Subcutaneous lumps represent a heterogeneous category of cutaneous disorders that usually present as palpable nodules in the deeper extents of the skin and soft tissue. Angiolipomas and lipomas, comprised of vessels and benign adipose, or adipose alone, represent the most common entities in this category of disease. Other neoplasms in this category include metastatic, neural, and fibrohistiocytic tumors.
Important History Questions
How long has the lesion(s) been present?
Benign tumors, such as angiolipomas and lipomas, typically grow slowly and have been present for years at the time of presentation. A new or rapidly growing subcutaneous growth should raise concern for a more aggressive neoplasm.
Has the lesion changed?
Benign neoplasms typically grow slowly, whereas malignant neoplasms (e.g., liposarcoma, malignant fibrous histiocytoma, metastatic tumors), and some select benign neoplasms (e.g., nodular fasciitis), often demonstrate rapid growth.
Is there a family history of similar lesions?
Angiolipomas and lipomas can both be familial (e.g., benign familial lipomatosis). Therefore, an affirmative answer could indicate an inherited disorder. However, it is important to realize that a negative response to this question does not exclude multiple lipomas or angiolipomas because most cases are sporadic.
Important Physical Findings
How many lesions are present?
Multiple lesions occurring in a person could indicate multiple lipomas, angiolipomas, or even a metastatic process. Other types of tumors, such as liposarcoma, malignant fibrous histiocytoma, or spindle cell lipoma, nearly always occur as a singular process.
How large is the tumor?
In general, small tumors are more likely to be benign, whereas larger tumors are more likely to be malignant. For example, most benign lipomas are less than 5 cm in diameter; most liposarcomas are over 10 cm in size at the time of presentation.
What does the tumor feel like on palpation?
Most lipomas are soft and compressible, whereas most fibrohistiocytic tumors and metastatic tumors often feel firm. Some invasive malignant processes may even seem tethered to underlying structures.
Does the lesion appear to be sharply circumscribed?
Most lipomas and angiolipomas, as well as rare lipomatous tumors, are usually sharply delineated from the surrounding fat. Some can even be moved laterally, whereas metastatic lesions and most fibrohistiocytic tumors usually do not have well delineated margins and infiltrate into the adjacent subcutis.
Where are the lesions located?
The distribution of the lesions can be important. Multiple lipomas and angiolipomas often affect the forearms, thighs, and lateral thorax. Spindle cell lipoma often involves the head and neck.
Lipoma
ICD10 code D17 (site dependent)
BENIGN NEOPLASIA
Pathogenesis
A lipoma is benign tumor of fat. It is a common condition and the most common neoplasm of the subcutis. There is evidence that lipomas, although benign, are often the result of one or more genetic abnormalities. Translocations and other gene rearrangements of the chromosome 12q15 area are among those most often observed. In many cases, multiple lipomas are inherited as an autosomal dominant condition (benign familial lipomatosis).
Clinical Features
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Lipomas usually develop during adulthood but may also present in younger or older patients.
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Rarely, lipomas are present at birth.
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Lipomas may appear anywhere on the body but the upper trunk and extremity are most often affected.
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Lipomas deeper than the subcutaneous tissue (e.g., intramuscular lipomas) can occur.
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Lipomas present as a skin-colored subcutaneous lesion that is soft and circumscribed on palpation ( Fig. 35.1 ). Some lipomas are slightly mobile on palpation.
Fig. 35.1
Multiple lipomas.
(From the Fitzsimons Army Medical Center Collection, Aurora, CO.)
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Lipomas are often asymptomatic but can be tender or painful, especially when compressed.
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Large lipomas may cause dilation of overlying blood vessels ( Fig. 35.2 ).
Fig. 35.2
Large lipoma with numerous vessels.
(From the Fitzsimons Army Medical Center Collection, Aurora, CO.)
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Rare lipomas may compress nerves to produce a peripheral neuropathy.
Diagnosis
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Lipomas often can be diagnosed simply based on the history and clinical presentation of a long-standing, slow-growing, soft, and well-circumscribed subcutaneous nodule, with a fatty consistency.
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If the diagnosis is in question, a biopsy may be performed. It must be remembered that the findings of interest exist deep in the soft tissue, and an incisional or excisional biopsy may be necessary.
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Rare cases potentially associated with a peripheral neuropathy may require magnetic resonance imaging (MRI) for assessment.
Treatment
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Lipomas are benign and do not require treatment.
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For symptomatic lesions, surgical excision may be performed. Many lipomas can be removed by shelling (or squishing) out the lipoma through a small opening, such as a punch biopsy, but this does not work in all cases. Large lipomas ( Fig. 35.3 ), or those located on the forehead or posterior neck, may lie beneath the galea or may be admixed with collagen (fibrolipomas), complicating removal. Liposuction can be done in select cases.
