Case Presentation

A 20-year-old lady presented with complaints of abdominal pain for 6 months, which was of mild intensity at first but gradually increased in intensity over the last few days before the presentation. It was present in the lower abdomen initially however progressed to generalized abdominal pain with an increase in intensity. She did not have any urinary complaints, fever, nausea or vomiting. She presented on the 3rd day of her menstrual cycle, which was of normal duration and flow in regular intervals of 28+/- 2 days. She did not give any significant medical or surgical history in the past. No significant history was found in the family either.
On examinations, she was a healthy-looking female, with no pallor, or lymphadenopathies. She had a soft, scaphoid abdomen, with a vague mass palpable in the left iliac fossa, ~6x6cm in diameter, with ill-defined margins, non-tender, and not attached to the overlying skin. Bowel sounds were present on auscultation. Other systemic examinations were normal.
On ultrasonography, a complex heterogenous solid-cystic lesion was seen in the left adnexa measuring ~9.9 x 6.0x 6.4 cm. MRI was then done to confirm the diagnosis, which showed an 11.7 x 8.2x4.8cm (CCxAPxT) size complex heterogenous signal intensity mass in the retroperitoneum just medial to the left psoas muscle and lateral to iliac vessels. (Figure 1) Anteriorly the mass was extending up to the anterior abdominal wall, displacing the psoas muscle laterally and iliac vessels medially. Multiple variable size irregular shape cystic areas were seen within it. Variable thickness septa and solid components were present. Multiple flow void areas were noted in the mass, suggesting marked vascularity. Which gave a differential diagnosis of retroperitoneal soft tissue sarcoma or neurogenic tumour.
So, with the provisional diagnosis of Primary Retroperitoneal Mass, the patient underwent “Laparoscopy Assisted Transperitoneal Excision of Retroperitoneal Mass”. During surgery, a large mass measuring ~15x10cm solid mass with 2 lobes with an irregular surface was seen with the larger lobe having cystic areas. (Figure 2) There was dense adhesion of the mass posteriorly with the psoas muscle. The visualized retroperitoneal organs were normal. There was blood loss of ~1000ml from the part of the mass adhered to the psoas muscle. An intra-abdominal drain was placed, which was removed on the 4th postoperative day. The rest of her stay in the hospital was uneventful and was sent home from the hospital on the 6th postoperative day.
In her histopathology report, gross examination showed 2 large nodular bosselated encapsulated soft tissue measuring 9x6x2cm and 4.5x3x3cm were seen with a cut section showing a grey-white area with a cystic area within it. (Figure 3 (A) and (B)) On microscopic examination, mitotic figures or necrosis were not present, Tumour was composed of compact cellular and loose myxoid areas with spindle-like cells and ovoid cells coursed by round to slit-like and occasionally ramifying capillary seized vessels, (Figure 4 (A)) punctuated by variously sized hemangiopericytomatous vessels, many with discernible fibromuscular walls and cystic spaces. The morphological features which were consistent with Solitary Fibrous Tumour and margins, however, were positive for tumour.
The Immunohistochemistry showed Tumour cells positive for CD34, SMA and STAT-6 and negative for CK, S100 and desmin. (Figure 4 (B) and (C)) The Ki67 proliferation index was 10%.
The risk of metastasis according to Demicco et al: overall risk class: low (2/7). Age <50 years (Score 0); Tumour size 10-15cm (Score:2); Mitotic count 0/10HPF (Score 0); Tumour Necrosis <10% (Score 0)
The patient was followed up at 3 months and 6 months with Contrast-enhanced computed tomography, which did not show any recurrences.