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PubMed2000

Characterization of an overexpressed spindle protein during a baculovirus infection.

The nucleopolyhedrovirus CfDEFNPV contains a gene encoding a viral protein, which accumulates as bipyramidal inclusion bodies (spindles) in the cytoplasm of infected cells. The spindles appear as early as 24 h postinfection, approximately 1 day earlier than viral occlusion bodies (OBs). Purification and characterization of the spindle protein was complicated by the fact that the OBs copurified with the spindles. We therefore modified CfDEFNPV by replacing the polyhedrin gene (plh) with a cassette containing the green fluorescent protein (GFP) gene. The recombinant virus did not produce OBs; however, the synthesis and morphogenesis of the spindles were not altered. When analyzed by SDS-PAGE, the spindles produced a 50-kDa protein, which was termed spindlin. Tunicamycin inhibition and endoglycosidase studies showed that spindlin was glycosylated. The N-terminus of spindlin was sequenced and its gene (gp50) was located on the viral genome. The gene was cloned and sequenced. Homologs of gp50 were found in several baculoviruses as well as in entomopoxviruses (EPV). In the latter virus, the homologous gene is that of fusolin, which also encodes a protein that forms spindle-shaped inclusion bodies in the cytoplasm of infected cells. Immunoblot analysis indicated that spindlin and fusolin were not serologically related, even though they share conserved polypeptide domains. Sequence analysis showed that gp50 of CfDEFNPV contains two late promoter motifs (TTAAG) in its 5' flanking region. Both were used, but the proximal motif (-14 to -18 nt relative to the ATG) was the primary sequence from which most of the mRNA was initiated. When gp50 was cloned in a heterologous baculovirus expression system, spindlin was synthesized, although the spindles were irregular in shape. This suggested that the spindle structure may be species-specific or it may require more than one gene product for its morphogenesis.

Amino Acid Sequence↗

PubMed2004

Desmin expression in spindle cell lipomas: a potential diagnostic pitfall.

The immunohistochemical analysis of the spindle cell lipomas has been for the most part limited to the study of S-100 protein, CD34, and Bcl-2 reactivity. To evaluate the immunoexpression of desmin and actins in spindle cell lipomas of different histological subtypes a retrospective immunohistochemical study of 25 spindle cell lipomas using archival formalin-fixed, paraffin-embedded tissue was performed. Strong positivity of the spindle cell component for desmin was found in 4 of 25 cases (16%). The expression was diffuse in two cases and focal (in up to 25% of the spindle cells) in the other two. Two of these cases were of the classical type and the other two were angiomatous spindle cell lipomas. Desmin-positive and desmin-negative spindle cells showed no morphological differences. The spindle cell component expressed CD34 in all cases and Bcl-2 in 14 of the 25 cases. There was no immunoreactivity for smooth muscle actin, muscle-specific actin, or S-100 protein. We conclude that a significant proportion of spindle cell lipomas express desmin, and therefore that the immunoreactivity for this antigen does not exclude the diagnosis, even in lesions with nonclassical histological features and/or atypical locations.

Adult↗

PubMed1986

Sleep spindles in normal elderly: comparison with young adult patterns and relation to nocturnal awakening, cognitive function and brain atrophy.

Visual measurements of sleep spindles were carried out in 48 elderly and 20 young normal adults. Computed tomography brain scans and psychometric testing were also performed. Earlier findings of reduced spindle abundance, amplitude and duration in the elderly were confirmed. In addition, we demonstrated a linear increase in spindle density and duration across NREMPs in young adults that was absent in the elderly, indicating that age affects the temporal pattern as well as the quantity of spindles. Contrary to what seemed a highly plausible hypothesis, the amount of waking in the elderly was not inversely correlated with spindle abundance, confirming earlier observations (Feinberg et al. 1967) but in a much larger group. This finding suggests that spindle abundance does not reflect the integrity of the systems that maintain the brain in NREM sleep. We also were unable to show any clear evidence that relative preservation of spindles in the elderly is associated with relative preservation of cognitive skills: psychometric performance and spindle measures were, in most instances, not significantly correlated. However, the test of this hypothesis was limited by the high level of function and the narrow range of impairment of these Ss. One intriguing positive finding was the significant inverse relation between ratings of sulcal atrophy and spindle amplitude. This observation suggests an etiology for the reduced amplitude of the sleep EEG in old age. This change is one of the most striking effects of age on brain electrophysiology.

Adult↗

PubMed1983

Relationship between focal penicillin spikes and cortical spindles in the cerveau isolé cat.

Using the unanesthetized, cerveau isolé preparation in the cat, the association between artificially induced penicillin (PCN) spikes and spontaneously occurring electrocorticographic (ECoG) spindles was investigated. Spikes were elicited by surface application of small pledgets of PCN. After the application of PCN, there was a decrease in spindle amplitude but no change in frequency, duration, or spindle wave frequency in the area of the focus. Examination of the times of occurrence of the spikes and spindles disclosed that in the majority of cases, within a few minutes of the initiation of the foci, there was very high simultaneity, usually 100% between the occurrences of these two events. Examination of the times of occurrence of the spikes within the ECoG spindles failed to disclose any compelling evidence which would favor either the hypothesis that spikes "trigger" spindles or the hypothesis that spindles predispose to focal spikes. Thus, whether spikes trigger spindles, or spikes simply occur in a nonspecific manner during the occurrence of the spindle, or whether it is a combination of both these explanations, must remain an open question on the basis of the data available.

Animals↗

PubMed1985

Cholinergic regulation of neocortical spindling in DBA/2 mice.

Brief episodes of high-amplitude, bilaterally synchronous, seven-cycles-per-second spindles appear in the EEG of DBA/2 inbred mice during active waking, quiet waking, and slow-wave sleep. They do not occur during waking in C57BL/6 mice. This difference might result from differences in acetylcholine-mediated arousal as nicotine powerfully blocks brief spindle episodes in awake DBA/2 mice. The following results are reported. (i) Physostigmine (0.1 and 0.3 mg/kg, i.p.) desynchronized the EEG and produced behavioral immobility, but did not block brief spindle episodes in free-moving DBA/2 mice. (ii) Atropine (1.0 mg/kg, i.p.) reduced arousal and provoked slow waves without facilitating brief spindle episodes. (iii) Mecamylamine (1.0 mg/kg, i.p.) weakly activated spindles without producing any noticeable behavioral alterations. Because these treatments had little effect on spindle occurrence, the action of nicotine in brain stem-transected DBA/2 mice was investigated. Nicotine (1.0 mg/kg, i.p.) had no effect on brief spindle episodes released by rostropontine transection but powerfully blocked those provoked by pentylenetetrazol (20 mg/kg, i.p.) in midpontine-transected mice. Hence nicotine's antispindling action may be mediated in the rostral pons. As both nicotine and physostigmine produce behavioral immobility and EEG activation in free-moving DBA/2 mice, but only nicotine inhibits cortical spindling, the mechanisms that produce EEG desynchronization are probably not identical to those that prevent spindling. They may, though, be linked, parallel processes that are somehow dissociated in DBA/2 mice.

Animals↗

PubMed2005

Spindle cells and their role in Kaposi's sarcoma.

Spindle cells represent the main cell type of the advanced final nodular stage of Kaposi's sarcoma lesions. Despite some clinical and epidemiological differences, the four Kaposi's sarcoma forms (classic, endemic, post-transplant and epidemic) display very similar histopathological features, with the proliferation of spindle cells (considered as the Kaposi's sarcoma tumor cells) associated with inflammation and neo-angiogenesis. Electron-microscopy and immuno-histochemistry studies have led to the consensus that the spindle cells originated from the endothelial lineage. However, only recently, studies that used specific lymphatic immunological markers (such as podoplanin) and molecular features (gene expression microarrays) strongly linked Kaposi's sarcoma spindle cells to the endothelium lymphatic cell lineage. Both hybridization and immuno-histochemistry techniques have demonstrated that human herpesvirus 8 also known as Kaposi's sarcoma associated herpesvirus was present in spindle cells at all stages of the disease (patch, plaque, nodule). Interestingly, while the human herpesvirus 8 latent genes are expressed in nearly all tumor spindle cells, only a small fraction of them expresses markers of viral lytic replication. Recent findings showing that nodular Kaposi's sarcoma lesions display all patterns of human herpesvirus 8 clonality support the model according to which this tumor begins as a polyclonal disease with a subsequent evolution to a mono/oligoclonal process involving infected spindle cells. Spindle cells appear to be the central masterpiece in KS tumorigenesis, however the exact respective role of each human herpesvirus 8 gene, in the initiation and the disease progression is still under investigation and the question of whether or not this tumor is a reactive process or a true malignant proliferation of spindle cells remains yet unclear.

Cell Lineage↗

PubMed2004

Evaluation of meiotic spindles in thawed oocytes after vitrification using polarized light microscopy.

OBJECTIVE: To investigate the efficacy of the PolScope on imaging the spindle morphology in oocytes at the metaphase II stage before vitrification and after thawing. DESIGN: In vitro study. SETTING: University infertility clinic and academic research laboratory. INTERVENTION(S): Oocytes at the metaphase II stage that were obtained from superovulating mice were vitrified and then thawed. MAIN OUTCOME MEASURE(S): Morphological features of the spindle in oocytes were evaluated by both the PolScope and immunofluorescent staining. RESULT(S): Using the PolScope, the morphological features of the spindle of intact thawed oocytes were undetected by 3 hours of thawing in only 25% of cases. Most of the spindle images were recognized during the first hour of observation. Additionally, the statistical analysis of agreement of spindle morphology by both the PolScope and fluorescent staining showed a weighted Kappa value of 0.70, indicating good agreement. Oocytes with good spindle morphology verified by the PolScope before vitrification had a higher survival rate of intact oocytes after thawing compared with those with poor or undetected spindle images. CONCLUSION(S): The morphological features of the spindle in oocytes evaluated by the PolScope before freezing and after thawing are significantly correlated with those assessed by immunofluorescent staining after fixation. With the assistance of the PolScope, thawed oocytes with good spindle morphology can be verified and selected for further manipulation without fixation and staining.

Animals↗

PubMed1989

Roles of muscle activity and load on the relationship between muscle spindle length and whole muscle length in the freely walking cat.

The objective of this research was to compare the length of muscle spindles to the length of the whole muscle, during normal movements. Pairs of piezoelectric crystals were implanted near the origin and insertion of muscle fibres in the medial gastrocnemius (MG) muscle of cats. The distance between crystals was measured with pulsed ultrasound, the origin-to-insertion length of the MG muscle was measured with a transducer made of saline-filled silicone tubing, MG force was measured with a tendon force transducer and EMG activity was selectively recorded in the vicinity of implanted crystals. These signals were simultaneously recorded during posture or locomotion on a motorized treadmill. Three periods were identified in the step cycle, during which the relation between muscle length and spindle length changed dramatically. In period I (roughly corresponding to the late F and E1 phases of swing), the MG muscle and spindles followed similar length changes: both were stretched and then shortened by about 6 mm. In period II (corresponding to the stance phase, E2-E3) the MG muscle yielded under the weight of the body and was stretched by 1-3 mm, whereas the MG spindles typically continued shortening. In period III, the MG muscle shortened rapidly by 6-8 mm after the foot left the ground and then stretched again by about the same amount, whereas the spindles could remain nearly isometric. We attribute these large discrepancies in muscle and spindle length to the architecture of the MG muscle and the compliance of long tendinous elements in series with the spindles. We conclude that the length changes imposed on muscle spindles during voluntary movements are not simply related to the parent muscle length changes and cannot be estimated without taking into account the muscle architecture, the location of the spindle within the muscle, the level of muscle activation and the external load.

Animals↗

PubMed2000

The role of the spindle in human information processing of high-intensity stimuli during sleep.

Sleep spindles are 12-14 Hz oscillations in EEG, which are thought to inhibit or 'gate' information processing. Event-related potentials may be employed to probe the extent of information processing during sleep. Previous research indicates that event-related potentials elicited by moderate intensity stimuli show increased positivity (or further removal of negativity) when stimuli are presented concurrent with spindles. However, the effectiveness of spindles to inhibit the processing of much louder stimuli remains unknown. The purpose of the present study was to investigate the extent of this gating, by using a range of stimuli including those that are loud and intrusive. Eight good sleepers were recorded during a single night. Auditory stimuli were delivered randomly at 0, 60, 80 or 100 dB SPL. Trials were sorted off-line by sleep stage, stimulus intensity and spindle characteristic (i.e. spindle absent, spindle present). During the sleep-onset period, the often-reported changes in event-related potentials were observed - N1 decreased and P2 increased in amplitude. In Stage 2 sleep, P2 was affected by the presence of spindles, particularly when stimulus intensity was loud. Its amplitude was greatest when spindles occurred following the onset of the stimulus. Scalp-recorded spindles might, therefore, be a consequence of the prior thalamic inhibition of information processing, especially when confronted by loud, intrusive external stimuli.

Acoustic Stimulation↗

PubMed2002

Spindle frequencies in sleep EEG show U-shape within first four NREM sleep episodes.

It has been shown in previous studies on sleep electroencephalogram (EEG) that spindles are slower in the beginning of the night fastening towards the end of the night. Corresponding findings have been obtained by spectral analysis. The present study was based on our preliminary observation that slower spindles are found in the middle of the non-rapid eye movement (NREM) sleep episodes as compared with the beginning or the end of the episodes. Eight healthy female and six male subjects were studied. Sleep spindles were visually selected and spindle frequencies calculated for 11 analysis points in each NREM sleep episode. The median spindle frequencies formed a clear U-shape within NREM sleep episodes with an initial decrease and final increase. The decrease was statistically significant within the first four NREM sleep episodes. It is possible that the spindle frequency pattern could be used to reveal variations in sleep depth within sleep stage 2. In animal studies the spindle frequency has been found to be associated to the duration of the hyperpolarization-rebound sequences of the thalamocortical cells. If it is assumed that the same cellular mechanisms are responsible for spindle frequencies in humans then the study of variations in spindle frequency could be used to examine the NREM sleep process in humans.

Adult↗

PubMed2003

Sleep spindles: an overview.

Sleep spindles are a distinctive EEG phasic feature of NREM sleep and are prevalent during stage 2 as compared to slow wave sleep. While the neurophysiological mechanisms of spindle generation, that involves thalamic and corticothalamic networks, have been recently delineated and are briefly reviewed, their definitive functional meaning still remains to be elucidated. This review summarizes the present knowledge on visually scored and automatically detected spindles, as well as the literature on EEG power in the sigma band. Among the factors known to affect sleep spindles and sigma activity, their intra-cycle temporal dynamics, their time-course across sleep cycles, the reciprocal relationship with delta activity, the effects of sleep deprivation, of circadian factors and of ageing, and their role in information processing have been discussed. Moreover, specific attention has been paid to the existence of functionally and topographically distinct slow- and fast-spindles, also taking into account the presence of large inter-individual differences. Nevertheless, several fundamental issues remain to be elucidated: the physiological mechanisms controlling age-related changes in spindle parameters; the role of melatonin as a spindle-promoting agent; the relationships between plastic mechanisms (after stroke, or as a consequence of learning) and modifications in spindle activity; the possibility of using some spindle parameters as an index of the severity of developmental disorders in abnormal maturational processes.

Aging↗

PubMed1976

Spindle and kinetochore morphology of Dictyostelium discoideum.

The metaphase spindle of haploid Dictyostelium discoideum (n = 7) is 2 mum long. It consists of some 20 microtubules which seem continuous between the spindle pole bodies and there are about 20 chromosomal microtubules at each end of the spindle. During anaphase the central spindle elongates and the chromosomal microtubules shorten. The spindle length and structure at this stage suggests that lengthening is caused by elongation as well as parallel sliding of the nonchromosomal microtubules. The nuclear envelope remains mostly intact during mitosis, and nuclear separation through medial constriction takes place when the spindle is 6 mum long. Cytokinesis occurs when the spindle is 10 mum long. At that time the kinetochores double in size. During interphase, the spindle pole body separates from the nucleus to a distance of 0.7 mum, and it returns at the onset of the next prophase when it becomes functionally double, thereby starting the formation of a central spindle. When comparing mitosis in the cellular slime molds Polysphondylium violaceum and D. discoideum, several similarities and some differences are apparent.

Cell Division↗

PubMed1979

Three-dimensional structure of the central mitotic spindle of Diatoma vulgare.

Central mitotic spindles in Diatoma vulgare have been investigated using serial sections and electron microscopy. Spindles at both early stages (before metaphase) and later stages of mitosis (metaphase to telophase) have been analyzed. We have used computer graphics technology to facilitate the analysis and to produce stereo images of the central spindle reconstructed in three dimensions. We find that at prometaphase, when the nuclear envelope is dissassembling, the spindle is constructed from two sets of polar microtubules (MTs) that interdigitate to form a zone of overlap. As the chromosomes become organized into the metaphase configuration, the polar MTs, the spindle, and the zone of overlap all elongate, while the number of MTs in the central spindle decreases from greater than 700 to approximately 250. Most of the tubules lost are short ones that reside near the spindle poles. The previously described decrease in the length of the zone of overlap during anaphase central spindle elongation is clearly demonstrated in stereo images. In addition, we have used our three-dimensional data to determine the lengths of the spindle MTs at various times during mitotis. The distribution of lengths is bimodal during prometaphase, but the short tubules disappear and the long tubules elongate as mitosis proceeds. The distributions of MT lengths are compared to the length distributions of MTs polymerized in vitro, and a model is presented to account for our findings about both MT length changes and microtubule movements.

Anaphase↗

PubMed1981

Decoration of spindle microtubules with Dynein: evidence for uniform polarity.

Studies were conducted to determine whether the microtubules present within native spindles isolated from eggs of the surf clam, Spisula solidissima, could bind dynein obtained from axonemes of Tetrahymena thermophila. SDS gel electrophoresis revealed that the high molecular weight polypeptides that make up dynein cosedimented with the isolated spindles. Moreover, the ATPase activity of dynein bound to the spindle microtubules was stimulated approximately sevenfold. The birefringence retardation of spindles incubated without dynein decreased from 1.4 nm to an undetectable level within 45 min, whereas that of spindles incubated for the same period of time with dynein was 1.0 nm, approximately 70% of its initial value, thereby indicating that dynein stabilized spindle birefringence. Ultrastructural analysis revealed that each spindle microtubule was decorated with four to seven dynein arms attached by their "B" end, that which cross-bridges the B-subfiber within native axonemes. In addition, the polarity of the spindle microtubules could be determined by the orientation of the bound dynein arms. The results of these studies suggest that the half-spindle is composed of microtubules possessing the same polarity.

Adenosine Triphosphatases↗

PubMed2006

Meiotic spindle configuration is differentially influenced by FSH and epidermal growth factor during in vitro maturation of mouse oocytes.

BACKGROUND: To ascertain whether different hormonal treatment protocols could affect metaphase II (MII) spindle morphology, meiotic spindle organization was detected in prepubertal mouse oocytes matured under conditions allowing spontaneous, FSH- or epidermal growth factor (EGF)-dependent meiotic maturation. METHODS: Oocyte-cumulus complexes (OCCs) were matured either spontaneously (control; n=270) or in the presence of hypoxanthine (Hx) plus FSH (n=400) or EGF (n=370). Spindles were detected by immunofluorescence analysis. In vivo ovulated (IVO) oocytes were processed similarly. RESULTS: IVO oocytes displayed spindles underlying the oolemma and with focused poles marked by spots of gamma-tubulin, whereas the majority (89%) of control oocytes had barrel-shaped spindles, positioned away from the oolemma, and with gamma-tubulin distributed along microtubules. Similar configuration/localization was found in 85% of the oocytes matured in vitro in the presence of Hx and FSH. In the presence of Hx-EGF, 35% of the oocytes showed spindles with an IVO-like configuration, although gamma-tubulin was homogeneously distributed throughout microtubules. Independently of spindle shape, 52% of EGF-stimulated oocytes had spindles positioned near the oolemma, in comparison to just 24% of FSH-treated and 13% of control oocytes. CONCLUSIONS: These results indicate that FSH and EGF can differently affect meiotic spindle morphology, and that EGF might be a stronger contributor than FSH to the acquisition of oocyte competence.

Animals↗

PubMed2001

The p75 neurotrophin receptor, relative to other Schwann cell and melanoma markers, is abundantly Expressed in spindled melanomas.

Seventeen cases of spindled melanomas and eleven cases of epithelioid melanomas were immunolabeled with various melanoma and Schwann cell markers. Standard melanoma markers included S100, HMB45, HMB50, tyrosinase, and Melan A. Schwann cell markers included the p75 neurotrophin receptor (p75NTR), glial fibrillary acidic protein (GFAP), and the L1 adhesion protein. The degree of immunocytochemical labeling was scored by levels of both intensity and pervasiveness. The results confirmed a distinct difference in labeling between epithelioid and spindled melanomas. The p75NTR was strongly expressed in spindled melanomas and weakly expressed in the epithelioid melanomas. The usual melanoma markers, including HMB45, HMB50, MelanA, and tyrosinase had the reverse pattern, being strongly expressed in virtually all epithelioid melanomas, but rarely expressed in the spindled variants. S100 was unique among the markers in being expressed by both epithelioid and spindled melanomas. Glial fibrillary acidic protein and L1 adhesion protein were expressed moderately, with preferential labeling of the spindled melanomas. The greatest immunophenotypic difference between spindled and epithelioid melanomas was the high abundance of p75NTR expression in spindled melanomas. The functional significance of the high level of p75 neurotrophin receptor expression may contribute to the high predisposition of perineural extension in the desmoplastic subset of spindled melanomas.

Biomarkers, Tumor↗

PubMed1993

Spindle cell variants of embryonal rhabdomyosarcoma in the paratesticular region. A report of the Intergroup Rhabdomyosarcoma Study.

We reviewed 173 cases of paratesticular rhabdomyosarcoma (RMS) of Intergroup Rhabdomyosarcoma Studies (IRS)-I, -II, and -III for evaluation of possible histological factors that might account for the good prognosis of these patients. Almost all cases (161 of 173 cases, 93.1%) occurring in this site were of embryonal histology. A spindle-cell subtype of embryonal RMS was identified that presented a storiform growth pattern with abundant collagen between the tumor cells in most cases. Other tumors of this subtype showed an arrangement of tumor cells in bundles with a low to moderate amount of collagen, resembling a leiomyosarcoma. The other embryonal RMS in this site had the classical embryonal cytology. The spindle-cell subtype was highly differentiated by immunohistochemistry and electron microscopy. Lymph node metastasis was found in seven of 43 patients (16.3%) with a RMS of spindle-cell subtype, compared with 40 of 112 patients (35.7%) with RMS of non-spindle-cell type. Clinical data from patients with spindle-cell subtypes of the paratesticular lesions revealed that they almost always had an association with clinical groups of limited disease (32 patients, 74.4%, with Group I; 10 patients, 23.3%, with Group II disease) and a significantly better prognosis (95.5% survival at 5 years) when compared with patients with the classic embryonal variant of RMS (80% survival at 5 years, p < 0.035). The incidence and anatomic distribution of this spindle cell subtype of embryonal RMS was estimated on 800 randomly selected patients from IRS-II. It was found in the head and neck, extremities, orbit, and some other sites, but 30.6% were located in the paratesticular area. Patients with spindle cell RMS of nonparatesticular sites usually had more extensive disease compared with patients having paratesticular lesions; two thirds of the cases had gross residual tumor after surgery or metastatic tumor at diagnosis. We conclude that spindle-cell RMS is a subtype of embryonal RMS with a very favorable prognosis. The site factor of the paratesticular localization may allow earlier diagnosis of the spindle-cell lesions compared with other sites. Other unknown factors may also play a role.

Child↗

PubMed1996

Desmoplastic and spindle-cell malignant melanoma. An immunohistochemical study.

The clinical, histologic, and immunohistologic features of 22 desmoplastic melanomas (DMM), 10 mixed desmoplastic and spindle-cell melanomas (DMM/SMM), and two cellular spindle-cell melanomas (SMM) were studied. Patients ranged in age from 35 to 91 years (mean, 67) and included 23 men and 11 women. Seventeen cases occurred in sun-damaged skin of the head and neck. 11 were on the extremities, and six on the trunk. Except for two cases, all were Clark's level IV or V. Twenty-two (65%) cases were associated with a recognizable overlying pigmented lesion. Thirty of 32 (94%) DMM and DMM/SMM were clearly positive for S100. S100 staining was limited to < 5% of the spindle cells in two DMM/SMM. All DMM were negative when stained with HMB45. Three DMM/ SMM were immunoreactive with HMB45, as were both SMM. CD68 staining was limited to < 5% of the spindle cells in two of 32 DMM and DMM/SMM and 20% of the cells in one of two SMM. Nine (32%) DMM and DMM/SMM contained significant numbers of spindle cells immunoreactive for SMA but not desmin. In five cases, the number of actin-positive spindle cells. Two color stains for SMA and S100 demonstrated that these smooth-muscle actin positive cells constituted a separate spindle-cell population, consistent with reactive myofibroblasts. This study indicates that the immunohistologic features of desmoplastic melanoma differ from those of conventional melanoma. If a problematic spindle-cell skin lesion is a suspected melanocytic process, HMB45 is unlikely to provide confirmatory (or exclusionary) evidence for the diagnosis of DMM. Similarly, because of the variability in S100 expression in this neoplasm, the absence of S100 staining should not be relied on too heavily to exclude DMM if the clinical and histologic features favor that diagnosis. Caution should be exercised in the interpretation of numerous actin-positive spindle cells in isolation of additional confirmatory or exclusionary data as desmoplastic melanomas may contain significant numbers of these cells.

Adult↗