Reactive nodular fibrous pseudotumor of the gastrointestinal tract and mesentery: a clinicopathologic study of five cases

Reactive Nodular Fibrous Pseudotumor Mimicking Metastatic Tumor After Gastric Cancer Operation: A Case Report and Literature Review

We describe a case of reactive nodular fibrous pseudotumor (RNFP) misdiagnosed as lymph node metastasis after gastric cancer surgery. Additionally, we summarize the clinical and imaging characteristics of RNFP, combined with the literature, to improve the understanding of preoperative diagnosis. Radiological features of RNFP are a homogenous, isodense, solid mass with gradually mild enhancement on multiphasic abdominal computed tomography (CT), and slight ¹⁸F-FDG uptake by positron emission tomography/computed tomography (PET/CT). To the best of our knowledge, this is the first report in the English literature of a case of reactive nodular fibrous pseudotumor associated with gastric cancer and its appearance on PET/CT images.

Calcifying fibrous tumor of the gastrointestinal tract: A clinicopathologic review and update

Calcifying fibrous tumor (CFT) is a rare mesenchymal lesion that has been documented throughout the gastrointestinal tract. Gastrointestinal CFTs may occur at virtually any age, with a predilection for adults and for females. They occur most commonly in the stomach and the small and large intestines. CFTs are most often found incidentally, cured by local resection, and have a low risk of recurrence. Histology shows three characteristic features: Spindle cell proliferations within a densely hyalinized stroma, scattered calcifications, and lymphoplasmacytic inflammation. CFTs are immunoreactive for CD34, vimentin and factor XIIIa, helping to distinguish them from other benign mesenchymal neoplasms. The differential diagnosis of CFTs includes sclerosing gastrointestinal stromal tumor, leiomyoma, schwannoma, solitary fibrous tumor, inflammatory myofibroblastic tumor, plexiform fibromyxoma, fibromatosis, sclerosing mesenteritis, and reactive nodular fibrous pseudotumor. The pathogenesis of CFTs remains unclear, but some have hypothesized that they may be linked to IgG4-related disease, inflammatory myofibroblastic lesions, hyaline vascular type Castleman disease, sclerosing angiomatoid nodular transformation of the spleen, or trauma.

Giant solitary fibrous tumor of the pelvis: A case report and review of literature

INTRODUCTION

Solitary fibrous tumors (SFTs) are rare spindle cells neoplasms most likely arising from mesenchymal cells. Usually they involve the pleura. Even if extra-thoracic SFTs are rare, lately they are diagnosed with increased frequency.

CASE PRESENTATION

We describe the case of giant pelvic and retroperitoneal neoplasm, a rare solitary fibrous tumor, in a 51-year-old man that was admitted for abdominal pain.

DISCUSSION

On CT a SFT appears usually as a smooth, lobulated mass with occasional calcifications, but the imaging differential diagnosis with other mesenchymal tumors is very difficult, if not impossible.

CONCLUSION

The histological and immune-histochemical features of SFTs are helpful for the differential diagnosis. The malignant potential of this cancer is low, but it is very important to perform an optimized surgery and a close follow up in the patient. We believe that this case is particularly interesting and complex because of the difficulty of predicting the future biological behavior.

A reappraisal of sclerosing nodular and/or polypoid lesions of the gastrointestinal tract rich in IgG4-positive plasma cells

AIMS

To describe additional cases of nodular and polypoid sclerosing lesions of the gastrointestinal tract (GIT) that are associated with numerous IgG4-positive plasma cells, review the pertinent literature to ascertain the relationship with systemic IgG4-related disease, and provide a reporting framework for such lesions.

METHODS AND RESULTS

Five new cases of sclerosing polyps or nodules were collected over a 10-year period, occurring in four females and one male ranging in age from 32 years to 56 years (mean, 41.6 years). Patients were asymptomatic or had epigastric pain, and one had rectal bleeding. None had autoimmune or other obvious IgG4-related disease, and serum IgG4 levels were normal. All were solitary nodules in the stomach (two cases), ileum, caecum, and rectum. Four lesions were submucosal and one was subserosal; all were well circumscribed, composed of hyalinised, keloidal fibrous tissue with lymphoplasmacytic inflammation. Obliterative phlebitis was not seen. Lineage-specific immunomarkers were negative. In excess of 10 IgG4-positive plasma cells per high-power field were seen, and the IgG4/IgG ratios were >0.4.

CONCLUSIONS

Very few IgG4-related lesions in the tubular GIT are associated with disease at other sites and/or elevated serum IgG4 levels. The majority may represent a lesion in the spectrum of IgG4-related disease. The use of the term 'IgG4-positive nodule or polyp with probable histological features of IgG4-related disease' is advocated for nodular and/or polypoid lesions in the GIT with ≥10 IgG4-positive plasma cells in a high-power field and an IgG/IgG4 ratio of >0.4.

Inflammatory pseudotumor secondary to urachal cyst: A challenging clinical case report

INTRODUCTION

There is a wide differential diagnosis for intraabdominal tumors. Surgical resection and microscopic analysis of tissue structure can identify tumor origin in most cases. Most rapidly growing invasive tumors are neoplastic. Inflammatory pseudotumors are a subcategory of intraabdominal tumors that are non-neoplastic and can be rapidly growing. Urachal cysts originate from the dome of the bladder; however they are typically not invasive. There is limited literature on the appropriate management of these tumors.

PRESENTATION

A 37-year-old female presenting with symptoms of abdominal pain was found to have a large intraabdominal mass invading multiple organs. Core biopsies demonstrated inflammation. The mass grew significantly over the course of a year and patient's abdominal pain worsened. The patient was taken to the operating room for resection. Final pathology revealed reactive fibrous tissue with acute and chronic inflammation invading bladder, urethra, abdominal wall, appendix, and ovary. Intraoperative frozen section demonstrated low grade spindle cells with concern for inflammatory pseudotumor but final pathology demonstrated inflammation.

DISCUSSION

Although benign, these tumors cause significant morbidity due to their size and level of organ invasion. Management should involve surgical resection as well as potential post-operative chemotherapy or NSAIDs based off clinical picture. We demonstrate the importance of close follow up for residual disease or recurrence of patients with inflammatory pseudotumors of the abdomen.

CONCLUSION

This case highlights difficulties in diagnosis of a tumor that has potential to cause significant morbidity. There is need for further research to discover the best management after surgical resection of these tumors.

Dedifferentiated Liposarcoma With Myofibroblastic Differentiation

CONTEXT.—

Liposarcoma is divided into myxoid, pleomorphic, well-differentiated, and dedifferentiated subtypes. Dedifferentiated liposarcoma displays the greatest histomorphologic diversity, including a subset with myofibroblastic differentiation that shares similarities with a spectrum of reactive, benign, and malignant soft tissue lesions. Misdiagnosis may lead to deleterious consequences, as dedifferentiated liposarcoma differs significantly in its prognosis and treatment from its mimics.

OBJECTIVE.—

To review the clinicopathologic, immunohistochemical, and molecular features of the myofibroblastic variant of dedifferentiated liposarcoma as well as the key distinguishing features from its mimics.

DATA SOURCES.—

Review of pertinent literature on major features and current understanding of dedifferentiated liposarcoma with myofibroblastic differentiation.

CONCLUSIONS.—

The myofibroblastic variant of dedifferentiated liposarcoma is an uncommon and underrecognized sarcoma with several important differential diagnoses, and likely represents the major subset of aggressive retroperitoneal tumors that may have been misdiagnosed as desmoid-type fibromatosis, inflammatory myofibroblastic tumor, or another type of sarcoma in the past.

Sclerosing Tumors of the Gastrointestinal Tract: A Systematic Approach

Some lesions in the gastrointestinal tract have a propensity for sclerosis such that it may mask the actual true nature of the lesion. The purpose of this review is to highlight those lesions of the gastrointestinal tract that can be attended by sclerosis. The sclerosis can mask the cellularity of the lesion; hence, knowledge of the key lesions that are known to have sclerosis will be aid the diagnostic pathologist.

Gastrointestinal manifestation of immunoglobulin G4-related disease: clarification through a multicenter survey

BACKGROUND

Several reports on immunoglobulin (Ig)G4-related disease (IgG4-RD) with gastrointestinal involvement (IgG4-related gastrointestinal disease; IgG4-GID) have been published, although this entity has not been fully established clinicopathologically. Thus, we carried out a multicenter survey.

METHODS

Patients with possible IgG4-GID who underwent resection were collected. Histologic slides were reevaluated, and eight cases with diffuse lymphoplasmacytic infiltration but without numerous neutrophils, granulations or epithelioid granulomas were further analyzed.

RESULTS

Overall, the IgG4 counts (87-345/high-power field) and IgG4/IgG-positive ratio were high (44-115%). The demographic findings included advanced age among the patients (55-80 years) and male preponderance (six cases). Six lesions (five gastric, one esophageal), consisting of lymphoplasmacytic infiltration with neural involvement in the muscularis propria and/or bottom-heavy plasmacytosis in the gastric mucosa, were histologically regarded as highly suggestive of IgG4-RD. Storiform fibrosis and obliterative phlebitis were found in two cases, and the former gave rise to a 7-cm-sized inflammatory pseudotumor (IPT) in one case. Ulceration and carcinoma co-existed in three and two lesions, respectively. All the patients had other organ involvement (OOI), and serum IgG4 levels were markedly elevated (four of five patients). The remaining two cases with gastric IPTs featuring reactive nodular fibrous pseudotumor or nodular lymphoid hyperplasia were regarded as possible cases of IgG4-RD because of the histologic findings and lack of OOI.

CONCLUSIONS

IgG4-GID is found in the setting of IgG4-RD, often with ulceration or cancer. Characteristic histologic findings are observed in the muscularis propria and gastric mucosa. Cases with IPT may be heterogeneous, and there may be mimickers of IgG4-GID.

Reactive Nodular Fibrous Pseudotumor Mimicking Metastatic Gastrointestinal Stromal Tumor to Perigastric Lymph Node: A Case Report and Review of the Literature

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal lesions of the gastrointestinal tract. Many are treated surgically with or without the use of adjuvant tyrosine kinase inhibitors. Metastases to lymph nodes are infrequent. In this article, we present a case of a perigastric nodule presenting 3 years postsurgical treatment for biopsy-proven GIST, clinically suspicious for a recurrent/metastatic GIST. The patient had also received adjuvant tyrosine kinase inhibitor therapy. Microscopic sections from the perigastric lesion showed a spindle cell nodule felt initially to represent a GIST with posttherapeutic changes. Together with morphology, immunohistochemical workup supported the myofibroblastic origin of the spindle cells, consistent with a reactive nodular fibrous pseudotumor, and definitively excluded metastatic GIST. This case highlights an important diagnostic pitfall and is the first known case of a GIST preceding a reactive nodular fibrous pseudotumor.

Elastotic Lesions of Intestinal Subserosal Fat: Report of Two Cases

We report 2 unusual elastotic lesions of intestinal subserosal fat. The first arose in the small bowel subserosa of a 64-year-old woman with volvulus. It was undetected macroscopically and consisted of a relatively circumscribed focus of elastosis, with essentially no evidence of fibrosis or blood vessel walls within. The second arose in the subserosa of the sigmoid colon in a 46-year-old woman with recurrent diverticulitis. It was also undetected macroscopically and consisted of a well-circumscribed nodule of elastic fibers surrounding prominent veins and arteries. Both patients had unremarkable postoperative courses. These lesions likely represent localized response to injury and are probably underrecognized.

Calcifying Fibrous Tumor of the Gastrointestinal Tract

Calcifying fibrous tumor is a benign mass lesion classically described as a soft tissue tumor. However, a thorough review of the literature reveals that it can occur virtually anywhere, including the tubular gastrointestinal (GI) tract. Its clinical manifestations are variable in the GI tract, and its imaging findings are nonspecific. However, it has unique histologic and immunophenotypical features that must be recognized by GI pathologists to differentiate it from an assortment of other rare mesenchymal lesions of the abdomen and GI tract. Calcifying fibrous tumor is composed of a paucicellular collagen matrix, interspersed calcified bodies, and a sparse inflammatory infiltrate. Although calcifying fibrous tumor is benign, pathologists must be aware that it may occur in the GI tract to differentiate it from other potentially more aggressive, rare mesenchymal lesions.

Reactive nodular fibrous pseudotumor involving the gastrointestinal tract and mesentery: A case report and review of the literature

Reactive nodular fibrous pseudotumor (RNFP) is a tumor-like lesion that is characterized by reactive fibroblast/myofibroblast proliferation within collagenic hyalinized stroma, due to its association with injury or inflammation. The current study describes the case of a 60-year-old female with a history of abdominal surgery and abdominal pain. Upon laparoscopy, multiple nodules attached to the outer layer of the colon and mesentery were identified, and therefore, complete surgical excision was performed. Macroscopically, the nodules were well-circumscribed, firm, tan-white in color and ranged in size between 2.0–10.0 cm at the greatest dimension. Microscopically, the nodules were composed of spindle and stellate cells in a dense collagenic hyalinized background with sparse lymphocytic infiltration. Immunohistochemical analysis demonstrated positive staining for vimentin, smooth muscle actin and cluster of differentiation (CD) 117, and focally-positive keratin staining with AE1/AE3; however, no staining was observed for gastrointestinal stromal tumor 1, CD34, S-100, anaplastic lymphoma kinase or β-catenin. Therefore, it was proposed that the lesion may be most accurately described as an RNFP. The current study reports a rare case of RNFP, emphasizing its histopathological features and differential diagnoses to promote an improved and broader understanding of this poorly understood condition.

Aggressive fibromatosis

Aggressive (deep or desmoid-type) fibromatoses are locally infiltrative collagen-forming tumours with potential for recurrence but not metastasis. They exert their clinical effects primarily in relation to location and have variable biological behaviour. In sporadic cases there are somatic mutations in the β-catenin (CTNNB1) gene on 3p21, resulting in immunohistochemically demonstrable overexpression in nuclei. Fibromatosis in patients with familial adenomatous polyposis (FAP) harbours inactivating germline mutations in the desmoid region of the adenomatous polyposis coli (APC) gene on 5q21-q22. The differential diagnosis includes other myofibroblastic lesions, perineurioma, low grade fibromyxoid sarcoma and, in the abdomen, gastrointestinal stromal tumour and liposarcoma with 'low-grade' dedifferentiation. The primary management is surgical, though some desmoids cease to grow and can be watched. Other therapies have a role in stabilising growth or shrinking tumours. Although no single therapy is effective in all cases, available modalities including irradiation, hormonal therapy, chemotherapy, and receptor tyrosine kinase inhibition can be of value in appropriate clinicopathological subgroups.

Reactive nodular fibrous pseudotumor: case report and review of the literature

We will describe a case of a patient diagnosed with a rare identity of a benign lesion, "reactive nodular fibrous pseudotumor" (RNFP). It is a tumor which preoperatively can present as a malignant tumor and is only reported in 19 cases. According to the very limited amount of information on this tumor in the literature it is mostly seen after trauma or intraperitoneal inflammation. Our case is the second one of RNFP associated with endometriosis, which is a frequently seen intraperitoneal inflammation process in women. Knowledge that these large pseudotumoral lesions can occur is important to direct the management of these patients.

Torsed reactive nodular fibrous pseudotumor in an adolescent: case report and review of the literature

We describe a case of a 13-year-old girl presenting with acute abdominal pain and imaging suggesting acute appendicitis. Upon laparoscopy, she was found to have a mass attached to the jejunum that had torsed upon its blood supply. On histopathologic studies, the mass was determined to be a reactive nodular fibrous pseudotumor. This lesion is a benign neoplasm that may arise from the gastrointestinal tract and has only been recently described in the literature. Our case is unique because it is the first report of reactive nodular fibrous pseudotumor presenting as a torsed polypoid lesion and the first arising in an adolescent.

Sclerosing nodular lesions of the gastrointestinal tract containing large numbers of IgG4 plasma cells

BACKGROUND

Hyalinised fibrous nodules have been encountered within the gastrointestinal tract (GIT) and been labelled as reactive nodular fibrous tumours. Several have a history of abdominal surgery and/or sepsis that acts as a precipitating cause for the fibrosis. Recently, much attention has been focused on IgG4 related fibrosing lesions that are typically associated with a high population of IgG4 positive plasma cells and tissue fibrosis. There may be attendant elevated serum IgG4 levels and associated autoimmune disease.

METHODS

We present four patients with well-circumscribed fibrous nodular lesions occurring in the GIT. Tissue was formalin fixed after microwave antigen retrieval and H&E stains and immunohistochemistry were performed. IgG4/IgG ratios were calculated from the three high power fields containing the densest concentration of positive plasma cells.

RESULTS

The patients were two females (45 and 56 years) and two males (47 and 60 years) who presented with gastric (2 cases), caecal and sigmoid flexure involvement. One case had four lesions while the other three cases were solitary nodules. Two patients had coexistent autoimmune disease. All lesions were nodular and composed of paucicellular, hyalinised fibrous tissue associated with chronic inflammation. In all lesions the plasma cell population was strongly IgG4 positive.

CONCLUSIONS

This paper describes unique, well-circumscribed sclerosing nodules containing IgG4 positive plasma cells within the bowel wall that may cause mucosal polypoid lesions. It is possible that these lesions may be related to the spectrum of IgG4 related sclerosing disease or belong to a separate subset of inflammatory reactive conditions that are rich in IgG4 plasma cells.

Reactive nodular fibrous pseudotumor: a first report of gastric localization and clinicopathologic review

Reactive nodular fibrous pseudotumor (RNFP) of the gastrointestinal tract is a distinct benign lesion, which could originate from a reactive proliferation of multipotential subserosal cells. This is the first case to be reported in the stomach. It was fortuitously discovered in a 60-year-old man with history of bulbar ulcer and gastritis. Gross examination revealed three lesions in the gastric wall and an adjacent lesion in the lesser omentum. Histologically, lesions were composed of a proliferation of spindle and stellate cells in a dense collagenic hyalinized background containing a mononuclear cell inflammatory infiltrate with numerous lymphoid aggregates and plasma cells with perivascular disposition. Immunohistochemistry showed staining for cytokeratins (AE1/AE3), vimentin and smooth muscle actin, without staining for the neurofilament and S100 proteins, synaptophysin, calretinin, CD117 (c-kit), CD34, desmin, caldesmon or anaplastic lymphoma kinase (ALK-1). Complete excision was performed, and no evidence of disease was found 4 months later. After analysing clinical, morphological and immunohistochemical features of this entity, the main differential diagnoses will be discussed, including calcifying fibrous pseudotumor, which shares morphological characteristics with RNFP, but which immunohistochemistry and the ultrastructural study suggest that it may be a result of another reactive process.

Calcifying fibrous tumor of the stomach: clinicopathologic and molecular study of seven cases with literature review and reappraisal of histogenesis

Calcifying fibrous tumor (CFT) is a rare benign mesenchymal tumor composed of hyalinized fibrous tissue with interspersed bland fibroblastic spindled cells, scattered psammomatous, and/or dystrophic calcifications and variably prominent mononuclear inflammatory infiltrate. CFTs show a predilection for the abdominal cavity and soft tissue. To date, 6 gastric and 3 intestinal CFTs have been reported. We analyzed 7 gastric CFTs including 6 new cases. Patients were 4 men and 3 women with a mean age of 53 years (range, 40 to 77). Mean tumor size was 2.2 cm. Most tumors originated in the gastric body (6/7). Six were incidental findings at autopsy or during surgery for other diseases. One ulcerated tumor caused iron deficiency anemia and ulcer symptoms. Six tumors involved the muscularis propria with variable submucosal and subserosal extension and 1 arose within thickened muscularis mucosae adjacent to a mucosal invagination. Histology was typical with uniformly hypocellular vaguely storiform collagen, lymphoplasmacytic infiltrates, lymphoid aggregates and psammomatous, and dystrophic calcifications. Peritumoral lymphoid aggregates were seen in 3 cases. Adjacent muscle coat contained lymphoid aggregates with fiber degeneration (2), minute CFT-like foci (1), and calcifications (1). In none of the cases were there remnants of burnt-out GIST, inflammatory fibroid polyp, inflammatory myofibroblastic tumor, leiomyoma, schwannoma, or other specific lesion. All tumors were negative for CD117, S100, smooth muscle actin, desmin, ALK1, h-caldesmon, and PDGFRA. Two stained focally with CD34. Scattered IgG4-positive plasma cells were seen in 4 of 6 cases stained with this marker. All 5 tumors with available tissue for molecular analysis were wild-type for KIT and PDGFRA. Three patients had follow-up (range, 12 to 24 mo); none developed recurrence. Gastric CFTs are distinct from sclerosing GIST and other mesenchymal gut lesions and may represent a localized inflammatory fibrosclerosis in response to immune-mediated or other-type tissue injury affecting the muscularis propria. They differ from soft tissue CFTs by smaller size, older age at presentation and lack of recurrence, and from peritoneal CFTs by equal gender distribution, older age, and absent multifocal occurrence.

Histologic evidence of repetitive blunt force abdominal trauma in four pediatric fatalities

In cases of acute fatal child abuse, certain injuries, including cutaneous blunt force trauma, skull fractures, subdural hematomas, intra-abdominal hemorrhage, and retinal hemorrhages are common and well described in the pediatric and forensic literature. These gross findings at autopsy, when taken into consideration with scene investigation and interviews with caregivers, may indicate both a clear manner and cause of death. In such cases, the discovery of additional pathologic changes attributable to older abusive injuries helps support a conclusion of death due to inflicted trauma. We discuss four cases of fatal child abuse in which acute blunt force abdominal trauma was the cause of death. In each of these cases, careful examination with proper sectioning and microscopy of select abdominal tissues revealed that the acute tissue trauma was superimposed on a background of older, healing injury. This older trauma was characterized by classic histologic elements of tissue repair, including fibroblast proliferation, early scar formation, increased vascularity, and hemosiderin-laden macrophages. Iron and trichrome stains were used to confirm the presence of hemosiderin and fibrosis in all four cases, but the recognition of fibroblast proliferation and a reactive vascular pattern was best seen on routine hematoxylin and eosin stains. The gross and microscopic autopsy findings, along with available investigative information, established the diagnosis of chronic physical abuse.

Gastrointestinal stromal tumors: diagnostic challenges and practical approach to differential diagnosis

Over the last decade, gastrointestinal stromal tumors (GISTs) have evolved from histogenetically obscure gastrointestinal mesenchymal tumors to well-defined tumors with distinctive clinical, morphologic, ultrastructural, histogenetic, and molecular characteristics, for which targeted therapy is available. This is largely attributable to the discovery of CD117 overexpression and activating mutations in c-kit or platelet-derived growth factor alpha genes in most of GISTs. The availability of specific diagnostic tests and targeted therapy for GISTs has led to an increased awareness of these tumors. At the same time, the list of potential GIST mimics has lengthened considerably and it has become increasingly important that GISTs be distinguished from their mimics because correct diagnosis has implications for both treatment and prognosis. The purpose of this review is to provide an update of the expanding differential diagnosis of GISTS, to draw attention to unusual GIST variants, to provide a practical approach the differential diagnosis of GISTs and to highlight some of the challenges faced by pathologists in resolving this differential diagnosis.

Interstitial cells of Cajal in health and disease. Part II: ICC and gastrointestinal stromal tumours

Mesenchymal tumours in the gastrointestinal tract have long been problematic in terms of diagnosis, prognosis and therapy, but recent advances in immunohistochemistry and related therapies have allowed more specific diagnosis. In particular, the recognition that both the interstitial cells of Cajal (ICC) and many gastrointestinal stromal tumours (GISTs) are positive for c-kit and CD34 and have other features similar to those of ICC has led to the use of imatinib, a novel small molecule therapy that blocks the CD117/c-kit tyrosine kinase receptor, which shows remarkable efficacy in treatment of malignant and metastatic GISTs as well as other malignancies.

Heterotopic mesenteric ossification: a distinctive pseudosarcoma commonly associated with intestinal obstruction

Heterotopic mesenteric ossification (HMO) is a rare intraabdominal bone-producing pseudosarcoma with fewer than 14 reported cases in the literature. We report our experience with 6 additional cases, all of which were referred to us with a diagnostic consideration of extraskeletal osteosarcoma (EO) or "sarcoma" and emphasize features which distinguish HMO from EO. Six intraabdominal lesions coded as "heterotopic mesenteric ossification," "ossifying pseudotumor," or "reactive myofibroblastic proliferation with ossification" were retrieved from our consultation files. Clinical follow-up information was obtained. Lesions occurred exclusively in males, with a mean patient age of 49 years (range, 22-72 years). The tumors occurred in the mesentery (N = 4), omentum (N = 1), or both (N = 1) and were preceded by significant abdominal surgery (4 cases) or trauma (1 case) in all but 1 case. Five patients presented with bowel obstruction and 1 with abdominal sepsis. Tumors were difficult to precisely measure; the mean size of the resection specimens was 11.8 cm (range, 3.5-20 cm). Grossly, the tumors resembled fat necrosis and often cut with a gritty sensation. Microscopically, all lesions demonstrated an exuberant, reactive (myo)fibroblastic proliferation resembling nodular fasciitis, with extensive hemorrhage and fat necrosis. All tumors produced abundant bone and osteoid, often "lace-like," and 2 contained cartilage. The proliferating (myo)fibroblasts, osteoblasts, and chondroblasts were mitotically active but cytologically bland. Follow-up (4 cases; mean, 47.3 months; range, 5-120 months) showed 3 patients alive without disease and 1 dead of unrelated causes. One case was recent. HMO is a distinct intraabdominal ossifying pseudotumor that typically occurs in males, almost always after surgery or abdominal trauma, and frequently presents with symptoms of intestinal obstruction. This clinical history, presence of clearly reactive zones resembling nodular fasciitis, thick osteoid, and absence of nuclear atypia, necrosis, and atypical mitotic figures allow the distinction of HMO from its most important morphologic mimic, EO.

Reactive nodular fibrous pseudotumor involving the pelvic and abdominal cavity: a case report and review of literature

There are several entities that can present with multiple nodular lesions within the peritoneal cavity, such as "disseminated peritoneal leiomyomatosis," "peritoneal fibrosis," "calcifying fibrous pseudotumor," and the recently described lesion of "reactive nodular fibrous pseudotumor of the gastrointestinal tract and mesentery." Here we present one such lesion in a 28-year-old woman with a history of dysmenorrhea and ergotamine use for migraine attacks. Intraoperative exploration of our patient disclosed numerous nodules located throughout the pelvic and abdominal peritoneum. Histopathologically, these lesions were fibrocollagenous nodules composed of sparse wavy spindle cells within hyalinized "keloid-like" collagen surrounded by an inflammatory infiltrate. Some of the nodules were associated with small foci of endometriosis. We believe this lesion is best described by the term "reactive nodular fibrous pseudotumor" and that endometriosis and the use of ergotamine derivatives may be contributing factors.

Reactive nodular fibrous pseudotumors of the gastrointestinal tract: report of 8 cases

Eight cases of reactive nodular fibrous pseudotumor of the gastrointestinal tract are presented. The patients included 6 males and 2 females between the ages of 1 and 68 years (mean age 41.5 years). Three tumors involved the small intestine, and 5 of the investigated lesions were located in the large bowel. Of these, 2 originated in the sigmoid colon, 1 in the cecum, 1 in the appendix, and 1 in the large bowel not otherwise specified. The tumors' size varied from 3 to 10 cm in the greatest diameter (mean 6.2 cm). Histologically they were composed of stellate or spindle shaped cells resembling fibroblasts arranged haphazardly or in intersecting fascicles, embedded in a collagen-rich stroma, with sparse intralesional mononuclear cells frequently arranged in lymphoid aggregates. Immunohistochemically, the lesions were positive for vimentin (7/7), smooth muscle actin (8/8), muscle-specific actin (5/7), cytokeratins AE1/AE3 (6/7), and CAM 5.2 (1/7), and antigen CD68 (1/7). No case (0/8) reacted positively with antibody to CD117 (c-kit). Genetically no substitutions, deletions, or insertions occurred in exon 11 in all analyzed samples. Likewise, no deletions or insertions in part of exon 9 were observed. Ultrastructurally the tumor cells revealed features typical of myofibroblasts. According to the morphologic, immunohistochemical, and ultrastructural features mentioned above, especially to the positivity of low-molecular-weight cytokeratins, we propose this lesion to be related to a proliferation of multipotential subserosal cells rather than ordinary myofibroblasts or fibroblasts.

Gastric fibromyxoma, a distinct entity of pure fibroblastic tumor--an ultrastructural study

A rare case of fibromyxoma arising in the stomach of a 78-year-old male is presented. A well-defined, encapsulated tumor measuring 27x17x8 cm showed a lobular growth in the submucosa and muscularis propria, with no association with the propria mucosa. Histologically, the tumor was characterized by a diffuse, widely spaced proliferation of small spindle, stellate and round cells with dendritic outlines with fibromyxoid stroma. Neither cellular atypia nor mitotic figures were observed. Immunohistochemically, the tumor was positive for vimentin and CD34 but negative for CD117, alpha-smooth muscle actin, muscle actin, desmin and S-100 protein. Ultrastructurally, the tumor cells had irregularly shaped nuclei and cytoplasm containing moderate amounts of mitochondria, rough endoplasmic reticulum, subplasmalemmal densities, and short interdigitating processes. These findings indicated the fibroblastic nature of the tumor. The patient was well without recurrence 20 months after surgery. It is important to recognize that gastric fibromyxoma is a distinct entity and to include it in the differential diagnosis of gastric mesenchymal tumors, as the tumors show a different clinical behavior and as limited surgery with local excision is possible.

Vanek's tumor (inflammatory fibroid polyp). Report of 18 cases and comparison with three cases of original Vanek's series

Eighteen cases of Vanek's tumors are presented. The patients included nine men and nine women between the ages of 45 and 93 years (mean, 66.2 years). Nine cases were clinically diagnosed as polyps of the gastric antrum, five cases as polyps of the stomach (not otherwise specified), one polyp was located in the ileum and the three remaining polyps in the small intestine (not otherwise specified). The thirteen polyps with available size information measured from 0.4 to 5 cm in the greatest diameter (mean, 2.2 cm). Immunohistochemically, the affections were positive for vimentin (18/18) and CD34 (15/18). All the cases negative for CD34 also lacked concentric onion skin-like formations of the spindle cells around glands and vessels. The different immunophenotype and absence of concentric formations could be explained by the existence of two different lesions commonly designated as Vanek's tumor (inflammatory fibroid polyp) or by the hypothesis of various evolutional stages. In the differential diagnosis, it is important to distinguish namely eosinophilic gastroenteritis, gastrointestinal stromal tumor, inflammatory pseudotumor, hemangioendothelioma, and hemangiopericytoma. In contrast to gastrointestinal stromal tumors, genetically no substitution, deletion, or insertion occurred in c-kit exon 11 in all analyzed samples. Likewise, no deletion or insertion in part of c-kit exon 9 was observed.