Age / Sex : 4 / M

Chief complaint :

Painless palpable mass, both ankle dorsum


What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : 이재혁 (Jaehyuck Yi), 계명대동산병원 영상의학과 (Keimyung University School of Medicine, Department of Radiology)

Subcutaneous granuloma annulare (deep granuloma annulare, pseudorheumatoid nodule, benign rheumatoid nodule)

Discussion

Findings:

USG: ill-defined hypoechoic nodular lesion confined to subcutaneous fat layer, both ankle dorsum _ relatively symmetric lesions

MRI: focal infiltrative lesion with T1 & T2 hypointensity & poor enhancement

Differential Diagnosis:

1) nodular fasciitis

2) fibrous hamartoma of infancy

3) pilomatricoma

4) foreign body reaction

Discussion:

Granuloma annulare is a benign inflammatory disorder and.is subtyped as localized (LGA), generalized, perforating, and subcutaneous (SGA) forms. The subcutaneous type is known to occur almost exclusively in children. It is the most common benign soft-tissue tumor during infancy and early childhood and has a strong predilection for the pretibial area.

Subcutaneous granuloma annulare is a benign inflammatory disorder that primarily affects healthy children and manifests as a rapidly growing, painless, nonmobile mass, most commonly located in the leg. . There is a moderately higher occurrence rate in girls (1:1.8). The most striking feature is the pretibial location. Other locations include the forehead, scalp, and extensor surfaces of the hands and the buttocks. The size of the mass is reported to range from 5 to 50 mm.

The etiology of SGA is unclear. Involvement of triggering events such as trauma, defects in cell-mediated immunity, insect bites, and infection has not been demonstrated. In contrast to SGA in adults, no association with connective tissue disorders has been identified in children.

Subcutaneous granuloma annulare (deep granuloma annulare, pseudorheumatoid nodule, benign rheumatoid nodule) shows a characteristic pathologic feature with formation of palisading granulomas. Other types of palisading granulomas are the rheumatic nodule of rheumatic fever, the classic juxta-articular rheumatoid nodule of rheumatoid arthritis, and necrobiosis lipoidica diabeticorum in association with diabetes mellitus.

Failure to consider SGA as a tentative diagnosis often leads to an extensive clinical and radiologic examination and inappropriate surgical interventions.

The non-surgical approach is unquestionably justified, since excising an SGA is associated with a reported high recurrence rate within a period of months in 19 to 87% of cases.

Although incisional biopsy is the criterion standard, ultrasound examination performed by a skilled physician can help confirm the diagnosis and avoid unnecessary invasive procedures.

Several reports described the sonographic characteristics of SGA including a solid, ill-defined, hypoechoic mass in the subcutaneous tissue that may adhere to the fascia or the periosteum but does not invade the underlying planes and it usually showed as poorly or nonvascularized lesion.

References:

1. Stenzel M, Voss U, Mutze S, Hesse V. A pretibial lump in a toddler— sonographic findings in subcutaneous granuloma annulare. Ultraschall Med. 2010;31:68-70


2. Navarro OM. Soft tissue masses in children. Radiol Clin North Am. 2011;49:1235-1259.


3. Vazquez OI, Qeuvedo A, Rodriguez VA. Usefulness of ultrasonography in the diagnosis of subcutaneous granuloma annulare