High-grade soft tissue sarcoma arising in a desmoid tumor: case report and review of the literature

Abstract

Desmoid tumors are rare benign monoclonal fibroblastic tumors. Their aggressiveness is local with no potential for metastasis or dedifferentiation. Here we report on a 61-year-old patient who presented a locally advanced breast desmoid tumor diagnosed 20 years after post-operative radiotherapy for breast carcinoma. After 2 years of medical treatment, a high-grade undifferentiated pleomorphic soft tissue sarcoma arose within the desmoid tumor. Despite extensive surgery removing both tumors, the patient showed locoregional relapse by the sarcoma, followed by multimetastatic progression, then death 25 months after the surgery. The arising of a soft tissue sarcoma in a desmoid tumor is an exceptional event since our case is the fourth one reported so far in literature. It reinforces the need for timely and accurate diagnosis when a new mass develops in the region of a preexisting desmoid tumor, and more generally when a desmoid tumor modifies its clinical or radiological aspect.

Keywords: Breast cancer; Desmoid tumor; Soft tissue sarcoma.

Fig. 1

Mammary desmoid tumor: radiological and pathological aspects. a Breast MRI of January 2011: T1-weighted Fat Sat images of the right breast after gadolinium injection. The white star shows the desmoid tumor. b Microscopic aspect (hematoxylin and eosin staining, HES) of the diagnostic biopsy showing a poorly cellular proliferation of bland elongated cells in a collagen-rich stroma. Proliferation infiltrates adipose tissue (right upper corner)

Fig. 2

Appearance of a tumor within the desmoid tumor: radiological aspect. Breast T1-weighted Fat Sat MR imaging of middle (top) and upper (bottom) sections of the right breast after gadolinium injection in January 2001 (a) and in January 2013 (b). The desmoïd tumor (white star) increased in size between the two dates. Surprisingly, a 2-cm tissue mass (white arrow), corresponding to an undifferentiated sarcoma, appeared in the upper-inner quadrant within the desmoid tumor in January 2013

Fig. 3

Pathological aspect of the surgical specimen containing the desmoid tumor and the sarcoma. a Macroscopic aspect: an ill-defined fibrous-like area occupies most of the specimen, with contact to resection margin (arrow). Within this lesion two less fibrous areas are identified (black lines). These ones correspond to high-grade sarcoma zones on microscopic examination. b Microscopic aspect (HES) showing abrupt transition between high grade sarcoma (left) and DT (right). c Microscopic aspect (HES) showing the DT: spindle cell proliferation of fibroblastic-like cells, interspersed within a collagenous matrix. Spindle cells are void of cytological atypia, and no mitosis or necrosis are seen. d Microscopic aspect (HES) showing the high grade sarcoma area. The neoplastic proliferation is more cellular and dense. Spindle cells are disposed in sheets infiltrating the skeletal muscle bundles. They appear small with indistinct cytoplasmic limits; nuclei are oval or round and display dense chromatin. Mitoses are easily found (black arrow)

Fig. 4

Relapse of the high-grade sarcoma: radiological aspect. a CT-scan in June 2013 showed the appearance of a 2-cm right pleural nodule in the operative field (white arrow). The percutaneous biopsy achieved 2 months later will identify high-grade undifferentiated spindle-cell sarcoma. b Major disease progression in September 2014, involving the pleura, the right anterior chest wall and the liver