Immature renal tissue occurring in cystic teratoma of ovary.

Abstract

A 25-year-old, G0P0 female had bilateral cystic teratoma history and had undergone laparoscopic partial oophorectomy at the ages of 18 and 22. A right ovarian mass was found on sonography during follow-up (Figure 1A). Subsequent contrast-enhanced computed tomography showed a 5.7 cm ovarian teratoma with ascites (Figure 1B). Two months later, she suffered from progressive abdominal cramping pain and visited the emergency room. Physical examination showed severe tenderness over the right lower abdomen. Lab data, including complete blood count, C-reactive protein, CEA, CA199 and SCC, were within the normal range. Under the suspicion of ovarian teratoma with torsion, laparoscopic partial oophorectomy was performed (Figure 1C). The specimen was totally embedded. Microscopically, the tumor contained solid and cystic components. The cystic part was lined by stratified squamous epithelium with pilosebaceous glands. The solid part included adipose tissue, hyaline cartilage, mature glial tissue, salivary gland, and islets of immature renal tissue-like structures, which were 9 mm in greatest dimension, consisting blastemal tissue, epithelial tubules, occasional glomeruli without atypia or conspicuous capsule. Immunohistochemical studies revealed that immature renal tissue was positive for WT1, partially positive for CD56 and CD99, and negative for ER, PR, INSM-1, S-100. Ki-67 index was focally increased (Figure 1D–H). The case was eventually diagnosed as teratoma with immature renal/nephroblastoma-like tissue. No adjuvant chemotherapy or radiotherapy was administered. The patient is alive and well 2 years after surgery without evidence of recurrence or metastasis. To the best of our knowledge, immature renal tissue in ovarian teratoma is extremely rare, with only three cases being reported previously (Table 1).1-3 The pathogenesis of the tumor was unclear, and various nomenclatures have been used to describe this phenomenon: immature renal tissue in teratoma, teratoma with nephroblastoma/Wilms tumor, and teratoid Wilms tumor. Coli et al. suggested that immature renal tissue is generally not aggressive and should be differentiated from a true Wilms tumor, based on atypia, atypical mitoses, marked pleomorphism and expanding growth.4 No standardized treatment has been established for teratomas with immature renal tissue or nephroblastoma. Li et al. proposed that the prognosis of teratoma with nephroblastoma is relatively good if the lesion is completely excised.5 According to the previous similar cases in Table 1, two cases received fertility-preserving surgery.1, 3 The other case showed intra-peritoneal dissemination shortly after primary excision of a ruptured tumor, and then complete remission after second complete staging surgery with adjuvant chemotherapy.2 1st surgery: Bilateral ovarian tumor removal 2nd surgery: Complete staging and maximum cytoreductive surgery + C/T Intra-peritoneal dissemination at 48 days after 1st surgery No disease progression after 2nd surgery + C/T and 1-year follow-up In conclusion, ovarian teratoma may contain immature renal tissue, which could be named as an immature component instead of nephroblastoma/Wilms tumor if no atypia or invasive growth is seen, as the nomenclature would affect the clinician in the evaluation of treatment. In the absence of atypia and invasive growth, complete tumor excision with careful follow-up seems an acceptable strategy. Chemotherapy can be considered when aggressive behavior occurs. The authors declare no conflict of interest.