Malignant Rhabdoid Tumor masquerading as Neuroblastoma: A rare Case-report

Abstract Introduction/Objective Malignant rhabdoid tumors (MRT) predominantly impact infants and young children, typically occurring around the age of 15 months. While they can emerge from soft tissues throughout the body, but commonly initiate in the kidneys. Neuroblastoma-like characteristics are seldom observed within the varied phenotypes of malignant rhabdoid tumors. Here, we present an exceptionally rare and distinctive subtype of malignant rhabdoid tumor exhibiting features akin to neuroblastoma localized within the unusal parapharyngeal space. Methods/Case Report A 2-month-old female presented to the ED with an enlarging right cervical neck mass. The mother reported a one-week history of upper respiratory tract symptoms and noticed an enlarging mass of her right neck. CT reported a “parapharyngeal abscess with airway compression”. The patient was started on Augmentin with no significant improvement. Repeat CT with contrast demonstrated an enlarging rim-enhancing 3 cm mass involving the right parapharyngeal space, trachea, and right carotid arteries. Laryngoscopy and incisional biopsy of right neck lymph nodes demonstrated a high-grade malignancy with prominent nucleoli, high N/C ratio and scant cytoplasm. The tumor tested positive for CD 99, synaptophysin, and neurofilament, leading to the initial diagnosis of neuroblastoma. However, molecular analysis uncovered the loss of INI-1 on 22q11.2, prompting a reevaluation and a final diagnosis of MRT with neuroblastoma-like characteristics was made. Results (if a Case Study enter NA) NA Conclusion A range of tumors displaying distinct “rhabdoid” cytological features are collectively termed as malignant rhabdoid tumors (MRTs). Conventional immunohistochemistry (IHC) staining for CD99, synaptophysin, neurofilament, and myogenin might suggest neuroblastoma, Ewing sarcoma, or rhabdomyosarcoma. However, the absence of INI-1 expression provides a definitive diagnosis. INI-1 loss, a purported tumor suppressor gene located on chromosome 22q11.2, solidifies the tumor’s classification as malignant rhabdoid tumor (MRT). Additionally, a positive neurofilament stain in MRT is crucial for diagnostic and therapeutic assessments. This differentiation is vital, given the dismal prognosis of MRT with a 5-year survival rate of less than 10%.