Mastitis occurs mainly in neonates and during adolescence but may be observed rarely at any time of childhood. Non-inflammatory enlargement of the breast occurs at any time even in the neonate.

Mastitis of the newborn may have a considerable morbidity requiring antibiotics and/or abscess incision, and conceals the danger of septicemia and osteomyelitis or underdevelopment of the involved breast.

On the other hand a general non-inflammatory engorgement of the breast is first of all a challenge of differential diagnosis, for instance differentiation from a malignancy.

Mastitis: Staphylococcus aureus and other pyogenic and gram-negative germs are the causative organisms.

Diffuse non-inflammatory enlargement of the breast: Mainly endocrinological or developmental causes are observed.

Mastitis: Mastitis of the neonate without or combined with a physiological breast enlargement (the latter has no causative effect on the inflammation). Mastitis in adolescence following sport or pregnancy.

Non-inflammatory enlargement of the breast: Breast enlargement of the neonate due to stimulation by maternal hormones. Premature thelarche in girls under 8 years without other signs of precocious puberty. Macromastia and juvenile hypetrophy: Overgrowth of the breast in puberty and adolescence, in the latter lesion extreme breast hypertrophy.
Precocious puberty with other signs of sexual maturation. Pseudoprecocious puberty (single signs of and atypical succession of sexual maturation). Adolescent gynecomastia with palpable and/or visible breast enlargement in boys.

The pathophysiological mechanism is not well known in some types of enlargement of the breast without inflammation (premature thelarche, macromastia in puberty and adolescent gynecomastia); in some types maternal or own hormones are responsible.

Depending on the stage of the inflammatory disease the overlying skin may be involved with redness, swelling, warmth and suppuration besides the infectious brest bud enlargement.

Diffuse non-inflammatory enlargement of the breast: It may be uni- or bilateral and there are no inflammatory signs of the skin.

Mastitis: Development of an abscess or a chronic inflammation.
Diffuse non-inflammatory enlargement of the breast: Depending on the cause and type of engorgement self-limited and spontaneously reversible or irreversible process.

Mastitis: Other inflammatory processes of the thoracic wall.

Diffuse non-inflammatory enlargement of the breast: Depending on the age of occurrence no differential diagnosis, or precocious or pseudoprecocious puberty, tumor-like benign masses or semimalignant or malignant tumors.

Mastitis: White blood cell count and differentiation, erythrocyte sedimentation rate and C-reactive protein and blood and pus cultures.
Diffuses non-inflammatory enlargement of the breast: Depending on the age, the local findings and the stage of the other signs of puberty endocrinological examinations, ultrasound of the breast, mammography and primary excision or open biopsy or fine-needle aspiration.

Mastitis: Antibiotics and in case of abscess formation incision.
Diffuse non-inflammatory enlargement of the breast: In case of self-limited causes regular follow-up. Treatment according to endocrinological principles, and if present excision of an endocrinologically active tumor. Subcutaneous mastectomy in gynecomasty of the boy depending on the size and the evolution of the breast bud. Reduction mammaplasty in anusual cases of macromastia or in some juvenile hypertrophy of adolescence after careful evaluation. Total excision in tumor-like masses and tumors without loss or the possibility of a later underdevelopment of the involved breast.

In general favourable prognosis concerning survival except for rare cases of breast cancer as in adults.
Depending on the underlying cause danger of a later maldevelopment of the breast and of psychological embarrassement.