same point mutation causing constitutive activation of KIT. Mast cells in both spleen and skin expressed tryptase, but only in the skin did a majority of mast cells express chymase. We conclude that chronic stimulation of the KIT-kit ligand axis does not irrevocably commit mast cells to a chymase-positive or chymase-negative phenotype. These findings suggest that factors other than kit ligand predominate in determining mast cell phenotype.

Somatic c-KIT activating mutation in urticaria pigmentosa and aggressive mastocytosis: establishment of clonality in a human mast cell neoplasm

Mastocytosis is characterized by accumulations of mast cells in various organs (1). Most cases are indolent and confined to the skin, where discrete mast cell infiltrates are associated increased epidermal melanin, a clinical picture known as urticaria pigmentosa (UP). Other forms of mastocytosis combine UP with aggressive involvement of other organs or with haemotologic abnormalities (1-4). It is not known whether all forms of mastocytosis are true neoplasms or whether some might represent reactive hyperplasias (5-7). The c-KIT proto-oncogene encodes a type III receptor tyrosine kinase (KIT) that is critical to the development and survival of mast cells and melanocytes (8-11). The ligand for KIT (KL) can stimulate mast cell development, proliferation, and mediator release (9,12-17), as well as melanocyte proliferation and pigment production (18-20). To determine the role of c-KIT in the pathogenesis of mastocytosis, we examined tissue and cells isolated from a patient with UP and aggressive systemic mastocytosis with massive splenic involvement. We found a mutation that results in constitutive activation and expression of c-KIT in mast cells of both skin and spleen. This is the first in situ demonstration of an activation c-KIT mutation in neoplastic cells. It also demonstrates the clonal and neoplastic nature of this form of mastocytes.

Disruption of CD40-CD40 ligand interactions results in an enhanced susceptibility to Leishmania amazonensis infection

To study the role of CD40 ligand (CD40L) in the host immune responses against intracellular pathogens, we infected CD40L knockout (CD40L-/-) mice with Leishmania amazonensis. Although wild-type mice were susceptible to infection and developed progressive ulcerative lesions, tissue parasite burdens in CD40L-/- mice were significantly higher. This heightened susceptibility to infection was associated with an impaired T cell and macrophage activation and altered inflammatory response, as reflected by low levels of IFN gamma, lymphotoxin-tumor necrosis factor (LT-TNF), and nitric oxide (NO) production. Furthermore, CD40L-/- mice failed to generate a protective immune response after immunization. These results indicate an essential role of cognate CD40-CD40L interactions in the generation of cellular immune responses against an intracellular parasite.

Papilloma formation in human foreskin xenografts after inoculation of human papillomavirus type 16 DNA

A mouse model of high-risk human papillomavirus infection was developed in which human papillomavirus (HPV) type 16 DNA was inoculated into human foreskin grafted to the skin of severe combined immunodeficient (scid) mice. Grafted skin contained human epidermis and dermis and, like normal human skin, expressed involucrin in differentiating keratinocytes. HPV type 16 DNA, attached to gold particles, was delivered directly into human epidermal cells and induced exophytic papilloma with histologic features of papillomavirus infection, including koilocytosis and expression of papillomavirus capsid antigen. This model should be useful for determining in vivo the functions of viral genes and for developing strategies to prevent and treat HPV-associated disease. It may also be of value in developing animal models of other human skin diseases.

Restoration of differentiation and suppression of tumorigenicity in somatic cell hybrids of human squamous carcinoma cells and keratinocytes

Somatic cell hybrid cell lines derived from the fusion of human squamous carcinoma cells (FaDu-Hyg) with human keratinocytes were used to examine the relationships between cell differentiation and tumorigenicity. Treatment of the parental keratinocytes or the two hybrid cell lines with the combination of calcium and fetal bovine serum increased the expression of the envelope precursor, involucrin, 4- to 8-fold, whereas it remained unchanged in FaDu-Hyg cells. Similarly, calcium- and serum-treated keratinocytes and the two hybrid cell lines displayed a 7- to 13-fold increase of the activity of membrane-associated type I transglutaminase, whereas transglutaminase activity in FaDu-Hyg cells did not change appreciably. FaDu-Hyg cells were tumorigenic in vivo, but tumorigenicity was suppressed in both hybrid cell lines. Analysis of additional tumor cell lines indicated that the expression of transglutaminase I and involucrin are under separate genetic control and that loss of transglutaminase activity can result either from a lack of protein or from a defect in the activation step. Thus, keratinization of squamous epithelial cells appears to be controlled by several different recessive genes, which cosegregate with but are probably only partly identical with the genes that suppress tumor formation in vivo.

Altered metabolism of mast-cell growth factor (c-kit ligand) in cutaneous mastocytosis

BACKGROUND AND METHODS

The lesions of cutaneous mastocytosis are characterized by dermal infiltrates of mast cells and may appear hyperpigmented because of the presence of increased levels of epidermal melanin. Mast-cell growth factor, the ligand for the product of the c-kit proto-oncogene, stimulates the proliferation of mast cells and increases the production of melanin by melanocytes. We therefore looked for the expression of the mast-cell growth factor gene in the skin of patients with cutaneous mastocytosis using immunohistochemical techniques and the polymerase chain reaction.

RESULTS

In the skin of normal subjects and those with unrelated diseases, immunoreactive mast-cell growth factor was associated with keratinocytes and scattered dermal cells, a pattern consistent with cell-bound mast-cell growth factor. In skin samples containing lesions and in clinically normal skin from patients with mastocytosis, however, mast-cell growth factor was also found free in the dermis and in the extracellular spaces between keratinocytes, suggesting the presence of a soluble form of this protein. Messenger RNA (mRNA) that can encode soluble mast-cell growth factor was present in the skin of patients as well as in that of normal control subjects. No sequence abnormalities were detected in mRNA for mast-cell growth factor from one patient.

CONCLUSIONS

The altered distribution of mast-cell growth factor in the skin of patients with cutaneous mastocytosis is consistent with abnormal production of the soluble form of this factor. This abnormality is probably due to increased proteolytic processing, since it was not explained by differences in the splicing or sequence of mast-cell growth factor mRNA in the patients. Soluble mast-cell growth factor may cause the characteristic accumulation of mast cells and the hyperpigmentation of skin found in cutaneous mastocytosis. These findings suggest that some forms of mastocytosis represent reactive hyperplasia rather than mast-cell neoplasia.

Primary cutaneous B-cell lymphoma. Diagnosis, treatment, and prognosis

BACKGROUND

An elderly woman with B-cell lymphoma confined to the skin of the lower extremity was treated with combination chemotherapy and radiation therapy. She relapsed with new skin lesions outside the original radiation port that responded to additional radiation therapy and remains in remission 12 months after her last treatment.

OBJECTIVE

This article investigates the diagnosis, treatment, and prognosis of primary cutaneous B-cell lymphoma.

METHODS

The relevant literature was researched through computer data bases and bibliographies.

RESULTS

Patients who present with localized lesions of primary cutaneous B-cell lymphoma have a favorable prognosis regardless of the type of therapy, although relapses may occur in the absence of systemic disease.

CONCLUSION

We advocate the use of local therapies as initial treatment in patients with localized primary cutaneous B-cell lymphoma.

Paracecal hernia: case report and review of the literature

A case of paracecal hernia successfully treated operatively is described. Review of the literature revealed 145 previously reported cases. Our case is added. Pertinent anatomy predisposing to paracecal hernia is reviewed. Roentgenographic signs of paracecal hernia are presented. Clinical signs and symptoms are discussed.