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Salivary hybrid carcinoma (HC) is defined as when two or more kinds of carcinoma exist at the same location in a single mass. We reestimated and examined three cases of salivary gland HC. Case 1 involved a 76-year-old male. Case 2 involved a 74-year-old female. Case 3 involved a 66-year-old male. Histologically, case 1 involved a combination of salivary duct carcinoma (SDC) and squamous cell carcinoma (SqCC). Immunohistochemically, the former was positive for gross cystic disease fluid protein (GCDFP)-15 and androgen receptor (AR). Case 2 involved a combination of SqCC and neuroendocrine carcinoma. Immunohistochemically the latter was positive for synaptophysin and neural cell adhesion molecule (NCAM). Case 3 involved a combination of SDC and epithelial-myoepithelial carcinoma (EMC). Immunohistochemically, the former was positive for GCDFP-15 and AR, whereas the inner cells of the latter were positive for cytokeratin 7, and the outer cells of the latter were positive for actin. Because of the transitional zone between SDC and EMC, it was speculated that high-grade SDC arose from low-grade EMC.

Urothelial carcinoma usually shows divergent differentiation and variant histology with squamous and glandular morphology being most common. In this report, we present a case of divergent malignant melanocytic differentiation in a high-grade urothelial carcinoma. A 98-year-old East Asian woman with an anterior bladder wall mass underwent resection, which revealed a high-grade poorly differentiated tumor. A minor component of high-grade papillary urothelial carcinoma and carcinoma in situ is also present. The majority of the tumor cells are morphologically and immunohistochemically consistent with melanoma, a minority of cells are positive for urothelial markers, and rare cells coexpress both melanocytic and urothelial markers. Cells that express melanocytic markers or urothelial markers are intimately admixed together. Taken together, a diagnosis of high-grade urothelial carcinoma with malignant melanocytic differentiation was rendered. This is the first report in the literature of malignant melanocytic differentiation in a high-grade urothelial carcinoma, a finding that may have important diagnostic and therapeutic implications.

Collision tumors are rare and there have only been a few previously described cases between an intestinal adenoma and a lymphoma. We report the first case of a 74-year-old woman who on investigation for iron deficiency had a tubulovillous adenoma with underlying follicular lymphoma. The atypical lymphoid proliferation showed immunohistochemical positivity for cluster of differentiation 20 (CD20), B-cell lymphoma 2 (BCL2), and B-cell lymphoma 6 (BCL6). Subsequent right hemicolectomy showed a superficially invasive adenocarcinoma.

Salivary duct carcinoma of the parotid gland is a highly aggressive epithelial malignancy morphologically resembling high-grade, invasive, and in situ breast carcinoma. It can occasionally present with variable morphology making it diagnostically challenging in cases with unusual morphological components. Ancillary testing, particularly androgen receptor (AR) positivity on immunohistochemistry, can be very helpful in cases that demonstrate extensive squamous morphology, since AR positivity is uncommon in both the primary salivary gland and metastatic squamous cell carcinomas to the parotid. In this report, we describe a case of salivary duct carcinoma that showed only a squamous cell carcinoma component on the initial primary tumor site biopsy, as well as in subsequent contralateral neck lymph node and skin metastases. Apart from the variable morphology, the typical salivary duct and squamous cell carcinoma tumor components also showed significant immunohistochemical differences, including differential staining of human epidermal growth factor receptor 2/neu. The associated diagnostic pitfalls, distinct immunoprofiles of the tumor components, helpful adjuncts for making the correct diagnosis, and associated therapeutic implications are discussed.

Ovarian Brenner tumors, accounting for ∼5% of overall ovarian epithelial neoplasm, are often reported in association with mucinous neoplasm. Histogenetically, the two tumors are thought to arise from similar precursors. To date, fewer than 60 borderline Brenner tumors alone have been reported, and the concomitant presence of atypical proliferative components in Brenner and mucinous tumors is even rarer. Therefore, the clinicopathological characteristics and prognosis of patients with the borderline Brenner tumors alone or coexisting with mucinous neoplasm are extremely limited. Herein, we report a unique case of a 53-year-old woman with a unilateral ovarian borderline Brenner tumor associated with focal atypical mucinous epithelial proliferation and her clinical presentations. The clinicopathological features of the tumor are documented and the literature review along with the clinical molecular advances are summarized in this study.

Adenocarcinomas and noninvasive intraepithelial neoplasms (either polypoid or flat) are the most common gallbladder tumors; however, neuroendocrine neoplasms (NENs) can also occur. The majority of NENs are represented by neuroendocrine carcinomas (NECs), while neuroendocrine tumors (NETs) are extremely rare in this location. Occasionally, NEN may present as a part of a mixed neoplasm, with a coexisting non-neuroendocrine component. The latest World Health Organization classification denotes these lesions as mixed neuroendocrine-non-NENs (MiNENs). A novel type of MiNEN, the mixed adenoma well-differentiated NET (MANET), has been increasingly recognized and reported. In such lesions, a dysplastic noninvasive neoplasm and a NET represent the exocrine and endocrine component, respectively. MANETs have mostly been identified in the colon, small intestines, and stomach. In this article, we report, we believe, the first case of mixed gallbladder neoplasm with both biliary intraepithelial neoplasia (BilIN) and NET components, which may be regarded as a variant of MANET. Given the expectably favorable prognoses of MANETs, it is imperative not to misdiagnose the infiltrative yet indolent neuroendocrine component as an invasive adenocarcinoma or a NEC.

Epithelial-myoepithelial carcinoma (EMCA) is a rare low-grade carcinoma of the salivary glands with multiple morphological variants. One such variant, sebaceous EMCA (SEMCA), has been reported in the literature. Distinguishing it from other tumors such as sebaceous carcinoma is crucial, as SEMCA typically behaves more indolently. We present a case of a SEMCA in the right parotid of a 71-year-old man that shows features of aggressive behavior such as facial nerve invasion and extraparenchymal extension. Also, we report evidence of preexisting pleomorphic adenoma within this tumor.

Introduction: Dedifferentiated endometrial carcinoma is an uncommon highly aggressive uterine tumor. It comprises 2 components: a well-differentiated, low-grade epithelial carcinoma and an undifferentiated carcinoma. The undifferentiated carcinoma frequently exhibits rhabdoid cytologic features. Many of these tumors are characterized by an aberrant switch/sucrose non-fermenting (SWI/SNF) complex. They may also exhibit aberrant expression of mismatch repair (MMR) proteins. Together, these play an important role in the pathogenesis and aggressive nature of the tumor., Material and Methods: We present a case of dedifferentiated endometrial carcinoma in a 63-year-old female showing loss of expression of SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4 (SMARCA4/BRG1), and aberrant expression of MMR proteins. We also review the literature starting from the earliest recognition of this entity and the various studies done to explain its molecular pathogenesis and prognostic importance., Results and Conclusions: Recognition of SWI/SNF complex-deficient dedifferentiated endometrial carcinoma is important as these tumors do not respond to platinum-based chemotherapy, and consideration of alternative therapies is often necessary. We also want to emphasize that though most of the studies have found MMR deficiency in the undifferentiated carcinoma component, it may be seen only in the low-grade, well-differentiated component, as observed in this case.

Pure invasive papillary carcinoma (IPC) is a rare subtype of breast carcinoma with good prognosis compared with classical invasive breast carcinoma (IBC) of no special type. The majority of IPC are estrogen receptor and progesterone receptor (ER/PR) positive and HER2 negative (luminal A-like). We report the case of a 72-year-old women who was referred to the Senology Clinic for a routine workup following surgery for an intraductal papilloma. The core needle biopsy (CNB) showed a lesion mainly composed of irregular papillae and micropapillae with apocrine epithelial cells of low-to-intermediate nuclear grade, without a myoepithelial cell layer within the papillae and at the periphery, as demonstrated with multiple immunostains. The diagnosis of apocrine papillary lesion of uncertain malignant potential was made. The subsequent lumpectomy showed an IBC with the same cyto-architectural features as the CNB. In addition, lymphovascular invasion and papillary/micropapillary apocrine in situ lesion were noted. Notably, the tumor was ER/PR and HER2 negative and strongly positive for androgen receptor. A final diagnosis of mixed apocrine papillary/micropapillary carcinoma with triple-negative status was made. To the best of our knowledge, this is the first report of an IBC with these features. Breast pathologists should be aware of this entity when dealing with CNB samples characterized by a complex papillary lesion with apocrine atypia that lacks a myoepithelial cell layer on multiple immunostains. These lesions should be classified at least as of uncertain malignant potential based on the cyto-architectural features prompting a surgery for removal.

Adult granulosa cell tumor (AGCT) and sex cord tumor with annular tubules (SCTAT) are distinct sex cord stromal tumors with different molecular signatures. We present a unique case of an incidental ovarian tumor with mixed AGCT and SCTAT morphologic patterns. Due to the unusual co-occurrence, molecular testing was separately performed on both components. Despite minimal overlap in morphology, both the SCTAT and AGCT components were found to have an identical mutation profile, including the prototypical FOXL2 p.C134W mutation characteristic of AGCT. We thus present the first report of AGCT with SCTAT-like pattern.

Mammary-type myofibroblastoma (MFB) is a benign spindle cell tumor of the breast and soft tissue characterized by 13q14 alterations leading to loss of Rb-1 protein expression, a feature shared among spindle cell lipoma and cellular angiofibroma. In this article, we present a novel case of MFB arising in the left breast of a 70-year old man that microscopically showed an abrupt transition from classic MFB morphology to an area with cytologic atypia and mitotic activity, akin to sarcomatous transformation described in cellular angiofibromas. A thorough workup of the molecular underpinnings of both components using chromosomal microarray and next-generation sequencing platforms supported a clonal relationship. Nearly identical copy number changes, including a single copy loss of 13q14, were found in both components; in addition, the sarcomatous component harbored biallelic TP53 alterations. It is important for pathologists to recognize that sarcomatous features can occur in mammary-type MFB to arrive at the correct diagnosis.

Thyroid-like follicular renal cell carcinoma (TLF-RCC) is an extremely rare tumor with less than 40 published reports. These tumors are morphologically distinct with striking resemblance to thyroid follicular tumors, but immunohistochemically different due to lack of thyroglobulin and thyroid transcription factor 1 expression. TLF-RCCs arise in younger patients (mean age = 41 years) with female predominance and in all reported cases were solitary tumors without coexisting epithelial or mesenchymal kidney neoplasms. In this article, we report a case of a 42-year-old woman who presented with an incidental 4-cm solid and cystic left renal mass of the upper pole, which was resected. A detailed imaging assessment, pathologic findings, and immunohistochemical studies revealed a partially encapsulated TLF-RCC arising in a background of mixed epithelial and stromal tumor.

Myxoid liposarcomas (MLS) are known to arise de novo and have not been shown to derive from previous benign lesions (lipomas), whereas lipomas occasionally harbor areas of other benign mesenchymal tissue. Rarely, tumors presenting with MLS or round cell liposarcomas together with conventional liposarcoma have been classified as mixed liposarcomas. However, no case of MLS arising in a conventional lipoma has been described. In this article, we report a case of a young male presenting with a deep-seated soft tissue tumor of the posterior part of the thigh. The tumor was removed en bloc. Grossing revealed a small encapsulated myxoid lesion (2.5 cm) within the larger lipomatous tumor (14 cm). Histological examination and cytogenetic analysis revealed a FUS-CHOP positive low-grade MLS arising in a conventional lipoma without histological atypia, FUS-CHOP fusion, or CDK4/MDM2 amplification. While we cannot conclude whether these were collision tumors or an MLS progression from a lipoma, this case highlights the value of careful grossing in the soft tissue setting.

The occurrence of smooth muscle differentiation in a liposarcoma is a very uncommon phenomenon, even in dedifferentiated liposarcomas. In dedifferentiated liposarcomas, the leiomyosarcomatous component frequently displays high-grade cytologic features, increased mitotic activity, and tumor necrosis. Even more unusual are rare reported cases of low-grade smooth muscle differentiation in atypical lipomatous tumors/well-differentiated liposarcomas (WDLS). The current case describes a 39-year-old female with a large retroperitoneal WDLS harboring a well-demarcated mass composed of benign-appearing smooth muscle fascicles completely lacking cytologic atypia and mitotic activity. In conjunction with the immunopositivity for estrogen and progesterone receptors, the morphology of this nodule was highly reminiscent of a uterine-type leiomyoma. Of note, the lipomatous component largely displayed a lipoma-like appearance with only rare foci of mildly atypical spindle cell proliferation among the adipocytes and few fibrous septae harboring atypical stromal cells. Immunohistochemical and fluorescence in situ hybridization studies revealed MDM2 gene amplification in both the lipomatous and leiomyoma-like areas, thus confirming the diagnosis of a WDLS with smooth muscle differentiation. A literature review on the subject of sarcomas with dual adipocytic and low-grade smooth muscle differentiation provided sufficient supporting evidence to categorize the tumor as a WDLS with "leiomyomatous" differentiation. Pathologists should be aware of the occurrence of uterine-type leiomyomatous differentiation in retroperitoneal WDLS to avoid potential diagnostic errors.

Thyroid-like follicular carcinoma of the kidney (TLFCK) is an extremely rare primary renal malignancy that typically has an indolent course and good prognosis. Histologically, this tumor mimics follicular carcinoma of the thyroid; however, typical thyroid markers are negative. There are fewer than 40 cases reported in the literature, and thus, the prognosis and course of disease is not well understood. Sarcomatoid differentiation has never been reported in a case of TLFCK. We present a case of a 48-year-old woman with an aggressive TLFCK with extensive sarcomatoid differentiation and metastatic disease at presentation. We performed targeted next-generation sequencing of both the thyroid-like component and the poorly differentiated sarcomatoid component using our solid tumor panel to evaluate for any disease-associated mutations and to better understand the molecular profile of these tumors.

Mixed adenoneuroendocrine carcinomas are rare and usually occur in the gastrointestinal tract. Although there have been several investigations regarding their developmental mechanism, the molecular origin of these tumors remains unclear. In this article, we present an exceedingly rare case of a mixed tumor of the urinary bladder with an adenocarcinomatous and a neuroendocrine component and a concomitant urothelial carcinoma in situ (CIS). Due to this extraordinary combination of tumor components, our goal was to extensively examine the 3 tumor components with regard to a representable common origin. Therefore, a comprehensive immunohistochemical analysis and review of the literature was performed. Besides expected outcome, our examination also revealed surprising staining results. Urothelial CIS, like the adenocarcinomatous component, showed strong staining for CDX2. In addition, parts of the adenocarcinoma were positive for synaptophysin like the neuroendocrine tumor component. All 3 components showed a significant overexpression of p53 and a moderate to strong membranous and cytoplasmatic staining for β-catenin. To our knowledge, we are the first to describe a case of a mixed tumor of the urinary bladder with an adenocarcinomatous and a neuroendocrine component and a concomitant CIS. The components share striking molecular features that argue for a common clonal origin and a development of the invasive tumor via the urothelial precursor lesion.

In this article, we describe a case of conventional epithelioid hemangioendothelioma (EHE) arising within an extra-adrenal myelolipoma. This composite neoplasm arose in the mediastinum of a 51-year-old female. The tumor was composed of a large myelolipoma that contained nodules of EHE consisting of CD31-positive epithelioid endothelial cells that grew in solid cords and were enmeshed in a basophilic hyalinized stroma. Both EHE and myelolipoma are characterized genetically by alterations of WWTR1. We demonstrated the expression of CAMTA-1 chimeric protein by immunohistochemistry both in the neoplastic endothelial cells of EHE and some of the endothelial cells lining the blood vessels in the myelolipoma. To the best of our knowledge, this is the first report of a malignant vascular neoplasm arising in association with myelolipoma.

Ovarian yolk sac tumors are germ cell tumors that usually present in children and young women. Rarely, these tumors can arise in older women, usually in conjunction with surface epithelial tumors, suggesting divergent differentiation from the latter. The combination of mixed ovarian yolk sac tumor and high-grade serous carcinoma is rare, with only one case documented in the literature. We present a case of mixed ovarian yolk sac tumor and high-grade serous carcinoma in a postmenopausal woman, including a brief discussion of the immunohistochemical findings and differential diagnosis. Despite the rarity of mixed ovarian yolk sac tumor and surface epithelial tumors, it is important to recognize the biphasic nature of the tumor, which should prompt a thorough immunohistochemical evaluation. The therapeutic and prognostic implications of proper diagnosis cannot be overemphasized., (© The Author(s) 2016.)

We report a case of a Ewing sarcoma/primitive neuroectodermal tumor in an 85-year-old woman who presented with an enlarging circumscribed left flank mass. Magnetic resonance imaging revealed a 3 × 5 × 10 cm heterogeneous mass arising from the 10th rib. Computed tomography demonstrated a small nodule in the right middle lobe and bilateral pleural effusions. The patient underwent computed tomography-guided biopsy followed by open biopsy. The tumor cells were characterized by loosely cohesive sheets of tumor cells with uniform nuclei, and scant, granular, eosinophilic cytoplasm with indistinct cell membranes. Frequent mitoses, apoptosis, and necrosis were present. The cells were positive for CD99 with a strong concentric staining pattern. Epithelial, hematopoietic, and neural markers were all negative. Fluorescence in situ hybridization was performed and demonstrated EWSR1 (22q12) gene rearrangement. Sanger sequencing of the reverse transcriptase polymerase chain reaction product from the patient's tumor demonstrated the EWSR1-FLI1 type 1 fusion. Following diagnosis the patient elected to proceed with localized radiation and declined chemotherapy. She developed progressive lung disease and subsequently died of her disease a year after her initial diagnosis. Ewing sarcoma is predominantly a pediatric disease and uncommon in patients older than 40 years of age. To the best of our knowledge, this is the oldest documented case of Ewing sarcoma, diagnosed using modern molecular techniques., (© The Author(s) 2015.)