Complete Regression of an 8-cm Desmoid Fibromatosis After Treatment With Tamoxifen

Abstract

We report a case of a relatively large desmoid fibromatosis that responded completely to tamoxifen as a single drug therapy. A 47-year-old Japanese man underwent laparoscopy-assisted endoscopic submucosal dissection for a duodenal polyp. He developed postoperative generalized peritonitis and underwent an emergency laparotomy. Sixteen months after the surgery, a subcutaneous mass was found on the abdominal wall. Biopsy of the mass revealed estrogen receptor alpha-negative desmoid fibromatosis. The patient underwent total tumor resection. Two years after the initial surgery, he was found to have multiple intra-abdominal masses, with the largest mass measuring 8 cm in diameter. Biopsy revealed fibromatosis, as in the case of the subcutaneous mass. Complete resection was impossible due to the proximity of the duodenum and superior mesenteric artery. Tamoxifen was administered for three years, resulting in complete regression of the masses. No recurrence was observed for the following three years. This case indicates that relatively large desmoid fibromatosis can be successfully treated with a selective estrogen receptor modulator alone and that its effect is not dependent on the estrogen receptor alpha status of the tumor.

Keywords: desmoid fibromatosis; estrogen receptor; gastroenterological surgery; selective estrogen receptor modulator; tamoxifen.

Figure 1. Computed tomography image of the subcutaneous mass.

Computed tomography image showing a 25-mm subcutaneous mass (white arrowhead) in the abdominal wall.

Figure 2. Pathological examination of the initial mass in the abdominal wall.

(a) A solid mass with a whitish-cut surface. (b) Long sweeping fascicles consist of uniform spindle-shaped cells without cellular atypia and nuclear hyperchromasia (hematoxylin and eosin stain). (c, d) The mass shows infiltration of adjacent adipose tissue (c) and striated muscular tissue (d). (e, f) The tumor is negative for estrogen receptor alpha (skeletal muscles are non-specifically positive) (e) but positive for β-catenin (f).

Figure 3. Computed tomography image of the abdominal masses

Axial (a) and coronal (b) abdominal computed tomography images showing multiple intra-abdominal masses (white arrowhead). The largest one is below the gallbladder, measuring 8 cm in diameter.

Figure 4. Positron emission tomography image of the abdominal mass.

Axial (a) and coronal (b) positron emission tomography images showing minimal uptake (maximum standard uptake value: 4.1) in the mass below the gallbladder (white arrowhead).