CT imaging of an unusual malignant inguinal mass: metastatic parafunicular dedifferentiated liposarcoma

Abstract

A man in his 50s was redirected by his general practitioner to our University Hospital for a radiological evaluation after the complaint of a left inguinal swelling. The preliminary ultrasound and CT scan showed a left parafunicolar mass located between the root of the penis and the spermatic cord. The lesion was biopsied shortly after and histologically diagnosed as a dedifferentiated liposarcoma. The patient underwent a cycle of neoadjuvant radiotherapy, which proved to be ineffective. He was then subjected to an organ sparing surgical removal of the mass, followed by a second organ sparing removal of some residual disease. The last CT scan showed absence of the inguinal disease; however, lung and hepatic metastasis were detected, which are scheduled to be treated with a course of chemotherapy and radiofrequency.

Background

Liposarcoma is one of the most common soft tissue malignant tumours that can potentially arise everywhere fat is present.¹

The retroperitoneum and extremities are the most common sites of origin while the spermatic cord and the parafunicolar location are very rare sites of presentation.^{1 2}

Most of these liposarcomas appear as slow-growing inguinal or scrotal masses and sometimes they present as large scrotal masses mimicking a testicular tumour. Preoperative diagnosis is uncommon.³

The recommended treatment is surgery in the form of a wide local excision, although organ sparing techniques have been reported in the literature. Adjuvant radiotherapy is used in cases with positive resection margins, high-grade tumours, lymphatic invasion or relapses.^4–7

Although they make up a minority of liposarcomas, the dedifferentiated subtype is most concerning for its aggressive behaviour and rapid recurrence, therefore a correct, prompt and early diagnosis is of great importance.^{2 8}

Case presentation

A man in his 50s was redirected by his general practitioner to our University Hospital for an ultrasound examination; the patient complained of a left inguinal bulge that appeared 1 month before.

The ultrasound showed a solid, inhomogeneous isoechoic vascularised mass without a clear cleavage plane with the left aspect of the root of the penis and the proximal aspect of the adductor muscles of the left leg; therefore, a diagnosis of enlarged lymph node, hernia or lipoma was excluded. The radiologist decided to perform an abdominopelvic CT to better characterise the mass, which resulted in a solid tissue lesion, with suspicious CT attributes. Given the imaging features, the suspect was that of an heteroplastic lesion of unknown origin, and the patient underwent an ultrasound-guided core needle biopsy, which confirmed the malignant nature of the mass. After a negative thorax CT scan, the patient underwent a cycle of neoadjuvant radiotherapy, which proved to be ineffective due to tumorous growth as proven by a follow-up CT. He was then redirected to the urologist, who performed an organ sparing excision of the lesion via an inguinal approach. The gross specimen was analysed by a pathologist, who confirmed the histological diagnosis of dedifferentiated liposarcoma and unfortunately identified positive resection margins.

Consequently, a contrast-enhanced CT (CECT) scan 3 days after surgery was performed and confirmed residual local disease, so a second surgical removal of the pathological tissue was performed 5 days after the first surgery.

The follow-up CECT scan did not show any local recurrence but demonstrated the presence of multiple lung and liver metastasis, scheduled to be treated with a course of chemotherapy and radiofrequency.

Investigations

The very first clinical examination of the patient was performed by his general practitioner, who suspected the formation to be an enlarged lymph node. On clinical examination, the lesion presented as a non-painful left inguinal mass, fairly rapidly growing and hard to palpate.

The following investigation was an ultrasound scan (images not available) performed with a high-frequency linear probe, showing an irregular, isohypoechoic mass immediately medial to the inguinal canal. The lesion showed rich internal vascularisation on Doppler imaging. It was evident to the radiologist that he was dealing with a mass that needed further characterisation; therefore, a first multiphase CE abdominopelvic CT scan was performed using 100 mL of 350 mg\mL iodinated contrast material with a flow rate of 3 mL\s.

The CT scan highlighted a solid left inguinal mass, avidly enhancing since the arterial phase (figure 1A), located between the root of the penis medially and the left inguinal canal (which was dislocated anterolaterally) and the adductor muscles of the left leg laterally, without clear fatty cleavage plains between the lesion and said structures. A marked enhancement of the pathologic tissue remained evident in the venous phase (figure 1B). The mass had, among others, a large arterial feeding vessel coming from the external femoral artery (figure 2).

Figure 1.

Contrast-enhanced computed tomography (100 mL of 350 mg\mL iodinated contrast media injected at a rate of 3 mL\sec), axial planes. (A) Arterial phase showing early enhancement of the lesion. (B) Venous phase showing pronounced and persistent enhancement. Both images reveal a solid lesion located between the left aspect of the root of the penis medially, and the spermatic cord and the adductor (brevis and longus) muscles laterally. No clear cleavage plane between the lesion and said structures is visible.

Figure 2.

Contrast-enhanced CT, tridimensional reconstruction highlighting the mass (violet) and a large feeding vessel arising from the external femoral artery (red).

An ultrasound-guided core needle biopsy of the lesion was then performed with a 19G needle under local anaesthesia (100 mL of lidocaine hydrochloride, subcutaneous injection), posing the histological diagnosis of dedifferentiated liposarcoma.

The patient underwent 42 days after the first scan a second CT scan after a single cycle of neoadjuvant radiotherapy; the scan proved such radiotherapy to be scarcely effective since the lesion showed fairly rapid enlargement with an increase of 15% in mass volume and the same avid contrast enhancement, and almost no internal colliquation or necrosis (figures 3 and 4).

Figure 3.

Contrast-enhanced CT performed after the first radiotherapy cycle, showing mild dimensional growth of the lesion, persistent enhancement, and no necrotic tissue within the mass.

Figure 4.

Inefficacy of the radiotherapy cycle shown by CT on reconstructed coronal planes: (A) before radiotherapy, and (B), after 25 administrations in 35 days. Note in (B) the slight increase in size of the mass and the lack of necrotic internal components.

The ultrasound executed to evaluate the possible funicular and testicular extension of the disease was negative, showing only a grade I varicocele in the left testicle.

Being the spermatic cord spared, the urologists opted for an organ-sparing resection of the mass via an inguinal approach.

After the surgical removal of the mass, the pathologist confirmed the diagnosis of dedifferentiated liposarcoma (G3 according to the French Federation of Cancer Centers Sarcoma Group) associated with a component referable to sclerosing liposarcoma. He also highlighted positive resection margins.

Consequently, a CECT scan was performed 3 days after surgery to identify residual local disease, which was confirmed (figure 5).

Figure 5.

Postoperative CT prescribed because of resection margins not free from disease, showing on an axial plane the presence of a small residual mass with contrast enhancement (yellow arrow), a finding strongly suspicious for residual disease. Diffuse surrounding fat stranding consistent with postoperative oedema in the soft tissues.

The first CT scan took only 3 days after surgery (figure 5) highlights in fact a small residual portion of pathologic tissue in the form of a small enhancing solid nodule in the same site of the primitive mass, showing the same enhancement pattern. A good amount of soft tissue oedema surrounding said finding is due to the recent surgery.

The subsequent follow-up CT at 60 days from the first surgery shows a hypodense hepatic lesion with ring enhancement in the eigth segment consistent with a metastasis (figure 6A, arterial phase and B, portal phase). What is more, the same CT highlighted the appearance of two round, solid nodules with soft tissue density and relatively smooth margins in the upper and lower lobes of the left lung also to be interpreted as repetitions (figure 7A, B).

Figure 6.

Follow-up CT scan after the second inguinal surgery, demonstrating the appearance of a liver lesion with ring enhancement (more evident in the arterial phase) in the VIIIth hepatic segment, to be interpreted as a metastasis. (A) arterial phase (B) portal phase.

Figure 7.

Follow-up CT scan after the second inguinal surgery showing the appearance of two nodular, solid lesions with smooth margins consistent with metastasis in the upper and lower lobes of the left lung.

Differential diagnosis

Due to the characteristics of the lesion at both ultrasound and CT imaging, diagnosis of common benign causes of inguinal swellings such as enlarged lymph nodes, hernia or lipoma was excluded.

Given that the patient was a man, pathology regarding the round ligament (cyst, leiomyoma, fibroid) was obviously excluded.

Indeed, since the first-line imaging modality (ultrasound), the lesion appeared to be solid (excluding the possibility of a hernia), inhomogeneous in its structure and lacking the typical nodal anatomy (excluding the possibility of a lymphadenomegaly). As said, the mass was not completely hypoechoic or hypodense but showed large solid isoechoic and isodense components, positive at Doppler imaging and richly enhancing at CT, excluding the possibility of a lipoma.

Treatment

Since the first discovery of the mass, the patient has been subjected to a single cycle of neoadjuvant radiotherapy directed to the left inguinal region, with a total dose of 50 Gy split into 25 administrations during a 35 days period, which turned out to be ineffective due to tumour growth (figure 4A, B).

Being the spermatic cord spared, the patient was subjected to an organ sparing surgical removal of the formation via an inguinal approach, but the resection margins were not free from disease as confirmed by a postsurgical CT scan (figure 5). Therefore, the patient underwent a second organ sparing surgical removal of the residual mass.

Finally, the follow-up CT scans showed the appearance of lung and liver metastases (figures 6 and 7), so the patient had been scheduled to be treated with a course of chemotherapy and a radiofrequency treatment for the liver metastasis.

Outcome and follow-up

After 70 days of the second surgery, the patient has started the first cycle of chemotherapy with Epirubicin and Ifosfamide and is awaiting radiofrequency treatment for the neoplastic liver lesion.

Discussion

Only a few case reports describe liposarcomas presenting as an inguinal mass; inguinoscrotal liposarcomas, which arise along the spermatic cord and testis, represent an uncommon soft tissue sarcoma.¹

Since parafunicolar liposarcoma is a rare finding, there is no standardised treatment for the disease.^{1 2}

In our case, immediately after the diagnosis, a multidisciplinary team composed of a radiologist, an urologist, and an oncologist was established to address the patient to a proper therapeutic path.

In the first instance, the multidisciplinary team opted to start with a cycle of neoadjuvant radiotherapy directed to the left inguinal region as reported in the literature,^{3 5 9} with a total dose of 50 Gy in 25 administrations during 35 days. Neoadjuvant radiotherapy in fact is proposed in case of poor prognostic factors such as an aggressive histotype while adjuvant radiotherapy is an option in case of positive margins or local recurrence.¹⁰ Liposarcomas are the most radiosensitive of all sarcomas, and in some cases, remission has been achieved with radiotherapy alone.^{9 11} Two prospective randomised trials involving soft tissue sarcoma established that the addition of radiation to surgery substantially reduces the likelihood of local recurrence.¹¹

The CT scan executed at the end of the radiotherapy cycle demonstrated that the lesion had progressed into a bigger solid formation with no significant signs of necrosis. This is a poor prognostic factor, since it is reported that high-grade liposarcomas present as a solid, heterogeneous, high-density mass.¹² The recommended surgical treatment for the liposarcoma of the spermatic cord is radical high orchiectomy,¹² but being the spermatic cord spared, the urologists opted for an organ-sparing resection of the mass.

Since the margins of the specimen were not free from tumour, the patient underwent, only 5 days after the first surgery, a second organ-sparing resection.

The further postoperative CT scan demonstrated that multiple lung and liver repetitive nodules had appeared.

This case represents an uncommon evolution of a parafunicolar liposarcoma since this entity usually does not metastasise after being surgically removed.¹ These cancers in fact are known for their mainly local recurrence, so long-term follow-up is mandatory.¹⁰

Learning points.

• Malignant tumours of the spermatic cord or the inguinal canal are a rare entity.

• When performing a clinical examination or any kind of investigation such as ultrasound or CT scan for an inguinal mass, despite the most common findings in this region are hernias, lipomas, enlarged lymph nodes and round ligament-related pathology, it is important to keep in mind that primitive malignant masses in this area do exist and need to be promptly recognised since they can rarely spread to further localisations.

• After resection, in case of positive margins, contrast-enhanced imaging (CT or magnetic resonance) should shortly follow the surgical removal of the mass to timely identify any residual local disease.

• Follow-up contrast-enhanced imaging is mandatory to promptly identify metastases.

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