Dermatology Online Journal
Adenolipoma of the skin
- Author(s): Agua, C Del
- Felipo, F
- et al.
Adenolipoma of the skin
Department of Pathology. Hospital General de Soria. Soria. Spain. firstname.lastname@example.org
C Del Agua, and F Felipo
Dermatology Online Journal 10 (2): 9
Adenolipoma of the skin is an unusual variant of lipoma recently described by Hitchcock et al. and characterized by the presence of normal eccrine sweat glands within a lipoma. We report a case and review the literature. A 45-year-old woman presented with a slow-growing, painless nodule on the thigh, clinically considered to be lipoma. Microscopically it comprised an adipose-tissue proliferation with a single eccrine secretory coil and associated duct in the periphery and in the center of the nodule. This benign lesion has been termed adenolipoma because of the presence of adipose tissue and eccrine glands. It probably represents only a histological curiosity in which the eccrine glands are entrapped by the adipose proliferation. Adenolipoma of the skin is a distinct lesion that can occur in the dermis or subcutaneous tissue.
Adenolipoma of the skin is an unusual variant of lipoma, recently described by Hitchcock et al. ; it is characterized by the presence of normal eccrine sweat glands in association with a lipoma. We report a case and review the literature.
A 45-year-old woman presented with a slow-growing, painless nodule on her thigh. The clinical impression was lipoma, and the lesion was excised. The gross examination revealed a soft, yellow, lobulated mass measuring 2.5 cm in greatest diameter.
|Figure 1||Figure 2|
|Eccrine glands situated within fatty proliferation (Figs. 1 and 2).|
|Figure 3||Figure 4|
|High-power views of eccrine ducts (Figs. 3 and 4).|
Microscopically, the nodule comprised adipose tissue proliferation with distinct lobulation within the tumor. A single eccrine secretory coil with an associated duct were seen in the periphery and center of the nodule. A well-developed capsule was present. Aside from the expansion of the coil by adipose tissue, no architectural nor cytologic alteration was seen in the eccrine glands.
In 1993 Hitchcock et al. described a lipoma of the skin with epithelial component and termed it adenolipoma of the skin . There are two series reports of these, including the first by Hitchcock et al.  with nine cases and the second by Ait-Ourhrouil et al.  with eleven cases. There is also an additional description of an adenolipoma in a case report . The most frequent locations of this tumor are the thigh, shoulder, chest, and arm. The diameter of the lesion varies from 1 to 6 cm.
These lesions present as a solitary, painless, slow-growing tumors. Most often they are diagnosed on clinical examination as lipomas, and less frequently as skin tags or neurofibromas. The average patient age is 50 (range 25-75 years).
On gross examination, they are described as yellow, soft, lobulated tumors.
Histologically, a well-developed capsule can be identified in most of the lesions. The tumors are composed of lobulated adipose tissue with larger and more prominent lobules than are present in normal subcutaneous adipose tissue. Within the neoplastic adipose issue are well-differentiated eccrine glands and ducts without fibrous stroma. In the cases in which a relation to the dermis could be assessed, the glands are situated more deeply than normal eccrine glands. Ait-Ourhrouil et al.  measured the distance between dermis and eccrine glands in normal skin and in adenolipomas, and they reported that mean distance was 40µn; in normal skin (range from 0, for intradermal glands, to 750µn; for subdermal glands) compared to 15 mm in adenolipomas (range from 6.70 to 20 mm).
The clinical data, the enlarged lobules of fatty tissue, and the abnormal presence of eccrine glands help clarify the diagnosis adenolipoma. However, there may be a problem in diagnosing fragmented specimens when it is not possible to assess the location of eccrine glands. Another diagnostic pitfall is the peripheral location of the eccrine glands in the specimens; it is difficult to assess whether the glands are contained within the tumor or are merely adjacent normal structures. Serial sectioning of lesions could be used to confirm the presence of glandular component within the tumor.
The normal anatomic variation in eccrine gland location suggests the possibility of dermal, subcutaneous, or combined locations for adenolipomas.
The differential diagnosis of adenolipoma includes the common lipoma and its variants, the lipomatous variant of eccrine angiomatous hamartoma , and nevus lipomatosus cutaneous superficialis . Adenolipoma has a similar presentation to common lipoma. The mean diameter of adenolipoma is smaller than that of common lipomas, but the age at time of resection and the tendency to spare distal sites are shared features. A subcutaneous lipoma may compress the dermis and produce an appearance similar to that of adenolipoma. However, displacement of the eccrine glands rather than incorporation into the lesion suggest the subcutaneous lipoma.
Eccrine angiomatous hamartoma is typically a single lesion present at birth on an extremity. On histology, it shows increased numbers of eccrine structures and numerous capillary channels surrounding or intermingled with the eccrine structures. Its rare lipomatous variant also contains fatty tissue.
Nevus lipomatosus superficialis usually presents as multiple papules or nodules linearly distributed on the buttock or hip. The lesion may be present at birth or begin in infancy. Solitary lesions have been described but it seems preferable to regard them as polypoid fibrolipomas. Microscopically, there are groups of fat cells among the collagen bundles of the dermis in variable amount. Aside from that, the dermis may be entirely normal, but the density of the collagen bundles, the number of fibroblasts, and the vascularity are greater than the normal skin. Perivascular inflammation and abundant mast cells are seen.
Because of the presence of adipose tissue and eccrine glands, Hitchcock et al. termed the lesion described in this report as adenolipoma , rejecting the term adnexal fat pad lipoma because of the absence of follicular, sebaceous, or apocrine glands. To these authors the term lipoadenoma is not appropriate because this name implies a neoplastic proliferation of the eccrine glands, and it is believed that the glands are entrapped and carried by the adipose proliferation rather than neoplastic.
On the other hand, Ait-Ourhrouil et al.  suggested the name perisudoral lipoma. They believe that this lesion develops from peripheral adipose tissue from eccrine glands and consider the term adenolipoma to be inappropriate because the glands or ducts never show a glandular proliferation component.
We agree with Hitchcock et al.  and believe that the adenolipoma is a fatty-tissue proliferation that includes and moves the normal (rather than neoplastic) eccrine glands to the center of the nodule. Although this lesion originates from the fatty tissue in the periphery of the sweat coils, we prefer the term adenolipoma because it does not connote a glandular proliferation component but an entrapped glandular component.
References1. Hitchcock M, Hurt M, Santa Cruz D. Adenolipoma of the skin: A report of nine cases. J Am Acad Dermatol 1993; 29:82-85.
2. Ait-Ourhrouil M, Grosshans E. Le lipome périsudoral. Ann Dermatol Venereol 1997: 124; 845-848.
3. Rongioletti F, Santa Cruz D. L´adénolipoma cutané. Ann Dermatol Venereol 1997; 124: 855-856.
4. Donati P, Amantea A, Balus L. Eccrine angiomatous hamartoma: a lipomatous variant. J Cutan Pathol 1989; 16: 227-229.
5. Dotz W, Prioleau PG. Nevus lipomatous cutaneus superficialis: A light and electron microscopic study. Arch Dermatol 1984; 120:376.
© 2004 Dermatology Online Journal