Neoadjuvant radiation to facilitate surgical treatment of a microcystic adnexal carcinoma with perineural invasion of the vulvar region

Microcystic adnexal carcinoma (MAC) is a locally aggressive carcinoma with proclivity for perineural invasion (PNI). Many MACs are found in the head and neck region; rarely are they reported in the vulva. Treatment typically involves Mohs surgery, wide-local excision (WLE), and radiation therapy (RT). RT alone is considered insufficient for treatment, but adjuvant RT after surgery has yielded results comparable to Mohs surgery. Here, we report a patient who had successful treatment of a vulvar MAC with neoadjuvant RT and excisional surgery. An 86-year-old female presented with a biopsy-proven MAC (4 X 6 cm2) with PNI in the right vulvar region. She had no history of ionizing radiation in the area. An MRI of the vulvar region demonstrated no deep invasion or metastases. Due to the difficulty of caring for the location and size of the lesion, the patient did not agree to WLE and instead opted for neoadjuvant radiation to shrink the MAC before excision. She had external beam radiation for 1 month, with follow- up PET/CT showing no abnormal FDG avidity in the vulva. She had an excision in 2 stages, with the initial en bloc resection displaying the MAC measuring 6.0 x 2.5 mm2. Treatment of MACs with surgery, due to their extension and indistinct margins, leads to extensive morbidity. Employing neoadjuvant RT is novel for treating MACs but not for the treatment of other tumors. Neoadjuvant RT with subsequent excision or Mohs surgery should be considered for large MACs in difficult-to-treat areas.