» THYROIDE involution adipeuse

involution adipeuse

Standard books dedicated to endocrine / thyroid pathology, do only very briefly address this topic. The most extensive citation was in a 22 years-old book (LiVolsi VA : Surgical pathology of the thyroid, vol 22 in the series Major problems in pathology : 331), I quote “the presence of adipose tissue in the thyroid gland is unusual, and in most cases is found in a subcapsular location ; most authors attribute this finding to inclusion of mesenchymal fat and sometimes muscle during embryologic development. Much rarer are tumors, or at least mass lesions, containing fat and thyroid gland mixed together, sometimes surrounded by a fibrous capsule.”
Our review of the 320 thyroid cases showed that indeed, very few adipocytes are rather frequently found in subcapsular position. They are rather difficult to identify, when they occur singly, because they are difficult to differentiate from artifacts / resorption of the colloid, or empty vessels. Even when easily recognizable, they very often go unnoticed, because attention is focused on the pathology of the thyroid. As example, the princeps case which harbored a 9 mm papillary carcinoma, the adipose involution was not noticed at once, only at first on the opposite lobe with nodular hyperplasia, but the intensity of adipose involution was the same on both lobes.
It is also very subjective to decide between some adipocytes in the thyroid parenchyma in subcapsular location, and an irregular outline of the thyroid gland, with adipocytes stemming from the adipose tissue of the mediastinum adhering to the thyroid.
Because in our review ; we did not notice other types of inclusions like muscular or cartilaginous tissue (with the exception of parathyroid tissue which is frequently found), we do not share the opinion that they represent inclusion of mesenchymal fat and sometimes muscle during embryologic development. We did not neither notice any relationship between adipose involution and malignancy, because with the exception of the princeps case (9 mm papillary carcinoma), there was a trend to notice fewer cases with adipocytes in the context of malignancy (6.5% vs 18.5 %.) compared to benign pathology.
Concerning the metaplastic or involutive nature of intraparenchymal adipocytes, it is in our opinion difficult to have a definitive opinion, we prefer to consider it as involutive in comparison with the parathyroid glands which very often show adipose involution. Lipomatosis of the thyroid is in our opinion a misnommer, our princeps case which was the only one with enough adipocytes to get noticed, showed no significant enlargement of the thyroid gland, and the adipose component was not macroscopically seen.

Documents de pathologie humaine du service d’anatomie pathologique du CFB de Caen et du CHPC de Cherbourg. L ’UTILISATION DES INFORMATIONS FOURNIES SE FAIT SOUS L’UNIQUE RESPONSABILITE DE L’UTILISATEUR. Les concepteurs et réalisateurs de cette base ne sauraient en aucun cas être tenus pour responsables des conséquences d’une utilisation non contrôlée des informations fournies.

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