Presentation
Mass noted in the right iliac fossa of a newborn a few days after birth, now stable up to 1 month of life.
Patient Data
Ultrasound shows a well-circumscribed intramuscular mass involving the internal oblique and transverse abdominal muscles of the right iliac fossa. Heterogeneous echogenicity with many internal vessels which have high resistance arterial waveforms on spectral Doppler.
Imaging findings are not typical of infantile hemangioma, so biopsy was performed.
These are in fact the ultrasound images at 1 month of life (after obtaining biopsy results), shown instead of the initial images which were of lesser quality. Mass had remained unchanged in size and appearance over the 2-week interval since initial ultrasound.
Several percutaneous core biopsies done under ultrasound guidance with semi-automatic 18- and 16 G needles. No notable bleeding after biopsy.
Intramuscular mass involving the internal oblique and transverse abdominal muscles of the right iliac fossa, mildly hyperintense on T2WI, isointense to skeletal muscle on T1 with diffuse homogenous enhancement that is mildly more than muscle. Mass measures 4.1 x 2.3 x 2.8 cm (AP x T x CC).
PATHOLOGY REPORT (translated from French)
Histology and immunohistochemistry
Histologically, the sample involves areas of mature striated muscle separated by
thickened conjunctival tissue trabeculations within which many small vascular structures are seen,
totally entangled with the striated muscle and sometimes the adipose tissue. These structures are characterized by a muscular layer, vein-like, the largest of which appear discreetly tortuous. The capillary structures are sometimes anastomosed. Endothelial cells do not show cytonuclear atypia
and are not turgid. No mitosis is seen. There is no significant inflammatory infiltrate associated with the lesion.
Absence of suspected element of malignancy.
The immunohistochemical study shows:
-AML: outlines vascular structures
-Glut 1: negative
-WT1: weak focal marking, rather in favor of a malformative process than a proliferative one
Case reviewed with a pediatric pathologist with expertise in vascular anomalies.
Pathology report conclusion
Biopsy of an intramuscular hypervascular mass of the right iliac fossa whose morphological aspect primarily evokes an intramuscular hemangioma.
Absence of elements suggestive of malignancy.
Genetic panel results (in French) for the most common vascular anomalies mutations show no identified pathogenic variant.
Case Discussion
Intramuscular hemangiomas are rare vascular anomalies, currently (at the time of writing in 2022) in the "Provisionally unclassified vascular anomalies" of the ISSVA classification of vascular anomalies. They should not be confused with infantile hemangiomas which are much more common and stain GLUT-1 positive, nor with intramuscular venous malformations which are sometimes referred to inappropriately as "hemangiomas".
This type of lesion is generally discovered later in life, either revealed by mild pain or discovered incidentally. Growth is generally proportional to somatic growth, or very slowly progressive over time. Some cases can mimic arteriovenous malformations (AVMs) on Doppler because of large arterialized vessels, but resistive index is generally high and there is usually no significant arteriovenous shunting, in addition to there always being a discrete mass which should not be seen in AVMs.
Though much remains unknown about these lesions, in the experience of our national reference center for superficial vascular anomalies having followed several patients with this entity over many years, treatment is likely unnecessary if asymptomatic due to its benign nature.
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