British Journal of Radiology 75 (2002),772-774 © 2002 The British Institute of Radiology
Primary osteosarcoma of the uterus with peritoneal osteosarcomatosis: CT features
J-W Lin, MD
1
S-F Ko, MD
2
S-H Ng, MD
2
H-L Eng, MD
1
C-C Changchien, MD
3 and
C-C Huang, MD
1
Department of 1 Pathology, 2 Radiology and 3 Obstetrics and Gynecology, Chang Gung University, Chang Gung Memorial Hospital, Kaohsiung, Taiwan
Correspondence: S-F Ko, MD, Department of Radiology, Chang Gung Memorial Hospital at Kaohsiung, 123 Ta-Pei Road, Niao-Sung Hsiang, Kaohsiung Hsien, 833, Taiwan
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Abstract
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A 67-year-old woman presented with lower abdominal pain for 1 month. Pelvic ultrasound revealed a calcified uterine mass and ascites. CT showed a heavily calcified uterine tumour, with ascites and disseminated calcified nodules in the peritoneum. Microscopic and immunohistochemical studies demonstrated features typical of osteosarcoma without any epithelial differentiation. Although rare, uterine osteosarcoma with associated peritoneal osteosarcomatosis should be included in the differential diagnosis of an elderly woman with a calcified uterine mass and disseminated peritoneal calcifications.
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Introduction
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Uterine sarcomas are uncommon, accounting for 1–2% of all uterine neoplasms [1]. They are frequently classified as either homologous, referring to tumours that consist of tissue normally found within the uterus, or heterologous, implying those with tissue foreign to the uterus [2]. Pure heterologous osteosarcoma is a very unusual type of uterine sarcoma and, to the best of our knowledge, only 16 cases have been previously documented [2–7]. We describe the CT features of a case of primary uterine osteosarcoma and suggest that the presence of disseminated calcified nodules in the peritoneum may be a clue to the diagnosis of this unusual tumour.
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Case report
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A 65-year-old Chinese woman, gravida 4, para 4, suffered from dull, lower abdominal pain for 1 month with no history of vaginal bleeding. Her last menstrual period occurred 15 years prior to this admission. A physical examination revealed a hard, non-tender mass in the upper pelvis. Laboratory findings and a chest radiograph appeared normal. Pelvic ultrasound revealed a large hyperechoic mass with a typical acoustic shadow in the pelvis suggestive of a calcified tumour in the uterine corpus. Ascites was also present. CT demonstrated a 10 cm, heavily calcified uterine mass with an eccentric necrotic area and poor demarcation of the mass with the adjacent pelvic structures. In addition to ascites, disseminated calcified nodules throughout the whole peritoneal cavity and omentum (Figure 1
) were also present, but no ovarian mass or abnormal retroperitoneal lymph nodes were observed. The liver, spleen and pancreas appeared normal. An exploratory laparotomy revealed a large and stony-hard tumour in the uterus with invasion of the bladder, rectum and adjacent pelvic fat and widespread dissemination of hard nodules within the peritoneal cavity. Since the tumour was unresectable, an omentectomy as well as multiple biopsies of the uterine tumour and thorough sampling of the peritoneal nodules were performed. Under light microscopy, all surgical specimens demonstrated the typical appearances of osteosarcoma with conspicuous malignant bone and osteoid components (Figure 2). Immunohistochemically the tumour cells stained positively for vimentin, although stains for antibodies to cytokeratins, epithelial membrane antigen, desmin, smooth muscle actin and S-100 (DAKO A/S, Glostrup, Denmark) were uniformly negative, indicating lack of epithelial differentiation. A final diagnosis of primary pure heterologous uterine osteosarcoma with peritoneal osteosarcomatosis was established. The patient underwent chemotherapy with cisplatin and 5-fluouracil post-operatively and was still alive at 6-month follow-up. However, owing to severe discomfort following chemotherapy, she refused any further treatment or follow-up.
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Figure 1. Enhanced CT at the level of (a) the mid abdomen and (b) the pelvis reveals ascites, multiple calcified nodules in the peritoneum and omentum, and an ill defined uterine mass with dense calcifications and an eccentric, hypodense necrotic area.
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Figure 2. Histopathological examination (haematoxylin and eosin, original magnification x330) reveals malignant osseous and osteoid components that are typical features of osteosarcoma.
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Discussion
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Leiomyosarcomas, mixed mesodermal tumours (malignant mixed Müllerian tumours (MMMT)) and endometrial stromal tumours are three predominant varieties of uterine sarcomas, accounting for more than 95% of reported cases [1, 2]. Leiomyoma appears to be the most common calcified uterine mass, with a prevalence of sarcomatous changes of 0.13% for patients undergoing surgery for leiomyoma [2, 8]. Endometrial stromal tumours appear rarely to calcify [2]. MMMT are uncommon tumours of the endometrium, presenting as calcified uterine masses derived from primitive Müllerian epithelial cells capable of differentiating to epithelial and mesenchymal elements. Sarcomatous changes of these elements typically result in a variety of heterologous mesodermal constituents, including rhabdomyosarcomatous, chondrosarcomatous, liposarcomatous and osteosarcomatous components [1–4, 9, 10]. Pure heterologous uterine osteosarcomas, as in our case, are extremely unusual tumours, which can be distinguished from MMMT microscopically and immunohistochemically by the absence of an epithelial component [2–4, 9, 10]. Primary osteosarcoma of the uterus may derive from primitive mesodermal cells with monomorphic mesenchymal differentiation or from smooth muscle neoplasm with malignant osseous metasplasia, but the exact histogenetic origin remains controversial [4, 6, 10].
Clinically, patients with uterine osteosarcoma usually present with post-menopausal bleeding, lower abdominal pain and the presence of a palpable lower abdominal mass [2–7]. Since these clinical findings are non-specific, imaging studies are important to enable a pre-operative diagnosis and to delineate the anatomical extent of the lesion [2]. Ultrasound is the most common initial imaging modality for gynaecological conditions. However, it cannot distinguish uterine sarcomas from the frequently encountered leiomyomas, which typically exhibit a variety of characteristics with regard to size, location, echo texture and degree of calcification [2]. CT is a valuable method for evaluation of malignancies of the uterus and screening for distant metastases. Similar to ultrasound, the CT findings of most uterine sarcomas are usually non-specific [2]. Nevertheless, CT is superior to ultrasound in the demonstration of tumoral calcifications and tumour extent. In our case, the CT demonstration of a calcified uterine mass with eccentric necrotic areas and poor demarcation with the adjacent pelvic organs was suggestive of an aggressive uterine malignancy rather than a benign calcified leiomyoma. Another important feature seen at CT but not at ultrasound in our patient was the presence of disseminated calcified nodules in the omentum and peritoneal cavity. The differential diagnosis of a pelvic mass with widespread peritoneal calcifications includes: ovarian cystadenocarcinoma with peritoneal seedings; ruptured appendiceal tumour with pseudomyxomatous peritonei; tuberculous peritonitis; hydatid disease; sclerosing peritonitis; and undifferentiated abdominal malignancies with peritoneal metastases [11, 12]. A lack of any prior history of ovarian tumour or ruptured appendix, as well as the CT demonstration of the absence of an ovarian or appendiceal mass are helpful in excluding an ovarian tumour with peritoneal seeding and pseudomyxomatous peritonei. In addition, calcification of pseudomyxoma peritonei is very rare and appears curvilinear rather than nodular. Healed tuberculous peritonitis may generate calcified tuberculoma or mottled, widespread peritoneal calcifications [11, 12]. Abdominal hydatid disease may rupture, and leakage of a large ecchinococcal cyst can lead to peritoneal implantation. Cysts may become inactive and calcify, forming ring-like calcifications in the peritoneal cavity [12]. Sclerosing peritonitis is excluded by the absence of a history of peritoneal dialysis [11]. The presence of calcified uterine tumour tissue suggests a high likelihood of undifferentiated uterine malignancies including leiomyosarcoma, MMMT and other pure heterologous sarcomas. Uterine leiomyosarcoma tends to metastasize to the liver as hypodense liver masses but hardly ever presents as calcified peritoneal nodules. Although both MMMT and primary osteosarcoma affect elderly females (mostly >60 years), these two tumours are biologically different. Most examples of MMMT manifest as polypoid masses occupying the uterine cavity with minimal myometrial invasion and infrequent metastases [2, 4, 10]. By contrast, primary heterologous osteosarcoma of the uterus displays an aggressive behaviour with early recurrence and frequent metastases to the liver and lung [2–8]. Metastases of uterine osteosarcoma manifesting as zonal peritoneal calcification and calcified psoas nodules have also been reported [5, 6]. Our patient exhibited a unique CT feature of peritoneal osteosarcomatosis appearing as disseminated calcified peritoneal nodules.
In summary, despite the rarity of our patient's condition, we report that a diagnosis of primary heterologous uterine osteosarcoma with peritoneal osteosarcomatosis was indeed the appropriate entity to fit the clinical and imaging characteristics of this patient—a heavily calcified uterine tumour with aggressive local invasion and disseminated calcified peritoneal seeding for an elderly woman.
Received for publication January 4, 2002.
Revision received April 16, 2002.
Accepted for publication May 9, 2002.
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Abstract
Introduction
