Skeletal Muscle-like and Rhabdoid Cells in Uterine Leiomyomas

An Epithelioid Smooth Muscle Neoplasm Mimicking a Signet Ring Cell Carcinoma in the Ovary

A 53-yr-old woman who presented with elevated renal indices was discovered to have a 4.5 cm right renal mass and an incidental 9.7 cm left ovarian mass on imaging studies. She underwent a partial nephrectomy and bilateral salpingo-oophorectomy, revealing a chromophobe renal cell carcinoma and an unusual ovarian neoplasm with epithelioid cells displaying prominent signet ring cell-like morphology. Immunohistochemical analysis of the ovarian neoplasm demonstrated that the tumor cells were diffusely immunoreactive for smooth muscle markers and negative for all tested cytokeratins and epithelial membrane antigen. On the basis of these results, the tumor was interpreted as an unusual epithelioid smooth muscle neoplasm with extensive signet ring cell-like features. Along with primary ovarian signet ring stromal tumors and sclerosing stromal tumors, this example adds epithelioid smooth muscle neoplasms with unusual cytologic alterations to the list of uncommon nonepithelial tumors that can simulate metastatic signet ring cell carcinoma (Krukenberg tumor) in the ovary.

Uterine leiomyomas with bizarre nuclei: a clinicopathologic study of 59 cases

Leiomyoma with bizarre nuclei (LM-BN) is an uncommon tumor with histologic features (mononucleated or multinucleated bizarre cells that may have a diffuse distribution, prominent nucleoli, and karyorrhectic nuclei that may mimic atypical mitoses) that often causes confusion with leiomyosarcoma. Fifty-nine LM-BNs were collected from our consultation files over the years 2000 to 2011. Features recorded included patient age, therapy, tumor size, border, gross appearance, density and distribution of BN, mitotic count, karyorrhectic nuclei, prominent nucleoli, cells with conspicuous dense eosinophilic cytoplasm (rhabdoid-like), vascular changes and type of vasculature, and presence of necrosis and its nature. Follow-up information was obtained for all patients. Patients ranged in age from 25 to 75 (average 45) years (11 patients between 25 and 35 y, 20 between 36 and 45 y, 22 between 46 and 55 y, and 6 between 56 and 75 y). Forty-two underwent hysterectomy and 17 myomectomy. For 51 tumors gross findings were known. Forty (78%) had a solid white and whorled cut surface and 11 (22%) a yellow appearance. Five (10%) neoplasms showed prominent cystic degeneration, and hemorrhage and/or necrosis was seen in 9 (18%). Forty-five LM-BNs had a pushing margin with the surrounding myometrium, whereas 1 showed irregular borders. Margins could not be ascertained in the slides available in 13 cases. Twenty-eight (48%), 19 (32%), and 12 (20%) LM-BN showed low, intermediate, and high BN density. Eighteen (30%) tumors showed diffuse, 26 (44%) showed multifocal, and 15 (26%) had focal BN distribution. Mitotic counts ranged from 0 to 7/10 high-power fields (HPF) (average 1 to 2/10 HPF). Thirty-seven (63%) had <2/10 HPF, 19 (32%) had 2 to 5 mitoses/10 HPF, and in 3 tumors (5%) mitotic counts were 6, 7, and 7/10 HPF (2 with focal and 1 with diffuse BN). All but 4 LM-BNs showed karyorrhectic nuclei, striking in 12 neoplasms, mimicking atypical mitoses. Nineteen (32%) LMs had prominent eosinophilic nucleoli surrounded by a clear halo. Ischemic necrosis was detected in 21 (36%) LM-BN. Rhabdoid-like cells were noted in 24 (41%) tumors. All patients had no evidence of recurrence, ranging from 1 to 13 years (overall average 6 y; in patients with myomectomy 6.3 y with a range of 2.6 to 11 y). Our results corroborate that LM-BN is associated with a favorable outcome even in those patients only treated by myomectomy and highlights that a conservative approach can be undertaken in these patients, as many of them are of reproductive age. Because of the favorable outcome, the term LM-BN is preferable to alternative terminology including "atypical leiomyoma."

Heterologous and rare homologous sarcomas of the uterine corpus: a clinicopathologic review

Pure sarcomas of the uterine corpus are uncommon, constituting less than 3% of all malignancies at this site, and most of them are leiomyosarcomas and endometrial stromal sarcomas. Rare histotypes of homologous sarcomas and heterologous sarcomas are occasionally encountered, and the absence of significant accumulated experience with these histotypes at this location may potentially raise diagnostic and patient management difficulties. In this article, the clinicopathologic attributes of all earlier reported sarcomas of the uterine corpus other than leiomyosarcomas and endometrial stromal sarcomas are summarized. Included are embryonal rhabdomyosarcoma, pleomorphic rhabdomyosarcoma, angiosarcoma, alveolar soft part sarcoma, malignant perivascular epithelioid cell tumors (PEComas), osteosarcoma, chondrosarcoma, liposarcomatous tumors, malignant extrarenal rhabdoid tumors, Ewing sarcoma/primitive neuroectodermal tumor, and other rare histotypes. Embryonal rhabdomyosarcoma (20%), Ewing sarcoma/primitive neuroectodermal tumor (17%), angiosarcoma (14%), and pleomorphic rhabdomyosarcoma (13%) appeared to be more common than the others, although there was no single overwhelmingly prevalent histotype in the group. A subset, including embryonal rhabdomyosarcoma, alveolar soft part sarcoma, and PEComas, peak in the premenopausal years, but most of the others were observed in postmenopausal women. Favorable outcomes have been reported for the patients diagnosed with alveolar soft part sarcoma, and the prognosis for their counterparts with PEComa remains a matter of debate. Multimodal therapeutic approaches to contemporary patients with embryonal rhabdomyosarcomas have resulted in significantly improved outcomes. Unfortunately, most of the other sarcomas have been associated with rapid tumor progression and unfavorable patient outcomes. The differential diagnosis for these sarcomas is often extensive and varies by histotype, but their accurate diagnosis fundamentally requires the careful exclusion of biphasic malignancies.

Uterine smooth muscle tumors other than the ordinary leiomyomas and leiomyosarcomas: a review of selected variants with emphasis on recent advances and unusual morphology that may cause concern for malignancy

Uterine smooth muscle tumors are classified according to their morphologic features that include architecture, growth pattern, cellular characteristics and constituents of the intercellular stroma. While terminologies used for the pathologic diagnosis of various subtypes may be eloquent and histologically accurate, some of these are confusing for the clinician and may also be open to interpretation by different pathologists: the labeling of atypical leiomyomas epitomizes this intricate system. Clinically, it is probably more useful to classify them as either tumors with or tumors without recurrent and/or metastatic potential. The term "atypical leiomyoma" has been used to label tumors that have a low risk of recurrence and is synonymous with benign tumors. The latter are known variously as leiomyoma with bizarre nuclei, symplastic leiomyoma, or pleomorphic leiomyoma. Variants of benign uterine smooth muscle tumors, such as mitotically active leiomyoma, cellular and highly cellular leiomyoma, epithelioid leiomyoma, and myxoid leiomyoma each have distinctive hallmarks that enable subclassification. Nevertheless, they may occasionally possess one or more unusual features that are cause for alarm. Tumors that have a dissecting growth pattern, with or without extrauterine extension, may mimic malignancy both grossly and microscopically. The current review discusses the pathologic diagnosis of and terminology applied to selected variants of uterine smooth muscle tumors other than the ordinary leiomyomas and leiomyosarcomas with emphasis on unusual reported features that may indicate malignancy. This includes an update on uterine smooth muscle tumor of uncertain malignant potential (STUMP), intravenous leiomyomatosis, benign metastasizing leiomyoma, and diffuse leiomyomatosis. Their clinicopathologic features, differential diagnoses, and management options based on findings in the previously reported cases will also be reviewed.

Smooth Muscle Tumors of the Female Genital Tract

Smooth muscle tumors are the most common among mesenchymal tumors in the female genital tract. The vast majority of these neoplasms are clinically benign and easy to diagnose. In contrast, leiomyosarcomas are highly aggressive tumors that may pose considerable diagnostic problems when they display unusual (myxoid or epithelioid) morphology, ambiguous histologic features for malignancy, or an unusual anatomic distribution. Diagnostic criteria for these problematic tumors vary depending on the site and type of histologic differentiation, and are based on a combination of 3 major criteria: (1) moderate to severe cytologic atypia; (2) increased mitotic index; and (3) tumor cell necrosis. Certain benign smooth muscle proliferations may show worrisome histologic features or unusual growth patterns, causing concern for leiomyosarcoma. Furthermore, other tumors, including perivascular epithelioid tumors, may mimic leiomyosarcoma. Careful attention to the clinical and anatomic setting, cytologic and architectural features, and immunohistochemical characteristics are helpful in distinguishing these entities. This article discusses conventional smooth muscle tumors as well as unusual subtypes, with emphasis on the diagnostic criteria and problems in differential diagnosis that arise at each site within the female genital tract.

Uterine leiomyomas with inclusion bodies: An immunohistochemical and ultrastructural analysis of 12 cases

We describe 12 cases of leiomyoma with intracytoplasmic inclusion bodies, which were detected in a group of 447 leiomyomas examined at our institution between December 2005 and March 2006. Ten of these tumors were typical leiomyomas, and two cases represented atypical (bizarre) leiomyoma. In some cases, the presence of intracytoplasmic inclusion bodies resulted in a rhabdoid or skeletal muscle-like appearance of the tumor cells. Ultrastructurally, there were two types of inclusions. One of them consisted of an abnormal aggregation of intermediate and actin filaments. Another type of inclusions was composed of dense granular material without an apparent fibrillar structure. The ultrastructure of the inclusions correlates with immunohistochemical and histochemical stainings. The inclusions with apparent fibrillar arrangements were PAS negative, stained red by trichrome, and were, at least at the periphery, actin-, desmin-, and h-caldesmon-positive. The dense granular inclusions were at least focally PAS-positive, stained red by trichrome, and were negative immunohistochemically. The intracytoplasmic inclusions were found in atypical (bizarre) leiomyomas of the uterus and occasionally in epithelioid leiomyomas and leiomyosarcomas. However, to the best of our knowledge, these inclusions have not been found in typical uterine leiomyomas to date.