Title : Keratoacanthoma-like cutaneous metastasis in a 40-year-old Asian female with invasive ductal breast carcinoma: A case report
Abstract:
Cutaneous metastasis occurs in approximately 5% of patients with internal malignancies and is generally associated with advanced disease and poor prognosis. Although breast carcinoma is the most common source of cutaneous metastases in women, presentation with a keratoacanthoma-like morphology is exceptionally rare. To date, fewer than 20 cases of keratoacanthoma-like cutaneous metastases have been reported in the literature. The majority originated from primary lung malignancies, with only a single previously reported case arising from breast carcinoma.
We report a case of a 40-year-old Filipino woman with a known history of invasive ductal breast carcinoma who developed a rapidly enlarging solitary erythematous nodule with a central keratin-filled crater on the anterior chest wall. The lesion arose at the site of a previously documented cutaneous metastasis and clinically mimicked a keratoacanthoma.
Histopathologic evaluation revealed atypical acantholytic cells with marked nuclear pleomorphism and increased mitotic activity, initially suggesting invasive squamous cell carcinoma. However, further immunohistochemical analysis showed CK7 positivity, CK20 negativity, and p63 negativity, supporting the diagnosis of keratoacanthoma-like cutaneous metastasis rather than a primary cutaneous malignancy. Subsequent imaging confirmed systemic disease progression with cerebral metastases.
This case represents one of the very few reported instances of keratoacanthoma-like cutaneous metastasis originating from breast carcinoma since the report by Cotton et al. in 1985, which described a solitary lesion on the upper lip two years after breast cancer diagnosis. Our findings highlight the extreme rarity of this presentation and emphasize the importance of maintaining a high index of suspicion for metastatic disease in patients with known malignancy who present with keratoacanthoma-like lesions. Careful clinicopathologic correlation and targeted immunohistochemistry are essential for accurate diagnosis and appropriate oncologic management.
