Dysgerminoma

* Malignant mesenchymal tumors of the gallbladder are exceedingly rare. We report a malignant stromal tumor of the gallbladder with a phenotype of interstitial cells of Cajal. To our knowledge, only the benign counterpart of this tumor has been described previously. A 34-year-old woman presented with right upper quadrant abdominal pain. At the time of cholecystectomy, the gallbladder was noted to have a thickened wall and a polypoid mass arising in the neck of the gallbladder. Histologic sections showed a cellular proliferation of spindle neoplastic cells that were arranged in short fascicles. Numerous mitotic figures and foci of necrosis were noted. The neoplastic cells expressed CD1 17 (c-Kit protein) and vimentin. They were negative for smooth muscle actin, desmin, myoglobin, cytokeratin, 5100 protein, and CD34. Our case demonstrates that a malignant stromal tumor that is histologically and immunohistochemically identical to gastrointestinal stromal tumor can occur in the gallbladder, and that the expression of CD117 may be of therapeutic importance.

(Arch Pathol Lab Med. 2002;126:481-483)

Malignant mesenchymal tumors of the gallbladder are exceedingly rare, and to date only single case reports have been described. They include leiomyosarcoma, rhabdomyosarcoma, angiosarcoma, and Kaposi sarcoma.1 We previously described a benign stromal tumor in the gallbladder with histologic and immunohistochemical features similar to a gastrointestinal stromal tumor (GIST).2 As expected, a malignant counterpart of this tumor exists. Indeed, herein we report a malignant stromal tumor of the gallbladder with CD117 expression-a phenotype of interstitial cells of Cajal.

REPORT OF A CASE

A 34-year-old woman presented with right upper quadrant abdominal pain. An ultrasound examination revealed a gallbladder with thickened wall and containing stones. A cholecystectomy was performed. Subsequent wedge resection of the adjacent liver parenchyma revealed no evidence of residual tumor or metastasis. Clinical workup failed to demonstrate a primary neoplasm at other sites. The patient is alive and free of disease after 6 months.

MATERIALS AND METHODS

Four-micrometer-thick sections were cut from the paraffin blocks and stained with hematoxylin-eosin. Additional paraffinembedded sections were obtained for immunohistochemical studies, which were performed using the standard avidin-biotin peroxidase complex technique and the heat-induced epitope-retrieval buffer. The following antibodies were used: CD117 (dilution 1:400, c-Kit, Santa Cruz Biotechnology, Santa Cruz, Calif), cytokeratin (dilution 1:100, AE1/AE3, BioGenex, San Ramon, Calif), smooth muscle actin (dilution 1:200, Dako Corporation, Carpinteria, Calif), desmin (dilution 1:40, Dako), myoglobin (1: 12000, Dako), S100 protein (dilution 1:400, BioGenex), vimentin (dilution 1:200, Dako), and CD34 (dilution 1:30, Qbend/10, BioGenex).

PATHOLOGIC FINDINGS

Grossly, a firm, tan, polypoid, 1.5-cm tumor was seen within the wall near the neck of the gallbladder. While the mucosa of the gallbladder appeared unremarkable, an expansile neoplasm had infiltrated the full thickness of the wall (Figure 1). Extension beyond the serosa was not noted. The neoplasm was composed of spindled to oval epithelioid cells arranged in short fascicles. Myxoid hypocellular areas were interspersed with densely cellular fascicles. The nuclei of the neoplastic cells were hyperchromatic with prominent nucleoli, and the cytoplasm appeared eosinophilic or vacuolated (Figure 2). Necrosis of variable extent was noted. There were 28 mitotic figures per 10 high-power fields (Figure 3).

The neoplastic cells were immunoreactive for CD117 (Figure 4) and vimentin. They were negative for cytokeratin, desmin, and myoglobin. CD34 and smooth muscle actin labeled only the intrinsic blood vessels. The sections of the uninvolved gallbladder wall did not show CD117-- positive interstitial cells of Cajal.

COMMENT

Malignant mesenchymal tumors of the gallbladder are exceedingly rare entities. Single case reports of leiomyosarcoma, botryoid rhabdomyosarcoma, angiosarcoma, and Kaposi sarcoma have been described.1 We previously described a benign stromal tumor of the gallbladder with a phenotype of interstitial cells of Cajal.2 To our knowledge, no malignant counterpart of this tumor has been reported to date.

Our case is clearly a malignant tumor, evidenced by high cellularity, nuclear pleomorphism, necrosis, and numerous mitoses. It does not express neural, smooth muscle, or skeletal muscle markers, yet it is positive for CD117 (c-Kit protein). CD117 antibody recognizes a transmembrane tyrosine kinase receptor, which is expressed by the interstitial cells of Cajal and also by hematopoietic stem cells, germ cells, mast cells, and melanocytes.3,4 The c-Kit gene product (stem cell factor receptor) is thought to play an important role in the development and maintenance of these cell populations.3,4

Gastrointestinal stromal tumor encompasses a major subset of gastrointestinal mesenchymal tumors that histologically, immunohistochemically, and genetically differ from leiomyomas, leiomyosarcomas, and schwannomas.5-7 The majority of GISTs do not display immunohistochemical evidence of smooth muscle or neural differentiation.6,7 Owing to the expression of CD117, GIST has been proposed to originate from the interstitial cells of Cajal.8 Recently, deletions or mutations of the c-kit proto-oncogene have been documented in these tumors.9 Moreover, recent documentation of therapeutic response to the tyrosine kinase inhibitor STI571 in a patient with metastatic GIST affirms the therapeutic implication of CD117 expression in these tumors and in our gallbladder tumor.10

In the adult gastrointestinal tract, the myenteric plexus of the stomach, small intestine, and colon showed CD117-- positive cells.3 In our previous study, sections from 10 gallbladders with chronic cholecystitis were stained with CD117.2 Occasional CD117-positive cells were seen in close contact to the smooth muscle cells of the muscularis propria in 2 of these 10 cases.2 These findings lend support to the hypothesis that GISTs originate from the interstitial cells of Cajal. However, primary tumors with a histologic appearance similar to GISTs and immunoreactivity with CD117 have been described in the omentum and mesentery.11 These tumors often coexpressed alpha-- smooth muscle actin.11 A possibly better explanation is that these tumors arise from a multipotential stem cell that differentiates into different phenotypes, including interstitial cells of Cajal, smooth muscle, or neural types.

The differential diagnosis includes primary or metastatic undifferentiated carcinoma, epithelioid leiomyosarcoma, rhabdomyosarcoma, epithelioid angiosarcoma, and metastatic melanoma. Before the advent of immunohistochemistry, the reported primary sarcomas of the gallbladder were likely undifferentiated carcinoma or sarcomatoid squamous cell carcinoma.1 These malignant epithelial tumors can now easily be excluded because they show immunoreactivity to cytokeratin. In addition, sections from the uninvolved gallbladder mucosa do not show an in situ change in the malignant stromal tumors, while they are usually present in carcinomas.1 A leiomyosarcoma would express smooth muscle actin and desmin, and likewise a rhabdomyosarcoma would express desmin and myoglobin. Metastatic malignant melanoma can express CD117; however, reactions for S100 protein and/or HMB-45 would be positive.

We have reported an unusual malignant mesenchymal tumor of the gallbladder that has the phenotype of interstitial cells of Cajal. Our case demonstrates that a malignant stromal tumor that is histologically and immunohistochemically similar to GIST can occur in the gallbladder, and that the expression of CD117 may be of therapeutic importance.

Note.-We recently learned that the patient developed local recurrence in the region of the cystic duct and is currently receiving chemotherapy.

References

1. Albores-Saavedra J, Henson DE, Klimstra DS. Tumors of the Gallbladder, Extrahepatic Bile Ducts, and Ampulla of Vater. Washington, DC: Armed Forces Institute of Pathology; 2000. Atlas of Tumor Pathology, 3rd series, fascicle 27.

2. Ortiz-Hidalgo C, Bojorge BL, Albores-Saavedra J. Stromal tumor of the gallbladder with phenotype of interstitial cells of Cajal: a previously unrecognized neoplasm. AmJ Surg Pathol. 2000;24:1420-1423.

3. Sarlomo-Rikala M, Kovatich At, Barusevicius A, Miettinen M. CD1 17: a sensitive marker for gastrointestinal stromal tumors that is more specific than CD34. Mod Pathol. 1998;11:728-734.

4. Tsuura Y, Hiraki H, Watanabe K, et al. Preferential localization of c-kit product in tissue mast cells, basal cells of skin, epithelial cells of breast, small cell lung carcinoma and semi noma/dysgerminoma in human: immunohistochemical study of formalin-fixed, paraffin-embedded tissues. Virchows Arch. 1994;424: 135-141.

5. Franquemont DW, Frierson HF. Muscle differentiation and clinicopathologic features of gastrointestinal stromal tumors. Am J Surg Pathol. 1992;16:947-954.

6. Hjermstad BM, Sobin LH, Helwig EB. Stromal tumors of the gastrointestinal tract: myogenic or neurogenic? Am J Surg Pathol. 1987;11:383-386.

7. Miettinen M, Virolainen M, Sarlomo-Rikala M. Gastrointestinal stromal tumors: value of CD34 antigen in their identification and separation from true leiomyomas and schwannomas. Am J Surg Pathol. 1995;19:207-216.

8. Sicar K, Hewlett RB, Huizinga JD, et al. Interstitial cells of Cajal as precursors of gastrointestinal stromal tumors. Am J Surg Pathol. 1999;23:377-389.

9. Hirota S, Isozaki K, Moriyama Y, et al. Gain-of-function mutations of c-kit in human gastrointestinal stromal tumors. Science. 1998;279:577-580.

10. Joensuu H, Roberts PJ, Sarlomo-Rikala M, et al. Effect of the tyrosine kinase inhibitor STI571 in a patient with a metastatic gastrointestinal stromal tumor. N Engl J Med. 2001;14:1052-1056.

11. Miettinen M, Monihan JM, Sarlomo-Rikala M, et al. Gastrointestinal stromal tumors/smooth muscle tumors (GISTs) primary in the omentum and mesentery. Am J Surg Pathol 1999;23:1109-1118.

Marisela Mendoza-Marin, MD; Mai P Hoang, MD; Jorge Albores-Saavedra, MD

Accepted for publication August 16, 2001.

From the Departments of Pathology, Regional General Hospital, Social Security System, Mexico City, Mexico (Dr Mendoza-Marin); and the University of Texas Southwestern Medical Center, Dallas, Tex (Drs Hoang and Albores-Saavedra).

Reprints: Jorge Albores-Saavedra, MD, Department of Pathology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75390-9073 (e-mail: Albores.jorge@pathology. swmed.edu).

Copyright College of American Pathologists Apr 2002
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