Mixed germ cell tumor of mediastinum/lung masquerading as hemangioma in fine needle biopsy.

The histological predominance of one component in a germ cell tumor can lead to a mistaken diagnosis. Here, we describe a mediastinal teratoma with predominant vascular proliferation (>90%) which on fine needle biopsy was diagnosed as a pulmonary hemangioma. Later, resection specimen revealed other components constituting ~4%, changing the diagnosis while illustrating theimportance of careful evaluation. A 37-year-old Caucasian male with shortness of breath, weight loss, and history of recently resolved pneumonia was diagnosed with hemangioma, after a computed tomography guided fine needle biopsy of a -16.3-cm mediastinal pulmonary mass revealed abundant benign vascular elements. Following tumor excision, ~94% of the sample exhibited predominant vascular elementsThe mass also exhibited rare focal areas of malignant epithelium in a reticular arrangement and undifferentiated pleomorphic cells associated with vascular invasion. These atypical epithelial cells were positive for CD30, pan CK, AFP, ß-HCG and CD 117, thusprocuring a diagnosis of mediastinal mixed germ cell tumor. Although mixed germ cell tumors consist of various tissue types, diagnosis can be easily overlooked if one component dominates. Therefore, obtaining adequate representative neoplasm samples, and sectioning the samples thoroughly, searching for coexisting tissue types is critical for accurate diagnosis.

The high mitotic count detected by phospho-histone H3 immunostain does not alter the benign behavior of angiocentric glioma.

Angiocentric glioma (AG) has been formally codified in the revised 2007 WHO Classification of Tumours of the Central Nervous System. AGs characteristically exhibit mixed features of ependymal and diffuse astrocytic differentiation and low proliferation rates, with Ki-67 labeling indices ranging from less than 1 to 5%. A single case with anaplastic recurrence and a labeling index of 10% has been reported. In the present study, we report a series of three AGs (Case 1: 4-year-old girl at right frontal lobe; Case 2: 4-year-old boy at left frontal lobe; Case 3: 9-year-old boy at right temporal lobe). Case 1 with elevated proliferation index (~10%) and increased mitotic activity (six mitoses per 10 high-power fields) on phospho-histone H3 (pHH3) immunostain at presentation, nonetheless, has shown protracted recurrence-free survival after 6 years of follow-up. So far, this is the first report for evaluating the mitotic activity in AGs using pHH3 immunostain.

Plexiform fibrohistiocytic tumor.

Plexiform fibrohistiocytic tumor is an uncommon mesenchymal tumor that can cause difficulty in diagnosis and surgical management. On clinical and histologic examination, these tumors can potentially be misdiagnosed as sebaceous/epidermal cysts. We report a case of plexiform fibrohistiocytic tumor in a young female, which on initial clinical evaluation was diagnosed as sebaceous cyst. The tumor was deeply invasive, with positive margins on two excisional biopsy specimens. The importance of recognition of this entity, potential pitfalls and prognosis are discussed and the literature is reviewed.

Monomorphous angiocentric glioma: a distinctive epileptogenic neoplasm with features of infiltrating astrocytoma and ependymoma.

We present 8 examples of a neoplasm with features of both astrocytoma and ependymoma that may represent a distinct clinicopathologic entity. The cerebral hemispheric tumors occurred in patients that were 3, 4, 12, 14, 15, 26, 30, and 37 years of age. All presented with seizures that, with the exception of 2, began in childhood. Magnetic resonance imaging studies showed ill-defined, T2-hyperintense, generally noncontrast-enhancing lesions that, although centered on the cortex or amygdala, extended into the underlying white matter for a short distance. Histologically, the variably infiltrative tumors were distinctively angiocentric with well-developed perivascular pseudorosettes in some cases. Longitudinal and/or circumferential orientations of perivascular cells were common also. The cells were uniform in their cytologic features from case to case and were bipolar in all but one case. A glial nature was inferred from immunoreactivity for GFAP, and ependymal differentiation was suggested by positivity for EMA in three cases and ultrastructural features in one. Overall, the tumors were biologically indolent except for one that recurred and ultimately proved fatal.