J Cutan Pathol 2007 doi: 10.1111/j.1600-0560.2007.00766.x Blackwell Munksgaard. Printed in Singapore Copyright # Blackwell Munksgaard 2007 Journal of Cutaneous Pathology Acne inversa complicated by squamous cell carcinoma in association with diffuse malignant peritoneal mesothelioma arising in the absence of predisposing factors: a case report Diffuse malignant peritoneal mesothelioma (DMPM) is a relatively rare neoplasm. Risk factors associated with its development include asbestos exposure, chronic irritation or inflammation of the peritoneum, abdominal radiotherapy, familial Mediterranean fever and simian virus 40. A familial segregation of this neoplasia has been reported in small villages of the Cappadocian region of Turkey, and it has been postulated that hereditary factors may predispose to mesothelioma, even with exposure to small amounts of asbestos. We report a case of DMPM, which apparently occurred in the absence of predisposing factors in a patient with a clinical history characterized by recurrent pre-sacral acne inversa of long duration. The association of this chronic inflammatory disease with DMPM has never been reported. The genetic locus for acne inversa has recently been identified within the 1p21.1–1q25.3 chromosomal region. Interestingly, frequent losses in chromosomal region 1p.21–22 have been found in mesothelioma as well. It is thus tempting to speculate that genetic mutations involving chromosome 1p.21–22 may account for the development of both diseases. Barresi V, Vitarelli E, Barresi G. Acne inversa complicated by squamous cell carcinoma in association with diffuse malignant peritoneal mesothelioma arising in the absence of predisposing factors: a case report. Valeria Barresi, Enrica Vitarelli and Gaetano Barresi Dipartimento di Patologia Umana, Policlinico Universitario G. Martino, University of Messina, Italy Dr Valeria Barresi, MD, Dipartimento di Patologia Umana, Policlinico Universitario G. Martino, Pad D, Via Consolare Valeria, 98122 Messina, Italy Tel: 0039902212537 Fax: 0039902338324 e-mail: valeriabarresi@hotmail.com Accepted for publication February 26, 2007 Diffuse malignant peritoneal mesothelioma (DMPM) is a relatively rare neoplasm arising from the pelvic and abdominal peritoneum and accounting for approximately one-third of all cases of mesotheli- oma. 1,2 The pathogenesis of DMPM has been linked to asbestos exposure, even if such a correlation is less obvious than that for pleural mesothelioma. 3,4 Aside from asbestos, other risk factors associated with the development of this neoplasia include abdominal radiotherapy, 5,6 familial Mediterranean fever, 7 recur- rent peritonitis 8 and simian virus 40. 9,10 Recently, hereditary factors have also been claimed to be determinants of the apparent auto- somal dominant transmission of malignant meso- thelioma in families living in small villages of the Cappadocian region of Turkey. 11 Hereditary factors seem to behave as cofactors with asbestos exposure in the pathogenesis of mesothelioma. Moreover, DMPM has been found in association with hered- itary syndromes, such as Marfan and Ehlers-Danlos syndromes, and it has been speculated that genetic factors in these patients may predispose them to 1