Pseudomyxoma peritonei
Pseudomyxoma peritonei | |
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Computed tomographic scan of an abdomen showing pseudomyxoma peritonei with multiple peritoneal masses (arrow) with "scalloping effect" seen. | |
Specialty | Oncology |
Pseudomyxoma peritonei (PMP) is a clinical condition caused by cancerous cells (mucinous
This disease is most commonly caused by an appendiceal primary cancer (
Signs and symptoms
Signs and symptoms of pseudomyxoma peritonei may include abdominal or pelvic pain and/or bloating, distension, digestive disorders, weight changes, increased girth, and infertility.[citation needed]
Cause
The primary tumor appears to arise from the
.Diagnosis
This disease is often discovered during surgery for other conditions, e.g., hernia repair, following which an experienced pathologist can confirm the diagnosis. Advanced stages may present as tumors palpable on the abdomen or distention of the belly ("jelly belly" is sometimes used as a slang term for the condition). Due to the rarity of this disease, it is important to obtain an accurate diagnosis so that appropriate treatment may be obtained from a gastrointestinal cancer surgeon. Diagnostic tests may include CT scans, examination of tissue samples obtained through laparoscopy, and the evaluation of tumor markers. In most cases a colonoscopy is unsuitable as a diagnostic tool because in most cases appendix cancer invades the abdominal cavity but not the colon (however, spread inside the colon is occasionally reported). PET scans may be used to evaluate high-grade mucinous adenocarcinoma, but this test is not reliable for detecting low-grade tumors because those do not take up the dye which shows up on scans. New MRI procedures are being developed for disease monitoring, but standard MRIs are not typically used as a diagnostic tool. Diagnosis is confirmed through pathology.[citation needed]
Classification
There is substantial debate regarding histopathologic classification of pseudomyxoma peritonei.[5] In 1995, Ronnett et al.[6] proposed separating pseudomyxoma peritonei cases into two diagnostic categories: adenoma (disseminated peritoneal adenomucinosis, DPAM) or carcinoma (peritoneal mucinous carcinomatosis, PMCA) with a third category reserved for cases with intermediate features. In this classification system, cases of DPAM were characterized by peritoneal lesions composed of abundant extracellular mucin containing scant simple to focally proliferative mucinous epithelium with little cytologic atypia or mitotic activity (in other words, most cells looked fairly normal and there was no evidence of mitosis which would indicate that cells were rapidly dividing), with or without an associated appendiceal mucinous adenoma. Cases of PMCA were characterized by peritoneal lesions composed of more abundant mucinous epithelium with the architectural and cytologic features of carcinoma (irregular cells, evidence that cells were rapidly dividing, and other criteria), with or without an associated primary mucinous adenocarcinoma. Bradley et al. (2007)[7] argued that continued use of non-malignant terms, i.e., adenoma, for those frequent cases with low-grade features (such as DPAM), is misleading because pseudomyxoma peritonei is a disease state that results from invasion of the abdominal cavity by cells with uncontrolled growth. Bradley states that an adenoma, by definition, is a tumor confined to the appendiceal mucosa with absolutely no evidence of invasion beyond the muscularis mucosae.
The term mucinous adenocarcinoma is used in different contexts depending on the reference material used by the pathologist for disease classification. For example, neoplasms characterized by high-grade features, invasive glands and or signet ring cells, are termed adenocarcinoma in pathology literature.[8] However, some pathologists (e.g., Odze and Goldblum, Surgical Pathology of the GI Tract, Liver, Biliary Tract and Pancreas, 2nd ed.) also use the term mucinous adenocarcinoma when referring to low-grade, well-differentiated tumors lacking high-grade features. Low-grade mucinous adenocarcinoma is used by the American Joint Committee on Cancer and World Health Organization and is nearly or completely synonymous with the DPAM designation.[9] For low-grade mucinous adenocarcinoma, disease may be designated as "benign" because tumors do not invade deeply into tissue and rarely metastasize to parenchyma of organs; this designation may be misleading and confusing to the layperson because pseudomyxoma peritonei is not a harmless condition, fatal if untreated. High-grade or poorly differentiated mucinous adenocarcinoma has a generally poorer prognosis, though surgical treatment with heated intra-peritoneal chemotherapy (HIPEC) is yielding promising outcomes (see surgical treatment).
Immunohistochemistry
Immunohistochemical features:
- Diffuse expression of SATB2, CK20, CDX2, and mCEA
- Sometimes patchy CK7; negative PAX8
- High-grade neoplasms may show loss of DPC4 (10%)[10]
Treatment
Treatment is variable, both due to its rarity and to its frequently slow-growing nature. Treatment ranges from
Surgical
The standard of care for mucinous adenocarcinoma with clinical condition PMP
In debulking, the surgeon attempts to remove as much tumor as possible. CRS or cytoreductive surgery involves surgical removal of the
Chemotherapy
Chemotherapy (typically utilising the chemotherapeutic agent Mitomycin C) may be infused directly into the abdominal cavity after cytoreductive surgery (surgery removing all visible disease to kill remaining microscopic cancerous tumors and free floating cells). The heated chemotherapy (HIPEC) is perfused throughout the abdominal cavity for an hour or two as the last step in the surgery, or ports are installed to allow circulation and/or drainage of the chemicals for one to five days after surgery, known as early postoperative intraperitoneal chemotherapy (EPIC). EPIC may be given in multiple cycles for several months after surgery.[15]
Systemic chemotherapy may be administered as additional or adjuvant treatment. Due to the increased availability of new chemotherapies developed for colorectal cancer patients, some patients have experienced stability in tumor growth with systemic chemotherapy. Systemic chemotherapy is generally reserved for patients with advanced disease, recurrent disease, or disease that has spread to the lymph nodes or distant sites.[citation needed]
This disease may recur following surgery and chemotherapy. Periodic post operative
Epidemiology
The overall incidence was previously estimated at 0.5 to 1 cases per 100,000 people per year.[16] Recent research in Europe indicates that the previous estimate of 1-2 persons per million may be underestimating the actual rate by approximately half, with the real incidence being approximately 3.2 persons per million, and the prevalence being 22 persons per million.[17] It is slightly more common in women than men (male:female ratio of approximately 1:1.3,[18][19]), although the actual ratio is difficult to identify due to potential misdiagnoses and possibly inclusion bias in reported studies. The median age at presentation is typically about 50 years with a range of 20–25 years, but PMP may strike persons of any age.[20][21]
History
The first case was described by Carl F. Rokitansky in 1842. Werth in 1884 coined the term pseudomyxoma peritonei, describing it in association with a mucinous ovarian tumor. In 1901 Frankel described the first case associated with a cyst of the appendix. Audrey Hepburn died of pseudomyxoma peritonei in 1993.
See also
References
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