Which of the following bone tumors occurs in young age group, arises in medullary cavity, and characteristically shows sheets of small uniform sized round cells and Homer Wright rossets?
Osteosarcoma
Ewing's tumor
Chondrosarcoma
Osteoid osteoma
Ans. b (Ewing's tumor) (Ref. Robbin's pathology, 7th/pg. 1301; 558).The four main types of rosettes in pathology :1. Homer Wright rosette: typically seen in neuroblastomas, medulloblastomas, and primitive neuroectodermal tumors (PNETs). It consists of a halo of tumor cells surrounding a central region containing neuropil.2. Flexner-Wintersteiner Rosette: characteristic of retinoblastomas. It consists of tumor cells surrounding a central lumen that contains cytoplasmic extensions from the tumor cells.3. True Ependymal Rosette: consists of tumor cells surrounding an empty lumen. Are characteristic of ependymoma, but not seen in all cases.4. Perivascular Pseudorosette: consists of tumor cells collected around a blood vessel. It's called a pseudorosette because the central structure isn't part of the tumor. These rosettes are common in ependymomas, but you also see them in medulloblastoma, PNET, central neurocytomas, and glioblastomas.EWING'S SARCOMA# Incidence: Constitutes ~10 to 15% of all bone sarcomas.# Age: Peak incidence in the second decade of life.# Origin: Arises in the medullary cavity of the bones.# Location:involves the diaphyseal region of long bones (especially femur) & flat bones (especially pelvis).# X-ray: permeative destructive lytic lesion with "onion peel" periosteal reaction with soft tissue mass.# Histopathology:- It is composed of sheets of monotonous, small, round, blue cells and can be confused with lymphoma, embryonal rhabdomyosarcoma, and small-cell carcinoma.- The cells are rich in glycogen (PAS positive cells).6- The presence of "Homer-Wright rosettes" is indicative of neural differentiation.- Most PNETs arise in soft tissues; they include:* Peripheral neuroepithelioma,* Askin's tumor (chest wall), and* Esthesioneuroblastoma.- The presence of p30/32, the product of the mic-2 gene (which maps to the pseudoautosomal region of the X and Y chromosomes) is a cell-surface marker for Ewing's sarcoma (PNETs).- The classic cytogenetic abnormality associated with this disease (and other PNETs) is t(11;22).- CD99 +.# It is very aggressive tumor and considered a systemic disease and mimics acute osteomyelitis.# Common sites of metastases are lung, bones (bone to bone metastases/), and bone marrow.# Rx:# Systemic chemotherapy is the mainstay of therapy, often being used before surgery.# Local treatment for the primary tumor includes surgical resection, usually with limb salvage or radiation.# Ewing's is a curable tumor, even in the presence of obvious metastasis, especially in children <11 years old.Also Know:TranslocationTtimor# (22q11)Chronic myelogenous leukemia# (12;22)(q 13 ;q 12)Malignant melanoma of soft parts (MMSP)# (11;14)(q13;q32)Mantle cell lymphoma# (14; 18)(q32;q21)Follicular lymphoma# (1;22)(q24;q12)Ewing's sarcoma# (1;7)(p34;q35)T cell acute lymphocytic leukemia (ALL)# (8;14)(q24;q32)Burkitt's lymphoma, B cell ALL# (11;22)(pl3;q12)Desmoplastic small round cell tumor (DSRCT)# (2;13)(q35;ql4)Alveolar rhabdomyosarcoma# (1; 13)(p36;q 14)Alveolar rhabdomyosarcoma# (10; 17)(q 11.2;q23)Papillary thyroid carcinomas# (x, 18)Synovial cell sarcoma
Osteology