Intrascrotal lipoblastoma diagnosed in adulthood - A rare presentation

A 37-year-old healthy man presents with a scrotal mass. The mass growth in the past few weeks. No scrotal pain. There were no scrotal oedema or inflammatory signs at the physical examination. Mobile testis of soft consistency, without nodules. The palpable scrotal mass is inferior to the right testicle. There is no other relevant clinical information.

A scrotal ultrasound was performed outside our institution, and we do not have images. The report refers to an intrascrotal nodular solid lesion, hypoechoic, with no vascularization at color-Doppler, measuring 7 cm, located inferior to the right testicle, without connection with them.

Subsequently, magnetic resonance imaging (MRI) was performed. The MRI revealed an oval intrascrotal mass, inferior to the testicles and independent from them, with well-defined contours, measuring 75 x 55 x 30 mm. The mass is hyperintense on T2-weighted images (Figure 1) and hypointense on T1 and T2 images with fat saturation (Figure 2), compatible with a mass of lipid nature. There are some thin septa inside the mass. There was no enhancement of the mass after gadolinium administration, but there was some discrete hyperenhancement of the septa (Figure 3). There is a cyst measuring 15 mm in the right epididymal head (Figure 4). Normal testicles (Figure 5).

Background

Lipoblastomas are benign tumours constituted of fat, presenting like painless nodules or masses, more frequent on the trunk and extremities, but they should arise in other locations: head, neck, mediastinum, mesentery, omentum, retroperitoneum, and scrotum [1,2].

The tumours arise from the embryonal fat tissue, presenting rapid growth but with an indolent and benign course. They are rare, presenting generally in children with less than 3 years (90%), with a male predominance [1–3]. This is extremely rare in any location after adolescence [2–4].

The histological diagnosis of these tumours is quite easy, but as it is a tumour typically found in children when it appears in adults, we must be sure that we are not dealing with a myxoid liposarcoma or a well-differentiated liposarcoma [5,6].

Clinical Perspective

Clinical signs and symptoms are subtle and nonspecific, being characterized by a palpable mass or nodule with rapid growth and painlessness, which, depending on the location and size, may cause some compression of adjacent structures [1,2]. On physical examination, it is characterized by a mobile mass or nodule with an elastic and soft consistency [4]. Clinically, it is impossible to have a diagnosis, so imaging and histology are essential to differentiate between benign or malignant intrascrotal pathology [5,6].

Imaging Perspective

Imaging features of lipoblastoma are nonspecific, and the differential diagnosis is difficult even with MRI [4]. On MRI, it is a lesion that presents hyperintensity in T1 and T2 and hypointensity in sequences with fat saturation [7–10]. The persistence of hyperintensity on T2 sequences with fat saturation is worrying, raising the possibility of malignancy [7–10]. The lesion does not enhance after contrast, and there may be thin septa, which may undergo slight enhancement [7–10].

Outcomes

Although asymptomatic, due to their growth and especially the uncertainty of the diagnosis, these lesions must be removed, and no specific follow-up should be done [1,4]. Our patient was submitted to surgery, and the mass was completely removed. The histological report shows macroscopic yellowish lobulated tissue with a microscopic proliferation of adipocytes and spindle cells, separated in lobules by septa, CD34, S100 protein, and PLAG1 positive and MDM2 and CDK4 negative, compatible with intrascrotal lipoblastoma. The patient is under clinical and imaging follow-up, and no scrotal abnormalities have been found.

Take Home Messages / Teaching Points

Lipoblastoma is a rare and benign disease usually diagnosed before adolescence, which makes its diagnosis doubtful when it appears in adults. Differential diagnosis is difficult using imaging methods, with the main possibilities in adults being lipoma or liposarcoma.

MRI is the preferred imaging method, allowing us to distinguish between benignity and malignancy.

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