An 88 Y/O Man with a Mass in the Neck

“An 88 y/o man with a mass in the Neck”

California Tumor Tissue Registry’s

Case of the Month

CTTR COTM Vol 9:4

January, 2007

An 88-year-old man complaining of a mass in the right side of his neck was found to have a well-circumscribed, 5.0 x 4.5 x 3.5 cm fatty tumor mostly involving subcutaneous tissues. It also had denser, white “fibrous” areas.

Microscopically, the tumor consisted of both fatty and fibrous elements. There were numerous pleomorphic, hyperchromatic cells present in what was otherwise mature fat (Fig. 1). The pleomorphic cells were sometimes bunched in fibrous areas consisting of dense collagen with spindled cells and were many-times multinucleated, “wreath-like” or “floret-like” (Figs. 2, 3, 4). Both the spindled cells and the floret-like giant cells were positive for CD 34 (Fig. 5).

Diagnosis: “Pleomorphic Lipoma”

Fouad Abdelhalim, M.D., Wafaa Elatre, M.D., Donald R. Chase, M.D,

Department of Pathology, Loma Linda University and Medical Center

California Tumor Tissue Registry

Pleomorphic lipoma (PL) was first reported by Franz Enzinger (1977) as a variant of lipoma that resembles sclerosing liposarcoma and is closely related to his previously-described spindle cell lipoma. PL is quite uncommon, occurring only one tenth as often as spindle cell lipoma, which in turn accounts for only 1.5% of all adipocyte tumors.

Like spindle cell lipoma, PL presents in men older than 45 years as a circumscribed mobile subcutaneous mass most commonly in the posterior neck, shoulder, or back region. Other sites are extremely rare. There is often a long history. The tumor rarely is multiple and virtually never occurs in women (<1%).

Grossly, PL is oval-discoid, yellowish to grayish white, with the color being dependent upon the relative amount of fatty and fibrous/spindle cell components. The tumor usually has a firmer texture than ordinary lipomas.

Microscopically, the presence of scattered giant cells with a floret-like appearance is characteristic, but not pathognomonic. Similar cells can also be found in well-differentiated liposarcomas and pleomorphic liposarcomas, tumors which like PL, may have lipoblasts. PL, however, is also characterized by ropy collagen bundles similar to those found in spindle cell lipoma and may also have myxoid change and numerous mast cells. Unlike liposarcoma, PL is superficially located, well-circumscribed and non-obliterative.

The floret cells and atypical spindle cells of PL show strong positivity for human progenitor cell antigen (CD34) in contrast to lipoblasts and normal adipocytes which are negative. This marker is quite helpful in making the diagnosis of PL, especially if clinical information as to size and location are lacking. It is also known that floret cells are negative for CD68 and, like spindle cell lipoma, are negative for S-100.

Recent studies have shown that both spindle cell and pleomorphic lipomas are closely related by their cytogenetic abnormalities. Both frequently show loss of 16q material and less frequently of 13q. These abnormalities coupled with the absence of giant marker and ring chromosomes (frequently seen in atypical lipoma/well-differentiated liposarcoma) support the relationship between spindle cell and pleomorphic lipoma and their distinction from lipocytic malignancies.

Differential Diagnosis:

Pleomorphic Lipoma Well-differentiated Pleomorphic

Liposarcoma Liposarcoma

Favored site(s) Neck, back, shoulders Deep extremity tissues Deep extremity tissues

Superficial tissues Retroperitoneum Retroperitoneum

Peak age (years)45-60 50-70 50-70

Floret-like cells Characteristic Present Rare

Pleomorphic lipoblastsAbsent Sometimes Characteristic

Cytogenetics Loss of 16q, 13q Giant marker Varied, complex

Ring chromosomes abnormalities

MetastasesNone Extremely rare, except Common

in dedifferentiated cases

Enzinger and Weiss, Soft tissue tumors (2001), 4th ed, pp 601

Distinction of PL from sclerosing well-differentiated liposarcoma may at times be difficult but usually can be accomplished on the basis of PLs typical location in the shoulder or head and neck region, its superficial location in subcutaneous tissue, its circumscription with encapsulation, and its lack of prominent vascularity. The characteristic cytogenetics abnormalities as well as the immunohistochemical staining for CD 34 may also be helpful.

An 88 Y/O Man with a Mass in the Neck

“An 88 y/o man with a mass in the Neck”

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