A better understanding of the mathematical practices performed in the process of problem solving is possible, when taken into consideration - as the minimum unit of analysis - both cognitive and metacognitive configurations. In this paper, the metacognitive aspect of an analysis model is presented in-depth. The goal, here, is demonstrating the role played by metacognitive processes to explain difficulties students have in solving problems. In order to do so, a case study involving a third grade student from Spain's high-school educational system is carefully examined. The subject answered a Metacognitive Skills Test, and, based on the analysis, the conclusion is that the difficulties students have might be related to either their cognitive or their metacognitive needs.

Es posible una mejor comprensión de las prácticas matemáticas realizadas en el proceso de resolución de problemas si se toma, como unidad mínima de análisis, configuraciones cognitivas e metacognitivas. Sin embargo, en este artículo, se presenta con profundidad la parte metacognitiva de un modelo de análisis. Concretamente, se pretende, bajo un examen cuidadoso de un estudio de caso, teniendo como sujeto un alumno del tercer curso de la etapa de Enseñanza Secundaria Obligatoria del Estado Español que contestó a una Prueba de Habilidades Metacognitivas, demonstrar el papel que juegan los procesos metacognitivos para explicar las dificultades de estudiantes en la actividad de resolución de problemas. Se concluye que las dificultades de estudiantes pueden estar relacionadas tanto con sus carencias cognitivas como metacognitivas.

A degeneração maligna do cisto pilonidal é rara. O tipo histológico mais freqüente é o carcinoma epidermóide e tem como fator desencadeante o processo inflamatório crônico. O tumor é de crescimento lento. O diagnóstico deve ser precoce e o tratamento cirúrgico adequado é a ressecção ampla incluindo a fáscia pré-sacral. Em alguns casos, como o que apresentamos, o diagnóstico é feito numa fase em que a doença progrediu e invadiu as estruturas adjacentes. Nestes a cirurgia necessária envolve a ressecção multiorgânica. Apresentamos paciente com degeneração carcinomatosa do cisto pilonidal, com doença volumosa que se estendia até a parede do reto. O tratamento realizado foi ressecção alargada, sacralectomia e ressecção abominoperineal do retossigmóide com colostomia definitiva.

Malignant degeneration of pilonidal cysts is rare. The most common histologic type is the squamous cell carcinoma, triggered by the chronic inflammatory process. The growth of the lesion is typically slow. The diagnosis must be early and the appropriate treatment is ample surgical resection, including the presacral fascia. In some cases, as the present one, the diagnosis is made at a stage when the disease has progressed and invaded adjacent structures. In these cases the surgery involves multiple organ resection. We report the case of a patient with carcinomatous degeneration of pilonidal cyst, with bulky disease that extended up to the wall of the rectum. The treatment was extended resection, sacrectomy and abominoperineal resection of the rectosigmoid with permanent colostomy.

As part of an investigation on the evaluation and development of visualization skills and spatial reasoning, we present the analysis of a task used with a sample of 400 student teachers. The analysis is carried out applying the notion of configuration of objects and processes introduced in the "onto-semiotic approach" to mathematical knowledge and instruction, which provides complementary analytical possibilities with respect to other cognitive tools. The identification of the networks of intervening and emergent objects in the resolution of the task allows us to formulate hypothesis on potential subjects' conflicts of meaning and to explain the difficulties in terms of the required knowledge and processes of interpretation.

En el marco de una investigación sobre evaluación y desarrollo de capacidades de visualización y razonamiento espacial, presentamos el análisis de una tarea propuesta a una muestra de 400 estudiantes de magisterio. El análisis se realiza aplicando la noción de configuración de objetos y procesos introducida en el enfoque ontosemiótico del conocimiento y la instrucción matemática, la cual aporta posibilidades analíticas complementarias respecto de otras nociones cognitivas. La identificación de las redes de objetos intervinientes y emergentes en la resolución de la tarea permite formular hipótesis sobre conflictos potenciales de significado de los sujetos y explicar las dificultades en términos de los conocimientos y procesos de interpretación requeridos.