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RESIDENT
CASE
STUDIES
Week 6 May 26 - May 30, 2003: Case
3
Table
of Contents | List
of Diagnoses | Case 1 |
Case 2
| Case
3 | Case 4
79
year old male with recently noticed 6cm
mass on his forearm following minor penetrating trauma
Discussion:
Leiomyosarcoma of the skin is a rare tumor that comprises approximately 2% to 3% of all
soft tissue sarcomas.1 Usually, it cannot be diagnosed
clinically because its gross appearance is nonspecific. It may arise de
novo in the dermis or in the subcutaneous tissue, or as a metastatic
lesion from an internal neoplasm.2The primary skin tumor usually appears as a solitary nodule.
Superficial leiomyosarcomas have been subdivided into cutaneous and
subcutaneous forms because of their different clinical and prognostic
implications.3 The cutaneous form is believed to derive from
the arrector pili or genital dartoic muscle, whereas the subcutaneous type
is thought to arise from the smooth muscle wall of blood vessels. There
may be history of trauma. Patients with superficial leiomyosarcoma range in age from infants to the
elderly, with the highest frequency in middle age. The majority of superficial leiomyosarcomas occur on the
hair-bearing surfaces of the extremities, particularly on the lower
extremities.2, 4 Myxoid leiomyosarcoma (a variant leiomyosarcoma), which
is the diagnosis in this case is very rare. Histologically, there are spindle
cells separated by pools of myxoid material (hyaluronic acid) and in cross
section have a cord like pattern resembling chondrosarcoma. Some cells may
have abundant eosinophilc cytoplasm with a vacuole located at one end of a
cigar shaped nucleus. To emphasize the superficial nature of the case, the
skin is at the edge of Image 1. Mitosis may be rare because of the myxoid
background, only 1
to 2 mitotic figures per 10
high field are necessary to indicate malignancy and aggressive
behavior. The
spindle cells are smooth muscle actin (Image 4 in this case), vimentin,
and S-100 positive. Variable positivity for desmin, cytokeratin and EMA
may be present. The
differential diagnosis include: Myxoid Chondrosarcoma (usually deep with
lacunae and rare mitosis; actin negative); Myxoid liposarcoma (usually
deep with thin chicken wire vascular pattern, lipoblasts are often
present; actin negative); Malignant fibrous histicytoma (usually deep with
thick arching vessels and pleomorphism; actin negative); Aggressive
angiomyxoma (vessels of variable thickness, actin negative). References:
1Stout AP, Hill WT.
Leiomyosarcoma of the superficial soft tissues. Cancer 1958;111:844-54.
2Kuflik JH, Schwartz RA, Rothenberg J. Dermal leiomyosarcoma. Journal
of the American Academy of Dermatology 2003;48(5B).
3Enzinger FM, Weiss SW.
Soft tissue tumors. St Louis: Mosby-Year Book; 1995.
4Fields
JP, Helwig EB. Leiomyosarcoma of the skin and subcutaneous tissue. Cancer
1981;47:156-69.
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