Mohs micrographic surgery of a plexiform fibrohistiocytic tumor

Background. Plexiform fibrohistiocytic tumor (PFT) is a rare mesenchymal ne oplasm first described by Enzinger and Zhang in 1988. Clinically it is char acterized by slow growth, frequent local recurrences, and rare systemic met astasis. These tumors occur chiefly in children and young adults and are mo st commonly located on the shoulders and forearms. Objective. To present a case report of an incompletely excised PFT, its com plete resection using simple excision and Mohs micrographic surgery, and re view of the literature. Methods. An 11-year-old Hispanic girl was evaluated for the treatment of an incompletely excised plexiform fibrohistiocytic neoplasm located in the ri ght axilla. Mohs micrographic surgery (MMS) was chosen because of the ill-d efined borders and the need for tissue conservation. The patient underwent a two-stage, six section, micrographically controlled excision. Upon comple tion of the MMS a 2 mm final stage, taken as a peripheral and deep section around and underneath the cleared area, was submitted for paraffin embeddin g. Residual plexiform histiocytic tumor was found at the margin of resectio n in one location. Reevaluation of the Mohs slides demonstrated the possibl e presence of tumor at one deep focus. The tumor was reexcised with a 5 mm margin and repeat hematoxylin and eosin staining showed no residual tumor. There has been no evidence of recurrence in 4 years. Results. Complete resection of the PFT and absence of tumor recurrence 4 ye ars later. Conclusion. Over the past few years the list of neoplasms for which MMS is the treatment of choice has steadily grown. PFT is a recently described loc ally aggressive mesenchymal neoplasm with potential for distant metastasis. To our knowledge this is the first time MMS has been used to resect this t umor. To ensure the chance of complete extirpation we recommend the harvest of an additional stage for hematoxylin and cosin staining, as is done in s ome aggressive squamous cell carcinomas.