Complicated retrorectal teratoma

A 57-year-old woman with no relevant past medical history was admitted to the emergency department for abdominal pain with one week of onset. She associated diarrhoea, vomiting, hypotension (88/52 mmHg) and low-grade fever (37.5º C).

Blood tests showed leukocytosis with neutrophilia.

Digital rectal examination was normal.

CT scan of the abdomen and pelvis was performed with intravenous contrast. An heterogeneous lesion was identified, located in the retrorectal space, displacing the rectum anteriorly. No invasion of the rectosacral fascia was observed. The lesion was composed of abundant fat content, as well as foci of calcification/ossification and areas of intermediate density. Within the lesion a liquid and encapsulated collection with inflammatory changes of the adjacent fat was identified, suggestive of abscess. On MIP reconstruction with bone kernel, morphological alterations of the sacral and coccyx bones were also observed, with abnormalities in the fusion of the midline structures.

Background:

The retrorectal or presacral space is a virtual space bounded posteriorly by the presacral fascia, anteriorly by the mesorectal fascia, laterally by the iliac vessels and ureters, superiorly by the peritoneal reflection and caudally by the levator ani muscle and the rectosacral fascia [1–6]. It contains loose conective tissue, lymphatic and vascular structures, nerve plexuses and osteochondral tissue from sacrum and coccyx [1,3,5,6]. 

Tumours originating in the retrorectal space can be classified as congenital (the most common), neurogenic, osseous, inflammatory or miscellaneous [1–3,6].

Clinical perspective:

Retrorectal teratoma is a congenital lesion and is most commonly diagnosed in children under two years of age [1], up to 60% in girls [1,3].  In adult patients, the most frequent clinical manifestation is pelvic pain, but also constipation, sexual dysfunction and gynaecological discomfort. [1,2,5]. In up to 40% of cases they can become malignant [1]. Germ cell tumours are the most frequent, followed by somatic neoplasms of epithelial type; neuroendocrine tumours are very rare (7).

Imaging perspective:

The diagnosis of retrorectal teratoma can be made by CT or MRI [1–6].  In both techniques it presents as a mass that displaces the rectum anteriorly, and the key finding characterising the lesion is the presence of macroscopic fat, with cystic areas and areas of calcification or bone [1,6]. Benign lesions are predominantly cystic, while malignant lesions tend to have a more solid component [1]. 

In our case, the lesion had the typical characteristics of a retrorectal teratoma, with abundant fat, some foci of calcification and cystic content. Also, it had areas of abscessation. After resection surgery, histopathological study confirmed the radiological diagnosis, but also evidenced a well differentiated neuroendocrine tumour 2 cm in size with an infiltrative pattern amidst the connective tissue. To our knowledge, less than ten cases of neuroendocrine tumours arising in retrorectal teratomas have been described. All of them were treated by surgical resection and most of them also with adjuvant chemotherapy, and showed a good clinical evolution [7, 8, 9].

Outcome:

The management of retrorectal teratomas is surgical [1–6].  Imaging studies allow characterization of the tumour, delimitation of its extension and are also useful for follow-up [2–6].

Take home message / Teaching points:

Retrorectal teratomas are benign lesions with characteristical radiological features of fat, bone and cystic content. However, they can undergo a malignant transformation, so management is surgical and the final diagnosis is histological.