Dr  Sampurna Roy  MD

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 .
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. (DermAtlas)
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.  IMAGE1 ;  IMAGE2

Fibrolipoma- There is increased stromal fibrosis.

Fibrolipomatous hamartoma of Nerve: CLICK HERE

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.

Chondroid lipoma: CLICK HERE

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.  D/D:Extramedullary hematopoiesis. IMAGE    

  IMAGE1 ;  IMAGE2    

Angiolipoma:CLICK HERE

Intramuscular lipoma: PUBMED LINK  Occurs in middle to late adult life. Presents as deep seated slow growing usually painless mass in the large muscles of the extremities specially those of the thigh, shoulder and upper arm and in the chest wall. They may be divided into infiltrative and well-circumscribed types. Histologically striated muscle fibres are diffusely infiltrated by mature.adipocytes. No atypical features are present.

D/D- well differentiated liposarcoma ;  diffuse lipoblastomatosis (occur in infants and children; subcutis and muscle are affected;more than one type of muscle involved).   IMAGE1 ;  IMAGE2  ; IMAGE3 ; IMAGE4 .

Myolipoma: Characterized by adipose tissue together with smooth muscle fibres usually located in the retroperitoneal location and the abdomen. D/D 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.

Synovial lipoma: (Lipoma Arborescens) PUBMED LINK This is a rare benign intrarticular lesion characterised by the replacement of the subsynovial tissue by mature fat cells giving rise to a villous proliferation. IMAGE

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.

Lipomatosis- Conditions in which diffuse masses of adipose tissue develop in the subcutaneous tissue.  Image (DermAtlas)
-Benign symmetrical lipomatosis
-Familial multiple lipomatosis
-Adiposis dolorosa
-Diffuse lipomatosis
-Pelvic lipomatosis
-Mediastinoabdominal lipomatosis

Cytogenetics-
Rearrangement of 12q, 13q, 6p