Endocrine Abstracts

JOINT1990

Introduction: Papillary thyroid carcinoma is the most common type of thyroid cancer. Metastases are often pulmonary and osseous, other sites, such as the pancreas, are possible but remain exceptional. We report the case of a patient with refractory and progressive papillary carcinoma under lenvatinib who, during follow-up, presented with a pancreatic mass, raising a diagnostic dilemma: is it a metastasis, a side effect of lenvatinib, or a primary tumor?

Case Report: A 75-year-old patient with a history of hypertension was diagnosed in 2018 with papillary microcarcinoma with lymph node metastases, classified as PT1aN1bMx. He underwent four courses of radioiodine therapy, totaling 550 mCi, with the last post-therapeutic scan revealing a right mediastinal fixation, confirmed by thoracic CT, with three additional pulmonary nodules. He did not return for follow-up until 2024, when imaging revealed inoperable pulmonary and cerebral metastases, leading to the initiation of treatment with lenvatinib, which showed a good therapeutic response. Five months after starting treatment, he presented with jaundice, fever, abdominal pain, and leukocytosis. CT imaging identified a 5 cm pancreatic mass, and histopathological analysis confirmed a well-differentiated adenocarcinoma of the pancreatic head with positive CK7 and CK19 immunostaining but negative TTF1. The patient was presented in a multidisciplinary (RCP digestive), where chemotherapy was decided upon; unfortunately, he passed away before treatment could begin.

Discussion: The discovery of a pancreatic mass raises several diagnostic hypotheses: Metastasis of thyroid cancer The multimodal metastatic nature in our patient suggests the possibility of pancreatic metastasis. However, this diagnosis is rarely reported and requires histopathological and immunohistochemical confirmation. Lenvatinib side effect Although lenvatinib is known for its efficacy, reported side effects include acute or chronic pancreatitis. The occurrence of neoplasia under tyrosine kinase inhibitors has been exceptionally documented Primary pancreatic neoplasia This association has been previously reported in the literature. Histopathology revealed an exocrine adenocarcinoma, strongly suggesting a primary origin. The occurrence of this second cancer could be incidental or linked to underlying genetic mechanisms.

Conclusion: This case highlights the complexity of diagnosis in such a challenging clinical context and underscores the need for a multidisciplinary approach to guide diagnosis and treatment.