Introduction
Cytosteatonecrosis is a common but poorly documented condition, which usually presents as a subcutaneous mass characterized by necrosis of adipose tissue [1]. It can occur from various causes, including trauma, and affects patients of all ages, with a female predominance [2,3]. The clinical presentation can be silent or made up of pain and/or cutaneous manifestations (ecchymosis, retraction, induration or thickening) [4], but can also mimic a neoplastic pathology [3,5]. We present a case of cytosteatonecrosis following neglected leg trauma without apparent skin lesion.
Observation
This is a 48-year-old patient, with no particular medical or surgical history, having been the victim of a sporting accident approximately 18 months ago with a normal initial post-traumatic assessment. The patient has been reporting for approximately 12 months, a sensation of subcutaneous nodule without exact precision on the date of appearance of the latter. On examination, it is a subcutaneous mass, not very soft, with no visible skin lesions. The usual biological examinations were unremarkable. MRI of the leg revealed a subcutaneous mass on the inside of the right leg, with lobulated contours and measuring 17 mm transversely. She was in T1 hypersignal (Figure 1) with attenuation on the Fat Sat sequences (Figure 2,3) and without enhancement after injection of Gadolinium (Figure 4,5). It was associated with neighbouring soft tissue infiltration and an old tibial fracture line. The results of the skin biopsy confirmed the radiological diagnosis by showing cytosteatonecrosis lesions.
Discussion
Cytosteatonecrosis is a common but poorly documented condition that can mimic other pathologies, in this case tumours, so it is important to be aware of this entity, which often has no known serious consequences [3,5]. It is characterized by adipocyte necrosis secondary to the release of adipocyte cytoplasmic lipases which degrade adipose tissue [1].
This condition affects patients of all ages and sexes with a female predominance [2,3], and is localized in all areas of the body exposed to the slightest trauma, generally in the shins, thighs, arms, buttocks. and breasts, especially the face and cheeks in children [2,3,6].
It often results from trauma or other conditions such as surgery, minor procedures, injections, and pancreatic disease [2,5].
Post-traumatic cytosteatonecrosis lesions are caused by the release of adipocyte cytoplasmic lipases which degrade adipose tissue. Triglycerides are broken down into glycerol, which is quickly resorbed into fatty acids, some of which crystallize in place. In pathology, after a phase characterized by cellular necrosis (“adipocyte ghosts”), a histiocyte granuloma forms, which then begins to harden, which can lead to a subcutaneous, pseudo-tumor lesion [7].
Clinically, cytosteatonecrosis most often presents as a palpable subcutaneous mass or local depression, which may be unifocal or multifocal [5]. The mass may regress spontaneously or grow over the weeks; This often encourages patients to consult so as not to overlook a serious condition (infection or tumour) [5]. In addition to the mass, post-traumatic skin manifestations such as bruising, erythema and soft tissue tenderness, or distant scarring may also be observed early [5]. On the other hand, there are also completely asymptomatic cases.
The differential diagnosis of post-traumatic cytosteatonecrosis includes Morel-Lavallée syndrome, thrombophlebitis, hematoma, subcutaneous abscess and post-traumatic infectious dermo-hypodermitis, as well as desmoid tumor, nodular fasciitis and myositis. ossifying [5,7].
In the large number of cases reported in the literature, laboratory evaluations were generally unremarkable [1].
Histologically, cytosteatonecrosis is organized into zones with a center of necrotic adipocytes of varying sizes surrounded by lipid-laden macrophages and numerous neutrophils. As the lesion ages, fibroblasts proliferate, vascular supply increases, and histiocytes sequester necrotic cells. The final stages involve replacement of inflammatory cells with fibrosis, encapsulation, calcification and/or cyst formation [5].
Magnetic resonance imaging helps determine the diagnosis. In the absence of a discrete mass, cytosteatonecrosis manifests as a linear abnormality in the signal intensity of subcutaneous fat, which is hypointense on T1-weighted sequences and hypointense to hyperintense on T2-weighted sequences. The appearance of the linear signal is more closely related to the temporal phase of necrosis. In the early stage, necrosis is associated with edema and therefore shows a bright signal on T2-weighted images. In contrast, in the later stages of necrosis, hemosiderin and fibrosis predominate, giving the lesion a darker appearance on T1- and T2-weighted sequences [8]. However, when a mass is present on MRI,
A biopsy is always recommended if there are any suspicious areas visible on the MRI.
The treatment of non-severe and non-extensive disease is based on symptomatic palliative care because the evolution can be spontaneously beneficial [1,5]. On the other hand, some authors recommend surgical resection in the event of cytosteatonecrosis with a bulky mass [1].
Conclusion
Cytosteatonecrosis is a common condition without serious consequences and its management is symptomatic. The notion of MRI characteristics and the notion of traumatic antecedents at the site of the lesion allow the diagnosis, although the confirmation is in the histological domain.
Conflicts of interest: None.