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Dysplastic nevi (DNs), also known as Clark's nevi or atypical moles, are distinguished from common melanocytic nevi by variegation in pigmentation and clinical appearance, as well as differences in tissue patterning. However, cellular and molecular differences between DNs and common melanocytic nevi are not completely understood. Using cDNA microarray, quantitative RT-PCR, and immunohistochemistry, we molecularly characterized DNs and analyzed the difference between DNs and common melanocytic nevi. A total of 111 probesets (91 annotated genes, fold change > 2.0 and false discovery rate < 0.25) were differentially expressed between the two lesions. An unexpected finding in DNs was altered differentiation and activation of epidermal keratinocytes with increased expression of hair follicle-related molecules (keratin 25, trichohyalin, ribonuclease, RNase A family, 7) and inflammation-related molecules (S100A7, S100A8) at both genomic and protein levels. The immune microenvironment of DNs was characterized by an increase of T helper type 1 (IFNγ) and T helper type 2 (IL13) cytokines as well as an upregulation of oncostatin M and CXCL1. DUSP3, which regulates cellular senescence, was identified as one of the disease discriminative genes between DNs and common melanocytic nevi by three independent statistical approaches and its altered expression was confirmed by immunohistochemistry. The molecular and cellular changes in which the epidermal-melanin unit undergoes follicular differentiation as well as upregulation of defined cytokines could drive complex immune, epidermal, and pigmentary alterations.

Background: Melanocytic nevi typically show a morphologic sequence of maturation from epithelioid “type A” cells to fusiform, Schwann cell-like “type C” cells with dermal descent. Nevi may also produce Wagner-Meissner-like structures (nevic corpuscles). Previous studies have shown that this maturation of intradermal nevi recapitulates intermediate stages in Schwann cell development. In intradermal nevi, we have evaluated the pattern of S100A6 protein, a form of S100 found in Schwann cells. Methods: Formalin-fixed, paraffin-embedded archival tissues were evaluated by immunohistochemistry using antibodies specific for S100A6 and S100B in 38 intradermal nevi (IDN). Ten neurofibromas (NF), 3 Schwannomas (SCH), 2 palisaded and encapsulated neuromas (PEN), and 2 granular cell tumors (GCT) were included as positive controls since these lesions have large numbers of Schwann cells. Results: Melanocytic nevi demonstrated preferential anti-S100A6 staining of “type C” cells (36/38; 28 strong, 8 weak) and nevic corpuscles (25/38; 19 strong, 6 weak) compared to “type A” cells (17/38; 17 weak) and “type B” cells (17/38; 4 strong, 13 weak). All NF, SCH, and PEN stained strongly with anti-S100A6. Both GCT were negative with anti-S100A6 but positive with anti-S100B. Conclusions: The pattern of S100A6 expression in intradermal nevi further supports the hypothesis that maturation in these lesions recapitulates features of Schwann cell differentiation. The lack of S100A6 expression by both GCT suggests that these lesions have lost this feature of Schwann cells, which may play a role in their peculiar phenotypic appearance.

Background: S100A6, an S100 calcium-binding protein, has been found in a variety of cutaneous and extracutaneous lesions including: melanocytic nevi, melanoma, some salivary gland and epithelial tumors, and malignant fibrous histiocytoma (MFH). Dermal dendrocytes (DD) in the papillary dermis of skin also express S100A6 protein. We evaluated a variety of cutaneous fibrohistiocytic lesions to determine if the immunophenotype of S100A6 positivity can be expanded to include some or all of these lesions. Methods: Formalin-fixed, paraffin-embedded tissues from fibrous papules (FP, 20), dermatofibromas (DF, 20), dermatofibrosarcoma protuberans (DFSP, 5), atypical fibroxanthomas (AFX, 5), oral fibromas (3), digital fibroma (1), and dermatomyofibroma (1) were evaluated with antibodies to S100A6, S100B, factor XIIIa, and MAC387 using a one-hour capillary action-based immunohistochemical procedure. Results: DD in 20/20 FP, 19/20 DF, and 4/4 fibromas stained positively with anti-S100A6 in a pattern similar to anti-factor XIIIa. No DFSP cases stained with anti-S100A6. Anti-S100A6 showed superior staining to anti-factor XIIIa in 4/5 AFX cases. Conclusions: The immunophenotypes of some fibrohistiocytic lesions can be expanded to include S100A6 protein. With the exception of AFX, the use of anti-S100A6 does not appear to offer added benefit over anti-factor XIIIa in the differential diagnosis of fibrohistiocytic lesions.

Immunohistochemical detection of certain low to intermediate molecular weight keratins often is impaired in routinely processed specimens due to masking of these antigens by formalin fixation. Despite standard enzymatic digestion, AE1:AE3 and CAM 5.2, two of the most currently utilized antikeratin antibody preparations, either stain weakly or fail to stain basal keratinocytes and tumors composed of basaloid keratinocytes in paraffin sections of formalin-fixed tissue. We present here our experience with the monoclonal antibody MNF116 which detects keratins 5, 6, 8, 17, and 19 (DAKO, Carpinteria, CA). We have studied 232 routinely-processed skin lesions with MNF116 and compared the staining with that of AE1:AE3 mixture or CAM 5.2. In normal skin, the staining achieved with MNF116 was particularly strong on the basal cells of the epidermis and adnexae. MNF116 was positive in all 154 epithelial tumors and negative in all but one (a leiomyosarcoma) of 78 mesenchymal and melanocytic tumors. AE1:AE3 mixture was positive in all but four poorly-differentiated squamous cell carcinomas and it was only weakly positive in most basal cell carcinomas. CAM 5.2 was positive in tumors of the sweat apparatus, Merkel cell carcinomas, metastatic carcinomas, and 5/15 basal cell carcinomas. We consider that, in routinely processed specimens, MNF116 is very useful and convenient for detection of cytokeratin expression in cutaneous lesions, and therefore helpful in the evaluation of tumors with small cells and other poorly differentiated neoplasms of the skin.

Three years after excision of a primary malignant melanoma from the lower back, a mass was noted in the right scapular region of a 51-year-old man. Histopathology revealed a malignant spindle-cell neoplasm invading the wall of a deep cutaneous blood vessel. Immunohistochemistry confirmed the diagnosis of angiotropic metastatic melanoma and ruled out primary leiomyosarcoma. Angiotropism is a rare pattern of metastasis of melanoma; the biochemical mechanisms that permit melanoma cells to undergo hematogenous dissemination, and the favorable milieu that the vascular wall offers for melanoma cells, may be responsible for this unusual growth pattern.

Cutaneous extramedullary hematopoiesis is rare, usually occurring in neonates following intrauterine viral infections, hereditary spherocytosis, or the twin transfusion syndrome. Only 20 cases of cutaneous extramedullary hematopoiesis have been reported in adults, all with myelofibrosis. The cutaneous infiltrates may be atypical and difficult to distinguish from leukemia cutis. We have studied a 65-year-old woman with myelofibrosis and approximately 40 violaceous, firm, non-tender cutaneous nodules measuring 1 to 4 cm in diameter, located on her abdomen near a splenectomy scar. Histologically, the lesions had a dense infiltrate of myeloid cells in all stages of maturation, atypical large cells with multilobate nuclei or multiple nuclei, resembling atypical megakaryocytes, and fibroblasts. Although the patient received erythropoietin therapy prior to the development of the nodules, erythroid progenitors were not seen. Reticulin was increased particularly surrounding the atypical megakaryocytes. The myeloid cells stained for chloroacetate esterase and with the polyclonal antibody MAC 387. Atypical megakaryocytes stained for Factor XIIIa and Factor VIII-related antigen. Dendritic Factor XIIIa positive cells were also increased. The skin lesions remain unchanged grossly one year after their development.

Porokeratoses are known to give rise to squamous and basal cell carcinomas. In this study, we examined 15 lesions of porokeratosis immunohistochemically for evidence of aberrant keratinization using several markers of keratinocyte (KC) maturation and differentiation, including involucrin, filaggrin, cytokeratins, and the growth activation marker psi-3. The staining patterns obtained were compared with several non-premalignant parakeratotic skin lesions including psoriasis, pityriasis rosea, pityriasis rubra pilaris, irritated seborrheic keratosis, atopic dermatitis, seborrheic dermatitis, and verruca vulgaris. The centers of porokeratoses stained in a pattern identical to that observed in other premalignant keratinocytic lesions including actinic keratoses, recessive dystrophic epidermolysis bullosa, and nonhealing wounds. KCs beneath the cornoid lamella (CL) stained in a pattern similar to that observed in squamous cell carcinomas. KCs peripheral to the CL in the epidermis showed a normal staining pattern. The control non-premalignant parakeratotic lesions displayed a variety of staining patterns, but none showed a pattern identical to that observed in porokeratosis. The failure of KCs in porokeratoses to mature and differentiate normally may be related to the increased incidence of carcinomas associated with these lesions.

Background/Aims: The clinical definition of an atypical naevus (“dysplastic naevus” or “naevus with architectural disorder and cytological atypia of melanocytes”) stresses size larger than 5 mm in diameter as a major diagnostic criterion. Because malignant melanomas and their precursors may arise in smaller lesions, a histological study of melanocytic lesions smaller than 4 mm in diameter was conducted to evaluate their histological appearance. Methods: Two hundred and sixty one naevi smaller than 4 mm in diameter were collected and characterised by histological examination into benign naevi without architectural disorder and naevi with architectural disorder and mild, moderate, and severe atypical melanocytes according to criteria used on larger lesions. Results: Small melanocytic naevi covered the same complex histological spectrum from benign naevi to severely atypical naevi when compared with larger lesions. A high proportion of small naevi (72%) exhibited features diagnostic for naevi with architectural disorder and cytological atypia. Conclusion: There is a discrepancy between histological and clinically defined atypical naevi. The same generally accepted criteria for the histological diagnosis of atypical naevi should be used for small melanocytic naevi in addition to large ones. Thus, small naevi exhibiting atypical features on histological examination should be categorised as atypical naevi, regardless of their small diameter.

CD34 antigen is expressed in normal human skin on endothelium, in spindle cells located around adnexal structures, and in a subset of interstitial cells in the reticular dermis. CD34 expression has also been identified in a number of fibrohistiocytic neoplasms, such as dermatofibrosarcoma protuberans and solitary fibrous tumors of soft tissue. CD34 expression has not previously been described in sclerotic, or "plywood" fibromas. Here presented are three lesions from three patients, in which histologic examination revealed a well-circumscribed dermal nodule composed of spindled cells with focal nuclear pseudo-inclusions. There was extensive fibrosis with hypocellular, storiform areas, characteristic of sclerotic fibroma. The spindled cells strongly expressed CD34, but not factor XIIIa or markers of melanocytic, neural, or muscular differentiation. A diagnosis of Cowden syndrome was considered in one of the cases. These cases provide evidence that CD34 expression can occur in sclerotic fibromas, either solitary or associated with Cowden syndrome. When diagnosing a sclerotic fibroma, one should comment in the report regarding the possibility of Cowden syndrome.

Nevoid malignant melanoma probably represents an early form of nodular malignant melanoma in which there is little proliferation of melanocytes in the epidermis and a dermal proliferation that mimics some features of a compound or intradermal nevus, which is difficult to recognize as being due to malignant melanoma. The lesions can contain either small nevoid cells or larger cells that resemble those in Spitz's nevi. Overall the lesions are symmetrical, have minimal proliferation in the epidermis, and often have dispersion of cells at the base. The lesions with small nevoid cells are particularly difficult to distinguish from common intradermal or compound melanocytic nevi. Reactivity of the intradermal component for HMB-45 antigen, without antigen retrieval, or for Ki-67 antigen can show that the dermal cells have an immature phenotype and, in combination with histological criteria, can support a diagnosis of nevoid malignant melanoma.

Retinoblastoma protein (pRB) is the product of a tumour-suppressor gene (rb) mapped to chromosome 13q14. pRB acts as a control checkpoint at the G1 phase of the cell cycle, preventing cells from entering into the S phase. Mutational inactivation of both normal alleles leads to loss of pRB expression and the development of malignant neoplasms. Absence of pRB occurs in retinoblastomas, sarcomas and several other types of tumours. The potential role of pRB in the pathogenesis of cutaneous melanoma is unknown, and was the subject of this investigation. Formalin-fixed, paraffin-embedded sections of four cutaneous melanoma metastases, 17 primary invasive melanomas and 10 predominantly intradermal melanocytic naevi were studied. Monoclonal antibodies directed against pRB and Ki-67 antigen were used after microwave heating of sections to restore antigenicity. pRB was not detected in morphologically normal epidermal melanocytes. In five naevi, only scattered cells (1%) expressed pRB, whereas in the other five naevi, pRB expression was undetectable. In contrast, pRB was detected in all primary and metastatic melanomas (5-70% of cells). Expression was always localized to nuclei. Ki-67 expression was detected only in the melanomas, with both cellular staining and regional localization similar to that shown by pRB in 13 of the 20 melanomas studied with both antibodies. pRB appears to be expressed at higher levels in melanomas than in benign naevi. It therefore seems unlikely that loss of rb expression is an important factor in the pathogenesis of melanoma.

The CD44 antigen (ECMRIII, Hermes antigen) is a highly glycosylated cell-surface polypeptide involved in diverse cellular functions, including cell adhesion and lymphocyte-homing receptor activity. CD44 is also expressed in vivo by several tumors, including astrocytomas, meningiomas, and colonic adenocarcinomas. In addition, it has been shown that expression of CD44 appears to confer metastatic potential to cell lines derived from certain adenocarcinomas. In the skin, CD44 is normally expressed in epidermal keratinocytes and hair follicular, sebaceous, and eccrine epithelial cells. However, there have been few data with regard to the expression in vivo of CD44 in primary cutaneous neoplasms. Furthermore, there have not been studies in vivo of the possible differential expression of CD44 in primary versus metastatic tumors in the skin. We have examined by immunohistochemistry the expression of CD44 in cutaneous invasive and metastatic squamous cell carcinomas, metastatic adenocarcinomas, and basal cell carcinomas. All invasive and metastatic squamous cell carcinomas, as well as metastatic adenocarcinomas, strongly expressed CD44 ; however, basal cell carcinomas were nonreactive or showed only focal, minimal reactivity. Adjacent normal skin demonstrated CD44 immunoreactivity throughout the epidermis, including the basal layer. In addition, hair follicles and sebaceous and eccrine glands expressed CD44. The results suggest that expression of CD44 in these cutaneous epithelial tumors is not related to malignant transformation, but instead may be related to tumor progression and the ability to metastasize.

Alterations in the tumor-suppressor gene p53 are common in many types of human malignancies, but the potential role of p53 in the pathogenesis of cutaneous melanoma is controversial. The gene product, p53 protein, is normally present in very small amounts in noncancerous tissues. Missense mutations lead to accumulation of mutant p53 in the cells, which makes it detectable immunohistochemically in many cancers. Formalin-fixed, paraffin-embedded sections of 14 primary invasive melanomas, 3 cutaneous melanoma metastases, and 10 predominantly intradermal melanocytic nevi were reacted with a panel of three anti-p53 monoclonal antibodies (mAbs) (PAb240, PAb1801, and DO7) and a mAb against Ki-67 (MIB-1), a marker of cellular proliferation. p53 was not detected in morphologically normal epidermal melanocytes or nevus cells. A single primary invasive melanoma, having a very high index of proliferation (Ki-67 expression in > 50% of cells), had diffuse nuclear labeling with all three anti-p53 mAbs used. Abnormalities of p53 expression occur rarely in cutaneous melanomas, but overexpression of p53 may occur in a subset of melanomas with a high index of proliferation.

Transforming growth factor-beta 2 (TGF-beta 2) is a potent regulatory of proliferation and differentiation of both normal and malignant cells. In addition, TGF-beta 2 can exert a variety of immunosuppressive effects, suggesting that the production of this molecule contributes to impaired immunological surveillance of tumor development. In vitro, TGF-beta 2 expression has been demonstrated in cell lines derived from metastatic malignant melanocytes. but not in those derived from normal melanocytes. We sought to evaluate a potential role of TGF-beta 2 in the initiation or progression of malignant melanoma in vivo. We examined by nucleic acid in situ hybridization the expression of TGF-beta 2 mRNA transcripts in 124 melanocytic lesions including metastatic and primary invasive melanomas, melanomas in situ, nevi with architectural disorder and cytologic atypia, ordinary benign melanocytic nevi, and Spitz nevi. All metastatic melanomas and a majority (94%) of primary melanomas invasive to Clark's level III, IV, or V expressed TGF-beta 2 mRNA. A minority (41%) of Clark's level II primary invasive melanomas expressed this factor. All definitive melanomas in situ and nevi were negative. The results suggest that TGF-beta 2 expression in malignant melanoma may be a critical event in the development of deep invasion and metastases in malignant melanoma.

Abnormalities in the p53 gene and in expression of its protein product are among the most frequent changes demonstrated in a variety of human cancers. p53 Is a nuclear phosphoprotein that in the natural form or "wild-type" can bind to DNA and prevent cells from entering into the S phase of the cell cycle. There is an increase in wild-type p53 after exposure of the skin to UV light, which allows for DNA repair before replication that would make DNA damage permanent. A loss of this protective influence destabilizes the genome. Mutation of the p53 gene commonly causes a defective protein that is degraded more slowly and accumulates in the cell to the extent that it becomes detectable by routine immunocytochemistry. These abnormalities precede the development of cancer in some examples. Studies of precursor lesions have used mainly immunohistochemical techniques that show p53 protein overexpression. The relationship between such overexpression and actual mutation of the p53 gene is controversial because overexpression of "wild-type" p53 protein also can occur. Mutations in the p53 gene have been observed in many actinic keratoses, basal cell carcinomas, and squamous cell carcinomas, and in a small proportion of malignant melanomas. Specific types of pyrimidine transitions have pointed to a role for UV light in these mutations. Molecular analysis is needed to determine whether or not immunocytochemical staining is truly reflective of mutation or is due to some other mechanism that causes an increased expression of wild-type p53.

Derangement of the p53 tumor suppressor gene has been implicated in the aetiology of a wide range of human neoplasias. We have previously determined that overexpression and mutation of the p53 gene in cultured metastatic melanomas is low (11%). However, two recent immunohistochemical studies have reported that > 85% of malignant melanoma specimens overexpress mutated p53 protein. In an effort to resolve this contradiction in the published literature, we have re-evaluated a range of cultured and non-cultured melanocytic lesions for the occurrence of point mutations in the p53 gene using DNA- and RNA-dependent single strand conformation polymorphism (RNA-SSCP) and direct DNA sequencing of polymerase chain reaction (PCR) amplified DNA, and overexpression of the p53 protein using immunohistochemistry. We found point mutations in 25% (9 of 36) of cultured melanomas and 0% in 34 fresh melanoma biopsies; however, increased p53 expression was found in 42% of paraffin-embedded melanoma specimens and 7% of benign lesions. The low frequency of p53 point mutations and high frequency of p53 expression suggests that derangement of the p53 gene by point mutations is not a common perturbation in the majority of melanoma cells, and that overexpression of p53 in this tumour type is due to a mechanism other than point mutation.

Lichen planus-like keratosis (LPLK) is a common skin lesion that has some morphologic features of lichen planus (LP) and lichenoid actinic keratosis (LAK). Although most authors consider LPLK to be a distinct lesion, surgical pathologists are often unfamiliar with it. We examined in detail the clinical and histologic features of LPLK in 100 consecutive cases. In our series, LPLK lesions occurred mostly in late-middle-aged individuals, on the trunk (64%) and extremities (31%) and predominantly in women (73%). Among the 14 histologic parameters that were studied, most LPLK had hyperkeratosis (81%) with hypergranulosis (77%), focal acanthosis (75%), and focal parakeratosis (59%). Solar elastosis was observed in 48% of the cases. Only a few cases had eosinophils (15%) or plasma cells (7%) in the inflammatory infiltrate. The adjacent skin was available for study in 71% of the specimens, and only 26.8% of the cases had an adjacent lesion, most frequently seborrheic keratosis (8.4%), solar lentigo (7%), and actinic keratosis (5.6%). According to our results, the most consistent features observed in LPLK are a lichenoid lymphocytic infiltrate with hyperkeratosis, hypergranulosis, focal acanthosis, and focal parakeratosis, without prominent atypia of keratinocytes.

We report the immunocytochemical identification of Rochalimaea henselae, a newly recognized fastidious, Gram-negative, Warthin-Starry-positive organism, as the common pathogen in bacillary angiomatosis (BA), bacillary peliosis (BP) of the liver and spleen, and persistent fever with bacteremia in immunocompromised patients. Immunogenic proteins of the R. henselae strain isolated from the blood of a febrile immunocompromised patient with BP of the liver were used to produce primary immune serum in rabbits. Using immunocytochemical procedures, the polyclonal antiserum reacted strongly not only with the immunizing strain of the bacteria, but also with other blood isolates of R. henselae (five cases) from both immunocompromised and immunocompetent patients and with the organisms present in the tissue lesions of cutaneous BA (five cases) and BP of the liver (two cases) and spleen (one case). The blood isolates and BA and BP tissue samples were obtained from widely separated geographic areas. The antiserum was weakly cross-reactive with cultures of Rochalimaea quintana, an organism closely related to R. henselae, but this reactivity was eliminated by specific adsorption. The antiserum did not cross-react with the Warthin-Starry-positive organisms associated with cat scratch disease (Afipia felis), syphilis (Treponema pallidum), Lyme disease (Borrelia burgdorferi) or chronic active gastritis (Helicobacter pylori). Likewise, the antiserum did not identify organisms in eight cases of Kaposi's sarcoma, a disorder of immunocompromised patients that is clinically similar to BA. Further studies are needed to determine the prevalence of this newly recognized organism as well as its possible involvement in other angioproliferative diseases.

Benign cutaneous polyarteritis nodosa has been described as having a benign course in contrast to that of systemic classic polyarteritis nodosa. We tested the hypothesis that this histologic distinction is false by reviewing nine consecutive cases with the histologic diagnosis of benign cutaneous polyarteritis nodosa. Our study revealed that on follow-up, seven (78%) of nine cases had evidence of involvement of at least one organ other than the skin, with the kidney being the organ most commonly involved. Four (44%) of nine patients had serologic evidence of hepatitis B infection, one had cryoglobulinemia, and one had polyclonal hypergammaglobulinemia associated with acquired immunodeficiency syndrome. We conclude that benign cutaneous polyarteritis nodosa is not necessarily benign and is closely related to systemic polyarteritis nodosa.

Porokeratoses are known to give rise to squamous and basal cell carcinomas. In this study, we examined 15 lesions of porokeratosis immunohistochemically for evidence of aberrant keratinization using several markers of keratinocyte (KC) maturation and differentiation, including involucrin, filaggrin, cytokeratins, and the growth activation marker psi-3. The staining patterns obtained were compared with several non-premalignant parakeratotic skin lesions including psoriasis, pityriasis rosea, pityriasis rubra pilaris, irritated seborrheic keratosis, atopic dermatitis, seborrheic dermatitis, and verruca vulgaris. The centers of porokeratoses stained in a pattern identical to that observed in other premalignant keratinocytic lesions including actinic keratoses, recessive dystrophic epidermolysis bullosa, and nonhealing wounds. KCs beneath the cornoid lamella (CL) stained in a pattern similar to that observed in squamous cell carcinomas. KCs peripheral to the CL in the epidermis showed a normal staining pattern. The control non-premalignant parakeratotic lesions displayed a variety of staining patterns, but none showed a pattern identical to that observed in porokeratosis. The failure of KCs in porokeratoses to mature and differentiate normally may be related to the increased incidence of carcinomas associated with these lesions.

The histogenesis of Kaposi's sarcoma (KS) has been the subject of controversy, much of which has centered around whether the spindle cells of KS are derived from vascular endothelium or from lymphatics. Recently, some investigators have speculated that the spindle cells of KS are derived from dermal dendrocytes, a population of mononuclear dendritic cells normally present in the papillary and upper reticular dermis. These cells have been shown to proliferate in response to a variety of stimuli and have been reported to express the plasma proenzyme factor XIIIa. We examined immunohistochemically sections fixed in formaldehyde solution and embedded in paraffin from 20 tumor-stage, 15 patch-stage, and 15 plaque-stage lesions of KS with antibodies directed against factor XIIIa, factor VIII-related antigen, Ulex europaeus lectin, and LN3 (anti-HLA-DR) to investigate the relationship of dermal dendrocytes to KS in general and to try to clarify the histogenesis of this tumor. Our results revealed that the dermis of patch- and plaque-stage KS lesions contains an increased number of factor XIIIa-positive dermal dendrocytes compared with normal dermis and that some of these cells are spindle shaped. Many of the spindle cells in patch- and plaque-stage lesions of KS, however, are negative for factor XIIIa. The cells lining the slitlike spaces and some spindle-shaped cells in close proximity to the vascular spaces stain for factor VIII-related antigen and for Ulex europaeus lectin. LN3 labeled many cells resembling macrophages within the lesions and in papillary dermis. Less than 25% of the dendritic cells within the lesions and in the adjacent dermis expressed both factor XIIIa and LN3. Tumor-stage lesions showed focal but unequivocal staining of the spindle cells for factor VIII-related antigen and Ulex europaeus lectin. Tumor spindle cells were negative for factor XIIIa. Factor XIIIa-positive dendrocytes were plentiful in the uninvolved dermis and were aggregated around the periphery of the tumor nodules. The expression of factor VIII-related antigen and Ulex europaeus lectin by the spindle cells of nodular KS, and their lack of expression of factor XIIIa, suggests that the spindle-shaped tumor cells in all stages of KS are derived from endothelial cells and not from dermal dendrocytes. Dermal dendrocytes appear to undergo hyperplasia in response to KS of all stages. In patch- and early plaque-stage KS lesions, dermal dendrocytes are near factor VIII-related antigen-positive spindle cells and tumor vessels. The mechanism reactive dermal dendrocyte hyperplasia in KS remains obscure.

Interferon-gamma-induced protein 10 is a 10-kd protein produced by human keratinocytes following an exposure to interferon gamma. Keratinocytes within psoriatic plaques and within delayed-type hypersensitivity reactions have been shown to stain strongly with an affinity-purified rabbit antibody prepared against interferon-gamma-induced protein 10, suggesting a possible role for interferon gamma in the production of the lesions. A psoriasiform eruption has been seen in patients with acquired immunodeficiency syndrome (AIDS). Its severity appears to correlate with the degree of immunodeficiency in the early stages of AIDS. We stained 10 lesions of psoriasiform dermatitis of AIDS with the anti-interferon-gamma-induced protein 10 antibody using immunoperoxidase techniques. As controls, we studied 10 lesions of non-AIDS psoriasis, six lesions of seborrheic dermatitis with psoriasiform hyperplasia, one lesion of lichen simplex chronicus, and four biopsy specimens of normal skin from patients with AIDS. In addition, normal skin specimens taken from patients with AIDS and human immunodeficiency virus-negative patients at time of autopsy were examined. An identical, strong and diffuse staining pattern was seen in all cases of psoriasiform dermatitis of AIDS, non-AIDS psoriasis, seborrheic dermatitis, and lichen simplex chronicus. The specimens of normal skin showed only weak basal layer staining with anti-interferon-gamma-induced protein 10. Thus, the presence of interferon-gamma-induced protein 10 in keratinocytes was associated with psoriasiform hyperplasia and could be detected in both AIDS-associated and classic psoriasis.

Neurofibromas are often clinically, as well as histologically, indistinguishable from completely neurotized melanocytic nevi. We tested the hypothesis that immunologic markers would differentiate the perineural fibroblasts and Schwann cells of neurofibromas from the neurotized cells of melanocytic origin. We examined eight partially neurotized acquired melanocytic nevi, three partially neurotized congenital melanocytic nevi, and five neurofibromas, with antibodies directed against S-100 protein, Leu-7(HNK-1), glial fibrillary acid protein (GFAP), and myelin-basic protein (MBP). A histologic diagnosis of neurofibroma was based on identification of a dermal proliferation of spindle-shaped cells with wavy nuclei, in a background of loose reticulated collagen. Neurotized nevi were diagnosed upon recognition of scattered nests of type A or B nevus cells, surrounded by basement membrane, present in the papillary dermis of lesions otherwise indistinguishable from neurofibromas. The congenital nevi were all large melanocytic nevi known to be present at birth. S-100 stained the majority of neoplastic cells in all neurofibromas, neurotized acquired nevi, and neurotized congenital nevi. Neurofibromas showed focal staining for Leu-7, GFAP, and MBP. In contrast, neurotized acquired and congenital nevi failed to express these markers. We believe that Leu-7, GFAP, and MBP may be helpful in differentiating neurofibromas from completely neurotized melanocytic nevi. The differences in the immunohistochemical profiles of neurofibromas and neurotized nevi support the concept that these neoplasms are histogenically distinct, despite their similar histologic appearance.

Neurofibromas, schwannomas, and neurotized melanocytic nevi may closely resemble one another at the light microscopic level. We studied 10 neurofibromas, 10 schwannomas, and 10 partially neurotized melanocytic nevi immunohistochemically using an antibody directed against factor XIIIa to determine if this antibody might provide a useful method of differentiating these lesions. The cases were also stained with S100 protein. All of the neurofibromas stained intensely for factor XIIIa. The proportion of cells staining within the tumors varied from 30% to 70%. In contrast, none of the schwannomas and neurotized nevi studied demonstrated staining of tumor cells with this antibody. S100 protein was expressed by 100% of neurofibromas, schwannomas, and melanocytic nevi. Our findings suggest that factor XIIIa may provide a reliable and practical means of differentiating cutaneous neurofibromas from neurotized nevi and cutaneous schwannomas. Distinguishing between these different tumor types may be important in some clinical situations, particularly with respect to rendering a diagnosis of von Recklinghausen's neurofibromatosis. The differences in the immunohistochemical profiles of neurofibromas and neurotized nevi support the concept that these tumors are histogenetically distinct, despite their similar histologic appearances.

While some cutaneous squamous cell carcinomas (SCC) arise from predisposing conditions such as burn scars, draining sinuses, and chronic, nonhealing wounds, the vast majority of these tumors arise from actinically damaged epidermis. It has been shown previously that keratinocytes within healing wounds show an "activated" immunophenotype when stained with antibodies to psi-3, involucrin, filaggrin, and cytokeratins. A similar pattern has been seen in keratinocytes from patients with recessive dystrophic epidermolysis bullosa (RDEB), in whom the incidence of cutaneous SCC is markedly increased. We tested the hypothesis that actinic keratoses (AK), recognized as precursors in the development of the majority of SCC, would show a similar activated immunophenotype when stained with the antibody panel described above. We examined 10 AK, biopsied from the facies and extremities of ten patients, ages 60 to 80, with antibodies to psi-3, involucrin, filaggrin, and AE1. All lesions examined had an immunostaining pattern indistinguishable from that seen in keratinocytes from patients with RDEB or within healing wounds. There was suprabasilar staining of keratinocytes with antibodies to psi-3 and AE1. Involucrin and filaggrin was expressed by all keratinocytes above the midstratum spinosum. Within the acrosyringia and acrotrichia, the staining pattern was that of the normal epidermis, i.e., AE1 staining of basal keratinocytes, granular layer staining of involucrin and filaggrin, and absence of psi-3 expression. These data suggest that an activated keratinocyte phenotype is a unifying feature in conditions which predispose to development of cutaneous SCC.

We describe two patients who presented with vasculitic, ulcerative skin lesions that had the histologic features of lymphomatoid granulomatosis or angiocentric T-cell lymphoma. These patients were found to have antibodies to human T-cell lymphotropic virus type I.

While histopathologic analysis may offer some clues as to the pathogenesis of vasculitis, observations must be interpreted with caution, as there is considerable overlap in the histologic pattern. In most cases, a predominantly neutrophilic vasculitis affecting small dermal venules suggests a relatively acute, immune complex-mediated reaction. Less commonly, this histologic pattern may be seen in non-immunologically mediated processes, such as in the presence of bacterial toxins or malignant hypertension, or in more chronic disease states, such as granuloma faciale or erythema elevatum diutinum. A predominantly lymphocytic vasculitis may represent several pathogenetic mechanisms. In lesions more than 24 to 48 hours old, a lymphocytic vasculitis may represent a resolving phase of an immune complex-mediated neutrophilic vasculitis. Alternatively, this histologic pattern may be seen de novo in conditions with a presumed cell-mediated immunologic pathogenesis. Lymphocytic vasculitis may also be seen in rickettsial infections such as Rocky Mountain spotted fever. The pathogenesis of granulomatous vasculitis remains poorly understood and is thought to be induced by a combination of circulating immune complexes and a cell-mediated immune response.

Epidermolysis bullosa represents a grouping of inherited skin diseases characterized by epidermal fragility and frequently wounded skin. The recessive dystrophic subtype of epidermolysis bullosa (RDEB) is characterized by extensive dermal scarring after healing of repeated epidermal injuries and by an unusually high incidence of squamous cell carcinoma occurring in chronically wounded skin. In contrast, the simplex form of epidermolysis bullosa usually heals without scarring and does not predispose to malignant neoplasms of the skin. The differences in scarring and the neoplastic potential of these two forms of epidermolysis bullosa prompted us to investigate growth activation and differentiation characteristics in epidermal keratinocytes in individuals with these disorders. The expression of filaggrin, involucrin, cytokeratins, and the growth activation marker psi-3 was examined by immunohistochemistry in skin biopsy specimens from four individuals with epidermolysis bullosa simplex and six individuals with RDEB. Previous experiments using this technique have demonstrated that these antibodies are good markers for identifying growth-activated keratinocytes in wounded and hyperplastic epidermis. All biopsy specimens of healed wounds in skin from patients with RDEB showed epidermis that reacted with antibodies to filaggrin, involucrin, specific cytokeratins, and psi-3 in a growth-activated pattern. This growth-activated phenotype was maintained in keratinocytes from previously wounded skin that had been healed for more than 2 years. The RDEB growth-activated phenotype detected by immunohistochemistry was not associated with microscopically detectable epidermal hyperplasia. In contrast, all cases of epidermolysis bullosa simplex examined showed an epidermal phenotype similar to that of keratinocytes in normal skin. Thus, healing with dermal scar formation in RDEB is associated with a persistent growth-activated immunophenotype of epidermal keratinocytes. This chronic growth activation state or failure of cells to differentiate in a normal fashion may be directly linked to the high incidence of squamous cell cancers in individuals with RDEB.

REPORT OF A CASE A 71-year-old white man with a history of multiple actinic keratoses, basal cell carcinomas, and squamous cell carcinomas of the head, trunk, and extremities presented with a slightly raised, erythematous, poorly circumscribed, scaly plaque (4×2 cm in diameter) on the right side of his chest ( Figure 1 ), of uncertain duration. A biopsy specimen was obtained from the center of the lesion. Histologic findings are depicted in hematoxylin-eosin-stained sections ( Figure 2 ). What is your diagnosis? DIAGNOSIS: Malignant melanoma in situ, amelanotic type. HISTOPATHOLOGIC FINDINGS Routine histologic examination showed a markedly atrophic epidermis with hyperkeratosis and focal parakeratosis. There was a diffuse, broad proliferation of melanocytes arranged as single cells or in irregular nests along the dermoepidermal junction and at higher levels of the epidermis. The cells had abundant, clear cytoplasm without evident melanin pigment and hyperchromatic nuclei with prominent eosinophilic nucleoli. The dermis contained abundant

A in the p53 gene and in expression of its protein product are among the most frequent changes demonstrated in a variety of human cancers. p53 Is a nuclear phosphoprotein that in the natural form or ''wild-type'' can bind to DNA and prevent cells from entering into the S phase of the cell cycle. There is an increase in wild-type p53 after exposure of the skin to UV light, which allows for DNA repair before replication that would make DNA damage permanent. A loss of this protective influence destabilizes the genome. Mutation of the p53 gene commonly causes a defective protein that is degraded more slowly and accumulates in the cell to the extent that it becomes detectable by routine immunocytochemistry. These abnormalities precede the development of cancer in some examples. Studies of precursor lesions have used mainly immunohistochemical techniques that show p53 protein overexpression. The relationship between such overexpression and actual mutation of the p53 gene is controversial because overexpression of ''wild-type'' p53 protein also can occur. Mutations in the p53 gene have been observed in many actinic keratoses, basal cell carcinomas, and squamous cell carcinomas, and in a small proportion of malignant melanomas. Specific types of pyrimidine transitions have pointed to a role for UV light in these mutations. Molecular analysis is needed to determine whether or not immunocytochemical staining is truly reflective of mutation or is due to some other mechanism that causes an increased expression of wild-type p53. (Arch Dermatol. 1994;130:225-232)

Benign cutaneous polyarteritis nodosa has been described as having a benign course in contrast to that of systemic classic polyarteritis nodosa. We tested the hypothesis that this histologic distinction is false by reviewing nine consecutive cases with the histologic diagnosis of benign cutaneous polyarteritis nodosa. Our study revealed that on follow-up, seven (78%) of nine cases had evidence of involvement of at least one organ other than the skin, with the kidney being the organ most commonly involved. Four (44%) of nine patients had serologic evidence of hepatitis B infection, one had cryoglobulinemia, and one had polyclonal hypergammaglobulinemia associated with acquired immunodeficiency syndrome. We conclude that benign cutaneous polyarteritis nodosa is not necessarily benign and is closely related to systemic polyarteritis nodosa.

• Neurofibromas, schwannomas, and neurotized melanocytic nevi may closely resemble one another at the light microscopic level. We studied 10 neurofibromas, 10 schwannomas, and 10 partially neurotized melanocytic nevi immunohistochemically using an antibody directed against factor XIIIa to determine if this antibody might provide a useful method of differentiating these lesions. The cases were also stained with S100 protein. All of the neurofibromas stained intensely for factor XIIIa. The proportion of cells staining within the tumors varied from 30% to 70%. In contrast, none of the schwannomas and neurotized nevi studied demonstrated staining of tumor cells with this antibody. S100 protein was expressed by 100% of neurofibromas, schwannomas, and melanocytic nevi. Our findings suggest that factor XIIIa may provide a reliable and practical means of differentiating cutaneous neurofibromas from neurotized nevi and cutaneous schwannomas. Distinguishing between these different tumor types may be important in some clinical situations, particularly with respect to rendering a diagnosis of von Recklinghausen's neurofibromatosis. The differences in the immunohistochemical profiles of neurofibromas and neurotized nevi support the concept that these tumors are histogenetically distinct, despite their similar histologic appearances. ( Arch Dermatol . 1990;126:472-476)

A monoclonal antibody (HMB-45) was previously reported to bind to melanoma cells, and the junctional component of nevus cells, but not to normal adult melanocytes. We have tested HMB-45 binding in several conditions under which melanocyte stimulation might be expected in adults, i.e. 3 simple lentigines, 2 solar lentigines, 7 recent surgical scars (from re-excision of non-melanocytic tumors), 2 surgical scars from re-excisions of melanomas (after complete primary excisions), 9 hemangiomas from non-sun-exposed skin, 1 basal cell carcinoma, 1 acute ecchymosis, 1 keloid, and 1 dermatofibroma. Positive controls included 6 malignant melanomas and 1 fetal skin sample. Melanocytes were strongly positively stained overlying hemangiomas, within or near recent surgical scars of melanocytic and non-melanocytic tumor re-excisions, near basal cell carcinoma, and in fetal skin. Melanocytes either were not stained or were stained only focally for trace amounts in the normal skin near the new margins of the wide re-excision specimens for melanoma, i.e., at a distance from the scar, in the simple lentigines and in the fibrotic lesions. Thus, HMB-45 is staining an antigen which appears in adult melanocytes during stimulation and in fetal skin, as well as in melanomas. This stimulation is associated with conditions that would have increased vascularity, suggesting a melanocyte response to a plasma factor, or other endothelial cell derived factor. HMB-45 would not be a useful marker for residual melanoma cells in melanoma re-excision specimens.

Choroid plexus and intestinal microvilli in thin sections have microfilaments in the cytoplasm adjacent to the membranes, and in replicas have broken strands of filaments in both cytoplasm and on E faces of plasm membranes. The microfilaments contain actin as indicated by their binding of heavy meromyosin (HMM). In sections of choroid plexus, the microfilaments are 7-8 nm in diameter and form a loose meshwork which lies parallel to the membrane and which is connected to the membranes both by short, connecting filaments (8 times 30 nm) and dense globules (approximately 15-20 nm). The filamentous strands seen in replicas are approximately 8 nm in diameter. Because they are similar in diameter and are connected to the membrane, these filamentous strands seen in replicas apparently represent the connecting structures, portions of the microfilaments, or both. The filamentous strands attached to the membrane are usually associated with the E face and appear to be pulled through the P half-membrane. In replicas of intestinal brush border microvilli, the connecting strands attaching core microfilaments to the membrane are readily visualized. In contrast, regions of attachment of core microfilaments to dense material at the tips of microvilli are associated with few particles on P faces and with few filamentous strands on the E faces of the membranes. Freeze-fracture replicas suggest a morphologically similar type of connecting strand attachment for microfilament-membrane binding in both choroid plexus and intestinal microvilli, despite the lack of a prominent core bundle of microfilaments in choroid plexus microvilli.

Dysplastic nevi are melanocytic tumors that occupy intermediate positions in the spectrum of melanocytic proliferations. Although they are invariably cured if completely excised, their biologic potential if left untreated is unknown. We examined a series of such lesions with HMB-45, a melanocyte-specific antibody, in order to explore protein expression within these borderline lesions. HMB-45 has previously been shown to label intraepidermal melanocytes within melanomas and within all nevi. Intradermal melanoma cells also label with HMB-45, but dermal nevus cells within common melanocytic nevi do not normally stain. In contrast, we found mild to moderate staining of nevus cells within the papillary dermis of dysplastic nevi and within residual nevus cells adjacent to malignant melanomas. In the same lesions, we demonstrated strong staining of intraepidermal melanocytes. Thus, dermal nevus cells within dysplastic nevi and within residual nevus cells adjacent to malignant melanomas are expressing low-level amounts of a protein expressed by melanoma cells, but not by dermal nevus cells within wholly benign melanocytic tumors. This lends support to the concept of these lesions as precursor lesions with undetermined biologic potential.

Quantitative electron microscopy was used to measure lymphocyte nuclear contours in skin biopsies from 109 patients, 77 with benign disorders, 16 with early mycosis fungoides (MF), and 16 with controversial lesions. A nuclear contour index (NCI) was calculated on electron micrographs by dividing the nuclear profile circumference by the square root of the nuclear area. Significant differences were found between the group mean NCI for MF (NCI = 6.1 +/- 0.1) and for the benign group (NCI = 4.6 to 5.4 +/- 0.1; P less than 0.005). The group mean NCI for the controversial cases was significantly lower than that of the MF group (P less than 0.05). It is suggested that a definite electron microscopic diagnosis of MF requires first a patient mean NCI of 6.1 or more, and second, at least 6% of lymphocytes with an NCI of 9 or more. These criteria give a false positive rate of 3% in benign and controversial disorders and a 50% false negative rate for early MF. Only lymphocytes with an NCI of 16 or more appear specific for MF (or Sezary's syndrome), but are not found in all cases.

Male CF-1 mice (24 to 34 gm.) were exposed to either 250 p.p.m. or 1000 p.p.m. of 1,1,1-trichloroethane in air continuously for 14 weeks. Control mice were exposed to room air. Serial sacrifice of exposed and control mice from 1 to 14 weeks demonstrated significant changes in the centrilobular hepatocytes of animals in the 1000 p.p.m. group. Moderate liver triglyceride accumulation was evident in the 1000 p.p.m. group and peaked at 40 mg. per gm. of tissue (wet weight) after 7 weeks of exposure. Partial recovery was indicated by a decrease in the hepatic triglyceride level of 16 mg. per gm. by 14 weeks of exposure to 1000 p.p.m. Electron microscopic evaluation revealed that cytoplasmic altertions were most severe in centrilobular hepatocytes in the 1000 p.p.m. group and were mild to minimal in the 250 p.p.m. group. These alterations consisted of vesiculation of the rough endoplasmic reticulum, with loss of attached polyribosomes, increased smooth endoplasmic reticulum, microbodies, and triglyceride droplets. Some cells had ballooned cisternae of the rough endoplasmic reticulum. Necrosis of individual hepatocytes occurred in 40 per cent of the mice exposed to 1000 p.p.m. for 12 weeks. This necrosis was associated with an acute inflammatory infiltrate and hypertrophy of Kupffer cells. Comparison of these findings to the results obtained by other investigators studying dichloromethane indicates that the pathologic alterations observed with 1,1,1-trichloroethane were similar to those observed with dichloromethane, except for different time courses of the effects and different degrees of recovery. The toxic effects of 1,1,1-trichloroethane were of a type similar to those produced by carbon tetrachloride, but they appeared to be much less severe.

Clinical features and histopathologic findings are described in this case of erythromelanosis follicularis faciei et colli in a 30-year-old man of Chinese descent. This is the fourteenth case in the world literature and the first which is unilateral. Electron microscopic examination revealed abnormalities consisting of a homogeneous mass of pigment in the center of the melanosome and a stippled appearance to the periphery of the organelle. In addition, many of the melanosomes appeared to be abnormally large.

• The name sarcolemma is used in many electron microscopic studies to designate the 7.5-9-nm "unit" plasma membrane that encloses the cytoplasm of the muscle cell (1, 2), but this definition of the sarcolemma is incomplete as a description of the actual boundary between the cellular cytoplasm and the extracellular space. Two specific omissions exist in the sarcolemma definition. First, on the external aspect of the membrane, there is a specialized surface coat composed of fibrillar material, probably glycoprotein, bound to the plasma membrane. This surface coat (glycocalyx) covers most of the external aspect of the sarcolemma. It is 20-60 nm thick on mammalian sarcolemma and is rich in carbohydrates with acidic residues as shown by ruthenium red and colloidal iron staining procedures (3). Second, adjacent to the internal aspect of the membrane, there is a specialized layer of fibrillar cytoplasm that influences the overall properties of the boundary between the cytoplasm and the exterior. In cardiac muscle cells, this specialized cytoplasmic layer is prominent, particularly in regions of cell-to-cell adhesion (4). In addition, research on other cell types has indicated that a relatively inconspicuous fibrillar layer is bound to the inner surface of the plasma membrane and may be important in determining the distribution of surface sites on the exterior of the membrane (5, 6). It is a minor semantic point whether these specialized layers internal and external to plasma membrane are included in the definition of the sarcolemma, but these layers must be considered in terms of their influences on the unit membrane and the interface between the cell and the exterior as a whole. The importance of the surface coat is exemplified in the work of Langer and Frank (7), who have identified the surface coat layer on the myocardial cell as a site of ionic lanthanum bind

A patient has an acquired, scarring, bullous eruption. The severity of the cutaneous, ocular, esophageal, and laryngeal scarring was suggestive of cicatricial pemphigoid or the severely dystrophic forms of epidermolysis bullosa. Clinical features and histologic and immunofluorescence and electron microscopic study led to the diagnosis of epidermolysis bullosa acquisita. The spectrum of epidermolysis bullosa acquisita includes cases that closely approximate the severity of disease previously recognized only for the recessive form of epidermolysis bullosa dystrophica.

Facial nerve paralysis developed in a man with tumor-stage mycosis fungoides (MF). Mastoidectomy disclosed that MF had involved the mastoid and middle ear. Meningeal lymphoma, confirmed by the finding of Sézary cells in the CSF, was subsequently established. Autopsy disclosed MF lymphoma in the leptomeninges, medulla, spinal cord, and cranial nerves. A unique feature was the formation of a communicating hydrocephalus. Case reports of 23 patients with MF of the CNS, including 21 autopsies, are reviewed. Practically all had tumor-stage or erythrodermic MF. Atypical mononuclear cells were found ante mortem in the CSF in eight patients. In contrast to other CNS lymphomas, bone marrow involvement was uncommon. Cranial, especially facial, nerve paralyses were often premonitory signs of meningeal lymphomas. Patients with MF having such symptoms should have cytologic examination of the CSF.