SLR - June 2017 - Kevin Tootle

Extraskeletal Myxoid Chondrosarcoma of the Foot Clinically Mimicking Plantar Fibromatosis

Reference: Saraggi D, Salmaso R, Montesco MC, Zamuner C, Tiengo C, Rugge M, Fassan. M. Extraskeletal Myxoid Chondrosarcoma of the Foot Clinically Mimicking Plantar Fibromatosis. Am J Dermatopathol. 2017 Mar;39(3):e38–e40.

Reviewed By: Kevin Tootle, DPM
Residency Program: Bethesda Hospital East, Boynton Beach, FL

Podiatric Relevance: A rare soft-tissue sarcoma that does not normally present in the lower portion of the extremities can be added to the differential diagnosis of a commonly identified condition in the foot. Pathomorphology of unknown lesions that are difficult to diagnose as plantar fibromatosis should be identified using markers to determine the prognosis and possibility of metastasis if the lesions are malignant in nature, like Extraskeletal Myxoid Chondrocarcoma (EMC), even if they have a rare presentation in the lower extremity.

Methods: A case report of a rare presentation of EMC was reviewed, in which the reported lesions appeared to clinically present as plantar fibromatosis. An incisional biopsy of the lesion in question from the plantar foot was done, and immunohistology was performed along with fluorescence hybridization and a polymerase chain reaction to determine the phenotyping of the cells making up the lesion.

Results: Microscopic examination of the excised lesion was used to reveal a growth pattern that was spindled and multinodular in nature. Immunophenotyping showed a strongly positive binding to vimentin and weak binding to S100. In further support, fluorescence hybridization showed positive for Ewings sarcoma breakpoint region 1 (EWSR1) and Nucleotide receptor 4A3 (NR4A3) fusion and was confirmed on real-time polymerase chain reaction (PCR), which indicated a higher specificity for EMC.

Conclusions: Plantar fibromatosis is a condition that is seen along the plantar fascia and is secondary to hyperproliferation, which leads to nodules and plaques along the course of the fascia. According to this article, only 16 cases of EMC in the foot have been reported, although there was one other presentation that was misdiagnosed as plantar fibromatosis. Immunohistochemistry does not solely support a pathological diagnosis; however, the majority of presentations have the EWSR1 and NR4A3 fusion of genes that are phenotypically seen with PCR. EMC is a slow-growing and often unrecognized lesion that commonly leads to recurrence and distant metastasis, most commonly to the lungs, and should be included in differential diagnosis for nodular soft-tissue lesions of the foot.

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