Nodular histiocytic/mesothelial hyperplasia as consequence of chronic mesothelium irritation by sub-phrenic abscess.

Nodular histiocytic/mesothelial hyperplasia (NHMH) is a benign localized alteration, first described in 1975 by Rosai in the hernia sac [1]. Few pulmonary cases have been reported in literature [2–6]. Sometimes it has been reported in the pericardium [7,8] or presenting as an inguinal mass [9]. The ‘mesothelial/monocytic incidental cardiac excrescence’, first described by Weinot et al. in 1994 [10] is now considered a similar lesion to NHMH [11]. It consists of a reactive proliferation of histiocytes and mesothelium secondary to chronic irritation and it has been observed in pleura-damaging processes, such as pneumothorax [5], or as consequence of cardiac catheterization, inflammation, mech…