Peritoneal dissemination complicating morcellation of uterine mesenchymal neoplasms

Abstract

Background: Power morcellation has become a common technique for the minimally invasive resection of uterine leiomyomas. This technique is associated with dissemination of cellular material throughout the peritoneum. When morcellated uterine tumors are unexpectedly found to be leiomyosarcomas or tumors with atypical features (atypical leiomyoma, smooth muscle tumor of uncertain malignant potential), there may be significant clinical consequences. This study was undertaken to determine the frequency and clinical consequence of intraperitoneal dissemination of these neoplasms.

Methodology/principal findings: From 2005-2010, 1091 instances of uterine morcellation were identified at BWH. Unexpected diagnoses of leiomyoma variants or atypical and malignant smooth muscle tumors occurred in 1.2% of cases using power morcellation for uterine masses clinically presumed to be "fibroids" over this period, including one endometrial stromal sarcoma (ESS), one cellular leiomyoma (CL), six atypical leiomyomas (AL), three smooth muscle tumor of uncertain malignant potential (STUMPs), and one leiomyosarcoma (LMS). The rate of unexpected sarcoma after the laparoscopic morcellation procedure was 0.09%, 9-fold higher than the rate currently quoted to patients during pre-procedure briefing, and this rate may increase over time as diagnostically challenging or under-sampled tumors manifest their biological potential. Furthermore, when examining follow-up laparoscopies, both from in-house and consultation cases, disseminated disease occurred in 64.3% of all tumors (zero of one ESS, one of one CL, zero of one AL, four of four STUMPs, and four of seven LMS). Only disseminated leiomyosarcoma, however, was associated with mortality. Procedures are proposed for pathologic evaluation of morcellation specimens and associated follow-up specimens.

Conclusions/significance: While additional study is warranted, these data suggest uterine morcellation carries a risk of disseminating unexpected malignancy with apparent associated increase in mortality much higher than appreciated currently.

Figure 1. Representative histologic fields of several of the most common diagnoses reviewed during this study.

Leiomyoma (case previously published) is characterized by smooth muscle cells without atypia, mitoses, or necrosis. In contrast, atypical leiomyoma (case #7) shows atypia, but rare mitoses (up to 2 mitoses per 10 high power fields). Smooth muscle tumor of uncertain malignant potential (STUMP, case #11) is characterized by a higher rate of mitoses (3 to 8 mitoses per 10 high power fields) and more frequent atypia. Leiomyosarcoma (LMS, case #15) shows significant mitotic activity (over 10 mitoses per 10 high power fields), prominent atypia, and tumor necrosis.

Figure 2. Unexpected diagnosis of leiomyoma variants, atypia, or malignancy following morcellation performed at BWH for clinically presumed uterine leiomyoma.

Figure 3. Follow-up exploratory laparoscopy in cases of uterine morcellation with unexpected diagnoses.

Figure 4. Intraoperative images of nodules on the peritoneal surface, suspicious for disseminated tumor.

Figure 5. A case of leiomyosarcoma (case #17) diagnosed following a uterine power morcellation, with subsequent diagnosis of dissemination throughout the peritoneum (all images 100x magnification).

The primary and disseminated lesions are characterized by very high mitotic rates (all lesions greater than 50 mitoses per 10 high power fields) and significant nuclear atypia and pleomorphism; focal necrosis was also appreciated (not shown).

Figure 6. A case of STUMP with peritoneal dissemination (case #11) showing implantation into the omentum.

The primary lesion showed scattered marked nuclear atypia and up to 9 mitoses per 10 high power fields; disseminated lesions showed nuclear pleomorphism and atypia as well as increased proliferation indices (40% by MiB-1/Ki-67 staining), but mitoses were not prominent.