A misleading presentation: skin sarcoma presenting as a breast mass

Atypical fibroxanthoma (AFX) is a rare cutaneous malignant neoplasm which manifests as solitary lesions in sun-exposed areas of elderly patients, commonly on the head and neck. Given AFX’s rarity and lack of specific immunohistological markers, there are no established standardized guidelines for the management of AFX, often leading to a misdiagnosis of more aggressive variants such as pleomorphic dermal sarcoma (PDS). The prognosis is generally favorable, with most cases responding well to complete surgical excision alone. We present a rare case of AFX in the breast, a 68-year-old woman with a left breast mass, which the patient described as a small pimple. A computed tomography (CT) scan revealed a superficially located lesion in the upper medial quadrant of the left breast, measuring 4.2×2.2×2.1 cm (Figure 1A, B). At the patient’s request, she proceeded with upfront wide local excision without prior biopsy or any breast imaging. Histopathological examination revealed a well-circumscribed tumor measuring 3.8×3.3 cm, with no connection to the overlying epidermis (Figure 1C). Given that the surgical margin was less than 1 cm, the patient underwent a re-excision with sentinel lymph node biopsy. Final pathology was negative for positive margins and any lymph node involvement. At one-year follow-up, there was no clinical or radiological evidence of recurrence or metastasis. This case highlights the importance of including cutaneous lesions in the differential diagnosis of breast masses located near the skin surface. Accurate diagnosis requires a high index of suspicion and meticulous histopathological evaluation.