Pulmonar collision tumor: Metastatic adenoid cystic carcinoma and lung adenocarcinoma

Introdução

Introduction Collision tumors are a rare condition in which two histologically different malignant neoplasms, originating from two separate primary sites, intermix with one another. The two malignancies may originate from the same organ or occur as metastases from other sites. There is no histological admixture or intermediate-transition cell population zone. These tumors are difficult to diagnose preoperatively and pathological identification of the dual components is often the only way to make a correct diagnosis.¹ Adenoid cystic carcinoma (ACC) is a malignant tumor that is commonly classified with the salivary gland tumors, although it may arise at any site where mucous glands exist. This tumor exhibits a unique malignant profile, which is characterized by slow growth and high propensity to systemic metastases. The lung is the most common site of metastasis, as pulmonary metastases have been reported in more than 38% of patients with ACC of the head and neck. Most patients with metastatic disease are relatively asymptomatic and may remain so for long periods.^{2, 3} Several case reports have been published in the literature, which describe a primary pulmonary collision tumor consisting of large-cell carcinoma and adenocarcinoma⁴ or squamous cell carcinoma and T-cell lymphoma.⁵ To our knowledge, this is the first report that describes a case of collision cancer in the lung consisting of a lung adenocarcinoma and a metastasis of an ACC diagnosed with immunohistochemical techniques performed after surgery. Case report A 56-year-old man with a previous history of adenoid cystic carcinoma of the right maxillary sinus (pT4N0Mx) that had been treated by right...