Purpose: Pleural nodular histiocytic/mesothelial hyperplasia is a nodular histiocytic/ mesothelial proliferation, often delimiting cystic cavities, due to irritation by a pulmonary noxa. Case report results: The patient had right pleural parietal and diaphragmatic thickness, with pleural effusion, without lung alterations. He previously underwent left hemicolectomy and liver resection, due to a diverticulitis and a liver histiocytes-rich abscess. Video-assisted thoracoscopy biopsy showed a double population of reactive mesothelial cells and histiocytes. Conclusion: Nodular histiocytic/mesothelial hyperplasia represents a potential pitfall for pathologists. Immunohistochemistry is crucial for the differential diagnosis with some malignancies. We suggest that in our patient, a chronic mesothelium inflammation happened by transdiaphragmatic involvement as a consequence of the liver abscess. Some pathogenetic mechanisms are hypothesized.
KEYWORDS• mesothelial hyperplasia • pleural effusion • VATS 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][3][4][5][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, mechanical or tumor stimulation [11].The rarity of NHMH and the moderate cytological atypia often present, make this lesion difficult to diagnose. It can be easily confused with primary mesothelial lesions and neoplasms such as adenocarcinomas, granulosa cell tumors or Langerhans' histiocytosis.We report a case of pleural NHMH in a patient with a subphrenic abscess, in which no pulmonary pathogenic noxa was evident. We hypothesize a transdiaphragmatic chronic irritation as a pathogenetic mechanism underlying NHMH.
Case reportA 57-year-old man presented to our department in June 2014, due to the presence of a right pleural effusion with undefined diagnosis. At admission he had no fever, infections or history of exposure to asbestos and other dust. Shortness of breath after moderate exertion was noted, blood pressure was 130/85 mmHg and heart rate 77 bpm with normal sinus rhythm. Physical examination showed abolition of breath sounds and fremitus on all fields on the right side and dullness plexus. The patients drug history was negative. Due to the onset of pleural effusion and dyspnea, the patient For reprint orders, please contact: reprints@futuremedicine.com