Case 736 -- Abdominal skin lesion and mass in a newborn

Contributed by Matthew Smith, MD and Miguel Reyes-Mugica, MD

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A patient is a five-day-old infant, born to a 27-year-old gravida 2 para 2 mother. Her prenatal course was uncomplicated with proper prenatal care and a normal fetal ultrasound. The patient was delivered via spontaneous vaginal delivery at 40 6/7 weeks.

He presented at birth with a large/giant, garment type, hyperpigmented, brown, plaque located circumferentially from the nipple line anteriorly and upper back (cervical vertebrae 8) posteriorly down to bilateral mid-thighs including his buttocks. Within the hyperpigmented plaque, there were areas of darker brown macules/patches and papules/plaques with superficial erosions and crusting. In addition there were multiple satellite or accessory lesions consisting of uniformly colored, well-circumscribed, oval, patches and plaques on his scalp, right posterior ear, tragus, neck, and bilateral upper and lower extremities. Finally, there was a subcutaneous, soft, nodule over his lower right flank without any thrills.

A magnetic resonance imaging (MRI) study of the patient's brain demonstrated abnormal T1 signal in the area of the amygdala, basis pontis and caudal medulla. There were also multiple parenchymal abnormalities in the bilateral cerebellar hemispheres, bilateral parietal lobes, frontal lobes and abnormal T1 signal involving atrophied optic tracts bilaterally, the optic chiasm and pre-chiasmatic optic nerve.

An MRI of the abdomen and pelvis demonstrated an 83.9 cm x 1.8 cm x 5.4 cm, soft tissue, and infiltrative lesion involving the subcutaneous right lower quadrant. This heterogeneous lesion did not appear to extend into the intraperitoneal cavity in the right lower quadrant area. There was an additional 22 mm x 9.4 mm, soft tissue lesion, in the left gluteal region, involving predominantly the subcutaneous soft tissue contiguous to the left gluteal.

The laboratory evaluation was unremarkable. Biopsies of the mass and additional areas of hyperpigmentation were performed.


The sections demonstrate skin with atrophic epidermis including flattening and a loss of rete ridges. The epidermis overlies a proliferation of nevomelanocytes replacing in the papillary and reticular dermis and extending to and through the subcutaneous tissue. The nevus cells are medium, epithelioid, occasional clusters in the papillary dermis and in the dermal-epidermal junction. Occasional cells contain coarse melanotic granules and occasional giant melanosomes. No pagetoid spread is identified. Beneath the capillary portion are smaller nevomelanocytes with spindled features and intermixed excellent vessels. There are areas of neurotization. Centered within the lesion is a nodule of smaller more spindled cells with mitoses, but lacking necrosis.

Immunohistochemical stains for CD56, Tyrosinase, HMB-45, S100, were positive.


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