CPC02 Breast carcinoma presenting as carcinoma erysipeloides/en cuirasse of the left neck sparing the chest: a rare diagnostic challenge
Authors: Choi Mi Joo , Stokes Natalie King , Carter Johnathan , Mesiano Domenico , Carr Richard 
Published: June 2024

Abstract
A 71-year-old woman presented with a 7-month history of a painful erythematous plaque on the left posterior triangle of the neck. Twelve months earlier, she was investigated for left level II and Vb cervical lymphadenopathy under ENT, and she was discharged after ultrasound of the neck showed benign reactive lymphadenopathy. She had a background of hypertension and was otherwise fit and well. On initial examination there was an extensive, indurated, erythematous plaque on the left neck, sparing chest and breast skin. Four weeks later the plaque had extended to the anterior upper chest and left posterior ear. There was no palpable lymphadenopathy or organomegaly. Breast examination was not performed during the initial consultation. Blood tests including beta-2-microglobulin, lactate dehydrogenase, C-reactive protein and erythrocyte sedimentation rate were normal. An urgent incisional biopsy for suspected cutaneous lymphoma showed extensive dermal and subcutaneous infiltration by plump, epithelioid, moderately pleomorphic, malignant-appearing cells with scattered mitotic figures. Occasional lumina were present, in keeping with a poorly differentiated adenocarcinoma. The tumour was expanding multiple dermal, and focally subcutaneous, with lymphatic involvement, highlighted by endothelial markers (CD31, CD34) and smooth muscle actin. Tumour cells diffusely expressed BerEp4, epithelial membrane antigen, CK7, CAM5.2, carcinoembryonic antigen, p53 and GATA3, and were negative for CK5, p63 and E-cadherin. Ca125 and GCDFP15 were expressed focally. HER2 was positive, while oestrogen receptor and progesterone receptor were negative. Metastatic, most likely breast, adenocarcinoma was suspected, with a differential of primary cutaneous adnexal carcinoma. A palpable mass was identified in the left breast, and core biopsy confirmed a diagnosis of high-grade solid and cribriform ductal carcinoma in situ with bilateral anterior cervical and axillary lymph node involvement. It was ascertained that the patient’s sister had recently died from breast cancer. She was commenced on weekly palliative chemotherapy and has shown marked improvement of her skin metastasis. Carcinoma erysipeloides is a rare form of cutaneous metastasis, most frequently caused by breast cancer. It often presents on the chest wall or breast skin, and is characterized by an erythematous plaque with oedema due to lymphatic vessel obstruction. Carcinoma en cuirasse is another dramatic presentation of cutaneous metastasis, where tumour cells infiltrate the collagen and lymphatics resulting in extensive thickening of dermis and subcutis. The initial clinical presentation limited to the neck is exceedingly rare, which led to delay in diagnosis and referral to the appropriate team. This case highlights the importance of having a high index of suspicion for breast cancer, especially in older women with a positive family history, and clinicians should have a low threshold for breast examination. This would not only avoid diagnostic delays but also lead to sustainable dermatological practice with more efficient use of immunohistochemistry.