Abdominal wall hard fibroma

　　First, etiology

　　The etiology of this disease is not yet fully understood and may be related to the following factors.

　　1. Abdominal wall injury:Most scholars outside of China believe that abdominal wall injury is one of the main factors leading to this disease. According to my statistics of 175 cases of abdominal wall hard fibromas in 5 groups in China in recent years, 152 cases (86.9%) had a history of pregnancy and childbirth, and 35 cases (24.8%) had a history of surgery and injury. The mechanism by which abdominal wall injury leads to hard fibromas is unclear, and may be related to abnormal hyperplasia during the repair process of muscle fiber damage, local hemorrhage, and hematoma. Some scholars also believe it may be related to an autoimmune response caused by muscle fiber damage. However, the injury factor cannot explain the etiology of abdominal wall hard fibromas in patients without a history of pregnancy, childbirth, surgery, or trauma. Common causes of abdominal wall injury include:

　　(1) Surgery: surgery directly cuts through the abdominal wall muscles or separates and stretches them, leading to muscle tears and hemorrhage.

　　(2) Blunt abdominal trauma: causes muscle fiber damage, local hemorrhage, or the formation of a hematoma.

　　(3) Pregnancy: Due to the long-term excessive traction on the abdominal muscles, chronic damage to the abdominal wall can occur. During childbirth, the sustained and intense contraction of the abdominal muscles can cause muscle fiber damage, rupture, and hemorrhage between muscle fibers.

　　2. Endocrine disorders:Recent clinical observations and experiments indicate that this disease may be related to female hormone imbalance. The evidence for this is as follows:

　　(1) This disease is more common in women of childbearing age between 18 and 36 years old, often occurring several years after childbirth, and is rare after menopause.

　　(2) After oophorectomy or entering menopause, the tumor tends to gradually regress spontaneously.

　　(3) Estrogen receptor antagonists (such as tamoxifen) have shown some efficacy in the treatment of a few cases.

　　(4) Animal experiments have shown that estrogen can induce the formation of this tumor. Brasfield et al. repeatedly injected estrogen into the abdominal wall muscle layer of white rabbits, resulting in the occurrence of hard fibromas in the experimental animals. Testosterone and progesterone can inhibit the development of the tumor.

　　(5) Estrogen receptors can be detected in the specimens of hard fibromas.

　　3. Genetic factors:As early as 1923, Nichols discovered that patients with familial adenomatous polyposis syndrome were prone to hard fibromas. Hizawa et al. reported that among 49 patients diagnosed with familial adenomatous polyposis syndrome, 6 were confirmed to have concurrent aggressive fibromatosis. Another statistical result shows that the incidence of hard fibromas in patients with familial adenomatous polyposis syndrome is as high as 8% to 38%, which is 8 to 52 times higher than that in the normal population. In view of the fact that this disease often occurs simultaneously with familial adenomatous polyposis syndrome, and that it can occur or affect siblings from neonatal stage, some scholars propose that the occurrence of hard fibromas may be related to heredity.

　　In recent years, foreign scholars have found that in some sporadic and familial adenomatous polyposis-related fibromatosis, abnormalities such as 5q deletion of APC gene and mutation in the 15th exon can be detected in the tumor tissue. It is now known that the APC gene can regulate the expression of B chain protein, which is a member of the protein with adhesion junction function on the cell membrane, and acts as a mediator in the nuclear Wingless signaling pathway, binding to transcription factors in the nucleus and activating gene transcription. The mutation of two intermediates in the WntAPC-β chain protein pathway shows that the stability of β chain protein plays a key role in the pathogenesis of fibromatosis. Experimental findings have shown that by cutting the APC gene, inserting an AluⅠ sequence of 337 base pairs at the 1526 codon, it is mutated and the level of β chain protein in fibromatosis cells is increased, which helps the proliferation of fibromatosis cells. Another experiment has found that although fibromatosis cells contain a high level of β chain protein, the expression level of β chain mRNA is normal, the same as that of surrounding normal tissue, suggesting that the degradation rate of β chain protein in the tumor tissue is lower than that of normal tissue, which is also an important factor for the high level of β chain protein. The above studies show that the loss and mutation of APC gene, the high expression and low degradation rate of β chain protein in the tumor tissue, and its important role in the activation of transcription factors play an important role in causing or promoting the occurrence and development of the disease.

　　In addition, through in situ hybridization and immunofluorescence examination, it has been found that there is a high expression of C-sis gene in the fibromatosis cells, which can promote the production of platelet-derived growth factor R, while platelet-derived growth factor R has the effect of promoting the mitosis of fibromatosis cells and surrounding fibroblasts.

　　Second, pathogenesis

　　Histopathological examination shows that fibromatosis is of unequal size, without a capsule, with irregular edges, infiltrating into surrounding tissues with unclear boundaries, often forming 'lobulated' masses. The cut surface is tough like rubber,呈grayish white, with fibrous bundles arranged in woven strips, infiltrating surrounding tissues (such as muscles, fat). The invaded muscles may appear atrophic and degenerative. The tumor tissue can infiltrate blood vessels and nerves and destroy these tissues. Occasionally, it may undergo malignant transformation into low-grade fibrosarcoma.

　　Under the microscope, the tumor is composed of well-differentiated fibroblasts proliferation and collagen fibers. The fibroblasts and fibers are often arranged in a wavy crisscross pattern, with collagen fibers interlaced between cells. The ratio of cells to fibers in different tumors or different regions of the same tumor varies greatly. Some have fewer fibers and more collagen, while others have more cells and less collagen, but their quantity is more than that of well-differentiated fibrosarcoma. The proliferative fibroblasts are more bulky, lightly stained, with clear boundaries, arranged in bundles, without atypicality; the nuclei are elongated, the chromatin is speckled, with small nucleoli, and nuclear division can be seen, but without pathological nuclear division.

　　In some cases, there may be adhesion between the tumor tissue and the surrounding muscle tissue. Some cells grow more actively, while others show glassy degeneration. Some are located between fat and muscle and grow invasively, separating the muscle fiber tissue into small island-like shapes, causing atrophy and degeneration, and multinucleated muscle giant cells can also be seen.

　　Abdominal hard fibromatosis grows infiltratively, and when it invades the intraperitoneal intestines or bladder, it can cause incomplete intestinal obstruction or bladder irritation symptoms.

　　1. Intraperitoneal tumor:Under normal circumstances, the Bouchocourt sign of abdominal hard fibromatosis is negative, and the abdominal intramural mass is positive, which can be used to differentiate.

　　2. Lipoma:It is more common in women who are relatively overweight, as the tumor occurs within the subcutaneous fat layer, so it has nothing to do with the contraction or relaxation of the abdominal muscles.

　　3. Abdominal bulging fibrosarcoma:This type of tumor is more common in adult males with faster growth; a significant feature is the involvement of subcutaneous fibrous connective tissue, with elevation of the skin and hyperplasia and dilatation of capillaries.

　　This disease can occur from neonates to the elderly, but it is more common in women aged 30 to 50 with a history of pregnancy and childbirth, as well as those with a history of abdominal surgery or abdominal wall trauma. It can be seen in any part of the abdominal wall, especially in the lower abdomen, and is prone to occur in the areas of trauma, original surgical incisions, and adjacent regions.

　　1. Symptoms:Abdominal ligamentous fibromatosis grows slowly, has a long course, and is often asymptomatic. A few cases may have local dull pain or occasional discomfort, often discovered incidentally as an abdominal wall mass. Due to the growth of abdominal ligamentous fibromatosis being restricted by the abdominal muscles and fascia, the long diameter of the tumor is usually less than 5cm. In contrast, ligamentous fibromatosis in other parts of the abdominal wall can grow into a large mass due to the absence of the aforementioned anatomical characteristics. In women of childbearing age, the growth of the tumor is faster, and the growth rate of the tumor before and after menopause.

　　2. Signs:It is a hard mass on the abdominal wall, the boundary of which is often not very clear, consistent with the direction of the abdominal muscle fibers. When the abdominal muscles contract, the mass is fixed and cannot be moved; after the abdominal muscles relax, the tumor can move with the abdominal wall.

　　Late-stage tumors infiltrate locally in a patchy manner, developing into giant abdominal hard fibromatosis, which can cause large areas of abdominal wall stiffness.

　　Abdominal hard fibromatosis does not metastasize but is prone to recurrence. It is reported that the recurrence rate can reach up to 50% to 66.8%, and it mainly occurs in the age group of 18 to 30 years. Plukker et al. believe that the recurrence of the tumor is related to the extent of surgical resection and the size of the tumor. The larger the tumor, the easier it is to recur, and the highest recurrence rate after surgery is observed in cases where the tumor is larger than 10cm. A few cases of abdominal hard fibromatosis can exist for a long time without growth even if the surgical resection is not thorough. However, some scholars report that repeated recurrence and multiple surgeries may lead to tumor metastasis.

　　The tumor has the possibility of spontaneous regression, and even some large abdominal wall hard fibromas can shrink or disappear naturally without any treatment.

　　1, Ultrasound:The ultrasound shows a relatively regular shape, clear boundaries, and internal low-level or isointense mass. The echo is enhanced when there is degeneration and necrosis. The mass generally has no blood flow. This examination can determine the location and extent of invasion of the tumor within the abdominal wall tissue and help to exclude abdominal masses.

　　2, CT scan:Most hard fibromas on CT show clear boundaries and uniform density soft tissue masses, but when the lesion is small, the boundary is often unclear, and when the lesion is large, a group of muscles has been 'eaten' by the tumor. There is subcutaneous fat around, which often shows a relatively clear boundary. The tumor shows uniform isodensity on plain scan, and contrast-enhanced scan can better show the tumor boundary, which is extremely irregular and infiltrative, and the tumor eats the normal muscle like a claw.

　　Comparison with muscle during contrast-enhanced scanning: When the tumor is large, the lesion density is slightly higher or there are small beam-like, strip-like, or eccentrically larger circular low-density changes scattered among the muscle density that is equal to or slightly higher than the muscle density; if the tumor is small, the histology shows that there is still a certain amount of normal muscle tissue between the tumor tissues, but it is not enough to be shown on the imaging, so the CT scan shows uniform isodensity or slightly higher density. There are also very few literature reports that hard fibromas can show calcification, chondrogenesis, or ossification, but some scholars believe that abdominal wall hard fibromas are usually small, and plain scan and enhancement are often uniform isodensity, only showing slight swelling of the local muscle and blurring of the fat space. Because the abdominal wall muscle groups are few and thin, the signs of claw-like infiltration and multiple eccentric low-density changes in the tumor often cannot be shown, and clinical consideration is required.

　　3, MRI:Compared to CT, MRI can more accurately show the location, scope, and shape of the lesion, the claw-like infiltration at the edge of the lesion, and whether there is a capsule. It can also clearly show whether there is fatty tissue inside the lesion and whether there is an edema area around the lesion. The abdominal wall hard fibroma is mainly composed of fascicles of interwoven spindle-shaped fibroblasts and an unequal amount of dense collagen tissue. In different cases, the proportion of spindle-shaped fibroblasts and collagen tissue in different parts of the same lesion is different. The multi-sequential scanning program of MRI can truly reflect the histological composition of the lesion. Due to the different proportions of fibroblasts and collagen tissue inside the lesion, the signal can change. Lesions with a cell-rich and collagen-poor composition can show low signal compared to muscles on T1-weighted imaging, and high signal on T2-weighted imaging; Lesions with a collagen-rich and cell-poor composition show slightly lower signal on both T1 and T2 weighted imaging. In the same case, due to the surrounding area often being collagen-rich and the central area being cell-rich, the peripheral signal on T2-weighted imaging is lower than the central area; Lesions with infiltrative growth or recurrence often have more cell components than collagen components. Some authors also believe that in long-standing diseases, due to the tumor's inherent contraction, the collagen component increases and the signal decreases.

　　The MRI manifestation of this disease is a muscle space-occupying lesion, relatively homogeneous, without necrosis, calcification, or fatty tissue. The lesion shows low or isointensity on the T1-weighted image, and all lesions show high signal on the T2-weighted image, slightly lower than subcutaneous fat. Some lesions may show small linear low signal areas consistent with muscle signal, which are caused by residual muscle islands. After enhancement, the lesions are significantly enhanced, while the residual muscle islands are not enhanced.

　　1. Foods that are good for abdominal wall fibromas:

　　Lotus root, large green vegetables, cabbage, tomatoes, cucumbers, eggplants, celery, tofu, lean meat, apples, pears, bananas, oranges, watermelons, melons, persimmons, walnuts, roasted peanuts, and pine nuts.

　　2. Foods that should not be eaten by abdominal wall fibromas:

　　Avoid cold and raw foods, small, greasy foods, spicy foods, and quit smoking and drinking. Avoid amaranth, honey, milk, coffee, soda, tea, ice cream, beef, mutton, seafood, chili, grapes, scallions, garlic, mung bean foods, and greasy foods.

　　(The above information is for reference only, for details, please consult a doctor)

　　Some scholars believe that abdominal wall desmoid fibromas may regress spontaneously during the early menstrual period or menopause, so short-term observation can be made. In addition, surgical resection of the tumor is the only treatment method.

　　1. Surgical resection

　　1. Local resection of the tumor:Simple local resection of the tumor can have a local recurrence rate as high as 70%. As early as 1889, Douffier advocated extensive and thorough resection of abdominal wall fibromas.

　　2. Large resection of the tumor:Generally, it is required that the resection range include at least 3cm of normal tissue around the tumor, and the peritoneum should also be resected, which is extremely important for preventing postoperative recurrence. Abdominal wall defects can be repaired with artificial synthetic meshes such as MarlexMesh, polypropylene, or polytetrafluoroethylene meshes, which have good efficacy.

　　3. To clarify the nature of the tumor and the extent of resection, and to prevent residual lesions, frozen section examination is routinely performed during surgery.For larger tumors or large abdominal wall hard fibromas, multiple frozen sections should be taken at the surgical margin, especially at the longitudinal axis margin, to confirm the absence of tumor tissue before closing the incision.

　　Two, radiotherapy:Whether radiotherapy is performed alone or as an adjuvant treatment for surgery, it is an effective method for treating abdominal wall desmoids. To reduce recurrence, radiotherapy can be used as adjuvant treatment before and after the surgery for larger tumors, or as a remedial method when the surgical excision range is insufficient or the tumor cannot be removed. For patients with negative resection margins, radiotherapy is not recommended. The dose of radiotherapy is 50-60 Gy, and it is generally recommended that patients with positive resection margins receive 50 Gy of radiotherapy after surgery, and tumors that cannot be removed should be irradiated with approximately 56 Gy of dose, with 75% of patients' conditions controlled. The radiation dose is related to the occurrence of complications; when 56 Gy or less is used, 5% of patients have complications within 15 years, and larger doses will cause complications in 30% of patients.

　　Three, endocrine therapy:Basic research has found that estrogens are closely related to the growth of abdominal wall desmoids, so some scholars have advocated the use of endocrine therapy in recent years. Wilcken et al. reported that endocrine therapy is effective in 60% of solitary tumors. For patients with estrogen receptor-positive resected specimens, tamoxifen can be selected as the first-line drug, and leutinizing hormone-releasing hormone can be chosen as the second-line drug, and the combined use can achieve an effective rate of 50%. There are also successful case reports of the use of progesterone, testosterone, and prednisone (prednisone) for treatment. However, some people believe that the exact effect of endocrine therapy is not yet certain and further observation and research are needed.

　　Four, adjuvant chemotherapy:Chemotherapy is applicable to young and children patients with residual tumor, progressive disease, and failure of surgery and radiotherapy, and may help reduce the local recurrence rate and effectively control the progression of the disease. Commonly used chemotherapy drugs include vincristine, methotrexate (MTX), doxorubicin (ADM, adriamycin), and actinomycin D (actinomycin D, actinomycin). The most effective treatment plan is vincristine and methotrexate, with acceptable toxic and side effects, and should be continued for at least 20 weeks.

　　Other drugs include adenosine cyclic monophosphate modulators (such as theophylline, chlorothiazide, vitamin C, etc.), non-steroidal anti-inflammatory drugs (such as indomethacin), and others.