Occult Invasive Lobular Carcinoma Presenting as an Axillary Skin Metastatic Lesion Underwent Neoadjuvant Endocrine Therapy and Surgical Resection: A Case Report and Review of Literature.

Introduction: Invasive lobular carcinoma (ILC) is the second most common type of breast cancer accounting for 5-15% of all breast cancer cases. It usually presents with nonspecific signs and symptoms. Occult breast cancer presenting as an axillary mass is rare, with prevalence of 0.3-1%, less likely with isolated cutaneous breast metastasis as a first presentation. There are limited data in the literature on patients who underwent endocrine therapy and complete surgical resection. Case Presentation: A 54-year-old woman with left axillary skin swelling that had been persisting for 6 years was diagnosed with ILC 18 months ago presenting with an ulcerated axillary skin lesion and was managed with letrozole in another facility as she was estrogen receptor (ER) and progesterone receptor (PR) positive. She received letrozole for 18 months and had a partial response in the form of healing of the ulcer with persistent subcutaneous nodules. Her breast mammogram, ultrasound, and magnetic resonance imaging findings were unremarkable; however, there were few prominent left axillary lymph nodes. A biopsy of the left axillary lymph node was positive for malignancy, consistent with ILC. A skin punch biopsy of the axillary skin lesion showed ILC extending to the dermis with no background breast tissue. The patient underwent left modified radical mastectomy with excision of the left axillary skin lesion. The breast specimen comprised 0.4 mm of ILC as the primary malignancy and nine positive axillary lymph node malignancies. The patient received adjuvant radiotherapy and continued to receive letrozole. There were no signs of complications or recurrence during the follow-up period. Conclusion: Ulcerated skin lesions in the axilla should raise concerns regarding breast cancer metastasis. In cases of isolated cutaneous breast metastases, surgical excision can be considered in combination with endocrine therapy.