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Canine cutaneous histiocytoma (CCH) represents a significant proportion of dog skin tumours, often manifesting as the most common neoplastic skin condition in young animals. Predominantly affecting dogs under four, these tumours appear primarily as solitary lesions that may regress spontaneously. This study, conducted over five years at the University of Trás-os-Montes e Alto Douro, involved a detailed histopathological and ultrastructural examination of 93 CCH cases. Histologically, these tumours showed distinct patterns of lymphoid infiltration, which contributed to their classification into four groups based on the inflammatory response and histological architecture. Most tumours displayed signs of epidermal invasion and frequent mitotic figures, with necrosis present in over half of the cases. Ultrastructurally, the neoplastic cells were characterised by pleomorphism, abundant organelles, and adherens-type junctions. This study offers significant insights into the pathophysiology and morphological characteristics of CCH, underscoring the importance of detailed histological and ultrastructural analysis in accurately diagnosing and understanding this common canine tumour.

Abstract: Generalized eruptive histiocytoma (GEH) is a very rare benign disorder belonging to the group of non-Langerhans cell histiocytosis (non-LCH). GEH is characterized by a nearly uniform infiltrate of histiocytes with classic immunological phenotype (CD68+, S-100- and CD1a-). Prominent eosinophilic infiltration and S100-positive histiocytes are rarely associated in GEH. In this article, we reported a middle-age man presented with disseminated reddish papules distributed on the trunk and proximal extremities. A skin biopsy of the papule showed a dense histiocytic infiltration with prominent eosinophils. By immunohistochemistry, the histiocytes revealed strongly positive for CD68 and S100 protein and negative for CD1a and Langerin (CD207). Based on clinical and histopathological criteria, the diagnosis of GEH was established. We presented this rare case of GEH with such distinctive features to strengthen the awareness of this uncommon form of non-LCH. Classical histopathological and immunological features cannot reliably distinguish GEH from other non-LCH., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Cutaneous histiocytomas (CH) are derived from epidermal Langerhans cells. Single CH are generally associated with a good prognosis in dogs because most undergo spontaneous remission. However, aggressive behaviour and lymph node metastasis have been reported in a small number of dogs with single CH., Objective: To describe the clinical presentation, treatment and disease progression of an aggressive CH located in the ear canal of a dog., Animal: An 8-year-old intact male Rottweiler dog., Methods and Materials: A unilateral ear canal mass was identified as a CH on routine haematoxylin and eosin stained samples. The diagnosis was confirmed by the demonstration of markers associated with Langerhans cells (Iba-1, E-cadherin and CD18) and the absence of markers associated with B cells (CD79a, CD20, Pax5), T cells (CD3), plasma cells (Mum-1) and macrophages (CD11d, CD204)., Results: A total ear canal ablation was performed, but tumour cells extended throughout the horizontal canal and to the deep surgical margin. Due to the locally invasive nature of the mass and incomplete excision, adjunctive chemotherapy with CCNU was pursued. No measurable local disease was appreciable at the time of the last treatment. At 250 days post-surgery the dog was euthanized owing to the development of multiple abdominal masses. No evidence of local tumour recurrence was noted., Conclusions and Clinical Importance: Although single CH are typically associated with benign behaviour, the mass in this dog demonstrated locally invasive behaviour. Cutaneous histiocytomas in the ear canals of dogs may represent a particularly aggressive variant of the condition., (© 2020 ESVD and ACVD.)

We report an unusual case of a 49-year-old woman who presented with persistent papulonodules over bilateral fingers and inframammary region in conjunction with features of connective tissue disease including symmetrical polyarthritis and Raynaud phenomenon. Skin biopsy showed an upper-to-mid dermal proliferation of bland spindled cells with thickened collagen bundles and occasional multinucleated giant cells. Dermal blood vessels were only marginally increased. On immunohistochemistry, both the spindled cells and multinucleated giant cells stained negatively for smooth muscle actin. Some of the spindled cells stained positively with CD68 and CD163, whereas the multinucleated giant cells stained negatively for both stains. Elastic fibers were absent on elastic Van Gieson. The clinical and histopathologic features raise a diagnostic dilemma between fibroblastic rheumatism and multinucleate cell angiohistiocytoma. The patient responded well to cyclosporine and methotrexate therapy, with gradual improvement of the finger nodules.

Multinucleate cell angiohistiocytoma is a rare, vascular, fibrohistiocytic proliferation that has a benign but progressive course. The clinical presentation is that of grouped red-purple papules and nodules characteristically located on the lower extremities in women. The histopathology shows a proliferation of narrow vessels within thickened collagen bundles associated with multinucleate giant cells. These lesions are probably reactive in nature, and several mechanisms of pathogenesis, including hormonal, have been proposed. Different modalities, including intense pulsed light and pulsed-dye laser, have been used for treatment of these lesions. We report a case of a 74-year-old Caucasian woman with long-standing multinucleate angiohistiocytoma on her bilateral thighs that eluded diagnosis for several years. Upon biopsy and histopathological analysis, the diagnosis was made. Treatment options were entertained, although ultimately not pursued by the patient. We report this case to increase clinical awareness of this rare disease and to contribute to the ongoing literature aimed to further characterize this condition., (© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Tumor metastasis to lymph nodes is an important contributory factor for cancer-related deaths despite recent developments in cancer therapy. In this study, we demonstrate that tumor in the proper axillary lymph node (PALN) of the mouse can be treated by the application of external laser light to trigger the unloading of doxorubicin (DOX) encapsulated in thermosensitive liposomes (TSLs) administered together with gold nanorods (GNRs). GNRs + DOX-TSLs were injected into a mouse lymph node containing cancer cells (malignant fibrous histiocytoma-like cells) and intranodal DOX release was activated using near-infrared (NIR) laser irradiation. The temperature changes arising from the laser-irradiated GNRs triggered the release of DOX from the TSLs. A greater degree of inhibition of tumor growth was found in the co-therapy group compared to the other groups. The treatment effect was achieved by a combination of chemotherapy and NIR-activated hyperthermia. In vivo bioluminescence imaging and histological analysis confirmed tumor necrosis in response to combined treatment. This work presents a theranostic approach with excellent treatment results that has the potential to be developed into an alternative to surgery for the treatment of breast cancer metastasis., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Posttraumatic fibro-osseous lesion (PTFOL) is a rare lesion that typically affects the ribs and is probably a posttraumatic reactive process. Because PTFOL is often misdiagnosed as fibrous dysplasia, osteoid osteoma, benign fibrous histiocytoma or rib metastases, chest wall resection, leading to a significant morbidity, is the main treatment modality. We report the case of a 30-year-old male patient with no history of previous trauma presenting with chest pain. Computed tomography scan showed an eighth left rib well-defined ovoid and hypodense lesion with circumferential sclerotic margin and no cortical breakthrough. Posterolateral thoracotomy was performed and a histological diagnosis of xanthomatous posttraumatic fibro-osseous lesion of the rib was made. PTFOL is a benign lesion that should be recognized to avoid unnecessary surgical treatment and complications. We provide a summary of clinical, histopathological, and radiological aspects of PTFOL and discuss differential diagnoses.

Erdheim-Chester disease (ECD) is a very rare disorder with only approximately 600 cases reported in the literature. ECD has been recently reclassified as a histiocytic dendritic cell neoplasm. The clinical spectrum ranges from asymptomatic tissue accumulation of histiocytes to invasive tissue infiltration, which can cause fulminant multisystem failure. It typically presents with bone pain and constitutional symptoms. Extraosseous manifestations are not uncommon. ECD-associated interstitial lung disease has been described in 20%-35% of patients. Diagnosis is primarily by tissue biopsy and immunohistochemistry showing xanthogranulomas composed of foamy histiocytes that stain positive for CD68, CD14 and CD163 and negative for CD1á and langerin. We report a case of ECD in a young man with cardiopulmonary involvement who presented with haemoptysis and dyspnoea., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Survivin is a member of the inhibitor of apoptosis family, which is known to inhibit mitochondrial apoptosis. Survivin is highly expressed in cancers and plays an important role in cancer cell survival, and increased survivin expression is an unfavorable prognostic marker in cancer patients. YM155, a novel small-molecule survivin suppressant, selectively suppresses survivin expression, resulting in the induction of apoptosis in various malignancies. However, the roles of survivin in human malignant fibrous histiocytoma/undifferentiated pleomorphic sarcoma (MFH/UPS) have not been studied. In the present study, we examined survivin expression in human musculoskeletal tumor tissues, and the effect of survivin inhibition by siRNA or YM155 on apoptotic activity in human MFH/UPS cell lines. In tumor tissues, mRNA expression of survivin was significantly higher in MFH/UPS samples than in benign schwannomas. Moreover, in vitro studies revealed that both survivin siRNA and YM155 suppressed survivin expression and inhibited MFH/UPS cell proliferation in a dose- and a time-dependent manner. Further, the numbers of apoptotic cells significantly increased with YM155 treatment. in vivo, tumor volume in YM155-treated groups was significantly reduced without significant bodyweight loss. Increased apoptotic activity along with decreased survivin expression was also observed in YM155-treated tumors. The findings in this study strongly suggest that survivin suppressants, including YM155, contribute to the suppression of human MFH/UPS cell growth via promoting mitochondrial apoptosis, and that survivin may be a potent therapeutic target for the novel treatment of human MFH/UPS.

The objective of this study was to determine common tumor types that occur on the canine scrotum in relation to other cutaneous locations and to identify potential risk factors for specific scrotal tumor development. A retrospective study was conducted and the database of pathology reports from the Surgical Pathology Service of the Department of Pathology and Toxicology, School of Veterinary Medicine, University of Pennsylvania from 1986 to 2010 was searched for canine neoplastic scrotal and non-scrotal cutaneous lesions. Neoplastic lesions were evaluated based on diagnosis, breed, age, and number and location of tumors (scrotal versus non-scrotal cutaneous). Mast cell tumor, melanocytoma, malignant melanoma, vascular hamartoma, hemangiosarcoma, hemangioma, and cutaneous histiocytoma were the most common tumor types identified on the canine scrotum. Breed predispositions and mean age at diagnosis were identified for each tumor type and should be considered when planning surgical excision of a canine scrotal tumor.

Canine cutaneous histiocytoma (CCH) is a common benign skin tumour originating from epidermal Langerhans cells. These tumours often display spontaneous regression and therefore represent a valuable animal model for investigation of tumour regression. Based on previous studies it was hypothesized that up-regulation of cytokines during CCH regression leads to up-regulation of matrix metalloproteinases (MMPs) favouring infiltration of lymphocytes and enhanced tumour regression. The expression of MMPs and their inhibitors (tissue inhibitors of metalloproteinases, TIMPs) was investigated immunohistochemically in 27 CCHs. The tumours were classified into four groups defined as having no regression (group 1), early regression (group 2), intermediate regression (group 3) or late regression (group 4). The distribution and expression intensity of MMP-1, -2, -3, -7, -9, -13 and -14 and TIMP-1 and -2 were determined in peripheral and central areas of each tumour. Group 3 and 4 CCHs showed up-regulation of expression of MMP-1, -9 and -14 at the periphery. Variable expression of MMP-2 and -3 was observed. Expression of the remaining MMPs and TIMPs showed no group-specific changes. Most MMPs and TIMPs displayed significantly higher expression at the tumour periphery compared with the centre, independently of the stage of regression and indicating more pronounced proteolysis in the peripheral areas. The results are consistent with cytokine-enhanced MMP expression, particularly of MMP-9, leading to enhanced lymphocyte recruitment in combination with elevated cleavage of extracellular matrix and basement membranes., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A case of epithelioid fibrous histiocytoma diagnosed in a 5-year-old female with a skin lesion: morphological description and immunohistochemical investigations performed.

Generalized eruptive histiocytoma is considered an extremely rare subtype of non-Langerhans cells histiocytosis. In the literature, there are few reports of this disease that mainly affects adults. In this report, we present a case of generalized eruptive histiocytoma in an elderly patient who had presented symptoms for over two months. Multiple erythematous papules, asymptomatic and symmetrically distributed were observed on the trunk and limbs. Histological examination showed a dense mononuclear cell dermal infiltrate. In the immunohistochemical analysis, the cells were CD68 positive, but CD1a, S100 and CD34 negative. A diagnosis of generalized eruptive histiocytoma was established. The aim of our paper is to report a case of a very rare disease, whose subtype and affected age group are even more unusual.

Presacral tumors are uncommon lesions that can be difficult to diagnose because of their nonspecific presenting signs and symptoms. Surgery is the mainstay of treatment as it establishes the diagnosis and prevents the adverse consequences associated with malignant degeneration and secondary bacterial infection. Large, highly vascularised pelvic tumors may pose intraoperative difficulties as bleeding and intraoperative tumor perforation. Cross-sectional imaging is essential in evaluating these lesions to determine the optimal surgical approach and the extent of resection. We emphasize a multidisciplinary expert individualized approach. We report a case of a presacral giant gastrointestinal tumor initially considered as unresectable but further on successfully managed by preoperative vascular embolization followed by resection via abdomino-perineal approach.

Classic granular cell tumors (GCTs) stain strongly and uniformly positive for S100 protein and are believed to show Schwann cell derivation. Polypoid cutaneous tumors composed of cells with large nuclei and abundant granular cytoplasm that do not stain for S100 protein or show apparent Schwannian differentiation have been reported by several groups under names including "primitive polypoid granular cell tumors," "dermal nonneural granular cell tumor," and "primitive nonneural granular cell tumors of skin." We report a polypoid tumor composed of S100-negative epithelioid cells with abundant eosinophilic granular cytoplasm that meets diagnostic criteria for (primitive polypoid dermal) nonneural GCT but also meets criteria for a granular cell variant of epithelioid cell histiocytoma. We have identified a single previous report of a similar lesion. We report the immunohistochemical characteristics of these lesions and address how they are best classified.

A newborn baby boy was referred to the Paediatric Dermatology Unit with a solitary asymptomatic nodule overlying his right nasolabial fold. Complete physical examination, full blood count, serum chemistry, liver function tests and baseline imaging were unremarkable. Histopathological examination showed an atypical dermal infiltrate of mononuclear cells that stained positive with CD1a and S100. A diagnosis of congenital solitary Langerhans cell histiocytoma was made. The lesion completely resolved by 4 months of age. The baby is now 15 months old and repeat systemic evaluation has remained normal., (© 2010 The Authors. Australasian Journal of Dermatology © 2010 The Australasian College of Dermatologists.)

Background: to describe clinical, radiologic and pathologic features of lung lesions in Birt-Hogg-Dubè syndrome (BHDS) (MIM 135150)., Method: review of 12 patients of BHDS from 3 unrelated Italian families evaluated at GB Morgagni Hospital, Forlì, from 2005 to 2010., Results: mean age (±SD) at diagnosis was 44.6 (±16) years, 8 (66%) were male. All three index cases presented with a history of recurrent pneumothorax and/or cystic lung lesions evaluated by CT scan request by referring pulmonary physicians, none were diagnosed to have BHDS at the time of initial pulmonary evaluation. One of the three cases was a middle-aged female patient with a clinical phenotype indistinguishable from lymphangioleiomyomatosis (LAM), characterized by cystic lung lesions and kidney angiomyolipoma. In one case of BHDS presenting with recurrent pneumothorax and a solitary lung nodule, surgical lung resection revealed a pulmonary histiocytoma. In one case a novel mutation of BHD gene was detected (c.771 del, exon 7)., Conclusions: BHDS is associated with cystic lung disease largely under-recognized by pulmonary physicians and can mimic LAM and may be associated with lung tumor, pulmonary histiocytoma. In one case we found a novel mutation in exon 7, c.771 del (ref.seq. NM_144997.5) never reported before., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The term 'fibrohistiocytic' tumour is a descriptive designation without histogenetic connotation for a group of heterogeneous lesions that share morphological features of histiocytes and fibroblasts on light microscopy. However, over the years it has become apparent that many so-called 'fibrohistiocytic' tumours are largely composed of relatively undifferentiated mesenchymal cells, but can also show areas of myofibroblastic differentiation. This review focuses on the clinical and histological features as well as differential diagnosis of so-called fibrohistiocytic tumours. Special emphasis is given to more recently described histological variants of fibrous histiocytoma, e.g. cellular, epithelioid, aneurysmal and atypical fibrous histiocytoma, to angiomatous and plexiform fibrous histocytoma (plexiform fibrohistiocytic tumour), lesions that are not true variants of fibrous histiocytomas but have erroneously been designated such, and to atypical fibroxanthoma. The literature on metastasizing fibrous histiocytoma is also reviewed.

Plexiform fibrohistiocytic tumor is a low-grade soft tissue malignancy that can at times be difficult to differentiate from the less biologically aggressive cellular neurothekeoma. The two entities, which may display identical clinical and histological features, cannot be distinguished by immunohistochemical or molecular diagnostic means. Electron microscopy may enable the accurate identification of problematic examples and thus aid in resolving these occasionally occurring diagnostic dilemmas. To illustrate typical variations in the ultrastructural appearance of plexiform fibrohistiocytic tumor, the authors present two diagnostically noncontroversial examples, and to demonstrate the potential diagnostic utility of electron microscopy in this setting, they present an example of plexiform fibrohistiocytic tumor that could not otherwise have been distinguished from cellular neurothekeoma.

Pulmonary crystal-storing histiocytoma is a very rare disorder and is characterized by infiltration of histiocytes with intracytoplasmic accumulation of crystallized immunoglobulins. It is usually associated with lymphoproliferative diseases or plasma cell dyscrasia. Here, we report a case of pulmonary crystal-storing histiocytoma in a 64-year-old man, presenting as a chronic pulmonary consolidation in the lung exposed to asbestos. Video-assisted thoracoscopic surgical biopsy displayed sheets of large, epithelioid histiocytes filled with a large number of needle-like crystals, showing the accumulation of crystallized polyclonal immunoglobulins. This lesion was consistent with crystal-storing histiocytosis or crystal-storing histiocytoma. With extensive clinical work-up, the current case was not associated with lymphoproliferative diseases. Herein, we present this extremely rare entity of pulmonary pathology, a pulmonary crystal-storing histiocytoma arising in the lung exposed to asbestos, and demonstrate the clinical, radiologic, and pathologic features of the tumor.

Adult T-cell leukemia/lymphoma (ATL) is characterized by monoclonal proliferation of tumor cells that harbor integrated human T-cell leukemia virus type-1 (HTLV-1). These malignant cells accumulate in various organs including the liver, spleen and skin in addition to blood and lymph nodes. Although there have been several reports of animal models of HTLV-1 infection in which proviral distribution has been examined, clonal expansion of the experimentally infected host cells has not been extensively analyzed. Here we provide experimental evidence that clonal proliferation of the infected host cells occurs in the spleen for more than one year. During a 15 month period of persistent infection, two out of ten mice developed spontaneous tumors. Although the tumors were not ATL-like, cells exhibiting mono- or oligoclonal proliferation and having the same site of HTLV-1 integration were identified in tumor tissues as well as in the spleen. Quantitative analysis of the cells belonging to each cell clone suggested that these proliferating cell clones were associated with the tumors and that spontaneous tumor tissues might provide a suitable microenvironment for proliferation and accumulation of infected cell clones at the late stage of infection.

Heat shock protein 90 (Hsp90) is a major molecular chaperone that plays an essential role in the maintenance of several signaling molecules, most of which are oncogenic kinases. Hsp90 inhibition by specific inhibitors leads to destabilization and loss of activity of such proteins, thereby leading to inhibition of multiple signaling cascades. Due to this, Hsp90 has emerged as an important target for the treatment of cancer. Inhibition of Hsp90 has been reported to induce apoptosis in certain cancer cell types. However, the molecular details of induction of apoptosis upon Hsp90 inhibition are not understood. We have investigated the effect of Hsp90 inhibition on a non-adherent rat histiocytoma cell line, BC-8, using geldanamycin and 17-Allylamino-17-demethoxygeldanamycin. We show that Hsp90 inhibition induces ER stress, which leads to disruption of mitochondrial homeostasis, leading to apoptosis. Induction of ER stress leads to increased expression of ER chaperones, Grp78 and Grp94, cleavage of caspase-12 and increase in cytoplasmic calcium. We show that calcium and Bax are responsible for the decrease in mitochondrial membrane potential (Deltapsi(m)), thereby leading to the release of cytochrome c and activation of caspase-9. Moreover, calcium chelator and over-expression of Bcl-2 is able to confer protection against apoptosis upon Hsp90 inhibition. We conclude that inhibition of Hsp90 leads to ER stress-induced mitochondria-mediated apoptosis and that Bax and Ca(2+) play an important role in mitochondrial damage.

Multinucleate cell angiohistiocytoma (MCAH) is an uncommon benign soft-tissue lesion with characteristic histological and immunohistochemical features. It is unclear if it represents a benign neoplasm or a reactive/inflammatory process. The overwhelming majority of these tumors have been described on cutaneous surfaces. One case has been reported on the skin of the lip. This is the first documentation of MCAH within the oral cavity. The clinical presentation, histopathological features and immunohistochemical reactivity pattern are described. Because of the benign nature of this lesion, a conservative approach is recommended in its management. Surgical excision appears to be curative.

Objectives: Non-melanoma skin cancer (NMSC) is common, slow growing, and rarely metastasizes. However, there are still nearly 400 deaths from NMSC in Australia annually. We aimed to investigate the accuracy of NMSC death coding and to describe the characteristics of these deaths and the potential for prevention., Methods: Histology reports for all deaths coded as NMSC (ICD-10 C44.0-C44.9) by the Western Australian Cancer Registry for the years 1996-2005 were reviewed for type of cancer, body site (primary tumor and metastases), and level of available documentation., Results: Of 368 deaths recorded as being due to NMSC only 3 were found to be miscoded. An additional 53 deaths contained inadequate information to confirm NMSC as the cause of death. Of the confirmed cases, 219 were due to squamous cell carcinoma, 53 to Merkel cell carcinomas, and 40 to other skin cancers. Cases were mainly males and were elderly. Most of the primary squamous and Merkel cell carcinomas were in areas of maximum sun exposure (face, ears, and hands, and scalp in males)., Conclusions: Misclassification of NMSC deaths in WA was minimal. The majority of NMSC deaths were due to squamous cell carcinomas; had primary sites associated with significant sun exposure; and occurred in older men.

Objectives: To study paratesticular malignant fibrous histiocytomas (FHM) from the clinical, histological, immunohistochemical and histogenetic, point of view., Methods: Through Medline and not index-linked search of international scientific literature we have found a total of 77 cases of paratesticular FHM that globally create diagnostic, terminological and therapeutic problems., Results: We include the case number 78 of FHM of spermatic cord, that presents a few special characteristics (not described before) of cutaneous fistula and infiltration of an inguinal leiomyoma, with histological and immunohistochemical confirmation. We performed a conceptual review of this type of tumours, including the evaluation of contradictions and reclassifications that has undergone from its first description, which causes that they are underestimated and their real prevalence in international series is very variable: from 7 to 37% of paratesticular sarcomas. Also, the fact of their low incidence has determined the lack of protocols for diagnosis and treatment., Conclusions: Paratesticular tumours, although infrequent, have a high rate of malignancy. The FHM concept has varied throughout the last 15 years. Today, this term is synonymous of pleomorphic undifferentiated sarcoma and has been an exclusion diagnosis (Vimentin [+]/ CD 68 [+]--occasionally--without ultrastructural differences), reserving the inflammatory subtype for which they have an inflammatory and histiocytic component. The accomplishment of an intraoperatory biopsy is essential in this location, since it is even difficult to know preoperatively, if a lesion is benign or malignant. The differential diagnosis is only solved after microscopic and inmunohistochemical study. Leiomyoma next to this location (inguinal) could be diagnosed and confused with a nodule of the main FHM. Their immunophenotype allowed us to diagnose it not only as leiomyoma (myogenic markers were positive -non skeletal muscle-), but also to observe the infiltration by the FHM.

Canine histiocytic diseases are an emerging spectrum of diseases characterized by proliferations of histiocytic cells. Nonneoplastic histiocytic disease (reactive histiocytosis, comprising cutaneous and systemic histiocytosis) is uncommon. Neoplastic histiocytic diseases include cutaneous histiocytoma, which is a benign histiocytic tumor, and localized and disseminated histiocytic sarcoma (previously known as malignant histiocytosis), which are malignant diseases. The differentiation of histiocytic diseases can be challenging. This article outlines the characteristics of each disease entity and details the clinicopathologic, histologic, immunohistochemical, prognostic, and therapeutic differences among them.

Generalized eruptive histiocytosis is a benign proliferative disorder of non-Langerhans cells. It is a very rare disease. The disease presents with soft to firm fleshy papules on face, neck and upper trunk. Biopsy is often needed to make the diagnosis because of its rarity and diverse presentation. There is tendency for the disease to regress spontaneously without treatment. Treatment, if any needed, suffices to topical modalities. We report here a case of generalized eruptive histiocytosis which presented with lesions of dual morphology. This is a very rare disease with diverse presentation being reported first ever in our country.

We report the case history and radiologic findings of a patient with a biopsy-proven dendritic cell histiocytoma presenting as a single intracranial extra-axial mass and no systemic disease. Even though this entity is relatively rare, it should nevertheless be considered in the differential diagnosis of dural-based space-occupying central nervous system lesions.

Canine histiocytic neoplasms include cutaneous histiocytoma, as well as localized and disseminated histiocytic sarcoma. These tumors have variable biologic behavior, although the malignant disorders often have a poor prognosis. Immunohistochemistry plays an essential role in differentiating histiocytic tumors from other neoplasias that may have similar histological appearances. This allows a definitive diagnosis to be established and provides a more accurate prediction of prognosis. This article reviews the biologic behavior, diagnosis, and treatment of histiocytic tumors in the dog.

Indeterminate cell histiocytosis is an exceptional and controversial entity with variable clinical, histopathologic or immunohistochemical findings, sharing morphologic and immunophenotypic features from both Langerhans and non-Langerhans cell histiocytoses. Neoplastic cells express S-100 and CD1a antigens, but lack Birbeck granules. It has been reported in both adults and children, as solitary or multiple cutaneous lesions with rare extracutaneous involvement. We describe a 12-year-old boy with an indeterminate cell histiocytosis manifesting as a solitary verrucous papule on the mucosa of the glans penis. The morphologic features and diagnostic criteria of cutaneous indeterminate cell histiocytic proliferations are reviewed. The possible relationship between indeterminate cell and Langerhans cell histiocytoses is discussed.

Retroperitoneal tumours are extremely rare neoplasms, most of them malignant. We described the case of a 48-year-old man with a large retroperitoneal mass detected during the study of a constitutional syndrome. The mass was treated surgerically and pathological diagnosis was malignant fibrous histiocytoma. Literature is reviewed and clinical features, histological findings, radiological techniques and therapeutic management are analyzed.

The success of renal transplantation brings with it the dilemma of managing patients with complications from lifelong immunosuppressive therapy. Immunosuppressed transplant recipients are a special population with significantly increased risk for development of skin cancers. Because malignant tumors are increasing as demonstrated on 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) positron emission tomography (PET) image, we report the unusual coincidence of multiple cutaneous cancers and two visceral malignancies 20 years after renal transplantation. The malignancies include basal cell and squamous cell carcinomas and malignant fibrous histiocytoma. FDG-PET images show, in this case, visceral masses with increased metabolism: one in the left upper lung and one in the abdomen, corresponding to individual mass lesions observed on computed tomography (CT) images of the chest and abdomen. A fine-needle biopsy of the nodule of the left upper lung lobe yielded a diagnosis of a sarcoma. The mass lesion of the abdomen had caused bowel obstruction, requiring exploratory laparotomy; histopathological findings from the resected mass from the abdomen confirmed the diagnosis malignant fibrous histiocytoma. This long-term immune suppressed transplant recipient developed viscerally located malignant lesions demonstrated by FDG-PET imaging and three types of cutaneous malignancies (skin cancers).