Pathology of Lipoma and Variants
Lipoma is a very common subcutaneous which accounts for more than 90% of the adipocytic tumours
reported by the pathologists.
These are usually located on the trunk, proximal limbs, thigh and the neck.
Rare cases have been reported in the vulva.Dermatopathology Quiz Case 201
Usually adults are affected, in the fifth and sixth decades of life.
Clinically, the tumour presents as a well circumscribed, encapsulated slowly growing, soft, mobile tumour.
The tumour varies in size from a few millimeters to 20 cms or more in diameter.
Cut surface mostly reveals mature adipose tissue.
In some cases fibrous or myxoid areas or areas of fat necrosis may be present.
Microscopically, the tumour is composed of mature adipocytes, with minimal variation in size of the adipocytes dissected by thin fibrous septa containing a few blood vessels.
Fibrolipoma- There is increased stromal fibrosis.
Angiomyxolipoma: The lesion consists of adipose tissue without lipoblasts, extensive myxoid areas, and numerous blood vessels.
Adenolipoma: Adenolipoma of the skin is a superficially located form of lipoma composed of large lobules of mature adipocytic tissue admixed with eccrine ducts and glands.
Chondrolipoangioma: Prominent chondro osseous and vascular component.
Myxoid lipoma , myxolipoma: A myxoid background stroma.
Myelolipoma: Benign, tumor-like lesion consisting of mature adipose tissue with hematopoietic elements arising in the adrenal.
Most are asymptomatic and are discovered accidentally.
Differential diagnosis : Extramedullary hematopoiesis.
Myolipoma: Characterized by adipose tissue together with smooth muscle fibres usually located in the retroperitoneal location and the abdomen.
Differential Diagnosis: angiomyolipoma and liposarcoma with heterologous elements.
Nevus lipomatosus: This lesion presents as plaque or solitary lesions.
Microscopically , mature adipocytes are present in the dermis.
These fat cells are usually not connected with the fat of the underlying subcutis.
Sometimes the adipocytes extend to undersurface of the epidermis.
There are increased number of ectatic vessels, fibroblasts and mast cells in the papillary dermis.
Infiltrating lipoma: Infiltrating lipoma is an uncommon mesenchymal neoplasm that characteristically infiltrates adjacent tissues and tends to recur after excision. These are usually located in the thigh, shoulder region, upper arm and in the chest wall. This type of lipoma may rarely occur in the head and neck region.
Lipedematous scalp: There is thickening of the subcutaneous fat of the scalp.
This is usually associated with alopecia.
-Benign symmetrical lipomatosis
-Familial multiple lipomatosis
Rearrangement of 12q, 13q, 6p
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