Congenital Malignant Ectomesenchymoma Presenting as a Neck Mass in a Newborn

Abstract

Background: Malignant Ectomesenchymoma (MEM) is a rare, aggressive soft tissue neoplasm with both neuroectodermal and mesenchymal differentiation. Congenital cases are extremely uncommon, posing significant diagnostic and therapeutic challenges. Case Presentation: We report a case of a full-term male neonate presenting with a large congenital neck mass and respiratory distress at birth. Imaging revealed a lobulated, heterogeneously enhancing mass in the left submandibular region with a mass effect on the airway. Open biopsy and gross resection on day six of life confirmed MEM with rhabdomyoblastic and neuroectodermal differentiation. Post-surgical staging classified the tumor as Stage I, Clinical Group II. Despite initial chemotherapy with Vincristine, Actinomycin, and Cyclophosphamide (VAC), tumor recurrence was detected at week nine of chemotherapy, necessitating a transition to Vincristine, Irinotecan, and Temozolomide (VIT). Discussion: MEM is an extremely rare neoplasm in infants, particularly in congenital presentations. Diagnosis is challenging due to its mixed histopathological features and broad differential diagnosis, including rhabdomyosarcoma, fibrosarcoma, lymphangioma, and neuroblastoma. Management typically involves multimodal therapy, with surgical resection being the mainstay of treatment. Chemotherapy is often tailored to the tumor's most aggressive component, though standardized treatment protocols remain undefined. Conclusions: This case highlights the importance of early recognition and a multidisciplinary approach in managing congenital MEM, as a differential diagnosis of soft tissue masses in infants, particularly in the head and neck region.

Keywords: congenital neck mass; malignant ectomesenchymoma; neonatology; newborn; soft tissue neoplasm.

Figure 1

Left lateral aspect of infant’s neck on day of life 0.

Figure 2

Coronal short tau inversion recovery (STIR) MRI image demonstrating 2.2 × 5.2 × 5.1 cm neck mass in left parapharyngeal space.

Figure 3

Gross specimen of a resected neck mass.

Figure 4

(a) Hematoxylin and Eosin (H&E) slide of neck MEM—neuroectodermal component (bottom) vs. RMS component (top left) (Desmin IHC, 10×). (b) H&E slide of neck MEM—neuroectodermal component (bottom) vs. RMS component (top left) (H&E, 10×). (c) H&E slide of neck MEM—Neuroectodermal component (bottom) vs. RMS component (top left) (Synaptophysin IHC, 10×). (d) H&E slide of neck MEM—neuroectodermal component (loose spindly stroma with clustered ganglion cells) (H&E, 200×). (e) H&E slide of neck MEM—rhabdomyosarcoma component. Spindled cells with wispy pink muscle differentiation including striations (central) (H&E, 200×).

Figure 4

(a) Hematoxylin and Eosin (H&E) slide of neck MEM—neuroectodermal component (bottom) vs. RMS component (top left) (Desmin IHC, 10×). (b) H&E slide of neck MEM—neuroectodermal component (bottom) vs. RMS component (top left) (H&E, 10×). (c) H&E slide of neck MEM—Neuroectodermal component (bottom) vs. RMS component (top left) (Synaptophysin IHC, 10×). (d) H&E slide of neck MEM—neuroectodermal component (loose spindly stroma with clustered ganglion cells) (H&E, 200×). (e) H&E slide of neck MEM—rhabdomyosarcoma component. Spindled cells with wispy pink muscle differentiation including striations (central) (H&E, 200×).

Figure 4

(a) Hematoxylin and Eosin (H&E) slide of neck MEM—neuroectodermal component (bottom) vs. RMS component (top left) (Desmin IHC, 10×). (b) H&E slide of neck MEM—neuroectodermal component (bottom) vs. RMS component (top left) (H&E, 10×). (c) H&E slide of neck MEM—Neuroectodermal component (bottom) vs. RMS component (top left) (Synaptophysin IHC, 10×). (d) H&E slide of neck MEM—neuroectodermal component (loose spindly stroma with clustered ganglion cells) (H&E, 200×). (e) H&E slide of neck MEM—rhabdomyosarcoma component. Spindled cells with wispy pink muscle differentiation including striations (central) (H&E, 200×).

Figure 5

Axial short tau inversion recovery (STIR) MRI image demonstrating post-surgical changes at the level of the larynx from interval resection.

Figure 6

Dixon sagittal post-MRI image demonstrating enhancing mass along left prevertebral soft tissue in retropharyngeal space after resection and nine cycles of VAC chemotherapy.