Development of Erythema Nodosum After Olaparib Treatment in a Patient With Recurrent Breast Cancer and BRCA2 Mutation: A Case Report

BRCA1 and 2 mutations are known to be associated with breast cancer, and olaparib, a poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitor, has been shown to be effective in cells carrying these mutations in some studies. Erythema nodosum (EN), which is one adverse event of olaparib and is discussed in this paper, is considered to be a very rare condition. A 69-year-old female patient underwent left breast conservative surgery with axillary lymph node dissection for left invasive ductal breast cancer (stage IIB). Her family history included a sister who developed ovarian cancer at age 63. Five years postoperatively, systemic metastases were discovered in the lung, bone, hilar, and poststernal lymph nodes. The surgically removed metastatic lung nodule was diagnosed as an estrogen receptor (ER)-positive, progesterone receptor (PgR)-negative, and human epidermal growth factor receptor 2 (HER2)-negative metastatic adenocarcinoma of breast cancer origin. And germline mutations of BRCA1/2 were assessed using BRACAnalysis CDx(®) (Myriad Genetics, Salt Lake City, UT, USA), and BRCA2 1241 delC was identified as a deleterious mutation. Oral administration of olaparib was started. On day 4 of this treatment, numerous erythematous plaques characterized by intense tenderness and infiltration appeared on the extensor surfaces of the bilateral lower legs. On the basis of the clinical findings, the lesions were diagnosed as EN. Oral prednisolone was started at the same time as olaparib discontinuation, and the EN lesions disappeared in one week. EN is an inflammatory lesion characterized by tender subcutaneous induration with a flushed surface, predominantly on the bilateral lower legs. EN occurring after olaparib administration is considered to be very rare. This article describes such a case and reviews the relevant literature.