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A rare case of primary retroperitoneal mucinous neoplasm in a male patient Sir, Primary retroperitoneal mucinous neoplasms [cystadenomas, mucinous tumours of borderline malignancy (MTBM) and cystadenocarcinomas] are extremely rare entities almost exclusively affecting women. However, less than 12 cases of primary retroperitoneal mucinous neoplasms (PRMNs), including cystadenomas, MTBMs and cystadenocarcinomas have been reported in males.1–3 Here, we present the fifth case of a primary retroperitoneal mucinous neoplasm with borderline malignancy presenting in a male patient in the English literature and, to the best of our knowledge, the first case reported in Australia. A 68-year-old Caucasian male, who was otherwise healthy, presented with a self-detected palpable right abdominal mass. Contrast computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated a large cystic mass occupying most of the right abdomen (Fig. 1A). An endoscopic ultrasound excluded a pancreatic neoplasm. Apart from a slightly raised CA19, all other serum tumour markers including AFP and CEA were within normal reference ranges. Bearing in mind a potential malignant retroperitoneal tumour (e.g., liposarcoma), laparotomy was performed for therapeutic and diagnostic purposes. The operative findings revealed a localised tumour in the right lateral retroperitoneal wall adherent to the ureter, which was dissected free and intact from surrounding structures. There was no evidence of peritoneal spread or involvement of the kidney, appendix, pancreas, large and small bowel. Both testes were descended and normal on examination. Grossly, the encapsulated tumour weighed 1348 g and measured 160  145  110 mm (Fig. 1B). Cut sections of the mass revealed multilocular cystic spaces (Fig. 1C), the largest of which measured up to 150 mm. The cystic spaces were filled with mucoid material and areas of calcification were also present. Microscopically, the fibrous walls of the cystic spaces were lined by flattened to cuboidal, intestinal-type mucinous epithelium. The epithelium showed focal nuclear stratification, occasional papillary excrescences, mild cytological atypia and a few mitoses (Fig. 2A–C). No ovarian-like stroma, mural nodules or stromal invasion were seen. PAS/D confirmed the presence of intracytoplasmic vacuoles and immunoperoxidase stains of the epithelial lining showed an intestinal phenotype with positive staining for CK20 and CDX2 (Fig. 2D,E). CK7 showed focal staining while TTF1 and PAX8 stains were

A

B

negative. Based on the morphology and immunophenotype, and more importantly on the clinical exclusion of metastases or extension of mucinous neoplasm from elsewhere, the diagnosis of a primary retroperitoneal MTBM was made. Motoyama reported the first case of primary retroperitoneal mucinous tumour in a male patient,4 following which only a few isolated cases of PRMNs in male patients have been presented.2,3,5,6 PRMNs are classified following their counterparts arising in the ovary7 into three pathological types: mucinous cystadenoma, mucinous cystic tumours of borderline malignancy (tumours of low malignant potential) and mucinous cystadenocarcinoma. PRMNs are classified as cystadenomas when the tumours are lined by a single layer of mucinous epithelium. MTBMs show nuclear enlargement and pseudostratification in at least 10% of the neoplasm and no cytological atypia. Criteria for the diagnosis of intraepithelial carcinoma, invasion/microinvasion and mural nodules with associated anaplastic carcinoma or sarcomatoid carcinoma are similar in application to their ovarian counterparts.7 PRMNs of borderline malignancy with areas of microinvasion, intraepithelial carcinoma or mural nodules are yet to be described in male patients. However, there are at least five reported cases showing frank invasion and qualifying as mucinous cystadenocarcinomas reported in males.8 Similar to our case, other PRMNs have shown extensive calcification of the wall with pools of extravasated mucin and collagenous stroma.2 An intestinal phenotype with focal or diffuse expression of CK7 has been consistent among the reported cases2,7,9 as well as the expression of pan-cytokeratins and CEA. Although ovarian-like stroma has been seen in some of the female cases,7 this finding has not been documented in any of the male counterparts including our case. FNA has failed to reveal the type of epithelial lining in a few of the published cases5 and, although this was not performed in our case, the dense mucinous content and the frequent denudation of the epithelium would explain the difficulty in obtaining diagnostic material. Similar to our case, other reported PRMNs were adherent to the kidney or ureter, and therefore have been clinically and radiologically considered to be arising from or involving the upper urinary tract.5,10 The pathogenesis of PRMNs is unknown and widely debated with several theories proposed. Due to their similarity to ovarian tumours on histology, one theory suggested that PRMNs originated from ectopic ovarian tissue.11 However, this does not explain the occurrence in male patients and only a handful of female cases have shown ovarian tissue.7 Alternative theories include origin from a retroperitoneal monodermal teratoma with preponderance of mucinous epithelium12 or that

C

Fig. 1 (A) Abdominal CT scan; (B) fresh specimen; (C) fixed bivalved tumour.

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B

A

C

D

E

Fig. 2 H&E section shows a multilocular cystic lesion (A) with an intestinal type mucinous epithelium with focal nuclear stratification and occasional papillary tufts (B). Mild cytological atypia and scant mitotic figures were present (C). The intestinal immunophenotype was confirmed with positive staining for CK20 (D) and CDX2 (E).

these tumours are remnants of the urogenital apparatus.2,7,9 However, the most widely accepted theory is that PRMNs are derived from multi-potential mesothelial cells which become entrapped in the retroperitoneum during embryonic development. These mesothelial cells subsequently undergo metaplasia to mucinous epithelium creating the mucinous cysts.11 Before assigning a diagnosis of PRMN, other considerations should be excluded by careful clinical examination, diagnostic imaging and thorough macroscopic and microscopic evaluation. The differential diagnosis includes other soft tissue retroperitoneal tumours (e.g., liposarcomas, fibrosarcomas, malignant fibrous histiocytomas, neurofibromas and rhabdomyosarcomas), and tumours arising from the kidney and ureter. More importantly relating to our case, the exclusion of a metastatic or extension of a mucinous tumour from the gastrointestinal tract, in particular from the pancreas and appendix, is required before rendering a diagnosis of PRMN. As the retroperitoneum has no epithelial cells, the exclusion of a cystic teratoma arising from an undescended testis is also paramount and it was excluded in our case. Although the hypothesis of PRMNs arising from a monodermal variant of teratoma is a consideration which cannot be completely discarded, there are some differences in clinical presentations comparing our case to other reported cases of primary retroperitoneal teratomas.13 – 15 The incidence of primary retroperitoneal teratomas is bimodal with peaks in the paediatric population and early adulthood and a 2:1 female predominance. Retroperitoneal teratomas in adult patients were most often located near the upper pole of the kidney, with preponderance on the left side.13,15 Despite a thorough search of the literature, none of the reported cases of primary retroperitoneal teratoma showed a pure population of intestinal type epithelium, with the majority showing differentiation from the three germinal layers.13 – 15 Hence, the preferred diagnosis of PRMN.

Overall, the prognosis of PRMNs in males has been excellent with no recurrence, metastasis or cancer-associated deaths reported,3 including cases of mucinous cystadenocarcinoma.8 The cancer-associated deaths due to PRMNs reported in women have been consistently associated with the presence of mural nodules with anaplastic carcinoma or high grade sarcoma,7 which again have not yet been described in the male counterparts. Resection in male PRMNs has been curative with no studies supporting the use of chemotherapy.8,16 However, due to limited surveillance data, the behaviour is difficult to predict and prognosis of recurrence is unknown. Although PRMNs are rare, they should be considered in the differential diagnosis of retroperitoneal tumours. They are a diagnosis of exclusion following careful clinical examination, diagnostic imaging studies and microscopic evaluation. Surgical excision remains the treatment of choice. In summary, we present a case of a primary retroperitoneal mucinous neoplasm with borderline malignancy, which to the best of our knowledge is a rare entity not previously reported in Australian literature. Acknowledgements: We would like to thank the patient for kindly giving consent to publish this case. We also thank Dr Joanne Brown for her contribution in the proofreading of the manuscript. Conflicts of interest and sources of funding: The authors state that there are no conflicts of interest to disclose. Ana Cristina Vargas1 Vincent Lam2 Chow Heok P’ng13 1

Tissue Pathology and Diagnostic Oncology, ICPMR, Westmead Hospital, 2Hepatobiliary, Pancreatic and

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Trasnsplant Surgery, Sydney Medical School and Westmead Hospital, and 3School of Medicine, University of Western Sydney, Sydney, NSW, Australia Contact Dr Chow Heok P’ng. E-mail: [email protected] 1. Bakker RF, Stoot JH, Blok P, et al. Primary retroperitoneal mucinous cystadenoma with sarcoma-like mural nodule: a case report and review of the literature. Virchows Arch 2007; 451: 853–7. 2. Falidas E, Konstandoudakis S, Viachos K, et al. Primary retroperitoneal mucinous cystadenoma of borderline malignancy in a male patient. Case report and review of the literature. World J Surg Oncol 2011; 9: 98. 3. Mattei J, Kim FJ, Phillips J, et al. Male primary retroperitoneal mucinous cystadenoma. Urology 2013; 82: e1–2. 4. Motoyama T, Chida T, Fujiwara T, et al. Mucinous cystic tumour of the retroperitoneum. A report of two cases. Acta Cytol 1994; 38: 261–6. 5. Prabhuraj AR, Basu A, Sistla SC, et al. Primary retroperitoneal mucinous cystadenoma in a man. Am J Clin Oncol 2008; 31: 519–20. 6. Benkirane A, Mikou A, Jahid A, et al. Primary retroperitoneal mucinous cystadenoma with borderline malignancy in a male patient: a case report. Cases J 2009; 2: 9098. 7. Roma AA, Malpica A. Primary retroperitoneal mucinous tumors: a clinicopathologic study of 18 cases. Am J Surg Pathol 2009; 33: 526–33. 8. Feng J, Liu H, Chen D. Primary retroperitoneal mucinous cystadenocarcinoma in a male patient: a rare case report. Hippokratia 2013; 17: 271–3. 9. Bosisio FM, Estevez Segura SJ. Mucinous cystadenoma of the retroperitoneum. Int J Surg Pathol 2013; 21: 150–2. 10. Fujita N, Nishie A, Asayama Y, et al. A male case of primary retroperitoneal mucinous cystadenoma: a diagnostic dilemma. Jpn J Radiol 2012; 30: 594–7. 11. Matsubara M, Shiozawa T, Tachibana R, et al. Primary retroperitoneal mucinous cystadenoma of borderline malignancy: a case report and review of the literature. Int J Gynaecol Pathol 2005; 24: 218–23. 12. Papadogiannakis N, Gad A, Ehliar B. Primary retroperitoneal mucinous tumour of low malignant potential: histogenetic aspects and review of the literature. APMIS 1997; 105: 483–6. 13. Chaudhary A, Misra S, Wahklu A, et al. Retroperitoneal teratomas in children. Indian J Pediatr 2006; 73: 221–3. 14. Sato F, Mirmata H, Mori K. Primary retroperitoneal mature cystic teratoma presenting as an adrenal tumour in an adult. Int J Urol 2010; 17: 817. 15. Bhatti A, Al-Hindi H, Azzam A, et al. Mature (benign) cystic retroperitoneal teratoma involving the left adrenal gland in a 22-year-old male: a case report and literature review. Case Rep Oncol Med 2013; 103: 610. 16. Shiau JP, Wu CT, Chin CC, et al. Long-term survival after hand-assisted laparoscopic approach of primary retroperitoneal mucinous cystadenocarcinoma in male: case report and review of literature. Eur Surg 2013; 45: 106–9.

DOI: 10.1097/PAT.0000000000000261

and early generation cephalosporins are potent inducers, yet are good substrates for AmpC activity, accounting for intrinsic resistance in these species. Carbapenems are strong inducers, but are stable to hydrolysis by AmpC, whereas cefotaxime, ceftriaxone, ceftazidime and piperacillin are less potent inducers.1 However, high level AmpC expression can occur, with a phenotype that demonstrates resistance to third generation cephalosporins (3GCs) and b-lactam/b-lactamase inhibitor combinations (such as piperacillin-tazobactam), by mutations in regulatory genes.1 Tazobactam is not an efficient inhibitor of AmpC, so the piperacillin component can be hydrolysed if enough AmpC is present. These AmpC hyper-producing (or ‘de-repressed’) variants may be selected by exposure to b-lactam antibiotics, and lead to clinical failure despite apparent initial susceptibility, especially with the use of 3GCs.2,3 There is uncertainty as to whether the concerns over clinical failure with 3GCs in the treatment of AmpC producers can be extrapolated to agents such as piperacillin-tazobactam. Few clinical studies have addressed this issue directly.4 There is considerable variation across Australia and other countries with respect to laboratory reporting practice for AmpC producers. We surveyed microbiologists and infectious disease physicians in Australia, New Zealand and Singapore to sample current practice in the region. The survey (using the web-based service www.surveymonkey.com) was distributed to infectious disease physicians and microbiologists who are part of the Australasian Society for Infectious Disease Ozbug network (a webmail discussion group) and the Society for Infectious Disease Singapore (SIDS) group in Singapore. There were a total of approximately 690 individuals on the combined mailing lists. Full details of the survey can be found in Supplementary Fig. 1, http://links.lww. com/PAT/A31. There were 84 respondents to the survey (approximately 12%); characteristics of the participants are presented in Table 1. The majority (99%) practised, at least in part, within public hospitals or laboratories. Only the 26 (31%) respondents who were routinely responsible for validation of laboratory susceptibility test reports were directed to complete questions on laboratory reporting. Of these, 52% used Clinical and Laboratory Standards Institute (CLSI) standards, 40% European Committee on Antimicrobial Susceptibility Testing Table 1

Antimicrobial susceptibility reporting and treatment selection for AmpC-producing Enterobacteriaceae: what do microbiologists and infectious disease practitioners actually practice? Sir, Antimicrobial susceptibility reporting for infections caused by bacteria that express inducible AmpC b-lactamases is problematic. AmpC b-lactamases are broad-spectrum cephalosporinases encoded on the chromosomes of several species within the Enterobacteriaceae. These are of key importance in Enterobacter species, Citrobacter freundii, Serratia marcescens, Providencia speciesand Morganella morganii. In these species, AmpC is inducible following exposure to b-lactams, which vary in their ability to induce AmpC production and their stability to the enzyme. For instance ampicillin, amoxicillin

Respondent characteristics

Participant details Professional status Infectious disease physician Clinical microbiologist Infectious disease physician/microbiologist Infectious disease or microbiology trainee Other Location of practice Australia – VIC Australia – NSW Australia – QLD Australia – WA Australia – ACT Australia – TAS Australia – SA Australia – NT Singapore New Zealand Other country Total

n

%

34 6 16 25 3

40.5 7.1 19.0 29.8 3.6

18 16 17 8 2 3 2 0 13 3 2 84

21.4 16.0 20.2 8.0 2.0 3.0 2.4 0 15.5 3.6 2.4

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A rare case of primary retroperitoneal mucinous neoplasm in a male patient.

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