RESUMEN
Objective: Malignant mucosal melanomas of the head and neck comprise a very small portion of all melanomas, particularly in the oral cavity. These lesions are associated with high rates of local recurrence, distant metastasis, and a very poor 5-year survival rate; however, the clinical outcomes of mucosal melanoma in situ of the oral cavity are unclear. Therefore, we present a case report of mucosal melanoma in situ and a systematic review of the literature to shed light on this rare but important disease. Methods: PubMed, Scopus, and CINAHL were searched per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies were only considered for inclusion if they described oral cavity melanoma in situ and documented specific data pertaining to treatment including modality, lesion size, or outcomes. Results: A total of 28 reported cases from the literature fulfilled the inclusion criteria, as well as one case from our own institution. Men comprised the majority (64.3%) of the cases, and the average age at presentation was 57.4 years. The hard palate was the most common location, and most cases were treated with surgical excision. Eight had no evidence of disease after a minimum of six months of follow-up, one reported spread to the cervical lymph nodes, and only one reported progression with distant metastasis. Conclusion: Oral mucosal melanoma in situ is a rare entity and most commonly treated with surgical excision. High rates of recurrence necessitate long term follow-up. Further studies may be useful to determine whether adjuvant therapy may play a role in reducing recurrence.
RESUMEN
We present a study of single-mode Rayleigh-Taylor instabilities with a modified direct simulation Monte Carlo (MDSMC) code in two dimensions. The MDSMC code is aimed to capture the dynamics of matter for a large range of Knudsen numbers within one approach. Our method combines the traditional Monte Carlo technique to efficiently propagate particles and the point-of-closest-approach method for high spatial resolution. Simulations are performed using different particle mean free paths and we compare the results to linear theory predictions for the growth rate including diffusion and viscosity. We find good agreement between theoretical predictions and simulations and, at late times, observe the development of secondary instabilities, similar to hydrodynamic simulations and experiments. Large mean free paths favor particle diffusion, reduce the occurrence of secondary instabilities, and approach the noninteracting gas limit.