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PubMed1983

Pleomorphic lipoma: a tumour simulating liposarcoma.

Pleomorphic lipoma or giant-cell lipoma is a recently recognized entity affecting predominantly elderly and middle-aged men. The neck, shoulder region and back are the sites of predilection. The clinical setting is similar to that seen with spindle-cell lipoma. The lesion is characterized by an intricate mixture of mature fibrous tissue, adipose tissue and myxoid tissue interspersed with cellular foci. Most characteristic of the latter are a variety of giant cells and especially the 'floret' giant-cells, so named because of the arrangement of their nuclei which is reminiscent of the petals of a flower. The pleomorphism of the lesion frequently leads to misdiagnosis as liposarcoma. Criteria for the differentiation from the various types of liposarcoma are discussed. The possible relationship of pleomorphic lipoma to some of the 'atypical lipomas' described in the recent literature is analysed. The pleomorphic lipoma is a benign lesion of subcutaneous tissue which must be sharply differentiated from sarcomas. Some of the liposarcomas alleged in the literature to have originated within a pre-existing lipoma possibly represented pleomorphic lipomas. Pleomorphic lipoma is an entity which must be added to the growing number of pseudosarcomatous lesions of soft tissue.

Adipose Tissue↗
PubMed2006

Classification of pleomorphic sarcomas: where are we now?

Until a decade ago, so-called pleomorphic and storiform malignant fibrous histiocytoma (MFH) represented the most frequently diagnosed sarcoma, accounting for approximately 40% of adult mesenchymal malignancies. However, the latest World Health Organization classification of soft tissue tumours considers MFH a synonym for undifferentiated pleomorphic sarcoma. Historically, the term MFH was introduced in the medical literature in 1963 by Ozzello, O'Brien and Stout, on the basis of the acquisition of phagocytic properties observed in cultured fibroblasts. The existence of MFH as a well-defined clinicopathological entity became rapidly very popular and by the mid 1980s MFH represented the most common sarcoma in adults. With the advent of electron microscopy, immunohistochemistry and molecular genetics, it became clear that the so-called "facultative fibroblast" theory had no scientific grounds and, in 1992, a milestone paper eventually brought attention to the concept that MFH merely represented a morphological pattern shared by a wide variety of poorly differentiated malignant neoplasms, which include specific subtypes of pleomorphic sarcomas. Currently, accurate subclassification of pleomorphic sarcomas is mandatory as it enables recognition of non-sarcomatous lesions as well as pleomorphic neoplasms not associated with aggressive behaviour. Furthermore, as myogenic differentiation predicts aggressive clinical behaviour among pleomorphic sarcomas, precise histotyping allows prognostic stratification of patients.

Humans↗
PubMed1988

Malignant pleomorphic adenoma (malignant mixed tumor) of the trachea. Report of a case.

Malignant pleomorphic adenoma arising in the trachea has not been reported in the literature. We report here a case of malignant pleomorphic adenoma (malignant mixed tumor) occurring in the trachea of a 65-year-old woman. The tumor metastasized to the lung and the chest wall 11 years after complete resection of the primary tumor, which was a polypoid submucosal tumor, 1.3 cm in diameter. Light microscopic examination of the primary and metastatic tumors showed the presence of epithelial and stromal elements, consisting of grandular structures, foci of squamous metaplasia and a myxochondroid stroma. Many tumor cells showed myoepithelial cell features by electron microscopy, and immunoreactivity for S-100 protein and GFAP was also seen in many of them. These findings were consistent with those of pleomorphic adenoma. However, the epithelial elements were cytologically atypical with prominent mitotic figures. Infiltration of the tumor cells into the surrounding soft tissue was also seen. No foci of benign pleomorphic adenoma were found in the primary tumor. These findings indicate that this tumor was not a carcinoma ex pleomorphic adenoma, but a true malignant pleomorphic adenoma (true malignant mixed tumor) of the trachea.

Aged↗
PubMed1983

Pleomorphism and acetylene-reducing activity of free-living rhizobia.

Cowpea-type Rhizobium sp. strain 32H1 and Rhizobium japonicum USDA 26 and 110 grown on a glutamate-mannitol-gluconate agar medium showed increases in the number of pleomorphic cells coincident with their acetylene-reducing activity. Pleomorphs appeared to be inhibited in growth nonuniformly, because acetylene-reducing cultures were mixtures of rod, branched (V, Y, and T), and other irregularly shaped cells. In contrast, strain USDA 10 consistently failed to reduce acetylene, even though it also could grow and yield pleomorphic cells under various conditions. With minimal inhibitory supplements (5 micrograms per ml of medium) of nalidixic acid and novobiocin as cell division inhibitors, an increase in pleomorphic cells was observed, but the inhibited cultures displayed lower acetylene-reducing activity. A study of pleomorphic cells derived in different ways indicated that not all pleomorphs reduce acetylene.

Acetylene↗
PubMedDate not supplied

Pleomorphic lobular carcinoma of the breast. A case report.

BACKGROUND: Pleomorphic lobular carcinoma of the breast is associated with aggressive behavior. CASE: Fine needle aspiration cytology was performed on a breast lump in a 55-year-old woman. The aspirates showed highly pleomorphic, large cells in a dyscohesive pattern, with a tendency of few cells to aggregate in small groups. A diagnosis of ductal carcinoma was made on cytology. On histology, the paraffin sections showed features of pleomorphic lobular carcinoma of the breast. CONCLUSION: The cytologic features of pleomorphic lobular carcinoma overlap with those of infiltrating ductal carcinoma. It is very difficult to make a diagnosis of pleomorphic lobular carcinoma prospectively on cytology. However, if Indian file arrangement and cytoplasmic vacuolation are present, pleomorphic lobular carcinoma must at least be suggested for the differential diagnosis as it has different clinical implications.

Breast Neoplasms↗
PubMed2002

Positron emission tomography in three children with pleomorphic xanthoastrocytoma.

The pleomorphic xanthoastrocytoma is generally considered a low-grade neoplasm with favorable prognosis. These tumors, however, can demonstrate primary anaplastic features, undergo malignant transformation, disseminate, or progress with poor outcome. Currently, there are no histologic or clinical features that reliably predict recurrent tumor or tumor progression. We report three children with confirmed pleomorphic xanthoastrocytoma who were studied with positron emission tomography (PET) using [18F]fluorodeoxyglucose (FDG) coregistered with magnetic resonance imaging. One patient had decreased FDG metabolism and, despite a gross total resection and benign pathology, had early local recurrence. Subsequent to a second surgical resection and radiation therapy, he has remained stable for 8 years. One patient with significant FDG uptake had gross total resection of an anaplastic pleomorphic xanthoastrocytoma. Follow-up FDG studies showed no abnormal metabolic activity, and he has been stable without adjuvant treatment for 5 years. The last patient had intermediate FDG uptake and a moderate-grade pleomorphic xanthoastrocytoma by histopathology. She showed early tumor progression with spinal metastases. Following a near-total resection of the recurrent intracranial lesion and neuroaxis radiation, she has been stable for 4 years. Although there are still no reliable prognostic indicators for pleomorphic xanthoastrocytoma, PET with FDG correlates with histopathology, and increased uptake may be a marker for more malignant or aggressive tumors. The extent of surgical resection in regard to prognosis in our limited study is unclear but appears helpful in the anaplastic pleomorphic xanthoastrocytoma case. Adjuvant radiation therapy also may benefit certain patients. Further PET studies are warranted in this group of tumors.

Adolescent↗
PubMed2002

Histopathology and biologic behavior of pleomorphic cutaneous mast cell tumors in fifteen cats.

Most feline cutaneous mast cell tumors (CMCT) are behaviorally benign; however, there is a subset of these tumors with, marked pleomorphism (previously termed poorly differentiated) that have been reported to be more aggressive. In this study, pleomorphic CMCT from 15 cats were identified from surgical biopsy submissions, and follow-up clinical data were obtained for 14 of these cats. Pleomorphic CMCT were discrete dermal nodules composed of sheets of pleomorphic round cells. Tumors from all 15 cats contained markedly cytomegalic and karyomegalic cells; 9/15 tumors (60%) contained multinucleated tumor giant cells. Typical mast cell granules were easily identified in sections stained with hematoxylin and eosin and with metachromatic stains and based on ultrastructural evaluation in cytomegalic as well as smaller tumor cells, indicating that the tumors were not poorly differentiated. The mitotic rate was very low (<1 mitosis per 10 high-power fields [hpf]) in 14 of 15 tumors (93%). Affected cats were 6-19 years old (mean age = 11.5 years), and there was no breed or sex predilection. Two cats had local recurrence. The only cat that had a pleomorphic CMCT with a high mitotic rate (1-2 mitoses/hpf) subsequently developed numerous other dermal neoplasms and was euthanatized. In this study, the large majority of feline pleomorphic CMCT were behaviorally benign. Mitotic rate is likely an important prognostic indicator of CMCT behavior.

Animals↗
PubMedDate not supplied

Spindle cell and pleomorphic lipoma: an ultrastructural study.

Spindle cell and pleomorphic lipoma are rare benign tumors of adipose tissue. Their histogenesis is poorly understood and pleomorphic lipoma has not previously been studied ultrastructurally. This study describes the morphology and ultrastructure of 6 cases of spindle cell and pleomorphic lipoma. Both spindle cell and pleomorphic lipomas showed similar ultrastructural features with an interrupted basal lamina, occasional non-membrane-bound lipid vacuoles and abundant rER. In all the cases mast cells were conspicuous and were intimately related to both spindle and pleomorphic cells. It is proposed that both the spindle and pleomorphic multinucleated cells that characterize these tumors are prelipoblastic mesenchymal cells. The possible significance of an interaction between these cells and mast cells is discussed.

Cell Nucleus↗
PubMed2003

Validation of the novel indices of nuclear pleomorphism, polarity and spatial distribution in the grading of urothelial carcinoma.

OBJECTIVE: To evaluate the role of the novel histomorphometric variables of pleomorphism, orientation and variability of spatial cytologic organization to objectively quantify histopathologic grade in urothelial carcinoma. STUDY DESIGN: As a validation model, we chose 51 papillary urothelial carcinomas. Thirty-six (70%) were low and 15 (29%) high grade tumors (World Health Organization grading system). Thirty-one cases (61%) were noninvasive, 12 (23%) exhibited lamina propria invasion, and 8 (16%) invaded the deep smooth muscle. Histomorphometric measurements were performed on noninvasive areas only. Pleomorphism was characterized by the anisokaryosis index (AIX), based on the autocorrelation function applied to classic nuclear shape descriptors. Additional indices of pleomorphism included standard deviations (sd) and coefficients of variation of these shape descriptors. Loss of polarity was assessed by the orientation index (ORX), based on Fourier transformation. Intraepithelial nuclear spatial distribution index (NSDX) was also computed. RESULTS: Low grade tumors exhibited less pleomorphism, higher orientation indices and a more homogeneous spatial distribution than did high grade tumors (area-AIX: P = .004, ORX: P < .0001, NSDX: P = .001). Multivariate analysis revealed the significant discriminators of grade to be nuclear size and orientation (size: max-diam, P < .0001; width: P < .0001; orientation: ORX: P < .0001). A discriminant score combining these independent variables distinguished between low and high grades in 98% of cases. The method was successfully validated using a testing sample of 40 new patients (accuracy, 94%). Lamina propria invasion was independently predicted by nuclear pleomorphism (width-sd: P = .0001, sensitivity = 64%, specificity = 91%). Muscle invasion was independently predicted by nuclear area (P < .0001) and pleomorphism (area-sd: P < .0001, max-diam-sd: P < .0001, width-AIX: P < .0001, sensitivity = 87%, specificity = 100%). CONCLUSION: These novel morphometric methods may serve as more objective methods of histopathologic grading and may contribute to the development of automated systems for quantitative grading of stratified and transitional epithelial neoplasms.

Aged↗
PubMed1991

Immunohistochemical study of pleomorphic adenoma of lacrimal gland.

Immunohistochemical examinations of lacrimal gland specimens were carried out with monoclonal antibodies to S-100 protein and glial fibrillary acidic protein (GFAP) in 3 cases of normal tissue, 2 cases of hypertrophy and 3 cases of pleomorphic adenoma of the lacrimal gland. In specimens of normal lacrimal gland tissue, S-100 protein was identified in myoepithelial cells and ductal epithelia, but GFAP was not identified in any part of the gland. In specimens of lacrimal gland hypertrophy, the findings were identical. In pleomorphic adenoma of the lacrimal gland, asteroid cells in the myxoid and/or chondroid areas were strongly stained by antibodies to both S-100 protein and GFAP. In the solid areas of pleomorphic adenoma specimens, S-100 protein-positive fusiform or round cells and GFAP-positive round cells were observed. It was thought that S-100 protein-positive cells could have originated from myoepithelial cells and that GFAP could be a tumor-associated antigen. These findings agreed with recent immunohistochemical findings in pleomorphic adenoma of the salivary gland. It was speculated that pleomorphic adenoma of the lacrimal gland could cause mesenchymal metaplasia of the myoepithelial cells, as happens in pleomorphic adenoma of the salivary gland.

Adult↗
PubMed1990

[Immunohistochemical study of pleomorphic adenoma of the lacrimal gland].

We performed immunohistochemical examinations in 1 hypertrophy and 3 pleomorphic adenomas of the lacrimal glands with monoclonal antibodies to S-100 protein and GFAP (glial fibrillary acidic protein). It was thought that hypertrophy of the lacrimal gland would be cytological equivalent to normal lacrimal gland tissue because of the lack of cytological atypia except when accompanied by lymphoid infiltration. In hypertrophy of lacrimal gland, S-100 protein was identified in myoepithelial cells and parts of the ductal epithelia, but GFAP was not identified in any part. In pleomorphic adenomas of lacrimal glands, asteroid cells of myxoid and/or chondroid areas were strongly stained with both antibodies to S-100 protein and GFAP. In solid areas of pleomorphic adenomas, S-100 protein-positive fusiform or round cells and GFAP-positive round cells were observed. It was thought that S-100 protein-positive cells could have originated from myoepithelial cells and GFAP could be a tumor-associated antigen. The results coincided with recent immunohistochemical findings of pleomorphic adenoma of the salivary gland. It was suspected that pleomorphic adenoma of lacrimal gland could develop from mesenchymal metaplasia of myoepithelial cells as in the case of pleomorphic adenoma of salivary gland.

Adult↗
PubMedDate not supplied

[Myxoid liposarcoma and pleomorphic liposarcoma: cyto-histological correlations].

Myxoid liposarcoma and pleomorphic liposarcoma: cito-histological correlations. A correlative cytologic and histologic study of a myxoid liposarcoma of the shoulder in a 72 year-old man and a pleomorphic liposarcoma observed in the retroperitoneum of a 84 year-old woman, are presented. A preoperative FNAB cytology performed in both cases showed necrotic material containing spindle-stellate shaped cells, interspersed in a myxoid matrix, with rare classical monovacuolated lipoblasts and fragments of plessiform vessels were seen in the first and scattered pleomorphic and multinucleated cells, with prominent nucleoli and numerous atypical mitosis in the second. A malignant mesenchimal spindle-cells tumor, with myxoid matrix and pleomorphic cells, consistent with liposarcoma, respectively were suspected. Gross and histological specimens confirmed the cytological suspect. Authors discuss main cyto-histological differential diagnoses of myxoid tumors, and point out the importance and a correct differentiation between myxoid liposarcoma and intramuscular myxoma. The cytologic appearance of pleomorphic liposarcoma is similar to histologic type and therefore the problem of a differential diagnosis with soft tissue tumors is analogous. When mono or plurivacuolated lipoblasts are absent, differential diagnosis between pleomorphic histiocytoma and liposarcoma is impossible. Nevertheless this is not a important problem at cytological level because both tumors have a had prognosis and must be treated with radical surgery. Definition of correct histologic type will be more suitable on histologic specimens.

Aged↗
PubMed1988

[Expression of epithelial and nervous-system-related antigens on pleomorphic adenoma of the salivary glands--an analysis of 20 cases].

The expression of cytokeratin (40-52 kD), carcinoembryonic antigen (CEA), vimentin, neuron-specific enolase (NSE), S-100 protein, glial fibrillary acidic protein (GFAP) were investigated in 20 cases of pleomorphic adenoma of the salivary glands and 10 cases of normal salivary glands, in order to analyze and correlate the antigens' expressions with the probably histogenetic mechanisms of the various histopathological differentiations in pleomorphic adenoma of the salivary glands and their probably original cells in normal salivary glands. Immunohistochemistry has provided some evidence for the relationship of the tumor cells to normal salivary glands: In the normal glands, the acinic cells exhibited cytokeratin, CEA and focal, predominantly nuclear S-100 protein staining. In both normal glands and pleomorphic adenomas, the duct-lining cells were immunoreactive for cytokeratin, CEA and had both cytoplasmic and nuclear S-100 positivity; The myoepithelial cells of the normal glands as well as the periduct cells, epithelial nests/cords, squamous metaplasia and the stellate/spindle/cartilaginous cells in the myxomatous-chondroid areas of the pleomorphic adenoma contain immunoreactive vimentin, NSE, S-100 proteins and GFAP, and lesser amounts cytokeratin (40-52 kD)/CEA. The varicosities of the terminal axon may lie directly on the basal membrane, or penetrate the basal membrane and lie in direct contact with the effector cells (duct-acinar-myoepithelial cells) of the salivary glands. The peripheral neurons and axons of the autonomic nervous system were identified by vimentin, NSE, S-100 proteins and GFAP. The combination of epithelial cytokeratin and nervous system-related vimentin, NSE, S-100 and GFAP immunostaining in myoepithelium of the normal glands and in all component elements (particularly the periduct cells) of pleomorphic adenoma reflects pleomorphic adenoma of the salivary glands is an epithelial tumor, the probably original cells or the probably histogenetic mechanisms of the various histopathological differentiations is correlated not only with "duct-acinar-myoepithelial cells" but also with the neuroectoderm in the normal salivary glands."

Adenoma↗
PubMed1981

[A case of pleomorphic xanthoastrocytoma (Kepes) (author's transl)].

A case of pleomorphic xanthoastrocytoma, the first case in Japan, is reported. This is a 25-year-old woman with a history of convulsive seizures which were initiated on her left arm 13 years prior to admission, On admission, physical and neurological examinations revealed no abnormalities. CT-scan disclosed a large well-defined low density area in the right fronto-temporal region. A small peripheral portion of the low density area was enhanced by contrast media. The high density area located immediately beneath the inner table of the skull. Right carotid angiogram showed a large avascular area corresponding to the cystic lesion. At the operation, there was a mural nodule in the frontal cortex involving the leptomeninges. The tumor was relatively soft and was milky-white in color. Under this tumor was a large cyst containing xanthochromic fluid. The mural nodule was totally removed and the cyst was widely opened. Postoperative course was uneventful and she received a radiation therapy (5500 rads). She was discharged without any neurological deficits. Histologically, the tumor was highly cellular. The tumor cells were markedly pleomorphic showing bizarre giant cells and multinucleated cells. However, tumor necroses and mitotic figures were absent. With immunoperoxidase method and PTAH stain, these tumor cells were confirmed to be astrocytic. In some areas, tumor cells were surrounded by reticulin fibers. Many tumor vessels presented marked hyalinous degeneration. By electron microscopy, many tumor cells contained lipid droplets. This case was considered to be pleomorphic xanthoastrocytoma (Kepes). Pleomorphic xanthoastrocytoma was designated by Kepes et al in 1979 as a new tumor entity. They described clinical and pathological characteristics of this tumor as follows. The age of the patients were young and the tumors were frequently cystic. The tumors were superficially located in the brain and involved the leptomeninges. Despite marked nuclear pleomorphism, mitotic figures of the tumor cells or necroses were rare. In contrast to their pleomorphic cytology, the biological behavior of this tumor appeared to be favorable. The authors stressed the clinical and pathological significance of this tumor. Because, this is the tumor with malignant appearance in light microscopy, but with favorable prognosis.

Adult↗
PubMed1993

Pleomorphic rhabdomyosarcoma in adulthood. Analysis of 11 cases with definition of diagnostic criteria.

Currently, pleomorphic rhabdomyosarcoma (RMS) in adults is considered to be extremely rare or nonexistent. The authors have identified 11 cases of pleomorphic RMS using the following criteria: pleomorphic sarcoma occurring within voluntary muscle, large polygonal or strap-like cells with copious eosinophilic cytoplasm, desmin and myoglobin immunoreactivity, or ultrastructural evidence of sarcomeric differentiation. Ten patients were male, the median age at presentation was 56 years (range, 27-84), and the thigh (seven cases) was the most common site. Of eight cases with clinical follow-up, one patient is alive at 20 months, and seven died 2 to 28 months following diagnosis. The tumors were generally patternless, but several had storiform areas. Cross-striations were not identified. Immunostaining for muscle-related antigens was positive as follows: desmin (in 10 of 11 cases), myoglobin (in 10 of 11 cases), actin HHF-35 (in all 11 cases), smooth-muscle actin (in six of eight cases), sarcomeric actin (in six of nine cases), and fast myosin (in five of five cases). Staining for S-100 protein was negative in all cases. On electron microscopy (six cases), two tumors had well-differentiated rhabdomyoblasts with sarcomeres, Z-disks, and hexagonal arrays of myofilaments; three were poorly differentiated; and one contained immature mesenchymal cells only. Pleomorphic RMS can be distinguished from other pleomorphic sarcomas provided that well-fixed tumor tissue is available for immunohistochemical staining and electron microscopy. We consider that this distinction is important in view of the poor prognosis associated with pleomorphic RMS in this series.

Adult↗
PubMed1999

Cytomorphological features of salivary duct carcinoma ex pleomorphic adenoma: diagnosis by fine-needle aspiration biopsy with histologic correlation.

We report a case of salivary duct carcinoma arising from a pleomorphic adenoma (ex pleomorphic adenoma) in a parotid salivary gland of a 70-yr-old man. Fine-needle aspiration biopsy showed two distinct subsets of cells. There was the typical biphasic pattern of pleomorphic adenoma consisting of bland epithelial cells admixed with uniform spindle-shaped cells and chondromyxoid stroma. In addition, there were features of salivary duct carcinoma best demonstrated by necrosis and the presence of large polygonal cells arranged either singly or in rosettes, clusters or sheets reminiscent of ductal carcinoma of the breast. This case illustrates that the presence of background large polygonal cells and necrosis in an otherwise typical pleomorphic adenoma may suggest the diagnosis of a high-grade carcinoma, namely salivary duct carcinoma, which portends poor prognosis and requires aggressive treatment. Differential diagnosis from other carcinomas known to arise in pleomorphic adenoma is discussed.

Adenoma, Pleomorphic↗
PubMed2002

Expression of estrogen receptor, progesterone receptor, and insulin-like growth factor receptor-1 and of MIB-1 in patients with recurrent pleomorphic adenoma of the parotid gland.

BACKGROUND: Patients with recurrent pleomorphic adenomas of the parotid gland are difficult to manage without considerable risk of facial nerve injury. The prognostic significance of progesterone receptor (PR) and estrogen receptor (ER) reported in these adenomas was evaluated in patients with recurrent pleomorphic adenomas, comparing the results in a group of patients with primary adenomas without recurrences during 10 years of follow-up. METHODS: Paraffin embedded tumor samples from 52 patients with recurrent pleomorphic adenoma of the parotid gland were collected and stained immunohistochemically. Expression of PR, ER, Ki-67 antigen, and insulin-like growth factor receptor-1 (IGFR-1) was analyzed in resected samples of recurrent tumors and was compared with samples from a control group of patients with primary pleomorphic adenoma. RESULTS: A difference (P < 0.05) in the type of tumor was observed between the recurrent group (more cell-poor variants) and the control group. ER expression was low in both groups (19% and 17%, respectively), but immunoreactivity for ER was higher (48%) in normal parotid gland tissue. PR expression in the recurrent group (96%) was higher compared with PR expression in the control group (61%; P < 0.001). PR expression and IGFR-1 expression were correlated weakly (correlation coefficient = 0.660; P = 0.053) in the recurrent group. The expression of growth fraction (Ki-67 score) and IGFR-1 was similar in both groups but was more extensive compared with normal parotid gland tissue. CONCLUSIONS: PR seems to be a prognostic factor in recurrent pleomorphic adenoma of the parotid gland. The PR pathway can be considered a potential target for hormone treatment in patients with these recurrent adenomas.

Adenoma, Pleomorphic↗
PubMedDate not supplied

Ultrastructural contributions to the study of morphological differentiation in malignant mixed (pleomorphic) tumors of salivary gland.

Ultrastructural studies of pleomorphic adenoma have shown a coordinated differentiation of luminal epithelial and modified myoepithelial cells with the latter cells related to processes resulting in the myxochondroid stroma. Five examples of various histologic types of malignant mixed tumor of parotid origin were examined by electron microscopy to see if underlying patterns of tumor cell differentiation and organization matched those of pleomorphic adenoma. Whether they were intracapsular tumors (with or without identifiable pleomorphic adenoma), carcinomas ex pleomorphic adenoma, or a true malignant mixed tumor, all lesions had cell types and organizations either identical to those in pleomorphic adenoma or, as in less-differentiated examples, displayed features suggesting origin from luminal cells, myoepithelial cells, or both. Even the chondroid cells in the true malignant mixed tumor expressed ultrastructural features indicating their epithelial derivation. On the basis of these findings, some alterations to the classification and terminology of the subtypes of malignant mixed tumor are suggested.

Adenoma, Pleomorphic↗