Frontal waves and transmissions for temporal laminates and imperfect chiral interfaces.

The analysis of wave patterns in a structure which possesses periodicity in the spatial and temporal dimensions is presented. The topic of imperfect chiral interfaces is also considered. Although causality is fundamental for physical processes, natural wave phenomena can be observed when a wave is split at a temporal interface. A wave split at a spatial interface is a more common occurrence; however, when the coefficients of the governing equations are time-dependent, the temporal interface becomes important. Here, the associated frontal waves are studied, and regimes are analysed where the growth of the solution in time is found. Imperfect interfaces, across which the displacements are discontinuous, are also considered in the vector case of chiral elastic systems. Analytical study and asymptotic approximations are supplied with illustrative numerical examples. This article is part of the theme issue 'Wave generation and transmission in multi-scale complex media and structured metamaterials (part 1)'.

Quasistatic cloaking of two-dimensional polarizable discrete systems by anomalous resonance.

Discrete systems of infinitely long polarizable line dipoles are considered in the quasistatic limit, interacting with a two-dimensional cloaking system consisting of a hollow plasmonic cylindrical shell. A numerical procedure is described for accurately calculating electromagnetic fields arising in the quasistatic limit, for the case when the relative permittivity of the cloaking shell has a very small imaginary part. Animations are given which illustrate cloaking of discrete systems, both for the case of induced dipoles and induced quadrupoles on the interacting particles. The simulations clarify the physical mechanism for the cloaking.

Determinants of outcome in melanoma patients with cerebral metastases.

PURPOSE: To analyze prognostic factors, effects of treatment, and survival for patients with cerebral metastases from melanoma. PATIENTS AND METHODS: All melanoma patients with cerebral metastases treated at the Sydney Melanoma Unit between 1952 and 2000 were identified. From 1985 to 2000, patients were diagnosed and treated using consistent modern techniques and this cohort was analyzed in detail. Multivariate analysis of prognostic factors for survival was performed. RESULTS: A total of 1137 patients with cerebral metastases were identified; 686 were treated between 1985 and 2000. For these 686 patients, the median time from primary diagnosis to cerebral metastasis was 3.1 years (range, 0 to 41 years). A total of 646 patients (94%) have died as a result of melanoma. The median survival from the time of diagnosis of cerebral metastasis was 4.1 months (range, 0 to 17.2 years). Treatment was as follows: surgery and postoperative radiotherapy, 158 patients; surgery alone, 47 patients; radiotherapy alone, 236 patients; and supportive care alone, 210 patients. Median survival according to treatment received for these four groups was 8.9, 8.7, 3.4, and 2.1 months, respectively; the differences between surgery and nonsurgery groups were statistically significant. On multivariate analysis, significant factors associated with improved survival were surgical treatment (P <.0001), no concurrent extracerebral metastases (P <.0001), younger age (P =.0007), and longer disease-free interval (P =.036). Prognostic factors analysis confirmed the important influence of patient selection on treatment received. CONCLUSION: This large series documents the characteristics of patients who developed cerebral metastases from melanoma. Median survival was dependent on treatment, which in turn was dependent on patient selection.

Melanoma: accuracy of clinical diagnosis.

Clinical diagnosis of melanoma can be difficult. A review of the accuracy of clinical diagnosis of melanoma, over a 12 month period, was undertaken at the Skin and Cancer Foundation Australia. The overall accuracy rate was 65.6% with seborrhoeic keratosis, melanocytic naevi and basal cell carcinoma the most common clinical misdiagnoses given to melanoma. Specialist doctors with more than 10 years experience had a higher rate of correct diagnosis than trainee doctors with 0-5 years experience.

Cutaneous melanoma in childhood: incidence and prognosis.

The incidence and prognosis of cutaneous melanoma in children under 13 years of age has always been difficult to assess. The main reasons for this difficulty include the rarity of melanoma in children, referral biases from investigating institutions, changing conceptions in the histological diagnosis of true melanoma, and the lack of large enough study groups with sufficient follow-up to estimate 10-year survival rates. The present study documents 32 cases of childhood cutaneous melanoma drawn from the records of two large referral centres in New South Wales, Australia: the Sydney Melanoma Unit and the Newcastle Melanoma Unit in order to demonstrate some of the difficulties in the assessment of incidence and prognosis in children.

Elective lymph node dissection in patients with primary melanoma of the trunk and limbs treated at the Sydney Melanoma unit from 1960 to 1991.

BACKGROUND: The value of elective lymph node dissection (ELND) in melanoma remains controversial. Published prospective and retrospective studies can be criticized, and results from two ongoing randomized trials are not yet available. A previous retrospective review from the Sydney Melanoma Unit (SMU) showed apparent survival benefit from ELND, especially in tumors of intermediate thickness. STUDY DESIGN: We undertook a retrospective analysis of all patients treated at the SMU since 1960 for melanoma of the trunk or limbs measuring 1.5 mm or more in thickness, without clinical lymph node metastases, whose definitive wide excision (WE) with or without ELND was performed at the SMU within 60 days of initial diagnosis. RESULTS: There were 1,278 patients who fulfilled these criteria. Of these, 845 (66 percent) were treated with ELND and the remaining 34 percent were treated with WE alone. The median follow-up period was 58 months. Patients with thicker tumors and younger age more commonly underwent ELND. Among patients with thinner tumors, males underwent ELND more commonly than females. A multivariate proportional hazard model of melanoma-specific survival stratified by tumor thickness was chosen to allow for the imbalances between the two groups. With or without allowance for covariates, no benefit from ELND was found in the whole group or any subset. In contrast to previous studies from the SMU, we deliberately excluded from the present study patients referred only after WE with or without ELND elsewhere, because these might have been a selectively biased poor prognostic group. CONCLUSIONS: This study does not indicate a benefit from ELND for melanomas of the trunk or limbs measuring over 1.5 mm in thickness.

Clinical features of secondary malignant melanoma.

Malignant melanoma recurring deep in the body can present with a considerable range of symptoms and although routine CT Scan and chest x-ray are probably not indicated as they are expensive, time consuming and give very meagre returns, the minute a patient complains of any of these symptoms full scale investigation is imperative. Although it may not be possible to do very much about the symptoms, sometimes suitable surgical removal will give the patient if not cure at least prolonged palliation.

Rare variants of malignant melanoma.

The personal experience with 5 rare types of malignant melanoma is reviewed to point out some of the practical problems in the diagnosis and management of these tumors. The rare forms discussed are conjunctival, nasal, oral, vulvar, and penile melanomas. All pigmented lesions in the oral cavity, but not the penis or vulva, should be prophylactically excised as lesions in the mouth have a higher malignant potential. Local excision of all 5 forms of primary melanomas, no matter how locally advanced they may be, is the sole treatment. Nevertheless, anatomic constraints often preclude surgery with generous margins and consequently local recurrence, particularly for conjunctival, nasal, and oral primary lesions, is usually the major first failure in treatment. Lymph node dissection is only performed if the regional nodes are palpable at the time of first presentation. Elective lymph node dissections are not performed since the patients are often elderly, the lymphatic drainage is usually ambiguous or multiple, and the disease tends to spread hematogenously rather than lymphatically. Surgery still remains the cornerstone of treatment for these rare forms of melanoma but prognosis is very poor since surgery is often a palliative rather than a curative measure. Improved survival may depend on identifying more effective chemotherapeutic and immunologic agents.

Experience with 998 cutaneous melanomas of the head and neck over 30 years.

Between 1960 and 1990, a total of 998 patients were treated at the Sydney Melanoma Unit for cutaneous melanoma of the head and neck. There were 595 male and 403 female patients, with a median age of 53 years. The most common primary lesion site was the face (47%), followed by the neck (29%), scalp (14%), and ear (10%). Histologic types were as follows: superficial spreading 30%, nodular melanoma 28%, lentigo maligna melanoma 16%, and other 26%. All patients underwent surgical treatment. Primary closure of wounds was achieved in 52% of patients, and excision margins were 2 cm or less in 45%. A total of 152 patients had therapeutic neck dissections, and 234 had elective neck dissections. The overall local recurrence rate was 13%, and this was significantly influenced by increasing tumor thickness and Clark level. The recurrence rate in the neck after neck dissection was 24%, and the rate of parotid recurrences was 14%. Melanoma-specific survival was 77% at 5 years and 66% at 10 years for the entire group. By univariate analysis, survival varied significantly with age, tumor thickness, ulceration, anatomic sub-site, histologically positive nodes, and the presence of distant metastases. A diagnosis of lentigo maligna melanoma and elective lymph node dissection both appeared to improve survival. With multivariate analysis, all of these factors remained significant prognostic factors except elective node dissection, which lost its beneficial influence.

Immunofluorescent localization of dopamine-like and leucine-enkephalin-like neurons in the supraoesophageal ganglia of the American cockroach, Periplaneta americana.

Leucine-enkephalin- and dopamine-like nerve cells and fibers were localized in the supraoesophageal ganglia (brain) of the American cockroach, Periplaneta americana, using immunofluorescence. The presence of leucine-enkephalin-like material was confirmed using immunoperoxidase staining. Several cells containing leucine-enkephalin-like material were found in the pars lateralis, and nerve fibers belonging to these cells were traced through the brain. Dopamine-like material was detected in deutocerebral neurons as well as the nerve processes arising from these cells which lead into the area of the deutocerebral glomeruli. Specific immunofluorescence was also obtained in the alpha and beta lobes of the corpora pedunculata with both the leucine-enkephalin and dopamine antibodies. However, the fluorescent banding pattern observed in both lobes was distinctly different with the two antibodies. No specific fluorescence was observed in the stalk or peduncle of the corpora pedunculata with either the leucine-enkephalin or the dopamine antibody. The findings suggest a possible interaction of leucine-enkephalinergic and dopaminergic nerve fibers in the alpha and beta lobes of the cockroach corpora pedunculata.

The justification for surgical treatment of metastatic melanoma of the gastrointestinal tract.

Fifty-six patients with symptomatic metastatic melanoma of the gastrointestinal tract (GIT) treated surgically at the Sydney Melanoma Unit between 1974 and 1989 were reviewed. The majority of these patients presented with abdominal pain or symptoms of anemia. The small intestine was the site of metastasis in more than 80 per cent. The mean over-all survival time was 11.7 months (range of one to 60 months) after surgical treatment of a first metastasis to the GIT and 3.6 months (range of zero to 12 months) postoperatively for a second GIT metastasis. Forty-four of the patients reported complete relief of their symptoms postoperatively. The results suggest that an aggressive approach to symptomatic GIT metastases from malignant melanoma is justified both to relieve distressing symptoms and to prolong life.

Thin regressing malignant melanoma: significance of concurrent regional lymph node metastases.

We attempted to clarify the prevailing controversy regarding the significance of regression in thin (less than 0.76 mm) primary melanomas. Of 7540 patients with cutaneous melanomas treated at the Sydney Melanoma Unit, 28 first presented with a thin primary lesion and concurrent regional lymph node metastases (stage II). Major differences in tumour histology existed between these patients and stage I patients with thin lesions that subsequently recurred. Regression was present in all 28 lesions in stage II patients. In 61 stage I patients ultimately developing a recurrence, 67% of lesions displayed regression. Significantly, however, in 735 stage I patients ultimately not developing a recurrence, 61% of lesions also displayed regression. Why regression occurs so frequently in thin lesions which never recur is unclear. Our results suggest that the histology of thin primary melanomas may be influenced by the presence or absence of metastases in patients at that time.

Time and frequency of recurrence of cutaneous stage I malignant melanoma with guidelines for follow-up study.

This study is based upon 3,171 patients with clinical Stage I cutaneous malignant melanoma treated at the Sydney Melanoma Unit (SMU) in Australia. The mean follow-up period was 9.8 years, ranging from 2.5 to 36.2 years. During the course of this follow-up study, recurrence developed in 886 patients. Three factors that predicted both the risk of recurrence and the disease-free interval were determined. These were thickness of tumor, the first definitive surgical treatment (whether or not the patient underwent elective dissection of lymph nodes) and the ulcerative state of the primary tumor. Follow-up schedules were designed taking all three of the factors into consideration. The schedules so derived reflected both the risk of recurrence and its alteration with time. It will obviously be necessary, however, to modify the frequency of follow-up visits according to the institutional resources available and the specific wishes of the patient. Annual review for an indefinite period for all patients with melanoma is recommended to detect both additional cancers and late recurrences.

Thin malignant melanomas and recurrence potential.

Of 846 patients with stage I malignant melanoma that was less than 0.76-mm thick who were followed up for two to 31 years, 61 (7.2%) developed a recurrence. For those patients who did not initially undergo an elective lymph node dissection, the majority of first recurrences were at regional lymph nodes. Attempts have been made to identify those patients at risk of relapsing. Axial lesions, particularly those on the scalp, had the highest recurrence rate, with 15% of all thin scalp lesions recurring compared with only 4% of all thin extremity lesions. Three histological features proved to be useful prognostic indicators when analyzed by single-factor analysis. Evidence of ulceration in the primary lesion increased the recurrence rate from 6.7% to 26.1%. While only 4.3% of lesions displaying low mitotic activity recurred, this rate rose to 23.8% for those lesions of a high mitotic grade. Only 5% of Clark's level II lesions recurred, compared with about 12% of lesions at either level III or IV. Evidence of regression in thin lesions had no deleterious effect on prognosis. This study defines a small subset of patients who may benefit from elective lymph node dissection.

Effects of exposure to ultraviolet light on epidermal Langerhans cells and melanocytes in Australians of aboriginal, Asian and Celtic descent.

The effects of 3 daily, 7-min exposures to artificial ultraviolet light (UVL), designed to simulate natural sunlight, on epidermal Langerhans cells (LC) and melanocytes were studied in 17 healthy Australian volunteers of differing skin pigmentation. Six were of Celtic, 6 of Asian and 5 of Aboriginal descent. LC were visualized using the immunofluorescence method for HLA-DR and T6 antigens, and the histochemical method for ATPase. UVL induced a transient reduction in the LC population density and an increase in the number of melanocytes in all subject groups. The reduction in number of immunocompetent LC or the disruption of their surface markers was greatest in the Celtic subjects, who had the fairest skin, and least in the Aboriginal and Asian subjects, who had the darkest skin. However, neither the inherently dark skin pigmentation nor the UVL-induced increase in pigmentation were sufficient to prevent the depletion of immunocompetent epidermal LC. Non-dendritic, rounded cells and very large dendritic, non-LC, which were present in the epidermis of some subjects, were stimulated to increase in number by exposure to UVL. The identity and function of these cells is uncertain and they require further investigation.