Subcutaneous granuloma annulare: MR imaging findings

The epifascial cap: A typical imaging sign for subcutaneous granuloma annulare in children

Objectives

Subcutaneous granuloma annulare (SGA) is a rare, self-limiting granulomatous disease in children, commonly diagnosed by histopathology following biopsy or surgical excision. This study aimed to identify imaging clues for SGA that could expedite accurate diagnosis and avoid the need for biopsy in children.

Methods

We retrospectively analyzed complete hospital records of all children diagnosed with SGA at our institution from January 2001 to December 2020. Detailed disease history, imaging findings, management, and outcome were evaluated.

Results

We identified 28 patients (20 girls) at a median age of 3.75 (range 1-12.5 years). Ten patients presented with multiple lesions. Most lesions were located on the lower extremities (n = 26/41). Ultrasound examinations were performed on all patients, and 12 (43%) patients also received an MRI. Surgical intervention was conducted in 18 (64%) patients either by incisional biopsy (n = 6) or total excision of the lump (n = 12). In all patients who did not undergo surgery, SGA resolved spontaneously. A careful review of the MRIs led to the discovery of a characteristic imaging shape of SGA lesions: the epifascial cap with a typical broad circular base laying on the fascia, extending towards the subdermal/dermal tissue. This distinctive shape was evident in every patient in our cohort.

Conclusions

The "Epifascial Cap Sign" is a specific imaging sign for SGA, which to the best of our knowledge, helps distinguish this disease from other subcutaneous lesions. Recognition of this novel diagnostic sign combined with the historical and physical findings should enable clinicians to establish SGA diagnosis easily and diminish the need for further invasive diagnostic procedures.

An unusual presentation of subcutaneous granuloma annulare in association with juvenile-onset diabetes: case report and literature review

Subcutaneous granuloma annulare (SGA) is a rarely reported subtype of granuloma annulare that occurs almost exclusively in children. The etiology of these lesions is unknown, although a possible relationship to insulin-dependent diabetes mellitus (IDDM) has been proposed in the literature. Here we present an unusual case of SGA on the right forearm in a 3-year-old girl. Unlike the typical lesions noted on the extremities, on magnetic resonance imaging her lesions involved the subcutaneous tissue and adjacent muscles in multiple locations. Histopathologically, the case was consistent with SGA but was unusual in its distribution involving multiple muscles, a finding that has not been previously reported. Weeks after incisional biopsy, she was readmitted with diabetic ketoacidosis (DKA) secondary to IDDM. After treatment of her DKA and control of her glycemia, the forearm SGA vanished, which supported the pathologic diagnosis and alleviated our concerns secondary to the unusual distribution.

Pseudotumoural soft tissue lesions of the hand and wrist: a pictorial review

Mimickers of soft tissue tumours in the hand and wrist are more frequent than true neoplastic lesions. Pseudotumours belong to a large and heterogeneous group of disorders, varying from normal anatomical variants, cystic lesions, post-traumatic lesions, skin lesions, inflammatory and infectious lesions, non-neoplastic vascular lesions, metabolic disorders (crystal deposition disease and amyloidosis) and miscellaneous disorders. Although the imaging approach to pseudotumoural lesions is often very similar to the approach to “true” soft tissue tumoral counterparts, further management of these lesions is different. Biopsy should be performed only in doubtful cases, when the diagnosis is unclear. Therefore, the radiologist plays a pivotal role in the diagnosis of these lesions. Awareness of the normal anatomy and existence and common imaging presentation of these diseases, in combination with relevant clinical findings (clinical history, age, location and skin changes), enables the radiologist to make the correct diagnosis in most cases, thereby limiting the need for invasive procedures.

Large benign rheumatoid nodules of the trunk in an elderly patient: radiologic appearance mimicking a soft-tissue sarcoma

An 80-year-old woman without any evidence of rheumatoid arthritis presented with two large (maximum diameter: 6 cm and 7 cm), rapidly growing, rubbery nodules on the trunk. Although the clinical and radiological appearance suggested malignancy, the nodules were pathologically identical to rheumatoid nodules in rheumatoid arthritis, and the nodules regressed spontaneously. The final diagnosis was benign rheumatoid nodules. Recognition of this rare clinical entity is important to avoid unnecessary examination and treatment.