During the physical examination of a client's breast, which finding should the nurse suspect of a malignant tumor?

Breast malignancy involves uncontrolled epithelial proliferation within ducts or lobules. Neoplastic invasion of suspensory ligaments causes structural distortion and skin dimpling. Advanced pathology presents as painless masses with fixed margins, lymphadenopathy, and serosanguinous discharge, requiring immediate mammographic or ultrasonographic correlation. Rationale: A. Nipple retraction occurs when a subareolar tumor infiltrates lactiferous ducts, pulling the nipple inward. This fibrotic tethering is a classic sign of underlying malignancy, as the growing mass disrupts the normal anatomical alignment of the mammary tissue and skin. B. Tenderness is more frequently associated with cyclical mastalgia or inflammatory conditions like mastitis. Malignant lesions are characteristically painless and firm, whereas pain often points toward benign fibrocystic changes or hormonal fluctuations during the menstrual cycle or perimenopausal transition. C. Stretch marks, or striae distensae, result from dermal scarring due to rapid expansion of breast volume. They are common during pubertal growth, pregnancy, or significant weight gain and do not indicate cellular mutation or the presence of a neoplastic process. D. A well-defined mobile lump is usually indicative of a fibroadenoma, a common benign tumor. Malignant tumors typically lack distinct borders and become fixed to the pectoral fascia or overlying skin, rather than moving freely within the breast parenchyma during palpation.