Solitary fibrous tumors (SFTs) of the head and neck are uncommon. Lesions previously diagnosed in the head and neck as hemangiopericytomas (HPCs), giant cell angiofibromas (GCAs), and orbital fibrous histiocytoma (OFHs) are now recognized as within the expanded spectrum of SFTs. To better understand the clinicopathologic profile of head and neck SFTs, we performed a multi-institutional study of 88 examples. There was no sex predilection (F:M ratio 1.2), and the median patient age was 52y (range 15>89). The sinonasal tract and orbit were the most common sites involved (30% and 25%), followed by the oral cavity and salivary glands (15% and 14%). Original diagnoses included HPC (25%), SFT (67%), and OFH (6%), with one SFT and one OFH noted as showing GCA-like morphology. On review, the predominant histologic pattern was classic SFT-like in 53% and cellular (former HPC-like) in 47%; lipomatous differentiation (8%) and giant cell angiofibroma-like pattern (7%) were less prevalent. Subsets demonstrated nuclear atypia (23%), epithelioid morphology (15%), or coagulative necrosis (6%). Infiltrative growth (49%) and osseous invasion (82%) were prevalent among evaluable cases. Of the 48 SFTs with follow-up (median 77mo, mean 100mo), 19 showed recurrence (40%). Of these, four patients were alive with disease and four dead of disease. Size and mitotic rate were negative prognosticators using a joint prognostic proportional hazards regression model. Three patients experienced metastasis, to lungs, parotid, bone, and skull base, including one case showing overtly sarcomatous “dedifferentiation”. As a group, SFTs present in a wide anatomic and morphologic spectrum in the head and neck. Only rare examples metastasize or cause death from disease. However, the fairly high local recurrence rate underscores their aggressive potential and highlights the importance of prospective recognition.

Prolapse of subconjunctival intraconal orbital fat is a rare cause of an intraorbital mass lesion. Over the past several years, we have seen a number of cases in which this prolapsed fat was confused pathologically with a neoplasm of adipocytic lineage, specifically pleomorphic lipoma and atypical lipomatous neoplasm (well-differentiated liposarcoma). We report the clinical, histopathologic, and immunohistochemical findings in 21 specimens from 17 patients, all of whom presented with prolapsed intraconal orbital fat. All specimens were routinely examined and processed for light microscopy. Immunohistochemistry for CD34, CD68, S100 protein, vimentin, alpha-smooth muscle actin, and Ki-67, and Giemsa, Masson trichrome, and alcian blue histochemical stains were performed. Clinical and follow-up information was extracted from a chart review. The mean age (+/-SD) of the patients was 65.6+/-11.9 years (range: 41 to 85 y); 2 were women and 15 were men. Subconjunctival prolapsed orbital fat was localized in the superotemporal quadrant or lateral canthus around the rectus muscle below the lacrimal gland. The lesions were unilateral in 10 and bilateral in 7 patients. No recurrence was clinically evident over a mean (+/-SD) follow-up time of 2.5+/-3.2 years (range: 1 mo to 13.5 y). Histopathologically, all specimens showed an admixture of mature fat, fibrous septae lacking hyperchromatic cells, adipocytes with intranuclear vacuoles (Lochkern cells), multinucleated giant cells with a wreathlike configuration of normochromatic nuclei (floret cells), and varying numbers of histiocytes, lymphocytes, plasma cells, and mast cells. "Control" sections of normal orbital fat showed occasional Lochkern cells but lacked floret cells. By immunohistochemistry, the floret cells expressed only CD34 and vimentin, whereas the Lochkern cells expressed CD34, S100 protein, and vimentin. We conclude that subconjunctival herniated orbital fat commonly contains multinucleated floretlike giant cells, fibrous septae, and Lochkern cells, features that may result in diagnostic confusion with pleomorphic lipoma and atypical lipomatous neoplasms. Importantly, specific diagnostic features, such as aggregates of bland spindled cells associated with wiry collagen, as seen in pleomorphic lipoma, and enlarged hyperchromatic cells within fibrous septae, as in atypical lipomatous neoplasms, are entirely absent in herniated orbital fat. Multinucleated floret cells present in prolapsed orbital fat likely represent a reactive phenomenon, as they are not present in normal orbital fat.

Calcifying fibrous tumor is a rare benign mass lesion characterized by bland spindle cells embedded in abundant collagenous matrix, interspersed dystrophic or psammomatous calcifications, and lymphoplasmacytic infiltrate. It shares several clinical and morphologic features with IgG4-related disease, a newly recognized fibroinflammatory disorder. Characteristic histologic features of IgG4-related lesions include dense fibrosis and abundant lymphoplasmacytic infiltrate, similar to calcifying fibrous tumor. They contain high numbers of IgG4-positive plasma cells in the tissue. Patients also often have elevated serum IgG4 levels. We report the case of a patient with an ileal calcifying fibrous tumor that contained 69 IgG4-positive plasma cells per high-power field and an IgG4-to-IgG ratio of 56% in lesional plasma cells. The patient's serum IgG4 level was 185 mg/dL, more than double the normal value. Altogether, these features suggest that calcifying fibrous tumor could be an unrecognized lesion of IgG4-related disease.

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BACKGROUND: Hernia mesh removal is growing in demand. Meanwhile, there is no standard for handling the mesh specimen or any consensus on the clinical value of the surgical pathology findings. STUDY DESIGN: All hernia mesh specimens gathered from 2013 to 2018 were analyzed. Patients were categorized based on indication for mesh removal. The "mesh reaction" group included those with clinical reaction deemed to be related to the mesh material. The "mesh nonreaction" group included patients who had mesh removed for a clinical indication unrelated to the mesh material. RESULTS: One hundred and one patients had 115 mesh specimens that were microscopically evaluated. Patients with clinical diagnosis of mesh reaction were significantly younger (39 vs 56 years; p ¼ 0.023) and more likely to be female (71% vs 39%; p < 0.001) than those without mesh reaction. Although the clinical symptoms were significantly different, the pathology findings were quite similar. CONCLUSIONS: There is no clinical value in submitting mesh specimens for microscopic surgical pathology evaluation, regardless of clinical indication for the mesh removal. Also, no clinical claims can be made based on pathology findings from explanted mesh. In addition, microscopic evaluation does incur additional costs to the consumer. We recommend explanted mesh be submitted for gross examination only for documentation purposes in the medical records.

Digital papillary adenocarcinoma (DPA) is a rare neoplasm that can exhibit local recurrence and distant metastasis. We present a series of eight cases of DPA showing two distinct clinical presentations, morphologies, immunophenotypes, and molecular features.Four cases were characterized by painless, slow-growing nodules located on the digits.The lesions were small, well-defined, and confined in the dermis. Histopathologically, these tumors were composed of glandular structures lined by cuboidal epithelium with luminal papillary infoldings. Only rare mitotic figures and minimal squamoid differentiation were present, and cellular necrosis was absent. All four cases were positive for the BRAF V600E immunohistochemistry but negative for p16, low-risk and high-risk HPV in situ hybridization (ISH). In contrast, the remaining four cases were characterized by painful, rapidly growing masses on the digits. These four lesions were located in the deep dermis and consisted of a solid, tightly packed papillary architecture lined by atypical epithelioid cells with inconspicuous nucleoli. Cellular necrosis, numerous mitotic figures, and prominent squamoid differentiation were seen. All cases were negative for the BRAF V600E IHC. However, they showed strong, patchy to diffuse reactivity for p16 and were positive for low-risk HPV ISH and negative for high-risk HPV ISH. Our findings suggest that the current classification of DPA encompasses tumors that show two discrete pathogenic pathways -BRAF mutation or low-risk HPV infection. DPAs with low-risk HPV infection exhibit aggressive clinical features, high-grade morphology, marked squamoid differentiation, and wild-type BRAF. DPAs with BRAF V600E have less aggressive clinical features, low-grade morphologic findings, mild to absent squamoid differentiation, and negative HPV infection.

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Case Report A 51-year-old female with NF-1 underwent flexible sigmoidoscopy, which revealed a 1.8-cm mass in the upper rectum. The noncircumferential mass was located predominantly at the posterior rectal wall and was suspicious for a neurofibroma. The biopsy revealed a WDNET arising in a ganglioneuroma that extended to the edges of the biopsy tissue. The patient underwent a segmental resection, and sections revealed residual grade 1 WDNET intimately admixed with DGN. The area of DGN also showed multifocal microscopic clusters of neuroendocrine cells limited to the lamina propria. Discussion NF-1 involves the gastrointestinal tract in 10% to 25% of affected individuals. DGN is a poorly circumscribed, frequently transmural gastrointestinal lesion composed of spindled and ganglion cells that may be seen in PTEN hamartomatous tumor syndrome, multiple endocrine neoplasia syndrome type 2B, and (less commonly) NF-1. Though malignant transformation of neurofibromas to malignant peripheral nerve sheath tumors is well documented in NF-1, malignant transformation of DGN is extremely rare. To our knowledge, this is the first reported case of a WDNET arising in DGN. In addition to being the first reported case of WDNET in this setting, this is the first case to describe microscopic neuroendocrine cell nests in DGN. Similar proliferations have been described in the setting of inflammatory bowel disease, termed microcarcinoid or neuroendocrine cell micronests, which are not thought to have malignant potential. However, given the presence of these microscopic neuroendocrine cell nests within the larger DGN lesions and adjacent to the WDNET, we hypothesize that in the setting of NF-1, microscopic neuroendocrine cell clusters may serve as a precursor of WDNET. While this is a rare situation, these novel findings should prompt careful examination for WDNET and microscopic neuroendocrine cell nests in future cases of DGN.