Case Seven – July 2017

  • Patient Information
    • 32 year old female presented with a firm, non-mobile subcutaneous nodule on her abdomen
  • Clinical Diagnosis
    • Dermatofibroma
    • Dermatofibrosarcoma protuberans
    • Lipoma
  • Histology

    Sections show a cellular spindle cell proliferation based within the deep dermis and subcutaneous tissue.

    The tumor is composed of monomorphic, hyperchromatic spindle cells with a storiform growth pattern.

    The lesion infiltrates diffusely through the subcutaneous tissue and entraps individual adipocytes leading to a characteristic honeycomb pattern.

    The tumor is strongly positive for CD34 immunohistochemical stain.

  • Final Diagnosis

    Dermatofibrosarcoma protuberans

    • Dermatofibrosarcoma protuberans, DFSP, is a malignant fibrohistiocytic neoplasm based within the dermis or subcutaneous tissue
    • It most commonly presents as a slow growing, firm, non-mobile subcutaneous nodule on the trunk of adults in their third to fifth decade of life
    • Histology shows a cellular, monomorphic spindle cell neoplasm with a storiform growth pattern and characteristic honeycomb pattern of invasion within the subcutaneous tissue
      • Admixed inflammatory cells and histiocytes (including foam cells) are rare
    • The main histologic differential diagnosis includes dermatofibroma, DF
      • DF is less cellular and has admixed inflammatory cells/histiocytes
      • DF shows a less infiltrative growth pattern, typically without significant invasion of the subcutaneous tissue
    • DFSP is strongly positive for CD34 immunohistochemical stain
      • Dermatofibroma is negative for CD34 negative and positive for FactorXIIIa
    • Almost all DFSPs harbor a t(17,22)(q21;q13) translocation involving the collagen type 1 alpha 1 gene and platelet derived growth factor beta chain gene
    • Giant cell fibroblastoma is the juvenile counterpart of DFSP which shares the same translocation
    • Fibrosarcomatous transformation from conventional DFSP can occur and is characterized by loss of CD34 expression
    • Bednar tumor is a rare variant of DFSP containing S-100+ pigmented dendritic cells
    • DFSP can be locally aggressive and recur but rarely metastasizes
    • Wide local excision is the treatment of choice
  • Summary
    • Dermatofibrosarcoma protuberans, DFSP, is a malignant fibrohistiocytic neoplasm that often presents as a slow growing, non-mobile subcutaneous nodule on the trunk
    • DFSP is strongly positive for CD34 immunohistochemical stain and shows a characteristic honeycomb pattern of invasion within the subcutaneous tissue
    • Almost all DFSPs harbor a t(17,22)(q21;q13) translocation involving the collagen type 1 alpha 1 gene and platelet derived growth factor beta chain gene
    • DFSP can be locally aggressive and recur but rarely metastasizes
    • Wide local excision is the treatment of choice