Unusual presentation of a rare venous tumour

A 54-year-old man was referred to hospital in January 2002 for an exercise electrocardiogram (ECG). He complained of a 6-week history of increasing shortness of breath on exertion with no other respiratory symptoms. There was no history of chest pain, orthopnoea, paroxysmal nocturnal dyspnoea or ankle swelling and no past medical history of note. The patient was taking no medication, was a non-smoker and had no family history of illness. Exercise ECG was terminated after 1 min when the patient complained of severe breathing difficulty and felt faint. On examination the patient was tachyopnoeic and tachycardic at 100 bpm. His blood pressure was 130/80, heart sounds were normal and his chest was clear on auscultation. ECG was normal. An urgent echocardiogram showed a dilated right heart, suggestive of pulmonary embolism. Blood gas analysis showed the patient was hypoxic (pO2 of 59.3 mmHg), despite oxygen therapy, with a respiratory alkalosis (pH 7.48, pCO2 25.2 mmHg). The patient was started on i.v. heparin and a lung perfusion-ventilation scan performed, which showed a high probability of pulmonary embolism. Thrombolysis was commenced with systemic tissue plasminogen activator (tPA). Duplex venography was performed 2 days after admission and a diagnosis of left gastrocnemius/popliteal vein thrombosis made. The duplex scan suggested abnormal dilatation of the popliteal vein, with a maximum diameter of 30 mm. The patient was warfarinized and discharged 1 week following admission. One month later the patient was referred to the Department of Vascular Surgery having noticed a lump behind his left knee. On direct questioning the patient revealed that he had been aware of a vague swelling behind the knee for 3 months but this had recently increased in size. Examination confirmed a 30 × 30 mm non-tender, non-pulsatile mass in the superolateral popliteal fossa. The mass was mobile from side to side and there were no skin changes. There was no regional lymphadenopathy and general and abdominal examination were normal. Neurological examination of the left lower limb was normal. Repeat duplex scan (Fig. 1) and magnetic resonance imaging (MRI) (Fig. 2) were performed and suggested a solid mass in the lateral popliteal fossa measuring 60 mm in length by 30 mm in diameter. The mass displaced the popliteal artery medially and a high degree of vascularity was seen on duplex imaging. No local lymphadenopathy was identified. Duplex appearance of the popliteal vein at initial presentation. Magnetic resonance imaging with i.v. gadolinium of the popliteal fossa. T2 weighted image showing (a) the soft tissue mass and (b) the popliteal artery displaced by the mass. No popliteal vein is seen within or adjacent to the sarcoma. The diagnosis of a soft tissue tumour possibly arising from the popliteal vein was made on the grounds of clinical, duplex and radiological findings and the popliteal fossa was explored through a posterior approach. Operative findings confirmed a 60 × 30 mm pale, irregular mass arising from a bifid popliteal vein with popliteal artery, one of the popliteal veins and posterior tibial nerve splayed over the surface of the tumour. There was no evidence of invasion of local structures and no local adenopathy. The artery, vein and nerve were carefully dissected off the surface. The tumour was completely excised macroscopically preserving nerve and vessels. The cavity was washed out with cetrimide and the tumour bed marked with surgiclips for subsequent radiotherapy. On table nerve conduction studies confirmed posterior tibial and sural nerve function was normal. The patient made an uneventful postoperative recovery and was discharged on the fourth postoperative day with referral for radiotherapy and chemotherapy. Anticoagulation was recommenced postoperatively. Histological diagnosis was of leiomyosarcoma arising from one of the paired popliteal veins with intersecting fascicular bundles of elongated pleomorphic spindle cells having ‘cigar’ shaped nuclei. Abundant atypical mitoses were present but no vascular space invasion was seen. Proximal and distal venous margins were free of tumour and the neoplasm was surrounded by vessel wall. Immunoperoxidase stains supported the diagnosis. Planned oncological management includes 6 weeks of radiotherapy with electron beam irradiation delivering 6000cGy to the popliteal area combined with 8 cycles of ifosfamide and epirubicin. Soft tissue tumours of peripheral veins are rare. From the few case series and reports that exist leiomyosarcomas of peripheral veins mimic deep vein thrombosis (DVT)1 or present as an asymptomatic mass2−4. To date no reports exist of these tumours presenting with pulmonary embolus. Diagnosis preoperatively can be difficult. Clearly if a mass is palpable on examination the clinician should be concerned as to the underlying pathology. In the absence of a palpable mass, in patients presenting with symptoms and signs of acute venous thrombosis, diagnosis will be difficult. However, in a report of 227 consecutive patients investigated for venous disease eight patients were found to have previously undiagnosed masses, of which three proved to be malignant. Three of the eight masses were impalpable and diagnosed by duplex scanning5. The rarer differential diagnoses of venous obstruction should be considered in patients whose symptoms do not resolve after conventional treatment. Diagnosis in such cases might be assisted by duplex scanning and MRI. The most important B-mode imaging criteria for diagnosis of DVT were formulated by Talbot6 and are shown in Table 1. On B-mode imaging leiomyosarcomas of peripheral vessels have been described as hetero- or hypoecchoic4,7. Duplex might be useful to assess arterial or venous involvement of a mass in the popliteal fossa and to identify intraluminal thrombus related to the mass. Persistent expansion of a popliteal vein is against the diagnosis of simple thrombosis8 and can be confused with aneur-ysm of the popliteal vein9. In the case of leiomyosarcoma of peripheral veins increased vascularity does not appear to be a consistent feature but this may reflect interobserver variation. Soft tissue tumours arising in flexor fossae are classified as extracompartmental since they are not contained by natural barriers to tumour invasion such as bone and fascia. Wide resection of tumours in the popliteal fossa with satisfactory tumour free margins and preservation of neurovascular structures can be difficult and, in the past, amputation has been recommended1,10. Reports on the prognosis of extracompartmental tumours include a heterogeneous group of soft tissue malignant neoplasms since each histological subtype is infrequent11. Until recently the prognosis for high grade soft tissue sarcomas of the flexor fossae was considered to be worse than for tumours confined to a compartment12,13. More recently disease free survival has been shown to be similar to intracompartmental tumours when compared retrospectively adjusting for size, metastasis and histological grade. Yang et al. reported a 5-year cumulative survival rate for soft tissue sarcomas of the flexor fossa of 76%11 and the same institution had earlier reported 70% survival at a median follow up of 82 months14. Multivariate analysis suggests size is a more important indicator of prognosis than the compartmental site11. With the evolution of adjuvant oncological therapy local control, with maintenance of extremity function, are realistic goals. Treatment consisting of limb-sparing resection with adjuvant radiotherapy and adjuvant or neoadjuvant chemotherapy may provide satisfactory outcomes in the majority of patients. Chemotherapeutic regimens of doxorubicin, doxorubicin and cisplatin, ifosfamide and ifosfamide in combination with doxorubicin have been described11,14. The theoretical advantage of preoperative neoadjuvant chemotherapy has been suggested14 but good clinical evidence of benefit in terms of improved survival, disease free survival and limb salvage is lacking and calls for prospective evaluation. In the current case it is uncertain whether the presenting pulmonary emboli were tumour emboli and the effect of this possibility on prognosis is unknown. Since the patients clinical condition improved following therapy for pulmonary embolus and a follow-up computed tomography scan at 3 months has shown no evidence of lung secondaries, it is hoped that the embolus was not tumour. Careful clinical examination at presentation should have detected the popliteal fossa mass. Thorough examination of the limbs, pelvis and abdomen is mandatory in patients presenting with pulmonary embolus. The initial duplex scan was incorrectly interpreted and the full significance of the dilated popliteal vein segment was not recognized. Only after the patient complained of a lump and repeat duplex scanning and MRI had been performed was a diagnosis of soft tissue tumour considered. This case demonstrates that with vigilance duplex scanning can suggest unusual causes of venous obstruction at an early stage. It also highlights the change in perception of treatment and prognosis for soft tissue sarcomas of the popliteal fossa with a multidisciplinary approach to diagnosis and treatment. Modern imaging techniques combined with improved understanding of tumour biology prompt diagnosis and appropriate treatment might lead to better functional results and improved prognosis. The authors would like to thank our colleagues from the Departments of Oncology and Radiotherapy who were involved in the care of this patient.