Neuroblastoma: Application of International Neuroblastoma Pathology Classification on fine needle aspiration cytology smears.

Background: Neuroblastoma (NB) is the fourth most common tumor of childhood. There is a paucity of literature on its subtyping of cytology and prognostic utility.

Aims: We aimed to study the cytopathological features of NB on the aspirated material, subtype it, and assess the role of International Neuroblastoma Pathology Classification (INPC) classification on cytology smears in the preoperative prognosis of NB.

Materials And Methods: Fifteen cases of NB reported on fine-needle aspiration cytology (FNAC) in the past 3 years were included. Detailed clinical, radiological, and cytological features were noted. Smears were assessed for characteristics such as cellularity, neuroblasts (cytoplasmic, nuclear details), rosettes, neuropil, Schwann cells, fibroblasts, calcification, and necrosis. Afterward, cases were categorized as undifferentiated (UD), poorly differentiated (PD), and differentiating (D) subtypes. Mitotic-karyorrhectic index (MKI) was calculated and correlated with histopathology. Follow-up was done to date.

Results: The age ranged from 19 days to 10 years with an M: F ratio of 3:1. Twelve cases were retroperitoneal, two cervical, and one mediastinal. Metastatic disease was seen in six cases, one to the cervical, four to the bone marrow, and two to the scalp. The International Neuroblastoma Risk Group (INRG) staging system was available in all cases, out of which three were in stage L1, six in stage L2, four in stage M, and two in stage Ms. On cytology, four cases were differentiating NB, five PD NB, and six UD NB. The MKI was high (>4%) in 80% of UD, intermediate (2-4%) in 100% of PD, and low (<2%) in 75% of D cases. MKI corroborated in both histology and cytology, except in one case.

Conclusion: NB can be subtyped on cytology on the basis of characteristics of neuroblasts, presence of neutrophils, rosettes, and necrosis. UD NB has a high MKI and is associated with a poor prognosis. A preoperative comprehensive reporting of NB on cytology can be very useful in guiding appropriate chemotherapy with some increment in survival. However, larger studies are needed to validate the calculation of MKI on FNA smears.