xtragenital adenomatoid tumour of the omentum: an unusual location

Introduction Adenomatoid tumours are benig - n neoplasms that are mesothelial in origin and are usually confined to the genital tract and have rarely been reported at other sites such as the omentum, pleura, heart, liver, adrenal gland, retroperitoneum and intestinal mesentery. This paper discusses the unusual location of an extragenital adenomatoid tumour of the omentum. Case report We report the case of a 32-year-old woman who presented to our hospital with a four-day history of fever and pain in the right iliac fossa. Ultrasonography revealed a right ovarian cyst which was 2.5 cm in diameter and fluid in douglaseio. A right partial oopho - rectomy was performed, and duri - ng the operation, a well circu - mscribed mass measuring 2 cm was observed in the omentum. Histological evaluation of the cyst showed features of a cracked lute - al cyst and the mass showed feat - ures of an adenomatoid tumour. In the immunohistochemical study, the lesional cells were positive for calretinin, D240, CK5/6, HMBE1, CKAE1, CKAE3 and calponin. The treatment in such cases is tumour excision. W e report the case of an unusual extragenital adenomatoid tumour.


Introduction
Adenomatoid tumours are benign neoplasms that are mesothelial in origin and are usually confined to the genital tract.In men, these tumours occur in the epididymis, testicular tunics, prostate, spermatic cord and the parenchyma of the testis.In women, these tumours have been reported to occur in the uterus, fallopian tubes and rarely in the ovaries 1,2,3,4 .However, rare, extragenital adenomatoid tumours have been reported at other sites such as the omentum, pleura, heart, liver, adrenal gland, retroperitoneum, intestinal mesentery and lymph nodes 5,6,7,8 .Initially, its mesothelial origin was suggested in 1942, but the term 'adenomatoid tumour' was coined by Golden and Ash in 1945 9 .Today, the mesothelial differentiation of adenomatoid tumours is well recognised from the histology, immunophenotype and ultrastructure of these tumours 1,2,10 .In this report, we have described another unusual location for adenomatoid tumours.

Case report
We report the case of a 32-yearold woman who presented to our hospital with a fourday history of fever and pain in the right iliac fossa.There was no family history of malignancy.Laboratory investigation including complete blood count, biochemical examination and tumour markers (CEA, Ca19-9, Ca125), was normal.Ultrasound and abdominal and pelvic computed tomography revealed a right ovarian cyst which was 2.5 cm in diameter and fluid in douglaseio.A right partial oophorectomy was performed, and during the operation, a well-circumscribed mass measuring 2 cm was observed in the omentum.Histological evaluation of the cyst showed features of a cracked luteal cyst.On microscopic examination, the mass had a variable structural pattern consisting of cysts, tubular channels and glandlike spaces lined by flattened or cuboidal cells.Many cells had vacuolated cytoplasms and signet-ring or lipoblastlike cell morphology.Stroma consisted of loose or dense collagen tissue with hyalinisation.Marked cytologic atypia, tumour cell necrosis or mitotic figures were not seen (Figures 1[A] and  1[B]).In the immunohistochemical study, the lesional cells were positive for calretinin, D240, CK5/6, HMBE1, CKAE1, CKAE3 and calponin (Figure 2).Histochemical analysis of the tumour showed a lack of mucin, a feature aiding distinction from metastatic adenocarcinoma.Based on the above characteristic morphological and immunohistochemical findings, a diagnosis of adenomatoid tumour was made.The patient was free of recurrence three years after surgery.

Discussion
The mesothelial origin of adenomatoid tumours is widely accepted and is supported by electron microscopy and immunohistochemical studies.However, multiple histogenetic origins have been proposed for these tumours by different authors, including mesothelial, mesonephric, müllerian and endothelial origins 1,2,10  Stroma may consist of loose or dense collagen tissue with hyalinisation and may contain aggregates of lymphocytes.A variety of immunohistochemical markers have been reported to identify adenomatoid tumours such as calretinin, CK5/6, D240, caldesmon, CKAE1, CKAE3, caplonin, HMBE1 and WT1 1,2,11,12,13 .Calretinin is a calcium binding protein that is located both in the cytoplasm as well as the cell nucleus and has a high sensitivity for identifying mesothelial cells.Adenomatoid tumours do not express the vascular markers CD31, CD34 and factor VIII 1,2,7,12 .These tumours are usually solitary and patients are commonly asymptomatic.The tumours are often found incidentally during radiological examination or surgical procedures 1,2,7 .Some case reports describe multiple adenomatoid tumours occurring mainly in the genital tract 13,14,15 .Although adenomatoid tumours have a distinct histological appearance, their differential diagnosis maybe problem-atic, including vascular neoplasms, germ-cell tumours, malignant mesothelioma and metastatic adenocarcinoma.Adenomatoid tumours may be difficult to diagnose on frozen section examination especially when rare, extragenital adenomatoid tumours are incidental surgical findings 2,7,14 .

Conclusion
Adenomatoid tumours are often found incidentally during surgical procedures.Tumour excision is therefore the treatment of choice.
. The reason for an apparent predominance of these tumours in the genital Licensee OA Publishing London 2013.Creative Commons Attribution Licence (CC-BY) F : Skafida E, Tsavari A, Koulia K, Myoteri D, Grammatoglou X, Zisi A, et al.Εxtragenital Adenomatoid tumour of the omentum: an unusual location.OA Case Reports 2013 Jan 31;2(1):4.tract has not been explained.Adenomatoid tumours have a distinct but variable structural pattern ranging from irregularly arranged, dilated tubular channel, cysts and gland-like spaces lined by flattened or cuboidal cells to solid nests.Many cells have vacuolated cytoplasms and a signetring or lipoblast-like cell morphology.

Figure 1 :
Figure 1: Microscopically, the cells of the tumour have a vacuolated cytoplasm and a signet-ring or lipoblast-like cell morphology; the stroma consists of loose or dense collagen tissue with hyalinisation.Marked cytologic atypia, tumour cell necrosis or mitotic figures, are not present.Figure 1(A): haematoxylin and eosin × 100. Figure 1(B): haematoxylin and eosin × 400.