Lipoma

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Subcutaneous lipoma on the trunk of a dog[1]

Lipoma are a relatively slow-growing neoplasia of canine cutaneous fat and subcutaneous muscle.

Although lipomas primarily involve fat cells, variants have been reported which are characterized by an additional component such as capillaries (angiolipomas)[2] or fibrous connective tissue (fibrolipomas, chondrolipoma), thymus (thymofibrolipoma)[3] and bone (osteolipoma)[4].

These tumors are rarely metastatic but can invade intermuscular sites[5]. They commonly occur on the trunk, although aberrant locations include the epiglottis[6], peritoneum[7], orbit[8] and pericardium[9] have been reported. Large lipomas may become centrally necrotic and result in toxemia[10]. Infiltration of regional bone, particular of the vertebrae can result in neurological disease due to spinal compression[11].

Clinically, these tumors vary in size from small pedunculated subcutaneous swellings to large solitary tumors weighing up to 1 kg or more. They are commonly diagnosed in dogs over 10 years of age[12]. Lameness may occur if the tumor infiltrates digital tendons of the limbs[13].

The causes of this tumor are multivariate, including:

  • Obesity
  • Exposure to various dietary and environmental toxins
  • Breed predisposition

Diagnosis is readily established by the location, shape and relatively benign nature of the mass, supported by histological examination of needle-biopsy or exploratory sampling.

A differential diagnosis would include mast cell tumor[14], liposarcoma and gangliosidosis[15].

Surgical excision is usually curative. Liposuction is an alternative surgical method, though more technically demanding and not recommended for infiltrative or giant inguinal lipomas[16].

Small tumor are often left untreated unless they interfere with critical organs or are aesthetically unpleasing to the owner. They are rarely life-threatening.

References

  1. All Pets
  2. Liggett AD et al (2002) Angiolipomatous tumors in dogs and a cat. Vet Pathol 39(2):286-289
  3. Morini M et al (2009) Thymofibrolipoma in two dogs. J Comp Pathol 141(1):74-77
  4. Ramírez GA et al (2010) Chondro-osteoblastic metaplasia in canine benign cutaneous lipomas. J Comp Pathol 142(1):89-93
  5. Case JB et al (2012) Anatomic distribution and clinical findings of intermuscular lipomas in 17 dogs (2005-2010). J Am Anim Hosp Assoc 48(4):245-249
  6. Carpenter M (2012) Lipoma on the epiglottis of a dog. Vet Rec 171(9):226
  7. Klosterman ES et al (2012) Transdiaphragmatic extension of a retroperitoneal lipoma into the intrathoracic extrapleural space via the lumbocostal trigone in a dog. J Am Vet Med Assoc 240(8):978-982
  8. Williams DL & Haggett E (2006) Surgical removal of a canine orbital lipoma. J Small Anim Pract 47(1):35-37
  9. Ben-Amotz R et al (2007) Pericardial lipoma in a geriatric dog with an incidentally discovered thoracic mass. J Small Anim Pract 48(10):596-599
  10. Rebhun RB et al (2008) What is your diagnosis? Necrotic lipoma. J Am Vet Med Assoc 233(11):1691-1692
  11. Kim HJ et al (2005) Infiltrative lipoma in cervical bones in a dog. J Vet Med Sci 67(10):1043-1046
  12. Villamil JA et al (2011) Identification of the most common cutaneous neoplasms in dogs and evaluation of breed and age distributions for selected neoplasms. J Am Vet Med Assoc 239(7):960-965
  13. Szabo D et al (2011) Carpal canal lipoma causing lameness in a dog. Vet Comp Orthop Traumatol 24(4):299-302
  14. Jakab C et al (2009) Cutaneous mast cell tumour within a lipoma in a boxer. Acta Vet Hung 57(2):263-274
  15. Rahman MM et al (2012) Pathological features of salivary gland cysts in a Shiba dog with GM1 gangliosidosis: a possible misdiagnosis as malignancy. J Vet Med Sci 74(4):485-489
  16. Hunt GB et al (2011) Liposuction for removal of lipomas in 20 dogs. J Small Anim Pract 52(8):419-425