Primary Cardiac Fibroma and Cardiac Conduction System Alterations in a Case of Sudden Death of a 4-month-old Infant
The infant was a female 4-months-old, born at 37 weeks of gestation, with a birth weight of 2270 g (low birthweight, at the 5th percentile). She was in apparent good health until the day she died, suddenly and unexpectedly. Her parents said that they knew of no illness or complaint of any nature, except for two episodes of vomit two days before. There was no significant family history relevant to the case. In particular, there was no familiarity for tuberous sclerosis and Gorlin’s syndrome (multiple nevoid basal carcinomas, jaw cysts, and bifid ribs), both associated with cardiac fibromas [].\nA complete autopsy was performed, according to the autopsy protocol usually followed by our center in cases of sudden death []. Multiple samples of all organs were fixed in 10% formalin buffer, processed, and embedded in paraffin. Five-micrometer sections were stained with hematoxylin and eosin. The heart had been regularly examined for pathological changes in the atria, septa, ventricules, pericardium, endocardium, and coronary arteries. Samples of the myocardium were stained with hematoxylin and eosin and trichromic Heidenhain (azan). Histological observations were focused on the cardiac conduction system, which was removed in two blocks, according to our guidelines []: the first included the sino-atrial node (SAN) and the “crista terminalis,” the second contained the atrioventricular node (AVN), His bundle, and bundle branches. The samples were stained alternately with hematoxylin and eosin and trichromic Heidenhain (azan).\nAt autopsy, the infant was described in good health, with body length and weight at the 5th percentile. There were no marks of violence. The lungs were congested and slightly edematous. The heart, arrived without the tip, weighed 25 g; the cardiac diameters were as follows: transverse 3.5 cm and anteroposterior 2.9 cm. We could not measure the longitudinal diameter due to the absence of the tip. The myocardium was brownish and homogeneous in appearance, without any evident alteration. The foramen of Botallo was open for about 3 mm. The coronaries appeared normal.\nHistological examination of the atrio-ventricular node showed an accessory fiber of Mahaim (nodo-ventricular), cartilaginous metaplasia of the cardiac fibrous body and pre-atherosclerotic lesions of the artery of the atrio-ventricular node (Fig. ). It was also present a non-encapsulated proliferation of fibroblasts with regular nuclei and an abundant network of collagen and elastic fibers that dissociated and entrapped the myocytes (Fig. ). These morphological features led to the diagnosis of primary cardiac fibroma compressing the atrio-ventricular node []. Mitotic figures and cytologic atypia were not observed. No foci of dystrophic calcification were present. The SAN, adjacent nerve plexuses, and internodal right atrial myocardium were free of alterations.