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  • Surgical Pathology Criteria

    Subcutaneous Leiomyosarcoma


    • Malignant neoplasm exhibiting smooth muscle differentiation located predominantly in the subcutaneous tissues

    Diagnostic Criteria

    • Subcutaneous location
    • Smooth muscle differentiation
      • Elongate eosinophilic cytoplasm
      • Pleomorphic or epithelioid cases may require desmin or caldesmon stain
    • Requires any one of the following
      • Cytologic pleomorphism or atypia
      • Tumor cell necrosis
      • Mitotic rate >4 per 50 HPF

    Richard L Kempson MD
    Robert V Rouse MD
    Department of Pathology
    Stanford University School of Medicine
    Stanford CA 94305-5342

    Original posting:: December 1, 2007

    Supplemental studies


    • Smooth muscle actin and muscle specific actin positive
    • Desmin or caldesmon positive but may be less extensive than actin
    • Keratin aind EMA may show occasional, usually patchy or dot-like staining
    • S100 has been reported in smooth muscle tumors of various sites
      • The combination of actin negative and S100 positive should strongly suggest nerve sheath tumor
    • CD34 is occasionally positive, usually weakly

    Differential diagnosis

    Dermal Leiomyosarcoma Subcutaneous Leiomyosarcoma
    90% of lesion must be in dermis >10% must involve subcutaneous tissue
    Does not metastasize May metastasize

    Malignant Fibrous Histiocytoma Subcutaneous Leiomyosarcoma
    Pleomorphic, histologically undifferentiated Elongate or spindled eosinophilic cytoplasm
    Typically lacks abundant desmin Typically desmin diffusely positive

  • MFH may be actin positive
  • The distinction between MFH and high grade leiomyosarcoma is not clinically important and may be one of convention
  • Nodular Fasciitis Subcutaneous Leiomyosarcoma
    Indistinct or pale cytoplasm Elongate or spindled eosinophilic cytoplasm
    Torn, tissue paper pattern Fascicular pattern
    Atypical mitotic figures not permitted May have atypical mitotic figures
    Pleomorphism not permitted May be cytologically pleomorphic
    Desmin rare Desmin frequent

    Benign Fibrous Histiocytoma Subcutaneous Leiomyosarcoma
    Frequent foam cells or giant cells Foam cells and giant cells rare
    Typically lacks abundant desmin Typically desmin diffusely positive
    Indistinct cytoplasm Elongate, eosinophilic cytoplasm


    • More common in men
    • More common in extremities
    • Metastasis rare if under 5 cm


    • According to the guidelines of the ADASP, grading may be prognostically useful
    • French Federation of Cancer Centers System grading scheme for adult sarcomas
      • Tumor differentiation score = 2 for leiomyosarcoma
      • Mitotic index
        • Score 1 0-9 mitoses per 10 hpf (0.1744 sq mm)
        • Score 2 10-19 mitoses per 10 hpf
        • Score 3 >19 mitoses per 10 hpf
      • Tumor cell necrosis
        • Score 0 No necrosis on any slide (one slide per 2 cm tumor diameter)
        • Score 1 <50% of tumor is necrotic on slides examined
        • Score 2 >50% of tumor is necrotic on slides examined
      • Final Grade (add the three scores above)
        • Grade 1 Sum of scores = 2 or 3
        • Grade 2 Sum of scores = 4 or 5
        • Grade 3 Sum of scores = 6 or more

    Use TNM Staging

    The surgical pathology report should contain or address the following:

      • Location
      • Type of resection or biopsy
      • Histologic diagnosis
      • Managerial category III (Local recurrence common; Metastasis occurs)
      • Extent of tumor cell necrosis
      • Grade
      • Stage
      • Size
      • Depth (dermis, subcutis, below fascia, body cavity)
      • Margins
        • Involved
        • Not involved
          • If under 2 cm give all such distances and sites
          • If over 2 cm give minimum distance and site
      • Results of supplementary studies if performed
      • Relationship to other specimens from the same patient


    Neoplasms with predominant smooth muscle differentiation


    • Kempson RL, Fletcher CDM, Evans HL, Henrickson MR, Sibley RS. Tumors of the Soft Tissues, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 30, 2001
    • Fletcher CDM, Unni KK, Mertens F. Pathology and Genetics of Tumours of Soft Tissue and Bone, World Health Organization Classification of Tumours 2002
    • Weiss SW, Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors, 4th edition, 2001
    • Svarvar C, Bohling T, Berlin O, Gustafson P, Folleras G, Bjerkehagen B, Domanski HA, Sundby Hall K, Tukiainen E, Blomqvist C; the Scandinavian Sarcoma Group Leiomyosarcoma Working Group. Clinical course of nonvisceral soft tissue leiomyosarcoma in 225 patients from the Scandinavian Sarcoma Group. Cancer. 2007 Jan 15;109(2):282-91.
    • Kulaylat MN, Karakousis CP, Doerr RJ, Karamanoukian HL, O'Brien J, Peer R. Leiomyosarcoma of the inferior vena cava: a clinicopathologic review and report of three cases. J Surg Oncol. 1997 Jul;65(3):205-17.
    • Jensen ML, Jensen OM, Michalski W, Nielsen OS, Keller J. Intradermal and subcutaneous leiomyosarcoma: a clinicopathological and immunohistochemical study of 41 cases. J Cutan Pathol. 1996 Oct;23(5):458-63.
    • Swanson PE, Stanley MW, Scheithauer BW, Wick MR. Primary cutaneous leiomyosarcoma. A histological and immunohistochemical study of 9 cases, with ultrastructural correlation. J Cutan Pathol. 1988 Jun;15(3):129-41.
    • Hornick JL, Fletcher CD. Criteria for malignancy in nonvisceral smooth muscle tumors. Ann Diagn Pathol. 2003 Feb;7(1):60-6.
    • Weiss SW. Smooth muscle tumors of soft tissue. Adv Anat Pathol. 2002 Nov;9(6):351-9.
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