a benign histological appearance in smooth muscle cells and lipoblasts.2,7 This comparison, but there have been rare case showed rare atypical lipomatous cases reported that included atypical cells, prompting the pathologist to order smooth muscle cells and lipoblasts.7 additional studies to rule out liposarcoma. Lipoleiomyomas can be distinguished Liposarcomas also contain a non-malignant from leiomyosarcomas by their bland smooth muscle component, but lipoblasts smooth muscle morphology.3 Scattered are present in all tumors.7 Liposarcomas lipocytes in a typical leiomyoma are fairly can show multinucleated cells and bizarre common.6 Some suggest lipoleiomyoma nuclei.7 Several cases of liposarcomas that can be differentiated from leiomyoma with appeared to originate in a lipoleiomyoma fatty degeneration by the striking number have been reported, including liposarcomas and even distribution of adipose tissue imperceptibly merged with a lipoleiomyoma Fig. 2. Micrograph of the tumor showing areas of throughout the lesion, but there is no specific and a liposarcoma that contained a well- adipocytes, smooth muscle cells, and necrosis. defined percentage of adipocytes that would demarcated, infarcted lipoleiomyoma.7 enable a diagnosis of lipoleiomyoma.4,6 Cytogenetics and immunohistochemistry Grossly, lipoleiomyoma differ from typical are used to characterize soft tissue tumors. uterine leiomyoma by being more yellow Well-differentiated and dedifferentiated and having a softer cut surface.1 Some liposarcomas are characterized by lipoleiomyomas can be firm and rubbery, amplification of the 12q13-15 region, causing while others are fibro-fatty with pale to yellow overexpression of multiple genes including irregular soft areas.2 All lipoleiomyomas those coding for high-mobility glycoprotein are nodular and well circumscribed by a (HMAG2), cyclin-dependent kinase (CDK4), thin connective tissue capsule.2 As in this and MDM2.7 Immunohistochemistry is often case, lipoleiomyomas have been reported utilized to test for these and other proteins to grossly arise from typical leiomyomas.7 instead of performing the expensive Reported cases have ranged from 0.5 to 55 and time-consuming genetics studies. Fig. 3. Micrograph of the tumor showing cm in diameter, with the majority of cases Immunohistochemically, the adipose several atypical lipomatous cells with multiple under 10 cm.2 Necrosis and hemorrhage tissue of lipoleiomyoma tests positive for small vacuoles reminiscent of lipoblasts. are thought to never be present, although vimentin and S100 protein and the smooth microscopic areas of necrosis were present muscle element for vimentin, desmin uterine bleeding, pelvic pain or pressure, in this case.2-5 Comparatively, liposarcomas and α-smooth muscle actin.2,6 Both test a palpable pelvic mass, urinary frequency, do tend to have focal areas of hemorrhage positive for estrogen (ER), progesterone and incontinence.1-4,6 Lipoleiomyomas most and necrosis present.7 Liposarcomas can (PR), and the Ki-67 protein and negative commonly grow in the uterine corpus in the also have a diverse gross appearance, for pancytokeratins (AE1/3, CAM5.2) CEA, subserosal or intramural level, but cases some showing a gelatinous cut surface with CA19-9, CA125, CD34, HMB45, p53, have been described in the cervix, ovary, others firmer and fleshy tan-white.7 The well MDM2, CDK4, and CD117.2,6 The markers retroperitoneum, and broad ligament.2-4 circumscribed mass seen in this case favors of well-differentiated liposarcoma, MDM2 There is disagreement in the literature the gross description of a lipoleiomyoma and CDK4, are negative in lipoleiomyomas. over whether uterine lipoleiomyomas vs a liposarcoma, but the presence of These markers are particularly important represent a variant of leiomyoma with microscopic necrosis is concerning. in cases, such as the one reported here, adipocyte differentiation or a degenerative of large lipomatous tumors. Tumors 2 suspicious for liposarcoma can also be or neoplastic change in a leiomyoma. Histologically, lipoleiomyomas are tested for the DNA damage inducible Generally, lipoleiomyomas are considered encapsulated tumors with interlacing transcript 3 (DDIT3) rearrangement an uncommon and benign variant of uterine bundles of spindle-shaped smooth muscle characteristic of liposarcomas.7 The leiomyomas, composed of an admixture of cells in a whorled pattern admixed with liposarcoma translocation is t(12;16) mature smooth muscle cells and adipocytes. lobules of mature adipocytes and fibrous (q13;p11) or more rarely t(12;22)(q13;q12).7 tissue.1,3-5 The ratio of smooth muscle to Like in this case, uterine lipoleiomyomas fat cells is inconsistent. One study found are often diagnosed preoperatively as a no significant correlation between amount The pathogenesis of adipocytes present liposarcoma or teratoma using radiographic of adipocytes and other clinical and in the myometrium remains unclear. scans. Imaging studies play an important pathological features, none between the Proposed mechanisms include lipomatous role in preoperative localization and proportion of lipomatous and leiomyomatous degeneration, multipotential undifferentiated diagnosis, but a histologic evaluation is components and the tumor size, and none mesenchymal cells, fatty differentiation necessary to confirm the diagnosis.2,4 The between the amount and distribution of or metaplasia of muscle or connective differential for a lipomatous pelvic mass the lipomatous component and the age of tissue, perivascular entrance of fat cells includes liposarcoma, lipoleiomyoma, the patient.2 Characteristically, the nuclei into the uterus, and misplaced embryonic leiomyoma with degenerative change, of the elongated smooth muscle cells fat cells.1-3,5,6 Uterine smooth muscle cells lipoma, carcinoma with heterologous show no atypia and have even chromatin, have divergent differentiation potential and liposarcomatous differentiation, and the adipocytes are entirely mature.3 can become adipocytes or skeletal muscle leiomyosarcoma with degenerative Some cases of lipoleiomyoma show cells.2 Numerous immunohistochemical change, ovarian fatty tumors including massive lymphocyte infiltration and, in studies affirm the complex pathogenesis cystic teratomas, and lipoplastic separate cases, angiomatous hyperplasia.2 of lipoleiomyoma, providing evidence that lymphadenopathy.1-4,7 Liposarcomas No mitoses, cytologic atypia, immature at least some cases result from lipomatous differ from lipoleiomyomas in cellular lipoblasts, necrosis, calcifications, or other metaplasia of leiomyomas, like the gross pleomorphism, the presence of mitotic degenerative changes are typically present description from this case hints at, and bodies and lipoblasts, and infiltrative in lipoleiomyomas, but there have been others from multipotential undifferentiated margins.7 Lipoleiomyomas typically have rare cases reported that included atypical mesenchymal cells.2,3 The presence of Page 14 THE CUTTING EDGE THE JOURNAL OF THE AAPA CD138, but negative for light chains.3 Once of PUC to neoadjuvant chemotherapy a primary plasma cell tumor can be ruled out, exist in the literature10,11, broader studies the identification of an epithelial component suggest that PUC may show an initial via immunohistochemistry solidifies the response to neoadjuvant therapy, but long- diagnosis of PUC.3,4 CK and CK7 will term survival is limited to a few patients.9 confirm the epithelial origin of transitional cells3. In this case, both the bladder biopsy This case is noteworthy on two levels. Not and tumor from the cystoprostatectomy only is PUC an interesting, rare variant of specimen stained positive for CK7. This bladder cancer, it can pose a challenge demonstrates the valuable role that at the grossing bench, and histologically. Fig. 3. A nest of tumor cells (arrow) within the immunohistochemistry plays, in conjunction Upon first look at the bladder mucosa, it muscularis of the bladder wall. with histology, to diagnose PUC. may resemble inflammation, rather than a discrete, readily identifiable mass. Under Because the tumor cells tend to form nests, the microscope, the tumor cells may be with cords of malignant cells extending deep misidentified as plasma cells, thus leading into the musculature of the bladder wall3, to misdiagnosis of a benign inflammatory the appearance of the tumor can make process or plasma cell derived neoplasm. grossing more challenging. Several of the Understanding the gross presentation of a case reports in the literature document an case diagnosed as PUC on biopsy will help ill-defined, diffuse lesion, affecting multiple guide sectioning and submitting decisions. areas of the bladder, with associated Further study into the effect of neoadjuvant rigidity of the bladder wall.3,5,6 In cases therapy on PUC is necessary to solidify a Fig. 4. Tumor cells (at arrow) in a background of like this, and the one presented here, it is specific grossing protocol for PUC. This is fibrofatty tissue, representing tumor extension into the difficult to approximate the overall size of an excellent example of a complex case perivesicular soft tissue. the lesion. We followed the same grossing requiring multiple levels of analysis in the guidelines that we use for nonvariant grossing room and beyond. A complete Discussion urothelial cancers, and submitted the clinical history, a pathologists’ assistant Plasmacytoid variant urothelial carcinoma grossly obvious lesional area entirely, with a keen eye and understanding of the (PUC) was first