Paratesticular congenital malignant rhabdoid tumor diagnosed by fine-needle aspiration cytology. a case report

Cytomorphologic Spectrum of SMARCB1-Deficient Soft Tissue Neoplasms

OBJECTIVES

The SWI/SNF complex core subunit SMARCB1 is inactivated in a variety of neoplasms that share characteristic "rhabdoid" cytomorphology. The aim of this study was to evaluate SMARCB1-deficient soft tissue neoplasms on cytology to identify diagnostic clues.

METHODS

Eleven SMARCB1-deficient tumors, including six epithelioid sarcomas, three malignant rhabdoid tumors, one epithelioid malignant peripheral nerve sheath tumor (MPNST), and one poorly differentiated chordoma with fine-needle aspiration (FNA), serous effusion, or touch prep (TP) from two institutions, were included. Targeted next-generation sequencing (NGS) was performed in two cases.

RESULTS

Evaluation of FNA (n = 4), effusion (n = 4), and TP (n = 3) in nine adult and two pediatric patients demonstrated cellular samples (n = 11), epithelioid cells with rhabdoid morphology (n = 9), eccentrically located nuclei with prominent nucleoli (n = 7), and cytoplasmic bodies (n = 4); two patients were diagnosed on FNA with cell block. Immunohistochemistry (IHC) demonstrated SMARCB1 loss in all cases and keratin and/or EMA expression in all but the epithelioid MPNST; NGS identified SMARCB1 inactivation in both cases.

CONCLUSIONS

SMARCB1-deficient soft tissue neoplasms comprise a variety of tumors with epithelioid morphology and frequent expression of keratin and/or EMA. Recognition of characteristic rhabdoid morphology on cytology can prompt IHC and/or NGS testing for SMARCB1 deficiency and help establish the diagnosis.

Congenital Disseminated Extrarenal Malignant Rhabdoid Tumor

Soft tissue tumors arising in association with genetic or malformation syndromes have been increasingly reported. Malignant rhabdoid tumor (MRT) is a highly aggressive neoplasm of infancy and young childhood, characterized by typical morphology and biallelic inactivation of the SMARCB1 (INI1/hSNF5/BAF47) gene on chromosome 22q.2 which encodes a subunit of the SWI/SNF ATP-dependent chromatin remodeling complex. Congenital infantile disseminated MRT represents a unique clinicopathologic presentation of this tumor. We report a case occurring in a female neonate who presented at birth a voluminous left thigh mass. Surgical biopsy performed at day 9 showed morphology and immunoprofile of MRT. Staging evaluation identified hypercalcemia and distant nodules. The mass showed rapid growth. Despite chemotherapy, the tumor progressed with exteriorization through the biopsy scar. Chemotherapy was discontinued and treatment limited to palliative care and the child died on day 51. The tumor was homozygous for the SMARCB1 deletion with apparent de novo heterozygous germ line deletion in the infant, not identified in the parents.

Surgery and actinomycin improve survival in malignant rhabdoid tumor

Purpose. Malignant rhabdoid tumor (MRT) is an uncommon tumor that rarely occurs outside of renal and central nervous system (CNS) sites. Data from the literature were compiled to determine prognostic factors, including both demographic and treatment variables of malignant rhabdoid tumor, focusing on those tumors arising in extra-renal, extra-CNS (ER/EC MRT) sites. Patients and Methods. A systematic review and meta-analysis was performed by extracting demographic, treatment, and survival follow up on 167 cases of primary ER/EC MRT identified in the literature. Results. No survival differences were observed between those treated with or without radiation, or with or without chemotherapy. A Cox regression of overall survival revealed several independent prognostic factors. Surgical excision had a 74% (P = 0.0003) improvement in survival. Actinomycin had a 73% (P = 0.093) improvement in survival. Older age was associated with improved survival. The four-year survival, by Kaplan-Meier estimates, comparing patients less than two years old versus older than two at diagnosis was 11% versus 35%, respectively (P = 0.0001, Log-Rank). Conclusion. ER/EC MRT is a rare, soft-tissue tumor with a poor prognosis most commonly occurring in children. Surgical resection, treatment with actinomycin, and older age at diagnosis are all associated with improved survival.