#dermpathJC January 2018:

Thursday, January 25th, 9pm EST

Article discussed: Primary Cutaneous Perivascular Epithelioid Cell Tumor (PEComa):  Five new cases and review of the literature.

Authors: Lauren N. Stuart, Russell G. Tipton, Michael R. DeWall, Douglas C. Parker, Christina D. Stelton, Annie O. Morrison, Landon W. Coleman, Scott W. Fosko, Claudia I. Vidal, Maria Yadira Hurley, Amy H. Deeken, Jerad M. Gardner

Journal of Cutaneous Pathology, 2017;44:713-721.

Open access article, PDF available at:  http://onlinelibrary.wiley.com/doi/10.1111/cup.12972/epdf

Summary author: Dr. Amy H. Deeken (@AmyHDeekenMD).

 

Journal Club Summary:

Perivascular Epithelioid Cell tumor (aka PEComa) is a rare mesenchymal clear cell neoplasm with a diverse nomenclature including: angiomyolipoma, lymphangiomyomatosis, clear cell tumor of the lung, and myomelanocytic tumor of the falciform ligament.

When these neoplasms occur primarily in the skin, they begin as a painless, irregular non-pigmented papule/nodule or plaque on the extremities (most commonly on the leg in this series).   Because these neoplasms are so uncommon, the authors include pictures of their five cases for illustrative purposes of the variety of presentations and histologic variability.

Photo Credit:  Dr. Wayne Breer

Photo Credit:  Dr. Amy Deeken

Photo credit:  Dr. Lauren Stuart

 

There is no accepted normal cell counterpart.  The tumor is comprised of epithelioid cells with bland nuclei, clear or granular eosinophilic cytoplasm, in a nested and trabecular pattern.  The clear cells characteristically stain positively with melanocytic and smooth muscle markers.  However, primary cutaneous location is associated with a much higher likelihood of negative smooth muscle stains (almost 50%).  When they are positive, the staining pattern is often patchy or focal with <5% of cells staining in some studies.  The most reliable positive marker was SMA (42%) followed by desmin (30%).  The other marker of interest in the discussion was CD 10.  This stained positive in all three cases in which it was tested.  This unexpected finding was discussed as it relates to the differential diagnosis which could lead to the mistaken diagnosis of metastatic renal cell carcinoma.  Other IHC results were included in this informative table which also includes the most common differential diagnoses considered in these lesions –

Molecular testing of PEComas arising from other locations reveal positive results for TFE3 gene fusions and TFE3 immunohistochemical staining.  However, these molecular alterations are lacking in the primary cutaneous form of the disease.  This observation in association with unconventional immunostain patterns for smooth muscle suggests the possibility of more than one subtype in the PEComa family of neoplasms.  The mTOR pathway has been suggested to be a contributing factor the development of the primary cutaneous PEComa.

This is a rare lesion, and the clinical behavior has not been entirely elucidated.  Most studies list small sample size as a limiting factor in their analysis.  Primary cutaneous PEComas have generally exhibited benign behavior, the cases included in this series are no exception.  There was discussion among the #dermpathJC participants regarding optimum surgical therapy.  The study’s principle author, Dr. Jerad Gardner, advocated for conservative excision to negative margins due to the low volume of data regarding their clinical behavior and rare case reports of metastatic lesions.

 

In short –

#DermPath JC #pearl of the evening from Dr, Joseph Susa, @CutisViaLux – “When people start bringing up metastatic balloon cell melanoma with unknown primary, it’s time to start thinking of PEComa”

 

See you all next on 02/22/2018 at 9pm EST for another great journal club.

 

Thank you,

Silvija Gottesman, MD