[25] A Novel Superficial CD34-Positive Fibroblastic Sarcoma

Jodi M Carter, Sharon W Weiss, Konstantinos Linos, David J DiCaudo, Andrew L Folpe. Mayo Clinic, Rochester, MN; Emory University, Atlanta, GA

Background: Most fibroblastic sarcomas fall into well-defined clinicopathological groups. We report our experience with a previously unreported fibroblastic sarcoma characterized by superficial location, distinctive histopathological features and CD34 immunoreactivity, which we term “superficial CD34-positive fibroblastic sarcoma”.
Design: 19 cases previously coded as "low grade sarcoma, not further classified" and "malignant fibrous histiocytoma, low grade" were retrieved from our consultation archives. Immunohistochemistry (IHC) for CD34, cytokeratins, desmin, Fli1, SMARCB1 and S-100 protein was performed. Because of some similarity to myxoinflammatory fibroblastic sarcoma (MIFS) and pleomorphic hyalinizing angiectatic tumor (PHAT), 5 cases were analyzed by fluoresence in situ hybridization for rearrangements of TGFBR3 and MGEA5.
Results: The tumors presented in 10 males and 9 females (mean age 40 years, range 20-76 years) as slowly growing masses of variable size (mean 4.2cm, range 1.5-10cm) confined to the superficial soft tissues of the thigh (6/19); arm, knee, groin (2 each); and neck, shoulder, hip, vulva, buttock, leg and foot (1 each). The tumors were composed of fascicles and sheets of spindled cells with abundant granular, fibrillar or “glassy” cytoplasm. They exhibited marked nuclear pleomorphism, out of proportion to the low mitotic rate (mean < 1/20 HPF). A prominent inflammatory infiltrate was present in all cases. Necrosis was present in one case. Ectatic vessels, stromal and perivascular hyalinization, and myxoid zones with pseudolipoblasts were absent. Tumors were diffusely CD34 positive (19/19), focally positive for keratin (11/16), and negative for other markers. All retained expression of SMARCB1. FISH for TGFBR3 and/or MGEA5 rearrangements was negative. Follow up (7 patients, median 5 months, range 2-96 months) revealed no local recurrences or distant metastases. One patient developed regional lymph node metastases following incomplete excision. All patients are currently alive.
Conclusions: Superficial CD-34 fibroblastic sarcoma is a unique low grade sarcoma. Its significance resides in the fact that it most likely has been confused with superficial undifferentiated pleomorphic sarcoma in the past but can be distinguished on the basis of distinctive histopathological features. The clinical, morphological and molecular genetic features of this tumor also differ from those of MIFS and PHAT. Limited follow up suggests it behaves as a low-grade sarcoma with limited potential for lymph node metastases.
Category: Bone & Soft Tissue

Tuesday, March 5, 2013 8:30 AM

Proffered Papers: Section G, Tuesday Morning


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