Parosteal lipoma with hyperostosis

Multimodality imaging features of parosteal lipomas

OBJECTIVE

To examine the multimodality imaging characteristics of parosteal lipomas.

MATERIALS AND METHODS

With IRB approval, our institutional imaging database and medical record were retrospectively reviewed from 1990-2020 for cases of pathologically-proven and/or imaging diagnosed parosteal lipomas.

RESULTS

There were 22 patients (12 males, 10 females) with a mean age of 57.1 ± 12.7 years (range 31-80 years). 11/22 cases (50%) were pathologically-confirmed on biopsy or surgical resection and 11/22 (50%) had imaging features compatible with parosteal lipoma. Lesions occurred most commonly along the femur (8/22, 36%), followed by the forearm (3/22, 14%). All cases demonstrated a juxtacortical fatty mass containing an osseous excrescence that was firmly attached to the cortical surface. The osseous excrescences were characterized as pedunculated in 16/22 (73%) and sessile in 6/22 (27%). The average largest dimension of the osseus excrescences was 2.4 ± 1.6 cm (range 0.8-6.1 cm) and the lipomatous portions 7.8 ± 3.8 cm (range 2.0-19.5 cm). The excrescences contained mature bone in 12/22 (55%) cases and a mixture of mature bone and radiating bone spicules in 10/22 (45%). There were non-lipomatous elements in the fatty portion of the mass in 13/22 (59%) of cases. Most cases (19/22, 85%) had cortical thickening/periostitis near the base of the osseous stalk. Two patients had a bone scan that demonstrated uptake in the osseous excrescence, and two patients had an FDG PET/CT that demonstrated no uptake.

CONCLUSION

Parosteal lipomas are a rare benign lipomatous tumor with pathognomonic multimodality imaging features that may obviate the need for biopsy.

Parosteal lipoma of the forearm: A case report and a literature review

RATIONALE

Parosteal lipomas are rare neoplasms comprising mature adipocytes situated in a proximity to bone. Although these tumors follow a benign course, the reactive osseous changes that may occur with such lesions might raise the suspicion of malignancy.

PATIENT CONCERNS

Here we present a case of a 33-year-old male patient complaining of pain and swelling in the right anterior forearm without history of trauma.

DIAGNOSIS

An magnetic resonance imaging of the region revealed a lobulated intramuscular fat intensity mass within the supinator muscle. Bony projection inseparable from the anterolateral radial diaphyseal cortex and periosteum was also seen. The radiological features suggested the diagnosis of parosteal lipoma.

INTERVENTION

After the radiological diagnosis of a parosteal lipoma, the patient was offered a total surgical excision of the mass.

OUTCOMES

The mass was removed successfully. Histopathology showed mature benign adipose tissue bordered by thin fibrous septa confirming the diagnosis of parosteal lipoma. Follow-up magnetic resonance imaging after 6 months did not reveal any signs of complications or recurrence.

LESSONS

Distinction of the features of parosteal lipomas is needed to establish the accurate diagnosis, discriminate it from malignant lesions, predict potential neurovascular compromises, and follow up until a curative action is planned.

Lipoma parosteal de arco costal: relato de caso

Os autores relatam o caso de um paciente com história de tumoração na região subaxilar esquerda, de crescimento progressivo, com início há vários anos. A radiografia e a tomografia computadorizada evidenciaram lesão expansiva com densidade menor do que partes moles adjacentes, com contornos bem definidos, contígua ao quinto arco costal esquerdo, com ossificações irregulares em seu interior. Histologicamente, foi diagnosticado lipoma parosteal, um raro tumor benigno de crescimento lento.

Parosteal lipoma of the rib

Parosteal lipoma is a rare benign tumor composed of adipose tissue contiguous to the periosteum of the underlying bone. These tumors are slow-growing, nontender masses that affect, almost exclusively, the diaphysis of the long bones of the upper and lower limbs. We hereby describe the CT characteristics with the correlative pathological findings in a rare case of parosteal lipoma of the rib.