Multiple endocrine neoplasia IIA, also known as Sipple syndrome, is a rare entity that is difficult to diagnose and potentially fatal and is caused by RET proto-oncogene mutations. The importance of its diagnosis and determination of this mutation in the patient and his/her consanguineous relatives lies in avoiding the appearance of medullary thyroid cancer by means of prophylactic thyroidectomy and follow-up at the appearance of pheochromocytoma or parathyroid adenoma. We present the case of a female asymptomatic patient with the TGC34AGC-Cys634Arg mutation who was diagnosed with medullary thyroid carcinoma and bilateral pheochromocytoma, had a family history of thyroid and adrenal tumor-related deaths, was treated for curative purposes, and in whom the diagnosis was suspected by screening studies. (creativecommons.org/licenses/by-nc-nd/4.0/).

78-83Resumen La neoplasia endocrina múltiple IIA, conocida también como síndrome de Sipple, es una entidad rara, de difícil sospecha diagnóstica y potencialmente mortal, ocasionada por mutaciones en el protooncogén RET. La importancia de su diagnóstico y de la determinación de esta mutación en el paciente y en sus familiares consanguíneos radica en evitar la aparición de cáncer medular de tiroides mediante la extirpación profiláctica de esta glándula y el seguimiento ante la aparición de feocromocitoma o adenoma paratiroideo. Presentamos el caso de una paciente asintomática con la mutación TGC634AGC-Cys634Arg diagnosticada de carcinoma medular de tiroides, con feocromocitoma bilateral e historia familiar de decesos por tumores de tiroides y suprarrenales; se trató con fines curativos y el diagnóstico se sospechó mediante estudios de tamizaje. (creativecommons.org/licenses/by-nc-nd/4.0/).

Gaceta Mexicana de Oncologia. 2017;16(5):295-298 Resumen La neoplasia endocrina múltiple tipo IIA, conocida también como síndrome de Sipple, es una entidad rara, de difícil sospecha diagnóstica, potencialmente mortal y ocasionada por abmutaciones en el protooncogén RET. La importancia de su diagnóstico y de la determinación de esta mutación en el paciente y en sus familiares consanguíneos radica en evitar la aparición de cáncer medular de tiroides mediante la extirpación profiláctica de esta glándula y el seguimiento ante la aparición de feocromocitoma o adenoma paratiroideo. Nosotros presentamos el caso de una paciente asintomática con mutación TGC634AGC-Cys634Arg, en la cual se diagnosticó carcinoma medular de tiroides, feocromocitoma bilateral, historia familiar de decesos por tumores de tiroides y suprarrenales, que fue tratada con fines curativos y en la que el diagnóstico se sospechó mediante estudios de tamizaje. (creativecommons.org/licenses/ by-nc-nd/4.0/). abstract Múltiple endocrine neoplasia IIA, also know as sipple syndrome, is a rare entity, difficult to diagnose and potentially fatal, caused by RET proto-oncogene mutations. The importance of diagnosis and determination of this mutation in the patient and their consanguineous relatives lies in avoiding the appearance of medullary thyroid cancer by prophylactic thyroidectomy and the follow up before development of pheochromocytoma and/or parathyroid adenoma. We present the case of an asymptomatic patient with a tail gut cyst 634 AGC (Cys 634 Arg) mutation who was diagnosed with medullary thyroid carcinoma, bilateral pheocromocytoma, family history of deaths from thyroid and adrenal tumors who was treated for curative purposes and in whom the diagnosis was suspected through screening studies. PalaBRaS ClaVENeoplasia endócrina múltiple tipo IIa; Carcinoma medular de tiroides; Feocromocitoma; Protooncogén RET KEy woRDSMultiple endocrine neoplasia IIa; Medullary thyroid carcinoma; Pheochromocytom; Proto-ongogen-RET

Multiple endocrine neoplasia IIA, also known as Sipple syndrome, is a rare entity, difficult to diagnose and potentially fatal, caused by RET proto-oncogene mutations. The importance of diagnosis and determination of this mutation in the patient and their consanguineous relatives lies in avoiding the appearance of medullary thyroid cancer by prophylactic thyroidectomy and the follow up before development of pheochromocytoma and/or parathyroid adenoma. We present the case of an asymptomatic patient with a tail gut cyst 634 AGC (Cys 634 Arg) mutation who was diagnosed with medullary thyroid carcinoma, bilateral pheocromocytoma, family history of deaths from thyroid and adrenal tumors who was treated for curative purposes and in whom the diagnosis was suspected through screening studies.