Desmoplastic small round cell tumor of the parotid gland-report of a rare case and a review of the literature

Abstract

Background Desmoplastic small round cell tumor (DSRCT) is a rare soft tissue tumor that generally involves the retroperitoneum, pelvis, omentum and mesentery in younger patients. However, extra-abdominal DSRCT is very rare. Case presentation A 49-year-old Japanese man noticed a mass in the right parotid gland. Ultrasound examination revealed a solid tumor about 2 cm in diameter. Computed tomography (CT) of the whole body revealed no other tumors or lymph node swelling. Superficial parotidectomy was performed. Histologically, the tumor was composed of various-sized tumor cell nests in an abundant fibromyxoid and collagenous background. The tumor cells were small to medium-sized. Immunohistochemistry showed that the tumor cells were immunoreactive for epithelial markers and desmin. They also showed strong nuclear staining with a Wilms tumor 1 (WT1) antibody detecting the C-terminal region (C-WT1), but not the N-terminal region (N-WT1). We also performed 3′/5′ expression imbalance assay based on reverse transcription polymerase chain reaction (RT-PCR) to determine whether aberrant WT1 gene expression was present. This tumor was found to lack 5′-regional expression of the WT1 gene, as well as immunoreactivity with the N-WT1 antibody. Finally, fluorescence in situ hybridization (FISH) and RT-PCR analyses revealed the presence of a gene showing fusion between exon 7 of EWSR1 and exon 8 of WT1. The tumor was diagnosed as a DSRCT of the right parotid gland. The patient has been followed for 3 years without recurrence or metastasis. Conclusions Although DSRCT in the salivary gland is extremely rare, it should be included in the differential diagnosis of poorly differentiated salivary gland neoplasms, especially with a fibromyxoid background. Pathologists should bear in mind that DSRCT may occur in major salivary glands and should perform immunohistochemistry with appropriate antibodies, not only those against keratin and desmin, but also one detecting the C-terminal region of WT-1. Furthermore, molecular detection of EWSR1-WT1 fusion gene conclusively confirmed the diagnosis of DSRCT in this uncommon location.

Clinicopathologic and molecular features of intracranial desmoplastic small round cell tumors

“…DSRCTs are less frequently reported in other locations such as the pleura (31), lung (49), parotid gland (26), kidney (12), pancreas (43), paratesticular region (3,44) or bone and soft tissues of the extremities (1,3,55). Seven intracranial DSRCT cases with confirmation of EWSR1-WT1 fusion have been reported previously (3,9,40,50,52).…”

Desmoplastic Small Round Cell Tumor: A Rare Location in the Parotid Gland

“…Other diagnoses like malignant melanoma, Merkel cell carcinoma, metastatic neuroblastoma, Ewing sarcoma, rhabdomyosarcoma or malignant lymphoma are more common. Also, we should differentiate it from a solid variant of an adenoid cystic carcinoma [2].…”

“…DSRCT cases in major salivary glands have been reported but in a very small number of patients. The origin of this tumor is not well-known, and some authors hypothesize that it could derive from mesothelial or submesothelial cells because of the usual location and because of the positivity for antigens like desmin and Wilms tumor 1 (WT-1) [2]. In this report, we present a case of a DSRCT involving the parotid gland of a young male.…”

A case of submandibular desmoplastic small round cell tumor: Diagnostic and management approaches to an atypical presentation of a rare tumor

“…One recent retrospective analysis reported on 16 such cases, occurring in the head/neck, intracranial, thigh, axilla, paratesticular, intraosseous, and uterine corpus, and a single case of a pediatric ocular primary DSRCT has also been reported . A recent review of the literature describing major salivary gland DSRCT found only six published cases, with five of those occurring in adult patients (range of 23‐49 years old at presentation) . The only pediatric case previously described was in a five‐year‐old male with a parotid lesion; no clinical data with regard to cancer‐directed therapy or outcome are available .…”

“…7 A recent review of the literature describing major salivary gland DSRCT found only six published cases, with five of those occurring in adult patients (range of 23-49 years old at presentation). 8 The only pediatric case previously described was in a five-year-old male with a parotid lesion; no clinical data with regard to cancer-directed therapy or outcome are available. 9 Of the five adult patients with outcome data in this series, three were alive and free of disease at the time of their reports, ranging from 7 to 36 months after the completion of therapy.…”