Revisando un órgano olvidado: Evaluación del timo en PET-CT / Revisiting a Forgotten Organ: Thymus Evaluation in PET-CT

Resumen La pesquisa incidental de lesiones tímicas ha aumentado. Una adecuada aproximación a esas lesiones en la tomografía computada por emisión de positrones (PET-CT) es fundamental, pues se usa como parte de la mayoría de los procedimientos de planificación oncológica. Se han seleccionado casos representativos respecto de los aspectos más importantes de las imágenes de timo en PET-CT y cómo esa técnica puede contribuir a un diagnóstico preciso o a la planificación del tratamiento. Específicamente, presentamos una descripción general de las lesiones tímicas comunes y los imitadores de enfermedad, con énfasis en los hallazgos en PET-CT, incorporando también ejemplos de resonancia magnética (RM).

Abstract Incidental thymic lesion findings have increased. An adequate characterization of these lesions in positron emission computed tomography (PET-CT) is essential, since it is used as part of most oncological planning procedures. Representative cases have been selected regarding the most important aspects of thymus imaging in PET-CT and how this technique can contribute to an accurate diagnosis or treatment planning. Specifically, we present a general description of common thymic lesions and disease mimics, with an emphasis on PET-CT findings, also incorporating examples of magnetic resonance imaging.

Timo cervical aberrante: masa cervical pediátrica inusual, revisión bibliográfica y reporte de caso / Aberrant cervical thymus: unusual type of pediatric cervical mass, bibliographic review and case report

Las masas cervicales representan un desafío habitual en pediatría, que en su mayoría son de etiología benigna. Una de las causas menos conocidas es el timo cervical aberrante, una entidad clínica resultante de anormalidades en el descenso del timo a lo largo de su ruta habitual (tracto timo-faríngeo). Este es un cuadro frecuentemente mal diagnosticado, del que se desconoce su incidencia real. Actualmente, su incidencia relativa parece ir en aumento en conjunto con la disponibilidad de la ecotomografía. En Chile no hay registro epidemiológico de este cuadro ni existen reportes de caso documentados. En este artículo se presenta una revisión bibliográfica sobre masa cervical pediátrica y un reporte de caso de un paciente chileno.

Cervical masses constitute a frequent challenge in pediatric care, mostly which are of benign nature. One of the lesser known causes is the aberrant cervical thymus, which results from embryological abnormalities during the thymus descent through its normal route (thymo-pharyngeal duct). This is a frequently misdiagnosed syndrome, for which its real incidence remains unknown. Nowadays, its relative incidence is on the rise along with ultrasound availability. There is no epidemiological record or documented case reports of this entity in Chile. In this article we present a bibliographic revision on cervical mass and a case report from a Chilean patient.

Hipoplasia de timo con trisomía del cromosoma10 / Thymus hypoplasia with chromosome 10 trisomy

INTRODUCCIÓN: La hipoplasia de timo es una entidad que puede asociarse a múltiples patologías fetales de ahí la importancia de su diagnóstico y su manejo. OBJETIVO: Utilidad y métodos de evaluación del timo en la ecografía morfológica y valor de la interpretación del análisis genético de los microarrays. CASO CLÍNICO: Se presenta el caso clínico de una gestante en la que se detecta una glándula tímica hipoplásica utilizando para su medición el índice timo-torácico en un plano de tres vasos. Ante estos hallazgos se realiza una amniocentesis para análisis genético usando la QF-PCR y un análisis ARRAY-CGH. RESULTADOS: En el análisis de ARRAY-CGH se observa una duplicación patológica en mosaico compatible con una trisomía del cromosoma 10, alteración genética infrecuente de la que se han reportado unos 50 casos en recién nacidos vivos. Esta alteración presenta un rango muy amplio de alteraciones, desde malformaciones graves a niños completamente normales. En los controles posteriores la gestación es normoevolutiva y finaliza en la semana 40 mediante un parto eutócico de inicio espontáneo naciendo un bebé fenotípicamente normal con un timo de menor tamaño del habitual siendo pronto para saber las consecuencias de esta alteración en su inmunidad. CONCLUSIONES: Por un lado, el timo es una estructura fácil de visualizar en la ecografía morfológica de la semana 20 y su medición mediante el índice timo-torácico nos aporta información útil acerca de posibles patologías fetales. Por otro, tener en cuenta que debemos ser muy cautelosos con la interpretación de resultados de pruebas genéticas cuando éstas no tienen un significado clínico claro.

INTRODUCTION : Thymus hypoplasia can associate many different pathologies so is highly important the diagnosis and the management. OBJECTIVE: Utility and methods in the evaluation of the fetal thymus in the morphological ultrasound and interpretation of microarray results. CLINICAL CASE: We present a case of fetal hypoplastic thymus gland in a pregnant woman. We measure it using the thymus-torax index in a three vessel view. A genetical analysis was made using QF-PCR and Array-CGH. RESULTS: In the ARRAY-CGH analysis it is found a pathological mosaicism that match with chromosome 10 trisomy, a very uncommon genetical alteration with only 50 reported cases. This trisomy can traduce from serious malformations to complete normal children. The parents decide to continue with the pregnancy and in week 40 it finishes with an uncomplicated delivery of a healthy child. In the newborn pediatrics remark a thymus gland smaller than expected but it is early to say if it will have or not consequences in its immunity. CONCLUSION: On one hand the thymus is a structure that we can easily display in the morphological ultrasound in the 20 week of pregnancy and its measure, using the thymus-torax index, can be very helpful in the detection of fetal pathologies. On the other hand, is important being careful when we interpret a genetical alteration without a clear clinical significance.

Graves' Patient with Thymic Expression of Thyrotropin Receptors and Dynamic Changes in Thymic Hyperplasia Proportional to Graves' Disease Activity

Thymic hyperplasia is frequently observed in Graves' disease. However, detectable massive enlargement of the thymus is rare, and the mechanism of its formation has remained elusive. This case showed dynamic changes in thymic hyperplasia on serial computed tomography images consistent with changes in serum thyrotropin receptor (TSH-R) antibodies and thyroid hormone levels. Furthermore, the patient's thymic tissues underwent immunohistochemical staining for TSH-R, which demonstrated the presence of thymic TSH-R. The correlation between serum TSH-R antibody levels and thymic hyperplasia sizes and the presence of TSH-R in her thymus suggest that TSH-R antibodies could have a pathogenic role in thymic hyperplasia.

Localized Thymic Amyloidosis Presenting with Myasthenia Gravis: Case Report

A mediastinal mass was incidentally found on chest radiography in a 46-yr-old woman who had had myasthenia gravis (MG) for 2 months. Computed tomography revealed a 4-cm in size, well-defined, and lobulating mass with nodular calcification that was located in the thymus. Microscopically, the mass consisted of diffuse amorphous eosinophilic materials. These deposits exhibited apple-green birefringence under polarized light microscopy after Congo red staining. Immunohistochemical analysis revealed that they were positive for both kappa and lambda light chains and negative for amyloid A. A diagnosis of localized primary thymic amyloidosis was finally made. After thymectomy, the symptoms of MG were controlled with reduced corticosteroid requirements. Localized thymic amyloidosis associated with MG has not been reported to date.

Anomalías congénitas del aparato branquial: estudio de imágenes / Congenital anomalies of the branchial apparatus: imaging study

: The branchial apparatus consists of six arches that are separated from each other by branchial clefts and pharyngeal pouches. Its development is complex and multiple congenital defects can occur; including branchial cleft cysts, sinuses and fistulas, thymic cysts, aberrant thymic tissue and parathyroid cysts. The majority arises from the second branchial arch and they correspond to vestigial remnants from incomplete obliteration of the branchial apparatus or buried epithelial cell rests. Imaging studies are very helpful in the diagnosis and characterization of these anomalies, and require a good understanding of the embryogenesis. Considering the anatomical location and the radiological appearance the diagnosis could be precised in most cases. The purpose of this presentation is to show the appearance of some of the most frequent congenital anomalies of the branchial apparatus using different imaging modalities and emphasizing the normal embryologic development.

El aparato branquial, formado por seis arcos separados por hendiduras extemas y bolsas faríngeas en su parte interna, tiene un complejo desarrollo del cual pueden derivar anomalías como senos, fístulas o quistes y alteraciones del timo o glándula paratiroi-des. La mayoría de las malformaciones derivan del segundo componente branquial. Los estudios de imagen son útiles para el diagnóstico y caracterización de estas lesiones que será más exacta con un adecuado conocimiento del desarrollo embriológico. El objetivo de esta presentación es revisar la embriología y el aspecto más común en imágenes de algunas de estas anomalías.

T-lymphocyte subsets and thymic size in malnourished infants in Egypt: a hospital-based study

Thymus size was assessed ultrasonographically and correlated to the percentage of CD4 and CD8 T-lymphocytes in peripheral blood in 32 infants with protein-energy malnutrition [PEM] and compared with 14 healthy control infants. The study revealed thymus atrophy in patients with PEM, especially the oedematous type, accompanied by changes in the peripheral lymphocyte subsets. These changes were reversible after nutritional rehabilitation. However, they may affect the immune status of PEM patients and may require a longer duration of nutrition rehabilitation than required for recovery of anthropometric measures. We recommend proper assessment of the immune functions of PEM patients during nutritional rehabilitation until full recovery

Undescended thymus presenting as midline neck swelling.

A seven month male child presented with midline neck swelling which was visible in the suprasternal notch when the child cried. Computed tomography revealed that it was thymic tissue (solid). There was no thymic tissue in the normal position. Undesended thymus or ectopic thymus is a rare cause of neck mass. Solid type as seen in this case constitute 10% of ectopic thymic tissue ,90% being of cystic variety. Caution should be exercised in excision of such masses as they may be the only thymic tissue.

Thymic index as a parameter for evaluation of neonatal sepsis

In various stressful conditions, the thymus subjected to incidental involution, mostly due to the thymocytolytic effect of secreted glucocorticosteroids. The thymus gland play a key role in the body's defense against infection. this study aimed at assessing the variations of thymic size by ultrasonography in normal and diseased neonates with proven sepsis and to find whether there is a significant correlation between thymic index [Ti] and several variables. Study design: This cross-sectional, case-control study included 30 neonates with sepsis, 17 males and 13 females. Their mean gestational age was [38.93 +/- 1.91] weeks and their mean weight was [2.93 +/- 0.55] kg. Thirty cases of healthy neonates, 16 males and 14 females, their mean gestational age was [39.6 +/- 1.23] weeks and their mean weight was [3.25 +/- 0.55] kg., Served as controls. Every case underwent complete history taking and thorough physical examination with special emphasis on anthropometric measurements and a full evaluation for sepsis including complete blood count [CBC], C-reactive protein [CRP] and blood culture.Thymic sonography was done for every case to detect the thymic index [Ti] which indicates the size of thymus as a volume estimate. The results of this study showed a significantly lower value of Ti [P<0.001] and significantly higher level of CRP [P<0.001], in patients compared to controls. Also, the value of Ti was positively correlated with birth weight of healthy controls [P<0.05]. Ti showed positive predictive value of 87%, while that of CRP was 66%. A highly significantly increase was found, regarding Hb, platelet, immature neutrophils and I/T ratio, [p<0.001], and significantly increase as regards RBCs, [p<0.05], in patients compared to controls. While, no significant difference was found between the two groups as regard absolute neutrophils count [ANC] and total leucocytic count [TLC]. Also, there was no significant correlation between Ti and gestational age, body length, head circumference and different blood indices in both groups. We concluded that sonographic estimate of the thymus in infants less than one month of age seems to be an easy, reliable and safe diagnostic modality for assessment of thymic size. Thymic index could be considered as a sensitive predictor of neonatal sepsis and reflects the immune competence status of infants