Myxoid dermatofibrosarcoma protuberans of the vulva in a postnatal woman: a case report

Background: Vulval Dermatofibrosarcoma protuberans (DFSP) is a rare cutaneous sarcoma that develops from the dermis, with less than 70 reported cases. This case discusses a holistic approach to vulval DFSP in a postpartum woman—with the balance of surgical excision against functional, psychosexual and cosmetic outcomes. Case: A 24-year-old woman noticed a rapidly enlarging vulval mass during pregnancy, which was an 8 cm left sided vulval mass which stretched from the periclitoral area to the inguinal crease. A core biopsy showed an indeterminate low grade myxoid lesion. Magnetic Resonance Imaging (MRI) reported no local metastasis or fascial involvement and Positron Emission Tomography (PET) and Computed Tomography (CT) scan showed metabolically active soft tissue mass without distant metastasis. Postpartum, she was referred to a Gynaecological Oncologist at a tertiary centre where it was discussed with Sarcoma and Plastic Surgeons. A radical local excision of vulvar mass, mesh reconstruction of rectus sheath and left inguinal ligaments and superficial circumflex iliac perforator flap of the left thigh was performed. Initial histopathology exhibited a myxoid lesion with negative staining including CD34, which is characteristic for DFSP. Due to indeterminate histopathology, RNA-sequencing was used and showed disease-defining chromosomal fusion (COL1A1::PDGFB fusion), which assisted the diagnosis, as this is present in over 90% of tumours. The tumour was excised over 10 mm laterally and 5 mm deep. Conclusions: Over 70% of DFSP is positive for CD34 and this shows the importance of RNA-sequencing in cases of indeterminate histology. Due to high recurrence, guidelines have suggested lateral margins from 10 mm up to 30 mm. Though, in a young woman this was considered against long-term sexual and functional outcomes. She will undergo close surveillance both clinically and with MRI.