Physiological yet Uncommon: A Case of Giant Neonatal Mastauxe

A 10-day-old male infant, born at 38 weeks of gestation to a primigravida mother following an uncomplicated antenatal course, was brought with progressively increasing bilateral breast swelling. The infant was delivered by normal vaginal delivery with a birth weight of 3100 g and had Apgar scores of 7 and 9 at 1 and 5 minute, respectively. The immediate postnatal period was uneventful, and the neonate was discharged on day 3 of life. The parents noticed bilateral breast enlargement beginning on the 5th day of life, which gradually increased in size and was associated with a clear, milky, nonbloody nipple discharge over the subsequent 3 days. The mother reported repeatedly squeezing the breasts. There was no history of fever, irritability, poor feeding, excessive crying, purulent discharge, or trauma. The infant was exclusively breastfed and thriving well. There was no maternal history of endocrine disorders, medication use, or intake of herbal preparations during pregnancy or the postnatal period. On examination, the neonate was active and hemodynamically stable, with a temperature of 37°C, heart rate of 143/min, respiratory rate of 38/min, and capillary refill time <3 s. Anthropometric parameters were appropriate for gestational age. There was no pallor, icterus, cyanosis, and lymphadenopathy. Local examination revealed bilateral breast enlargement with soft, nontender, nonfluctuant swellings measuring 4.8 cm × 4.3 cm on the right and 5.2 cm × 4.4 cm on the left [Figure 1a and b]. The overlying skin showed mild erythema without warmth or induration, and no discharge could be expressed on pressure. The systemic examination was unremarkable.Figure 1: Bilateral breast enlargement (Red Arrows) in a 10- day neonate (a and b)The primary differential diagnoses considered were neonatal mastitis, breast abscess, and giant neonatal mastauxe. Laboratory parameters, including hemoglobin, leukocyte count, and C-reactive protein, were within the normal limits. Ultrasonography of both breasts demonstrated well-defined retro-areolar hypoechoic glandular tissue measuring 3.7 cm × 3.4 cm on the right and 4.4 cm × 4.3 cm on the left, without increased vascularity or loculated fluid collections, thereby excluding mastitis and abscess and confirming the diagnosis of giant neonatal mastauxe [Figure 2].Figure 2: Ultrasonography of the breast with arrows demonstrating well-defined retroareolar hypoechoic glandular tissue (Red arrows) without increased vascularityThe neonate was managed conservatively involving parental reassurance, education regarding the benign and self-limiting nature of the condition, and strict avoidance of breast manipulation, which can exacerbate swelling and predispose to secondary infection. No antibiotics or surgical intervention is indicated in the absence of infection. At a 2-week follow-up, the breast swellings in this infant had regressed significantly without complications, reinforcing the importance of accurate diagnosis and avoidance of unnecessary treatment. Neonatal breast enlargement is a benign proliferation of glandular tissue caused by transplacental maternal estrogens or a rebound prolactin surge following estrogen withdrawal at birth.[1] It occurs in 60%–90% of neonates, may be unilateral or bilateral, appears within the 1st week of life, enlarges over several weeks, and usually resolves spontaneously by 6 months, though persistence may occur.[2] Giant neonatal mastauxe refers to exaggerated physiological enlargement with a breast bud diameter >3 cm. Neonatal mastitis presents with unilateral painful swelling, erythema, warmth, induration, and systemic symptoms such as fever or irritability, most commonly due to Staphylococcusaureus, while abscess is characterized by fluctuation and localized pus on imaging. In the present case, the absence of tenderness, inflammatory signs, and systemic features made infection unlikely. Unlike mastitis or abscess, which require antibiotics and sometimes drainage, physiological breast enlargement and giant mastauxe are managed conservatively with reassurance and follow-up.[3] Long-term observation, especially in female infants, has been suggested due to a theoretical risk of altered estrogen sensitivity.[4] Accurate diagnosis and counseling prevent unnecessary antibiotics, hospitalization, or surgery while ensuring appropriate care. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal patient identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.