November 2016



Slide A

Signalment (JPC # 1647900):  Age and breed unspecified, dog

HISTORY:  A slow growing soft subcutaneous mass

HISTOPATHOLOGIC DESCRIPTION:  Haired skin, subcutis:  Expanding the subcutis and compressing the underlying skeletal muscle, is a 1.5 cm diameter, well-circumscribed, partially encapsulated, moderately cellular neoplasm composed of mature adipocytes on a fine fibrillar stroma.  Neoplastic adipocytes have distinct cell borders and a single 60-130 micron clear vacuole that compresses and peripheralizes the nucleus.  Nuclei are flattened and hyperchromatic.  Anisocytosis is marked depending on the size of the vacuole, but anisokaryosis is minimal.  Mitoses are not seen.  There are two focal areas of hemorrhage within the neoplasm with associated dark brown to golden globular pigment (hemosiderin).

MORPHOLOGIC DIAGNOSIS:  Subcutis:  Lipoma, breed not specified, canine.

Slide B

Signalment (JPC # 1958368):  Age and breed unspecified, dog

HISTORY:  A large, soft, subcutaneous mass

HISTOPATHOLOGIC DESCRIPTION:  Haired skin, subcutis, and panniculus carnosus:  Expanding the subcutis; elevating the overlying dermis and epidermis; widely separating adnexa; and separating, surrounding, and replacing skeletal muscle bundles is a poorly circumscribed, infiltrative neoplasm composed of densely packed adipocytes with distinct cell borders and a single, clear, 50-80 um cytoplasmic vacuole that compresses and peripheralizes the nucleus.  Nuclei are flattened and hyperchromatic.  Mitoses are not observed.  Multifocally, apocrine glands are mildly ectatic.  Skeletal muscle bundles are multifocally mildly atrophied characterized by disorganization of myofibers with paler staining.

MORPHOLOGIC DIAGNOSIS:  Haired skin, subcutis:  Infiltrative lipoma, breed not specified, canine.

Slide C

Signalment (JPC #1900656):  Age and breed unspecified, dog

HISTORY:  A firm subcutaneous mass from the shoulder

HISTOPATHOLOGIC DESCRIPTION:  Haired skin and subcutis, shoulder:  Effacing the subcutis, elevating the overlying dermis, and extending to the deep margins, is an infiltrative, unencapsulated, multilobulated neoplasm composed of polygonal to spindle cells that are solidly cellular or arranged in short streams separated by a fine fibrovascular stroma.  Neoplastic cells have indistinct cell borders and a moderate amount of eosinophilic cytoplasm that often contains one large (up to 80 um) distinct, clear vacuole (lipocyte) or several small (10-15 um) distinct vacuoles (lipoblast).  Nuclei are round to oval, vesiculate and occasionally centrally located, with a single prominent magenta nucleolus.  Mitoses average 2 per 10 400X HPF.  There is marked anisokaryosis and anisocytosis.  The center of the neoplastic lobule is necrotic.  Multifocally there is mild hemorrhage admixed with few hemosiderin-laden macrophages.  

MORPHOLOGIC DIAGNOSIS:  Haired skin and subcutis, shoulder (per contributor):  Liposarcoma, breed not specified, canine.



Infiltrative Lipoma



Other Lipocytic tumors:          






Spindle cell lipoma

Atypical lipoma

Myxoid liposarcoma

Pleomorphic liposarcoma

Intracranial lipomatous hamartoma



Infiltrative Lipoma









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