Pleomorphic Dermal Sarcoma

 Deep subcutaneous/fascial/muscular extension, necrosis, &/or lymphovascular invasion


image Shows no identifiable line of differentiation (i.e., diagnosis of exclusion)


• Synonyms: Superficial malignant fibrous histiocytoma, undifferentiated pleomorphic sarcoma of skin




Clinical Issues




• Older and elderly adults (most > 50 yr)

• Male predilection

• Usually affects head region, particularly scalp

• Treatment: Complete surgical resection with negative margins

• Local recurrences in up to 30% of cases

• Metastases in 10-20% of cases


Macroscopic




• Median: 2.5 cm


Microscopic




• Poorly marginated, usually with deep tissue extension

• Prominent cytologic and nuclear atypia and mitotic activity

• Frequent coagulative necrosis

• Lymphovascular invasion in some cases


Ancillary Tests




• Negative for keratins, S100, desmin, CD34, most others

• Immunohistochemical best utilized to exclude other diagnoses


Top Differential Diagnoses




• Atypical fibroxanthoma

• Carcinoma, melanoma

• Angiosarcoma

• Other superficial pleomorphic sarcomas

image
PDS
Pleomorphic dermal sarcoma (PDS) originates superficially in the dermis, as depicted, but usually shows deeper extension with involvement of the subcutis, fascia, &/or underlying muscle image.


image
PDS With Resemblance to Atypical Fibroxanthoma
PDS shows histomorphologic features similar to atypical fibroxanthoma (AFX), and these 2 entities can be indistinguishable on a superficial/partial biopsy. The presence of deep tissue extension, necrosis, or lymphovascular invasion would be most consistent with the former.

image
PDS With Marked Nuclear Atypia
Nuclear and cytologic atypia is often prominent and diffuse in PDS, as depicted, similar to its counterpart in deep soft tissues (undifferentiated pleomorphic sarcoma). Multinucleated tumor giant cells image are common, as are atypical mitotic figures.

image
PDS With Coagulative Necrosis
Coagulative tumor necrosis image is common in PDS but varies in amount and distribution. The presence of necrosis in a pleomorphic dermal neoplasm favors PDS over AFX, assuming that carcinoma, melanoma, and other tumors are first excluded.


TERMINOLOGY


Abbreviations




• Pleomorphic dermal sarcoma (PDS)


Synonyms




• Superficial malignant fibrous histiocytoma

• Undifferentiated pleomorphic sarcoma of skin


Definitions




• Pleomorphic sarcoma exhibiting morphologic similarity to atypical fibroxanthoma (AFX), but also demonstrating aggressive growth characteristics
image Deep subcutaneous/fascial/muscular extension, necrosis, &/or lymphovascular invasion

image Shows no identifiable line of differentiation (i.e., diagnosis of exclusion)


ETIOLOGY/PATHOGENESIS


Environmental Exposure




• History of long-term sun exposure usually exists


CLINICAL ISSUES


Epidemiology



Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Pleomorphic Dermal Sarcoma
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