RESUMEN
Elucidating the detailed structure and formation mechanism of lignin, especially understudied syringyl (S) lignin, advances our knowledge of lignocellulosic biomass. To examine the early stages of S-lignin formation from sinapyl alcohol (SA), the FMR (flow microreactor) method and the Zutropf (gradual addition of SA) method with limited amounts of H2O2 were employed for the peroxidase-catalyzed dehydrogenative polymerization of SA. Only ß-ß dimers and not ß-O-4 dimers were obtained as initial dimerization products. Six new oligoligognols up to pentamers with ß-ß and ß-O-4 structures were identified. The erythro isomer was preferentially formed over the threo isomer in the ß-O-4 structures, similar to that found in naturally occurring S-rich hardwood lignin. Although minor substructures, the α-oxidized ß-ß and ß-O-4 structures and spirodienone (ß-1) structure identified in this study demonstrate the characteristic features of S-rich lignin. Based on the identified products, the initial formation mechanism of S-lignin from SA was proposed.
RESUMEN
BACKGROUND: Little information is available about the clinical and pathologic characteristics of local recurrence (LR) after nipple-sparing mastectomy according to the locations of LR. METHODS: This study classified 99 patients into the following two groups according to the location of LR after nipple-sparing mastectomy: nipple-areolar recurrence (NAR) group and other locations of LR (oLR) group. The study evaluated whether the location of LR was associated with disease-free survival (DFS) after LR resection. RESULTS: For about half of the patients (44.4 %) with NAR, the primary cancer was estrogen receptor (ER)-negative and human epidermal growth factor receptor 2 (HER2)-positive. Conversely, in most of the patients with oLR (79.2 %), the primary cancer was ER-positive and HER2-negative. Among the LR tumors, the frequency of noninvasive carcinoma in the NAR tumors was significantly higher than in the oLR tumors (51.9 % vs 4.2 %, respectively). During a median follow-up period of 46 months, the location of LR was not associated with DFS after LR. In the NAR group, the presence or absence of LR tumor invasiveness was the only factor associated with DFS. In the oLR group, age at primary surgery was the only factor associated with DFS. CONCLUSION: This multi-institutional retrospective study demonstrated that the features of NAR, such as the characteristics of the primary and recurrent tumors and the prognostic factors after LR resection, were quite different from those of oLR.
