Desmoplastic Small Round Cell Tumor

Key Facts

Clinical Issues

Most common in children and young adults (median age: 20 years)
Male predilection
Large pleural-based mass on chest x-rays and CT scans
Poor prognosis
Median survival is 24 months

Macroscopic Features

Large, bulky tumors (> 10 cm in greatest dimension)

Microscopic Pathology

Nests, trabeculae, or sheets of small round blue cells embedded in abundant desmoplastic fibrous stroma
Rosette-like structures
Small to intermediate-sized round to oval cells with scant cytoplasm
High mitotic rate, often with atypical (abnormal) mitoses
Staining pattern is polyphenotypic
Vimentin, keratin, desmin, EMA, and WT1 consistently stain tumor cells in ˜ 90% of cases
Staining pattern for desmin and vimentin is characteristically dot-like and paranuclear
May also show focal positivity for CD56, NSE, chromogranin, synaptophysin, and S100 protein
Shows t(11:22)(p13;q12), similar to Ewing sarcoma/PNET
Unlike Ewing sarcoma, site on chromosome 11 is WT-1 gene rather than FLI-1 gene

Desmoplastic small round cell tumor of the pleura shows islands of small round blue tumor cells surrounded by abundant, paucicellular, and desmoplastic connective tissue stroma.

Small island of tumor cells in small desmoplastic round cell tumor shows primitive small blue cells with dispersed nuclear chromatin, small inconspicuous nucleoli, and occasional mitoses.

TERMINOLOGY

Abbreviations

Desmoplastic small round cell tumor (DSRCT)

Synonyms

Desmoplastic small cell tumor with divergent differentiation
Polyphenotypic small round cell tumor
Desmoplastic primitive neuroectodermal tumor

Definitions

Primitive malignant neoplasm arising in serosal surfaces with distinctive histology composed of primitive small round blue cells embedded in abundant desmoplastic stroma

ETIOLOGY/PATHOGENESIS

Unknown

May represent primitive mesothelial neoplasm (i.e., “mesoblastoma”)

CLINICAL ISSUES

Presentation

Male predilection
Pain and weight loss
Large pleural-based mass on chest x-rays and CT scans
Most common in children and young adults (median age: 20 years)

Treatment

Surgical excision
Chemotherapy

Prognosis

Poor prognosis
Frequent local recurrence; rarely metastasizes
Median survival is 24 months

MACROSCOPIC FEATURES

General Features

Large, bulky tumors (> 10 cm in greatest dimension)
May also grow in multinodular fashion
Firm, homogeneous cut surface
Hemorrhage and necrosis

MICROSCOPIC PATHOLOGY

Histologic Features

Nests, trabeculae, or sheets of small round blue cells embedded in abundant desmoplastic fibrous stroma
Nests may display peripheral palisading of tumor cells
Rosette-like structures

Cytologic Features