Biomaterials and scaffold design: key to tissue-engineering cartilage.

Cartilage remains one of the most challenging tissues to reconstruct or replace, owing to its complex geometry in facial structures and mechanical strength at articular surfaces in joints. This non-vascular tissue has poor replicative capacity and damage results in its functionally inferior repair tissue, fibrocartilage. This has led to a drive for advancements in tissue engineering. The variety of polymers and fabrication techniques available continues to expand. Pore size, porosity, biocompatibility, shape specificity, integration with native tissue, degradation tailored to rate of neocartilage formation and cost efficiency are important factors which need consideration in the development of a scaffold. The present review considers the current polymers and fabrication methodologies used in scaffold engineering for cartilage and postulates whether we are closer to developing the ideal scaffold for clinical application.

Undifferentiated large cell carcinoma of the thymus associated with Castleman disease-like reaction: a distinctive type of thymic neoplasm characterized by an indolent behavior.

Five cases of a distinctive type of undifferentiated large cell thymic carcinoma accompanied by an inflammatory reaction having morphologic features closely resembling those of Castleman disease (CD) of the hyaline vascular type (HVCD) are reported. The tumors occurred in 3 men and 2 women with a median age of 53 years. Three patients were asymptomatic and the tumors were found incidentally; 1 patient presented with fatigue, weight loss, dyspnea, and chest pain, and another with acanthosis nigricans. The tumors were characterized by the admixture of two components: a neoplasm of cytokeratin (+)/CD5(-) undifferentiated large tumor cells and an inflammatory reaction resembling the late stage of HVCD. Some of the cases were associated with a remarkably indolent clinical course, especially when considering their high-grade morphology. Three patients were alive without disease at 1, 10, and 22 years. One patient was alive with persistent disease at 1 year. One patient's clinical course was unique in that the primary thymic tumor was found 16 years after a metastasis had been detected in two distant lymph nodes. The two possible explanations for the coexistence here described are as follows: 1) a CD-like reaction to the tumor as the morphologic manifestation of a host immune response; and 2) a malignancy engrafted upon preexisting HVCD of the thymus, in a manner analogous to that operating in the reported cases of tumors of dendritic/reticulum cells complicating HVCD at other sites. The first hypothesis is favored, with the added suggestion that the CD-like reaction may bear a relationship to the peculiarly indolent behavior that these tumors exhibit.