LETTERS TO THE EDITOR

Cytogenetic Abnormalities in an Intraabdominal Desmoplastic Small Cell Tumor

We report a nonrandom complex three-way translocation of chromosomes in a rare desmoplastic small cell tumor derived from the pelvis. The patient is a 14-year-old Hispanic female who had a large pelvic mass. Exploratory laparotomy disclosed extensive peritoneal implants, and multiple metastatic deposits in the ovaries, fallopian tubes, and liver. After extensive immunohistochemical studies and consultations at several institutions, a diagnosis of desmoplastic small cell tumor was made. The patient had an initial partial response to chemotherapy but developed progressive disease and died 10 months later. Chromosomal analysis was made of a second-look biopsy

specimen. The cells were harvested in a 7-day culture from mechanically disaggregated tumor tissue. Tumor cells were analyzed cytogenetically by standard GTG banding; twenty metaphases were examined. Each metaphase contained 46 chromosomes with a female sex chromosome complement and an apparently balanced three-way translocation between chromosomes 2, 21 and 22 with breakpoints at 2p23, 21q22.11, and 22q13. The chromosome segments distal to these bands were exchanged from chromosome 2-*22, from 22-.21, and from 21-.2 (Fig. 1). Karyotype of this tumor according to the international nomenclature is 46,XX, t(2;21;22)(p23;q22.11;q13)(GTG) (Fig. 2).

Figure 1 (A) Breakpoint (short arrows) and exchanges (dotted lines a, b, and c). (B) Derivative chromosomes in t(2;21;22)(p23;q22.11;q13).

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Intraabdominal Desmoplastic Small Cell Tumor

191 The name desmoplastic small cell tumor was initially proposed by Gerald and Rosai as a separate entity of small round cell tumors [1]. Several case reports followed in recent years confirming the unique location and histochemical features of this tumor (2-4). It is a rare tumor occurring in children and young adults, usually arising diffusely in the abdominal cavity with a predilection for the pelvic region. Under the light microscope, the tumor is composed of nests of small cells surrounded by an abundant desmoplastic stroma (Hg. 3). Immunohistochemical findings show multidirectional differentiation with coexpression of keratin, epithelial membrane antigen, NSE, vimentin, and desmin (2-4). The tumor is extremely aggressive clinically; 80% of reported patients died of the disease despite multiagent chemotherapy and radiation therapy. No previous cyiogenetic analysis of this tumor has been reported. The cytogenetic changes observed in this tumor are clearly different from those of other small round cell tumors, i.e., Ewing sarcoma, primitive neuroectodermal tumor, neuroblastoma, rhabdomyosarcoma, or lymphoma. Additional cytogenetic studies of desmoplastic small cell tumor may disclose a specific cytogenetic marker useful in clinical diagnosis and molecular genetic investigation of this tumor.

W. R VIOLET S H E N BARBARA TOWNE

TOURAN M. ZADEH

Departments of Pediatric Hematology-Oncology Pediatric Surgery and Genetics Children's Hospital of Orange County Orange, California 92668

REFERENCES

Figure 3 Histologic section of the tumor showed numerous welldefined cellular nests separated by stroma. The cellular nests were composed of tightly packed small and round tumor cells. The cells appeared homogeneous with no signs of morphologic differentiation such as glands or rosettes. The stroma contained abundant extracellular substance with few spindle-shaped fibroblasts. These are characteristic of desmoplastic tumor. Top: original magnification x 40; bottom: original magnification x 200. Bar = 100 ~tm.

1. Gerald WL, Rosai J (1989): Case 2: Desmoplastic small cell tumor with divergent differentiation. Pediatr Pathol 9:177-183. 2. Gerald WL, Miller HK, Battifora H, Miettinen M, Silva EG, Rosai ] (1991): Intraabdominal desmoplastic small round cell tumorreport of 19 cases of a distinctive type of high-grade polyphenotypic malignancy affecting young individuals. Am J Surg Pathol 15:499-513. 3. Gonzalez-Crussi F, Crawford SE, Sun CJ {1990): Intraabdominal desmoplastic small cell tumors with divergent differentiation: observation on three cases in childhood. Am J Surg Pathol 14:633-642. 4. Layfield LJ, Lenarsky C (1991): Desmoplastic small cell tumors of the peritoneum coexpressing mesenchymal and epithelial markers. Am J Clin Pathol 96:536-43.