Clinical and histopathological spectrum of cranial small round cell tumors: An experience from a tertiary care center

BACKGROUND

Small round cell tumors (SRCTs) are a group of malignant neoplasms with minimal or no differentiation, characterized by the presence of round cells with high nuclear-cytoplasmic ratio. Although SRCTs can occur in any part of the body, involvement of central nervous system (CNS) is uncommon.

AIM

We aimed to study the clinicopathological spectrum of cranial SRCT diagnosed in our institute over a period of four years (2016-2019).

MATERIAL AND METHODS

A retrospective review of medical records (2016-2019) with a morphological diagnosis of cranial SRCT was made. Both intra-axial and extra-axial tumors were included. A total of 60 cases were retrieved, and the clinical and histopathological features were studied. Special cytochemical staining and immunohistochemistry were performed, where needed.

RESULTS

The mean age at presentation was 18.4 years (range, 1-60 years), with a male-to-female ratio of 2.5:1. The most common site was posterior fossa of brain (n = 28, 47%), followed by dorso-lumbar spine (n = 9, 15%). The most common type of tumor was medulloblastoma (n = 29, 48.3%), followed by Ewing sarcoma (ES)/peripheral primitive neuroectodermal tumor (pPNET) (n = 11, 18.3%), non-Hodgkin lymphoma (NHL) (n = 9, 15%), neuroblastoma (n = 3, 5%), and CNS embryonal tumor, NOS (n = 2, 3.3%). One case each of atypical teratoid rhabdoid tumor (ATRT), rhabdomyosarcoma, pineoblastoma, melanoma, rhabdomyosarcoma, and undifferentiated pleomorphic sarcoma was also documented.

CONCLUSIONS

SRCTs have a variable age of presentation. Their incidence in CNS is low as compared to other organ systems. On light microscopy, the histopathology of these lesions is overlapping, posing a great diagnostic dilemma for the pathologist. The use of ancillary techniques like immunohistochemistry helps in arriving at the correct diagnosis. Treatment strategy and tumor prognosis also vary along the entire spectrum of SRCT, thus making exact characterization essential for proper management.

Adult Patient With Neuroblastoma Presenting as Acute Leukemia

Neuroblastoma (NB) is the most common extra-cranial cancer of early childhood and rarely occurs in adults. The clinical symptoms of NB can be diverse. We discuss a rare case of an adult NB presenting as acute leukemia. A 45-year-old woman presented with persistent hip pain, weight loss, anemia, and incidental fever for several months. Imaging studies showed diffuse bone marrow (BM) uptake and hypermetabolic lesions involving the left adrenal gland, bilateral axillary nodes, and left lateral aspect of the abdomen. Her 24-hour urine catecholamines were within the normal range. On the peripheral blood film, blast-like cells were noted, occupying approximately 2% of leukocytes. The BM imprints showed infiltration of blast-like cells with convoluted nuclei and scant cytoplasm in more than 85% of the total nucleated cells. Acute leukemia was initially suspected based on morphology. Blast-like cells were negative for myeloperoxidase, combined esterase, periodic acid-Schiff, CD45RB, CD68, and CD138. In a further study, these cells were positive for CD56, synaptophysin (SYN), and CD99 with negativity for desmin, myogenin, NKX-2.2, CD31, cytokeratin (AE1/AE3), Melan-A, ERG, S-100, and SALL4. Morphologically similar neoplastic cells in axillary node biopsy were positive for CD56, chromogranin A, SYN, and neurofilament, but negative for GFAP, CD246, and vimentin. Based on laboratory, pathological, and imaging studies, metastatic NB with BM and multifocal involvement was diagnosed. The differential diagnosis of metastatic small blue round cell tumors should be considered for adult patients with circulating blast-like cells, and an accurate diagnosis would enable the patient to receive appropriate and timely treatment.