Histopathological characteristics of small diameter melanocytic naevi.

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.

S100A6 preferentially labels type C nevus cells and nevic corpuscles: additional support for Schwannian differentiation of intradermal nevi.

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.

S100A6 expression in fibrohistiocytic lesions.

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.

Lichen striatus. Histological, immunohistochemical, and ultrastructural study of 37 cases.

BACKGROUND: Lichen striatus (LS) is a papulosquamous disorder with a distinctive linear distribution. The linearity has been shown to correspond in many cases to the pattern of Blaschko's lines. The etiology is unknown. LS can usually be identified by clinical history and histology of typical lesions. However, the histologic features are diverse and some have stated they are nonspecific. METHODS: In an effort to identify those characteristic features, we have reviewed the routine slides in 37 cases for their diagnostic criteria. Ten cases were studied further by immunohistochemistry. RESULTS: The patient's ages ranged from 1.3 to 49 years with mean age of 17.5 years. A female-to-male ratio was 1.6 to 1. The lesions were predominantly distributed on the extremities in 26/34 cases. The consistent histologic features were: hyperkeratosis (29/37), parakeratosis (21/37) with a few necrotic keratinocytes (28/37) in the epidermis, mild spongiosis (29/37) with exocytosis of lymphocytes (33/37). The dermal infiltrate comprised mainly lymphocytes and macrophages. At the dermal-epidermal junction, the infiltrate was either focal (20/37) or lichenoid (17/37) patterns. Superficial and deep perivascular lymphocytic inflammatory infiltrate was present in most of the cases (33/37). Appendageal involvement (34/37) was in hair follicles (24/37) or eccrine glands or ducts (22/37) or both (12/37). Satellite cell necrosis may be seen (11/37). Colloid bodies were present in 16/37 of the cases. Immunohistochemistry showed that most of the small lymphocytes in the upper dermis and epidermis were positive for CD7. Most of the lymphocytes in the epidermis were positive for CD8. CD1a Langerhans' cells were either decreased (5/10) or increased (3/10) or normal (2/10) in the epidermis. CONCLUSION: The histologic diagnosis of LS can be made on the basis of the combination of these histologic features in the appropriate clinical context. Multiple biopsies may be necessary to determine whether all of these features are present in a given case.

Expression of CD34 in sclerotic ("plywood") fibromas.

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.

Conjunctival melanocytic nevi of childhood.

Two young patients with conjunctival compound nevi are presented to illustrate two types of abnormalities that lead to difficulty in distinction of these nevi from invasive melanomas. In Case 1, inflammation is associated with disruption of the nevus cell architecture and cytologic atypia. In Case 2, the occurrence of a combined nevus (compound and blue nevus types) in the conjunctiva leads to diagnostic problems. Circumscription of the lesions, lack of mitoses in the substantia propria, and lack of pagetoid spread of atypical cells in the adjacent conjunctival epithelium support benign diagnoses in both cases.

The S100 family of multipurpose calcium-binding proteins.

Antibodies reactive with S100 protein are useful markers in a diagnostic immunohistochemistry laboratory dealing with cutaneous tumors. However, S100 protein is not a single protein but instead a group of S100 proteins with diverse functions. S100 proteins constitute a family of acidic calcium-binding proteins that are important in intracellular calcium metabolism. Recent evidence that some S100 proteins are secreted makes it likely that they are also involved in cell-cell interactions. The exploration of the status of the different members of the S100 family may yield not only diagnostic clues but also relevant functional information about the cells. Considerable recent progress has been made in our understanding of S100 proteins. This review surveys some of these findings that may be either directly or indirectly relevant to cutaneous pathology.

Multibacillary leprosy: lesions with macrophages positive for S100 protein and dendritic cells positive for Factor 13a.

In the defense against Mycobacterium leprae, macrophages play an essential part in the mechanism of bacterial lysis but require the presence of cytokines such as interleukin 2 and gamma interferon from lymphocytes in order to effectively kill the organisms in any number. While there have been many studies of the lymphocytes in lesions of leprosy, less attention has been given to the immunohistochemical characterization of the macrophage populations. In this study, the cutaneous lesions of 69 patients with leprosy (42 lepromatous, 5 mid-borderline, and 22 tuberculoid) were evaluated by immunohistochemistry for the expression of S100 protein, CD1a, CD68, muramidase, HLA-DR, and Factor 13a. The macrophages from lesions of polar, subpolar, and borderline lepromatous leprosy patients expressed S100 protein intensely and constantly. In contrast, the lesions of polar and subpolar tuberculoid leprosy had very few cells that were immunoreactive for S100 protein ('S100+') in the granulomas in the dermis. The macrophages in all lesions were reactive for CD68 and muramidase. In paraffin sections, macrophages of lepromatous lesions failed to stain for HLA-DR, whereas in tuberculoid lesions, they were strongly positive for HLA-DR. Three patients with histoid leprosy (relapse lesions) had lesions that were strongly positive for Factor 13a and were negative for S100 protein ('S100-'). Given the possible chemotactic and migration inhibition effects of the calcium-binding proteins of the S100 family, these data suggest a possibly important role for S100 protein in the accumulation of macrophages in lepromatous leprosy, and also reveal infection of Factor 13a + dermal dendritic cells in histoid leprosy.

Hermansky-Pudlak syndrome: report of a case with histological, immunohistochemical and ultrastructural findings.

We report a 38-year-old female of Puerto Rican descent with Hermansky-Pudlak syndrome and decreased levels of von Willebrand factor. Histologic and ultrastructural findings of non-sunexposed skin showed melanocytes with short dendritic processes and decreased numbers of melanosomes. Ultrastructural examination of platelets revealed greatly reduced numbers of delta granules. Recognition of this syndrome is important because skin neoplasms, ceroid deposition and hemorrhagic manifestations can be causes of morbidity and of potential death in patients affected with this syndrome.

Quantitative immunohistochemical differences in Langerhans cells in dermatitis due to internal versus external antigen sources.

Cutaneous hypersensitivity reactions can develop against antigens delivered through the epidermis (contact dermatitis) or through the blood vessels (e.g., drug eruptions). On routine histology alone, it is not always possible to determine the route of the antigen. Langerhans cells (LC) are the main antigen-presenting cells in contact dermatitis. Dermal dendrocytes (DC) are antigen-presenting cells and may be involved in dermal reactions. We tested the hypothesis that there is a difference between dermatitis due to external and internal antigen sources with regard to the number or function of LC and DC. In 85 cases of dermatitis, numbers of S100 and HLA-DR reactive cells per linear millimetre of epidermis were counted. The amount of epidermal spongiosis was evaluated qualitatively. In 35 cases, the number of DC per mm2 (as defined by Factor XIIIa expression) was evaluated. The patients were then divided into two groups based on whether the final clinical evaluation considered the dermatitis to be secondary to an external (35 cases) or internal antigen (50 cases). Dermatitis due to external antigens had significantly more LC/mm and more frequent HLA-DR expression than dermatitis due to internal antigens, mean +/- SEM; 21.2+/-2.04 vs. 9.1+/-1.02 (p<0.00001) and 16.3+/-2.49 vs. 6.0+/-0.92 (p=0.0001), respectively. Spongiosis was more marked in external antigen cases. DC were more numerous in internal than in external antigen cases, but the differences were not statistically significant. In our model, determination of numbers of LC/mm is the variable with the highest power to discriminate between internal and internal sources. Quantification of HLA-DR+ LC and degree of spongiosis provide little additional discriminatory power.

"Triggered trap": nevoid malignant melanoma.

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.

Distal pachydermodactyly.

An 80-year-old white woman had a 6-year history of enlarging, intradermal plaques on the distal, volar, and lateral surfaces of the fingers. A biopsy specimen showed whorled, densely aggregated bundles of coarsely thickened collagen within a sparsely cellular papillary and reticular dermis. The fibrosis entrapped eccrine sweat coils and focally extended into the subcutis. This case represents an unusual, predominantly acral form of acquired, progressive, cutaneous fibrosis, which we propose to call distal pachydermodactyly.

Differential expression of the intermediate filament peripherin in cutaneous neural lesions and neurotized melanocytic nevi.

Peripherin is an intermediate filament involved in growth and development of the peripheral nervous system, and is produced by neurons and the beta cells of the islets of Langerhans. Recently, malignant melanomas and some melanocytic nevi have been shown to express peripherin. It is unknown if Schwann cells, also derived from the neural crest, express peripherin. Expression of peripherin was evaluated by immunohistochemistry in cutaneous lesions characterized by a prominent Schwann cell component including 26 neurofibromas (NF), 10 schwannomas (SCH), seven granular cell tumors, and five palisaded encapsulated neuromas (PEN); 13 neurotized melanocytic nevi (NMN) also were evaluated because these lesions contain Wagner-Meissnerlike structures and type C nevus cells, which exhibit a "schwannian" phenotype. Peripherin was detected in the axons of normal peripheral nerves. NF and PEN contained numerous axons dispersed throughout the lesions, whereas only scattered small nerves were seen in GCT. In SCH, only rare axons were labeled, mostly at the periphery of the lesions. All other cells in these four types of lesions, therefore including Schwann cells, were not labeled. In most NMN, labeled axons were identified within the lesions. In a few cases, rare epithelioid melanocytes within the superficial portions of the nevi were labeled. The Wagner-Meissnerlike structures and type C nevus cells (schwannian) were not labeled in any lesion; however, numerous labeled axons invested these areas. Because there are different relative numbers of peripherin-labeled axons throughout NF, PEN, some nevi, and SCH, analysis of peripherin expression may be helpful in the diagnosis of these lesions. Neurons and some epithelioid melanocytes, in contrast to type C nevus cells and Schwann cells of NF and SCH, express peripherin, providing further evidence for a transition from a more neuronal to a more schwannian phenotype during the normal maturation sequence of melanocytes in nevi.

The intermediate filament peripherin is expressed in cutaneous melanocytic lesions.

Peripherin is an intermediate filament involved in growth and development of the peripheral nervous system and is localized to neurons, some other cells derived from neural tube and neural crest, and some neuroendocrine cells (e.g. beta cells of islets of Langerhans). Peripherin also has been demonstrated in neuroblastomas and cutaneous neuroendocrine (Merkel cell) carcinomas. The expression of peripherin by other cells derived from the neural crest is unknown. We evaluated by immunohistochemistry 74 cutaneous melanocytic lesions including primary invasive malignant melanoma (IMM), melanoma in situ (MIS), atypical nevus (nevus with architectural disorder and cytologic atypia of melanocytes) (AN), spindle and epithelioid cell nevus (Spitz nevus) (SN), blue nevus (BN), and common intradermal benign melanocytic nevus (BMN) for expression of peripherin. Peripherin was detected in a cytoplasmic distribution within tumor cells in 14/14 IMM and 8/10 MIS. For IMM, peripherin localized to both the intraepidermal and invasive dermal components. Peripherin was detected in 10/10 AN and 9/9 SN, being localized to the intraepidermal component and, focally, to the superficial dermal component of the lesions. The dendritic nevus cells in 15/15 BN also expressed peripherin. For most of the BMN, expression of peripherin was absent or limited to rare, scattered cells in the superficial portion of the lesions. Melanocytes in adjacent normal skin were not labeled in any of the lesions studied. These results indicate that expression of peripherin is common in both benign and malignant melanocytic lesions, but not in normal resting adult melanocytes. Among benign lesions, expression of peripherin in the dermal component is rare except in the dendritic cells of BN. These findings provide evidence that the expression of peripherin, a marker of neuronal differentiation, is maintained by IMM, MIS, and BN, but is lost in the normal maturational sequence of the dermal component of other melanocytic lesions.

Expression of the mast cell growth factor interleukin-3 in melanocytic lesions correlates with an increased number of mast cells in the perilesional stroma: implications for melanoma progression.

The molecular events responsible for tumor progression in human cutaneous malignant melanoma remain unclear; however, critical to the process is the dysregulated proliferation of tumor cells and the development of new vascular channels which allow further growth and dissemination. Connective tissue mast cells (MC) have been implicated in tumor progression because they concentrate around tumors (including melanomas) prior to the formation of new blood vessels, and because they contain many chemical mediators, including basic fibroblast growth factor (bFGF), known to have mitogenic and angiogenic effects. Several MC chemotactic and mitogenic factors have been described including interleukin-3 (IL-3). In order to determine whether there is a differential expression of this MC chemotactic/mitogenic factor with tumor progression in vivo, we evaluated by immunohistochemistry 85 melanocytic lesions including primary invasive malignant melanoma (PIMM), melanoma in situ (MMIS), and ordinary intradermal benign melanocytic nevi (BMN) for expression of IL-3. Nucleic acid in situ hybridization also was used to evaluate the melanocytic lesions for IL-3-specific mRNA transcripts. Intracellular IL-3 protein was detected in 29/33 (88%) PIMM and 15/25 (60%) MMIS, but was not detected in any (0/27; 0%) BMN (p < 0.0001). IL-3-specific mRNA transcripts were present in 3/4 PIMM and 2/10 MMIS in which IL-3 protein was not identified, but were not detected in any BMN. IL-3 mRNA or protein was not detected in normal melanocytes present in the perilesional epidermis of any of the specimens studied. Immunohistochemistry also was used to confirm the presence of IL-3 alpha-specific receptors on human cutaneous MC. As demonstrated by others, a significantly increased number of MC was present in the perilesional stroma of PIMM and MMIS vis a vis BMN (p < 0.0001). The results suggest that melanoma cells may attract MC in vivo by producing MC chemotactic/mitogenic factors such as IL-3. The recruitment of MC and the subsequent release of their potent mitogenic and angiogenic factors such as bFGF may thus represent a tumor-host interaction which favors tumor progression. Reed JA, McNutt NS, Bogdany JK, Albino AP. Expression of the mast cell growth factor interleukin-3 in melanocytic lesions correlates with an increased number of mast cells in the perilesional stroma: implications for melanoma progression.