Myolipoma

Classification according to ICD-O-3
8890/0	Myolipoma
ICD-O-3 first revision online

A myolipoma (synonymous with extrauterine lipoleiomyoma ) is a rare benign tumor that is composed of mature adipose tissue and smooth muscles in varying proportions. Often the tumors are large and tend to occur in the area of the pelvis and abdomen . They show no tendency to malignant degeneration and do not recur after complete removal.

Epidemiology

Myolipomas are very rare tumors that are seen more often in women (2: 1).

pathology

Macroscopically , myolipomas appear as partially or completely encapsulated yellowish tumors with strands or nodules of light brownish, fibrillary or vertebral textured tissue. In the deep soft tissue, the tumor size is usually between 10 and 25 cm, smaller lesions are usually observed in the subcutaneous tissue.
Histologically , a tumor made up of mature adipose tissue and smooth muscle can be seen, with the muscular component usually dominating in a ratio of 2: 1. The smooth muscles are often evenly distributed over the lesion and organized in short fascicles, which can lead to a sieve-like tissue pattern. The muscle cells show a deep eosinophilic , fibrillary cytoplasm . Atypia or any noteworthy mitotic activity are not observed here, as in the fatty tissue component. The latter sometimes shows signs of fibrosis and inflammatory changes .

Immunohistochemistry

The smooth muscle component of myolipoma shows diffuse and strong positivity for smooth muscle actin and desmin . Expression of estrogen and progesterone receptors has been described. The melanocytic marker HMB45 , which is expressed in angiomyolipoma , which can be used for differential diagnosis , is negative.

diagnosis

The diagnosis is made after obtaining a tissue sample ( incisional biopsy , excisional biopsy , fine needle aspiration ) by means of a histological examination. Imaging procedures ( sonography , computed tomography , magnetic resonance tomography ) are used preoperatively.

Differential diagnosis

From the pathologists ruled out especially the angiomyolipoma , shows the histological also thick-walled vascular structures. The differentiation from highly differentiated liposarcoma with heterologous smooth muscle components is clinically important .

genetics

Alterations of the HMGA2 gene have been described in myolipoma.

therapy

The treatment of choice is surgical removal of the tumor.

forecast

It is a benign lesion that neither shows a tendency to degenerate nor does it recur after complete surgical removal .

Individual evidence

↑ ^a ^b ^c C. DM Fletcher: Histopathology of Tumors. 3. Edition. Churchill Livingston Elsevier, 2007, ISBN 978-0-443-07434-9 .
↑ ^a ^b ^c ^d ^e ^f ^g J. M. Meis-Kindblom, LG Kindblom: Myolipoma of Soft Tissue. In: Pathology and Genetics of Tumors of Soft Tissue and Bone. IARC Press, Lyon 2002, ISBN 92-832-2413-2 .
↑ JM Meis, LG Kindblom: Myolipoma of Soft Tissue. In: WHO Classification of Tumors of Soft Tissue and Bone. IARC, Lyon 2013, ISBN 978-92-832-2434-1 .
↑ ^a ^b V. B. Shidham, SM Acker, D. Vesole, DA Hackbarth: Benign and Malignant Soft Tissue Tumors: Workup. (March 30, 2009); http://emedicine.medscape.com/article/1253816-diagnosis

[fletcher-1] C. DM Fletcher: Histopathology of Tumors. 3. Edition. Churchill Livingston Elsevier, 2007, ISBN 978-0-443-07434-9 .

[who-2] ↑ ^a ^b ^c ^d ^e ^f ^g J. M. Meis-Kindblom, LG Kindblom: Myolipoma of Soft Tissue. In: Pathology and Genetics of Tumors of Soft Tissue and Bone. IARC Press, Lyon 2002, ISBN 92-832-2413-2 .

[who2-3] JM Meis, LG Kindblom: Myolipoma of Soft Tissue. In: WHO Classification of Tumors of Soft Tissue and Bone. IARC, Lyon 2013, ISBN 978-92-832-2434-1 .

[emedicine-4] V. B. Shidham, SM Acker, D. Vesole, DA Hackbarth: Benign and Malignant Soft Tissue Tumors: Workup. (March 30, 2009); http://emedicine.medscape.com/article/1253816-diagnosis