Tumors of fat, muscle, cartilage, and bone

Chapter 21

Tumors of fat, muscle, cartilage, and bone


Lipomas typically present as asymptomatic, mobile soft nodules in the deep soft tissue or subcutis. Histologically, they are thinly encapsulated tumors composed of sheets of mature adipocytes that are indistinguishable from the fat cells in the subcutaneous tissue. Each adipocyte has a single vacuole and an eccentric nucleus. The thin fibrous septa, which contain sparse blood vessels, are delicate and inconspicuous. Intramuscular lipomas, commonly of the forehead, consist of mature fat cells that displace muscle, splaying the fibers.

There are several rare syndromes in which multiple lipomas occur. Hundreds of slow-growing subcutaneous and deep or visceral lipomas develop in early adulthood in the autosomal-dominant condition familial multiple lipomatosis. Benign symmetric lipomatosis (Madelung’s disease) has a predilection for middle-aged men with a propensity to develop multiple lesions, especially in the region of the neck in a “horse-collar” distribution. Tender, circumscribed or diffuse fatty deposits of the lower legs, abdomen, and buttocks in obese patients exemplify adiposis dolorosa (Dercum’s disease), sometimes associated with weakness and mental disturbances. Lipomas may also be a component of Gardner’s syndrome, Bannayan–Zonana syndrome, Cowden’s syndrome, and Proteus syndrome.

Pleomorphic lipoma

Pleomorphic lipomas have a firm consistency and similar distribution to spindle cell lipomas on the neck and shoulder girdle of older men.


Hibernomas are rare tumors that demonstrate differentiation toward brown (fetal) fat. While brown fat occurs anywhere in a fetus, hibernomas in adults most frequently arise in the subcutis of the shoulder girdle, posterior neck, and axilla. The gross brown color is a result of the prominent vascularity and many mitochondria within the tumor cells.

Mulberry cells with central nuclei predominate in most hibernomas. Smaller cells with granular cytoplasm and univacuolated cells may sometimes be seen.

Apr 26, 2016 | Posted by in Dermatology | Comments Off on Tumors of fat, muscle, cartilage, and bone
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