Ana Echegoyen-Silanes

Varón de 57 años de edad, fumador, al que se le realiza punción aspiración con aguja fina guiada por ecobroncoscopia por presentar adenopatías hipercaptantes en la tomografía por emisión de positrones. La citopatóloga procesó in situ extensiones citológicas para evaluación rápida (Diff-Quick) y diferida (Papanicolaou). Con los fragmentos sólidos y los coágulos obtenidos realizó un bloque celular que se procesó como biopsia. En las extensiones se observaron células de aspecto histiocitoide con núcleos hendidos, inmunorreactivas para CD68, CD1a, Langerina y S100, con abundantes eosinófilos; el diagnóstico final fue de histiocitosis de células de Langerhans. El diagnóstico citológico preciso de esta entidad en ganglios mediastínicos supone un gran reto. Este caso queremos resaltar que un buen manejo del material por el citopatólogo presente en la sala es clave para rentabilizar el tejido y poder realizar las técnicas complementarias necesarias para un diagnóstico completo, evitando abordajes diagnósticos más agresivos.

Cribriform morular thyroid carcinoma (CMTC) is a rare malignant thyroid tumor with a peculiar growth pattern secondary to permanent activation of the WNT/β-catenin pathway. CMTC may be associated with familial adenomatous polyposis or sporadic; it shares morphological features with papillary thyroid carcinoma (PTC) and was considered a variant of PTC in the 2017 WHO classification of tumors of endocrine organs. The new 5th edition of the WHO classification of endocrine and neuroendocrine tumors considered CMTC an independent thyroid neoplasm of uncertain histogenesis. A thymic/ultimobranchial pouch-related differentiation in CMTC has been recently postulated. We, however, have used the pathological and immunohistochemical features of this case of CMTC with 2 novel oncogenic somatic variants (c.3428_3429insA, p.(Tyr1143Ter) and c.3565del, p. (Ser1189Hisfs*76) of the APC gene to propose an origin from follicular cells (or their endodermal precursors). As usual in CMTC, the morular component of this tumor was positive for CDX2. Given the fact that WNT/β-catenin signaling, through CDX2, activates large intestine and small intestine gene expression, we postulate that in CMTC, the tumor cells have their terminal differentiation blocked, thus showing a peculiar primitive endodermal (intestinal-like) phenotype negative for sodium-iodide symporter, thyroperoxidase, and thyroglobulin. Establishing the histogenesis of CMTC is very relevant for the development of appropriate therapies of redifferentiation, particularly in patients where the tumor cannot be controlled by surgery.