Teaching Case

A 13-day-old female neonate presented with multiple subcutaneous nodules. Uneventful antenatal course. Born at full term by caesarean with an Apgar of 9/9. Family history was unremarkable.
Physical examination showed multiple subcutaneous nodules up to 4 cm in diameter. Laboratory results were normal except for mildly elevated C-reactive protein (8.8mg/L).

Chest radiograph was normal. Ultrasound showed multiple subcutaneous and muscular hypoechoic nodules. (Fig. 1) Skeletal survey at admission was normal. Whole body MRI confirmed the presence of multiple well-defined nodules diffusely distributed in muscle and subcutaneous tissue with low signal on T1-weighted imaging, high-signal centre on T2-weighted images and peripheral enhancement following IV contrast administration. (Fig. 2-6)
Excisional biopsy of a nodule demonstrated a lesion with zonal distribution with peripheral bundles of myofibroblastic spindle cells and a central area with hyalinization. The cells stained positive to vimentin and actin. (Fig. 7-9)
By the 6th month, the skeletal survey demonstrated multiple lytic lesions predominantly affecting the lower limbs. (Fig. 10, 11) Abdominal ultrasound showed a hypoechoic hepatic nodule in the 8th liver segment measuring 10 mm. (Fig 12) Whole body MRI was repeated demonstrating progression of the known nodules and confirmation of the osseous and hepatic involvement. (Fig. 13, 14)

The case presented describes a case of congenital infantile myofibromatosis (IM) in a female newborn. This entity was first described in 1954 and renamed in 1981 as infantile myofibromatosis to emphasize lesion characteristics and occurrence in newborns and infants. [1] As with our case, 60% are noted shortly after birth.[2]
Differential diagnosis includes other entities presenting as nodular lesions, such as leiomyomas and neurofibromas. Diagnosis is usually dependent on histology analysis of the nodules that present a peripheral area resembling smooth muscle and a central portion containing less differentiated rounder cells often arranged in a haemangiopericytoma-like pattern. The cells stain positive to vimentin and actin but not for desmin and S-100. [2, 3]
IM can be divided in solitary and multicentric types. The solitary type is defined by the presence of only one nodular lesion, most commonly in the skin, subcutaneous tissue, muscle or bone. The multicentric type is subdivided according to the presence or absence of visceral involvement. Visceral involvement usually affects lung, heart, gastrointestinal tract, pancreas or liver and is associated with a worse prognosis. [4, 5] Lesions often present a rapid growth initially followed by spontaneous regression in the first two years. After excision the recurrence rate is 7-10%. [6] Prognosis is usually good with a mortality rate of zero in the solitary form and 1.3% in the multicentric form without visceral involvement. [7]
The newborn presented with multicentric IM with skin and subcutaneous involvement. There was no regression of the lesions with conservative management. Instead, progression was noted in imaging follow-up with bone involvement in tibia and femur bilaterally, a common location of bone involvement. Also, visceral involvement was demonstrated as a nodular hepatic lesion.
There is no management protocol established for this rare entity. Considering the high rate of spontaneous regression, conservative management and imaging follow-up are chosen when there is no visceral involvement. Surgical excision is reserved for lesions that can affect vital functions. In aggressive cases, different combinations of radiation therapy, chemotherapy, steroids and alpha interferon have been tried. [8-10]
The mortality rate in multicentric form with visceral involvement is as high as 76% with deaths more related to the extent and location of visceral lesions, rather than their presence alone. [11]
In the case presented there was no regression but a progression of the disease, with bone and visceral involvement “de novo” identified in the follow-up. Therefore chemotherapy with methotrexate and vinblastine was initiated with regression of the lesions and resolution of the hepatic nodule.