Prepared by Feng Tao, MD, Evan Dillon, MD, David Follet, MD, of the Department of Radiology, and Frank Bieuei, MD, of the Department of Pathology, Lenox Hill Hospital, New York, NY.

CASE SUMMARY

A 69-year-old man with a history of myocardial infarction, hypertension, and noninsulin-dependent diabetes mellitus was admitted to the hospital for a right lower quadrant mass found on physical examination. A CT scan (figure 1) demonstrated an 8 * 11 cm multiloculated mixed density mass in the region of the cecum. This mass has irregular thick wall and internal septations. There is no evidence of metastases in other organ systems. A subsequent laproscopic exploration and resection of the mass and cecum with iliocolic anastomosis was performed. Postoperatively, a right lower quadrant abscess developed and was drained. Following radiation therapy, patient has been disease-free for 6 months.

DIAGNOSIS

Malignant fibrous histiocytoma (MFH)

IMAGING FINDINGS

Gross pathology examination (figure 2) revealed a well-circumscribed 8.7 * 7.3 * 6.5 cm tumor beneath or in the wall of the cecum with no mucosal extension. Sectioning of the specimen showed abundant hemorrhage, necrosis, and numerous degenerative cystic foci, which constitute the bulk of the tumor, solid tissue being a comparatively small component. Microscopically (figures 3 to 5), the tumor is lying predominantly beneath the colonic wall in the subserosal/peritoneal fat. It invades the outer longitudinal layer of the muscularis, but not the inner circular layer, submucosa, and mucosa. The tumor is composed, in part, of spindle cells, which are present in long fascicles, and more rounded histolytic-like cells. A very prominent and distinctive feature is the presence of numerous osteoclast-like giant cells. They vary considerably from area to area. There is moderately brisk mitotic activity, and many atypical mitoses are seen. Some fibrous bands and several foci of more diffuse fibrosis are also present. Infiltration into the surrounding serosal adipose tissue at the tumor margins is seen. These findings are consistent with a diagnosis of MFH, giant cell type (or malignant giant cell tumor of soft part).

DISCUSSION

Malignant mesenchymal tumors of the large intestine seldom occur and the great majority of them are leiomyosarcomas ¹ while other types of colonic sarcomas are exceedingly rare.

In the present case, the CT imaging demonstrates nonspecific features of a large pericecal mass without evidence of local invasion or remote metastases. The differential diagnosis includes colonic adenocarcinoma, unknown origin metastatic focus, leio-myosarcoma, lymphoma, inflammatory fibro-sarcoma of mesentery and retroperitoneum, ^2,3 sarcomatoid carcinoma, or malignant peripheral nerve sheath tumor.

A recent review reported 13 cases of colonic MFH (pleomorphic or myxoid type). ³ The mean patient age was 57 years (range 17 to 74 years), with nine patients older than age 50. This age distribution is similar to that of patients with soft tissue MFH, where the majority of patients are 50 to 70 years old. The ratio of male to female is 10:3, which is consistent with the occurrence of soft tissue MFH. Japanese men are most commonly affected. Most of the tumors are large, with a mean diameter of 8.2 cm (median diameter 8 cm). The gross features were categorized into two types: 1) polypoid or pedunculated; and 2) others, such as nodular masses. Direct involvement of the mesentery at initial operation, rather than peritoneal involvement may be a good prognostic factor for large bowel MFH.

It has been proposed that regional lymph node metastases of soft tissue MFH formerly believed to be common, are quite uncommon ⁴ with an incidence of lymph node metastases being 4%, ⁵ 12% ⁴ and 17%. ⁶ However, the reported lymph node metastases of large intestinal MFH is as high as 30%. ³ The only other metastatic site of large intestinal MFH is the liver. ³ The overall mortality rate for these colorectal tumors appears roughly parallel with that of their soft tissue counterparts.

In summary, we describe the first case of colonic MFH, giant cell type. MFH of the large intestine is similar to soft tissue MFH in its incidence and prognosis. However, it is possible that a high incidence in Japanese patients and higher incidence of lymph node metastases characterize MFH of the large bowel when compared with soft tissue MFH.

Currently, no diagnostic imaging features of large intestine MFH have been characterized. Future efforts should be made in finding out the possible specific presentations of this entity on different imaging modalities for the purpose of early diagnosis and differential diagnosis.

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