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The structure of the human skin is directly dependent on its location and the mechanical forces to which it is subjected. In the present work, we have performed a comprehensive analysis of the human ridged and non-ridged skin to identify the differences and similarities between both skin types. For this purpose, human skin samples were obtained from dorsal hand skin (DHS), palmar hand skin (PHS), dorsal foot skin (DFS) and plantar foot skin (PFS) from the same cadaveric donors. Histological, histochemical and semiquantitative and quantitative immunohistochemical analyses were carried out to evaluate the epidermis, dermis and basement membrane. Results show that the epithelial layer of ridged skin had larger cell number and size than non-ridged skin for most strata. Melanocytes and Langerhans cells were more abundant in non-ridged skin, whereas Merkel cells were preferentially found in ridged skin. The expression pattern of CK5/6 was slightly differed between non-ridged and ridged skin. Involucrin expression was slightly more intense in non-ridged skin than in ridged skin. Collagen was more abundant in foot skin dermis than in hand skin, and in ridged skin as compared to non-ridged skin. Elastic fibers were more abundant in DHS. Biglycan was more abundant in foot skin than in hand skin. No differences were found for blood and lymphatic vessels. The basement membrane laminin was preferentially found in foot skin. These results revealed important differences at the epithelial, dermal and basement membrane levels that could contribute to a better knowledge of the human skin histology.

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BACKGROUND: Cutaneous leishmaniasis (CL) is underestimated in Spain as in other European countries due to the polymorphism of its clinical manifestations and histopathological features discouraging doctors from suspecting leishmaniasis. Mucosal manifestations (ML) are misdiagnosed due to the fact that they often mimic cancer. OBJECTIVES: Given that leishmaniasis may be masked as different granulomatous diseases in Leishmania infantum endemic areas, the aim of this study was to verify this misdiagnosing and contributes to the improvement of CL/ML diagnosis. METHODS: A retrospective study involving formalin-fixed paraffin-embedded tissue biopsies with histopathological features of granulomatous lesions of unknown origin (GLUO) detected in 17 patients. This study included 13 patients with CL that was used as positive controls, nine patients with other confirmed diseases used as negative controls and seven patients with histological features suggestive of CL or ML without confirmation. Molecular analysis was blindly performed using two different PCR techniques. RESULTS: The PCR detected 15 CL cases in which the diagnosis was neither clinically nor histologically suspected. Leishmaniasis was confirmed in seven suspected patients in whom the classical techniques failed to detect the parasite. L. infantum was identified in all cases. A systematic review of CL cases in GLUO patients from European countries identified 45 reported cases. CONCLUSIONS: In L. infantum endemic areas, a high percentage of GLUO are due to Leishmania infection. The main consequences are delayed diagnosis and underestimation of the real incidence. PCR performed on paraffin-embedded tissue proved to be a reliable tool for diagnosis of CL/ML and must be performed routinely in any granulomatous dermatitis, even when the morphological features are no stereotypical of leishmaniasis.

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BACKGROUND: T1 melanoma substaging was recently modified by the American Joint Committee on Cancer (AJCC). Although sentinel lymph node (SLN) positivity is the most important prognostic factor in melanoma, there is a lack of consensus on whether SLN biopsy should be performed in patients with thin melanoma (≤1 mm). OBJECTIVE: The main aim of this study was to investigate predictors of SLN positivity in patients with thin melanoma, with a special emphasis on mitotic rate. A secondary aim was to evaluate survival in this group of patients. MATERIALS AND METHODS: Retrospective multicenter observational study with analysis of age, sex, tumour location, thickness, mitotic rate, regression and microscopic satellites. Predictive factors were identified using a classification and regression tree (CART) approach. Melanoma-specific survival according to SLN status was estimated using Kaplan-Meier curves. RESULTS: We analysed 203 patients with a melanoma ≤1 mm. Using the new AJCC staging criteria, the CART algorithm identified a 7.5% likelihood of SLN positivity in T1a patients. In the case of T1b melanoma, there was a 14.3% likelihood of SLN positivity in patients with a mitotic rate >1 mitosis/mm2 and a 3.2% likelihood in those with ≤1 mitoses/mm2 . None of the patients with T1b disease who had ≤1 mitoses/mm2 and regression had SLN positivity. In T1b patients, 5-year melanoma-specific survival was 98.7% in the SLN-negative group and 75% in the SLN-positive group (P = 0.05). When stratified by mitotic rate, survival was 100% for patients with a mitotic rate of ≤1 mitoses/mm2 and 91.4% for those with >1 mitosis/mm2 (P = 0.022). There were no deaths in the T1a subgroup. CONCLUSIONS: Sentinel lymph node metastasis was less common in patients with T1b melanoma who had a mitotic rate of ≤1 mitoses/mm2 . Performance of SLN biopsy should be carefully considered in this subgroup of patients, particularly considering the good prognosis.

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