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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5204_Библиотеки_им_академика_М_И_Перельмана.pdf
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R. Sciot et al.
3. When dealing with a mammary tumor, always consider silicon granuloma, often
associated with leakeage of silicon from the ssured prosthesis and showing a
high number of lipoblast-like macrophages.
4. In lipomatous tumors, inltrative margins are not a sign of malignancy (see intra-
muscular lipoma).
5. The exact location of the tumor is often very informative. Facing a well-
differentiated adipocytic tumor in the retroperitoneum, a well-differentiated LPS
(lipoma-like) is most likely, and MDM2 amplication should be searched for, by
in situ hybridization-based techniques.
6. Nuclear pleomorphism in a fat tumor does not equal malignancy. Pleomorphic
lipoma is a notable example.
Cell types occurring in lipomatous tumors (Fig.1.1)
1. Mature adipocytes
2. Spindle cells
3. Lipoblasts
4. Floret-like multinucleated cells
5. Multivacuolated brown adipocytes
6. Bizarre hyperchromatic stromal cells
7. Pleomorphic lipoblasts
Lipoma (Fig.1.2)
Denition It is the most frequent soft tissue tumor. It is generally solitary, but it
may present as multiple tumors in +/− 5% of cases. It may be dened as a proliferation of mature adipocytes.
Age at Presentation
Gender Men are more affected, particularly obese individuals.
Localization Lipomas may present in any anatomic location. When insurging in
the retroperitoneum or in the abdomen, a well-differentiated liposarcoma (WDLPS)
should always be considered rst, given that benign lipomas in these locations are
very rare. In other locations like the extremities and trunk, when a well- differentiated
fatty lesion is deep-seated, more than 10cm in diameter, and occurring in a patient
older than 50years, or the lesion is recurring, the possibility of an atypical lipomatous tumor (ALT) should always be considered and testing for MDM2 is mandatory
(see chapter on ALT/WDLPS).
Clinical Presentation Painless, slow-growing mass of long duration. In deep
lesions, the clinical presentation depends on the localization.
Adults, 30–50years.
1 Adipocytic Tumors
3
Mature adipocytes
Lipoblasts
Floret-like multinucleated cells
Spindle cells
Multivacuolated brown adipocytes
Bizzarre hyperchromatic stromal cells
Pleomorphic lipoblasts
Fig. 1.1 Cell types occurring in lipomatous tumors
Macroscopy Well-circumscribed mass– unless intramuscular– surrounded by a
thin capsule, yellow on cut surface. Diameter ranges from 1 to 5cm in supercial
tumors, whereas deep tumors may reach larger dimensions.
Microscopy Proliferation of mature adipocytes. The size and shape of adipocytes
are uniform, with minimal or no variation. Nuclei are small, inconspicuous, compressed at the cell periphery. Atypical nuclei or lipoblasts are generally absent.
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R. Sciot et al.
Fig. 1.2 Schematic representation of lipoma
Prominent nuclei with some atypia, associated with marked variation in size and
shape of adipocytes, should lead to the suspicion of ALT/WDLPS. Focal brosis, fat
necrosis, foamy histiocytes, multinucleated giant cells, and myxoid areas may be
present.
Variants
(a) Fibrolipoma. Presence of foci of brosis and/or brous septa with spindle stro-
mal cells. Adipocytes are characterized by uniformity in size and shape. Stromal
cells do not show any atypia.
(b) Myolipoma (Fig.1.3). Presence of bundles of mature desmin-positive smooth
muscle cells (Fig.1.4). Ittypically occurs in women in deep-seated locations
(pelvis, retroperitoneum).
(c) Myxoid lipoma. Foci of myxoid stroma, scattered among adipocytes.
(d) Intramuscular lipoma (Fig.1.5). Presence of atrophic striated bers separated
and inltrated by adipocytes. It is characterized by a high rate of local recur-
rence, around 20%, when the involved muscle is not completely removed.
1 Adipocytic Tumors
Fig. 1.3 Schematic representation of myolipoma
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(e) Lipomatosis. A diffuse overgrowth of mature adipocytes, mainly localized in
the subcutaneous regions, but occasionally extending to visceral organs. Some
cases belong to the PIKC3A overgrowth syndromes.
1. Symmetric lipomatosis (Madelung’s disease). A massive lipomatous over-
growth localized in the neck region, which frequently inltrates the underlying muscles.
2. Asymmetric lipomatosis. A massive lipomatous overgrowth mainly localized
in the extremities and trunk.
3. Pelvic lipomatosis. Massive lipomatous overgrowth occupying the pelvis,
leading to compression of the pelvic organs.
(f) Osteolipoma (Fig.1.6). Presence of foci of metaplastic mature bone.
(g) Chondrolipoma. Presence of foci of metaplastic mature cartilage.
Immunohistochemistry
Adipocytes in lipoma are S100-positive; however, in
clinical practice, this stain does not play any role.
MDM2 and CDK4 expression in the nuclei of adipocytes and/or in spindle cells
in the stroma exclude the diagnosis of lipoma.
Molecular Genetics
50% of adipocytic tumors carry an abnormal karyotype,
including rearrangement of 12q13–15 or 6p21–23, or a deletion of 13q.
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Fig. 1.4 Intraperitoneal myolipoma from a 51-year-old female (HE-stained section)
R. Sciot et al.
Fig. 1.5 Intramuscular lipoma (HE-stained section)
1 Adipocytic Tumors
Fig. 1.6 Intermuscular osteolipoma from the arm of a 26-year-old female (HE–stained section)
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Prognosis The complete excision of lipomas is curative.
Differential Diagnosis
1. ALT/WDLPS: absence of atypia in adipocytes and in stromal cells associated
with uniformity of fat cells is in favor of lipoma. Nevertheless, in some instances,
MDM2 FISH should be done (see above in the section “Localization”).
2. Intramuscular hemangioma: many intramuscular hemangiomas show a promi-
nent adipocytic component.
3. Fat necrosis: it is often associated with marked variation in size of adipocytes,
mimicking ALT/WDLPS.
Lipomatosis ofNerve (Fig.1.7)
Denition Fibrolipomatous proliferation arising from the epineurium of a nerve.
Age at Presentation 10–30years. It may be congenital.
Gender M=F
Localization Median nerve > ulnar >radial >peroneal >cranial nerves.
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Fig. 1.7 Schematic representation of lipomatosis of nerve
R. Sciot et al.
Clinical Presentation (Fig.1.8) Enlargement of the affected area, in about 50%
associated with macrodactyly and/or compression neuropathy and local pain.
Macroscopy An epineurial rm mass, yellow on cut surface.
Microscopy (Fig. 1.9a, b) Mature adipocytes intermingled with a hypocellular
brous component extending from the epineurium of the affected nerve. Perineural
thickening can be seen as well.
Immunohistochemistry No signicant diagnostic role.
Molecular Genetics No signicant change. Rare PIKC3A mutations have been
described.
Prognosis A wait-and-see approach and a nerve-sparing conservative approach are
mandatory, given the functional damages which follow local excision.
Differential Diagnosis 1. Perineurioma: This differential diagnosis is restricted to
rare cases of lipomatosis of nerve showing the pseudo-onion bulb pattern.
1 Adipocytic Tumors
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Fig. 1.8 Clinical picture of lipomatosis of nerve, showing the macrodactylyof the second nger
Angiolipoma (Fig.1.10)
Denition Supercial tumor consisting of mature adipocytes and a capillary pro-
liferation, with characteristic microthrombi.
Age at Presentation Young adults (20–30years).
Gender Males predominate.
Localization Upper limbs (forearm)>trunk < lower limbs.
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ab
Fig. 1.9 Lipomatosis of nerve (a, b: HE-stained section), illustraing the bro-fatty overgrowth in
te epineurium
R. Sciot et al.
Fig. 1.10 Schematic representation of angiolipoma
1 Adipocytic Tumors
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Clinical Presentation Multiple (70%) subcutaneous (supercial) nodules, often
painful.
Macroscopy Nodular lesion(s), well circumscribed with a capsule. On cut surface,
yellow and reddish areas.
Microscopy (Fig.1.11) Proliferation of mature adipocytes associated with a vascular network, consisting of capillaries. Fibrin microthrombi are frequently found.
Variants Cellular angiolipoma (Fig.1.12): characterized by the predominance of
the capillary component over the adipocytic component, simulating a vascular lesion.
Immunohistochemistry Does not play a signicant role in this diagnosis.
Molecular Genetics A low level of protein kinase D2 mutations has been
described.
Prognosis Local excision is curative.
Fig. 1.11 Angiolipoma (HE-stained sections), arrows indicate microthrombi in capillary vessels