The Pathologic Spectrum of Pregnancy- and Lactation-Associated Breast Lesions

Lactational lesions of the breast encompass a wide range of entities, ranging from physiologic changes to aggressive malignant tumors. Topics discussed under this umbrella include lactational change, galactocele, mastitis (acute and non-lactational), lactational adenoma, and pregnancy and lactation-associated breast carcinoma. Although the literature suggests that the histopathology of atypia and carcinoma in this context is similar to that in patients of comparable age without associated pregnancy or lactation, diagnosing these on core needle biopsies may be difficult, particularly in the presence of concurrent mastitis.

To review the clinical, radiologic, and specific histopathologic features of lactational lesions of the breast, their differential diagnoses, and challenging aspects as frequently encountered on core needle biopsies.

The existing scientific and clinical literature from a PubMed search as of August 2024 is the primary source of the review. Select cases of pregnancy and lactation-associated lesions from the Thomas Jefferson Hospital breast pathology archives are included and discussed in this review.

Accurate diagnosis of pregnant and lactating patients with breast lesions requires clinical, radiologic, and histopathologic correlation. Careful examination of biopsy cores and maintaining a high index of suspicion, even without clear radiologic findings, are essential for identifying atypia. When significant acute mastitis and overlapping secretory/lactational changes complicate the characterization of atypia, requesting additional tissue, using appropriate immunohistochemical stains, or deferring to excisional biopsy is appropriate. Awareness of these entities, given their varied prognoses and the sociopsychological challenges of postpartum and lactation, is crucial for guiding effective management.