Breast Carcinoma En Cuirasse: Proposal of a Novel Diagnostic Criterion.

Breast carcinoma en cuirasse (CeC) is a rare form of cutaneous metastases, named as such due to the unique "breastplate" appearance. It is described as diffuse cutaneous induration, thickening, fibrosis, and leathery texture, with erythema and/or hyperpigmentation. Limited literature exists on this rare topic, and subsequently, cases can be misdiagnosed and not appropriately or efficiently managed. As such, we propose the preliminary framework for a novel diagnostic criterion. This is a case of a 93-year-old woman presenting with a one-year history of progressive left breast swelling, peau d'orange, acute mastalgia, and chest wall and abdominal "breastplate" appearance on examination. No distinct breast masses were palpable, but examination was limited due to the increased skin thickness and leathery texture. Diagnostic breast and abdominal dermal punch biopsies were done urgently at first consultation. Mammogram, breast ultrasound, and computed tomography (CT) were requested. Histopathology confirmed invasive lobular carcinoma involving the dermis. Immunohistochemistry (IHC) showed positive estrogen receptor (ER) and progesterone receptor (PR). Human epidermal growth factor receptor-2 (HER2) and E-cadherin were negative. Staging CT revealed multiple breast masses, not extending to the skin or chest wall, along with breast and abdominal skin thickening. Since breast mass biopsies were not performed, we cannot ascertain whether the dermal pathological findings were similar to a primary breast mass. However, since dermal histopathology demonstrated a breast primary and there was CT evidence of left breast masses and no evidence for an alternate source of cutaneous metastases, we can say with fair confidence that the histopathology of the breast masses will be similar to that of the dermal punch biopsies. The diagnosis of breast CeC is therefore supported. Breast CeC contraindicates surgical intervention; thus, definitive medical oncological treatment was implemented. Unfortunately, the patient expired before commencing treatment. Breast CeC usually develops after initial therapy, and prognosis is typically poor. Differentiating between stage III inflammatory breast cancer (IBC) and breast CeC is crucial, as the management of the former is with curative intent while the latter is with palliation. We introduce the preliminary framework for a novel diagnostic criterion entitled "OG Triple Assessment of Breast Carcinoma En Cuirasse" to elucidate breast CeC and increase diagnostic efficiency. The criterion details conditions that are all required to be present for the proposed diagnosis: (1) clinical appearance of "breastplate"/"armor," (2) no radiological evidence of the direct extension of primary breast tumor to the skin, and (3) histopathological confirmation of carcinoma within the dermis demonstrating morphological and/or immunohistochemical concordance with breast carcinoma. Breast CeC rarity is evident by its absence in Caribbean-based studies. This being the primary presentation, lobular phenotype, and the only source of metastases made our case even more unique. We aim to introduce breast CeC into Caribbean literature to aid in augmenting pre-existing data. Additionally, establishing future management and diagnostic guidelines, such as the proposed preliminary framework "OG Triple Assessment of Breast Carcinoma En Cuirasse," may aid efficient diagnosis and management and subsequently improve prognosis.