Incidentally Discovered Pulmonary Hamartoma: A Case Report and Review of the Literature.

Pulmonary hamartoma is a rare benign tumor of the lung. It predominantly affects older males and is frequently peripherally located. On chest radiography, it classically appears as a "coin lesion" exhibiting characteristic popcorn-like calcifications. We report the case of a 62-year-old male patient, a former smoker, being treated for multiple myeloma. A computed tomography (CT) scan revealed a solid, bilobed pulmonary nodule in the lingula measuring 8 mm in the long axis, for which he underwent surgical resection. Macroscopically, the tumor appeared whitish, multilobulated, well-defined, and firm in consistency. Histologically, the lesion is composed of four components: a predominant cartilaginous component with a lobulated architecture, made up of regular chondrocytes; an adipose component, made up of mature adipocytes; a muscular component made up of smooth, non-atypical muscle fibers; and, focally, a fibromyxoid component, associated with an entrapped ciliated respiratory epithelium. Immunohistochemical staining demonstrated positivity for smooth muscle actin and desmin in the smooth muscle cells. Through this case, we discuss the clinical, radiological, histopathological, molecular, and therapeutic aspects of pulmonary hamartoma, as well as the main differential diagnosis, based on data from the literature.