March 2015 Case of the Month

A 35-year old man presented to his primary care physician with a nodule on the left thigh, described as painless and increasing in size over time.  Conservative excision of the subcutaneous mass was subsequently performed, with the following photomicrographs displaying the histologic features.  What is your diagnosis?

4x
4x

The dermis is expanded by a spindle cell lesion. A thin region of uninvolved dermis separates the lesion from the epidermis.

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10x
10x

The spindle cell lesion diffusely infiltrates into the subcutaneous adipose tissue, surrounding individual adipocytes and displaying storiform architecture.

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CD34
CD34

The spindle cell lesion is diffusely positive for CD34 by immunohistochemistry.

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4x
4x

The dermis is expanded by a spindle cell lesion. A thin region of uninvolved dermis separates the lesion from the epidermis.

press to zoom
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March 2015 Case of the Month

   Answer: Dermatofibrosarcoma protuberans (DFSP)

The morphologic and immunophenotypic features support the diagnosis of DFSP.  This tumor has a male predilection, and typically occurs in both middle aged adults and the pediatric population.  The trunk and lower extremities are the usual sites of occurence.  This fibrohistiocytic tumor is considered to be of intermediate malignancy with a potential for local recurrence; however, low risk of metastasis.  DFSP characteristically shows diffuse infiltration into the subcutaneous adipose tissue and positivity for CD34.  Cytogenetic analysis reveals a translocation between chromosomes 17 and 22, t(17;22), involving the collagen type 1 alpha-1 gene and platelet derived growth factor beta gene, respectively.