There are few early warning signs that a patient has a DSRCT. Patients are often young and healthy as the tumors grow and spread uninhibited within the abdominal cavity. These are rare tumors and symptoms are often misdiagnosed by physicians. The abdominal masses can grow to enormous size before being noticed by the patient. The tumors can be felt as hard, round masses by palpating the abdomen.

First symptoms of the disease often include abdominal distention, abdominal mass, abdominal or back pain, gastrointestinal obstruction, lack of appetite, ascites, anemia, and/or cachexia.

Other reported symptoms include unknown lumps, thyroid conditions, hormonal conditions, blood clotting, kidney or urological problems, testicle, breast, uterine, vaginal, or ovarian masses.

GISTs may present with trouble swallowing, gastrointestinal bleeding, or metastases (mainly in the liver). Intestinal obstruction is rare, due to the tumor's outward pattern of growth. Often, there is a history of vague abdominal pain or discomfort, and the tumor has become rather large by time the diagnosis is made.

Desmoplastic small-round-cell tumor is an aggressive and rare cancer that primarily occurs as masses in the abdomen. Other areas affected may include the lymph nodes, the lining of the abdomen, diaphragm, spleen, liver, chest wall, skull, spinal cord, large intestine, small intestine, bladder, brain, lungs, testicles, ovaries, and the pelvis. Reported sites of metastatic spread include the liver, lungs, lymph nodes, brain, skull, and bones.

The tumor is classified as a soft tissue sarcoma. It is considered a childhood cancer that predominantly strikes boys and young adults. The disease rarely occurs in females, but when it does the tumors can be mistaken for ovarian cancer.

In dogs, mast cell tumors are the most frequent round cell tumor.

A pattern of multiple small nodular metastases has been described as miliary carcinosis which has a radiographic appearance similar to miliary tuberculosis.

Typical signs and symptoms of Wilms tumor include the following:

- a painless, palpable abdominal mass

- loss of appetite

- abdominal pain

- fever

- nausea and vomiting

- blood in the urine (in about 20% of cases)

- high blood pressure in some cases (especially if synchronous or metachronous bilateral kidney involvement)

When most tumors metastasize to the lung, they form distinct nodules, but about 7% spread through the lymph vessels of the lung. They may impair breathing in several ways; the lung becomes stiffer; blood vessels traveling alongside the distended lymph vessels become compressed.

Symptoms of peritoneal mesothelioma include weight loss and abdominal pain and swelling due to a buildup of fluid in the abdomen. Other symptoms of peritoneal mesothelioma may include bowel obstruction, blood clotting abnormalities, anemia, and fever. If the cancer has spread beyond the mesothelium to other parts of the body, symptoms may include pain, trouble swallowing, or swelling of the neck or face.

Cytologic features of serous carcinoma are:

- Marked intragroup nuclear pleomorphism.

- Macronucleoli.

- "Knobby" group borders (in large groups).

- Hydropic vacuoles.

Symptoms of serous carcinoma may include:

- Discomfort/pain or bloating in abdomen

- Frequent urination

- Weight loss

Initially, nearby lymph nodes are struck early. The lungs, liver, brain, and bones are the most common metastasis locations from solid tumors.

- In lymph nodes, a common symptom is lymphadenopathy

- Lungs: cough, hemoptysis and dyspnea (shortness of breath)

- Liver: hepatomegaly (enlarged liver), nausea and jaundice

- Bones: bone pain, fracture of affected bones

- Brain: neurological symptoms such as headaches, seizures, and vertigo

Although advanced cancer may cause pain, it is often not the first symptom.

Some patients, however, do not show any symptoms.

When the organ gets a metastatic disease it begins to shrink until its lymph nodes burst, or undergo lysis.

GISTs are tumors of connective tissue, i.e. sarcomas; unlike most gastrointestinal tumors, they are nonepithelial. About 70% occur in the stomach, 20% in the small intestine and less than 10% in the esophagus. Small tumors are generally benign, especially when cell division rate is slow, but large tumors disseminate to the liver, omentum and peritoneal cavity. They rarely occur in other abdominal organs.

GISTs are thought to arise from interstitial cells of Cajal (ICC), that are normally part of the autonomic nervous system of the intestine. They serve a pacemaker function in controlling motility.

Wilms tumor, also known as nephroblastoma, is a cancer of the kidneys that typically occurs in children, rarely in adults. It is named after Dr. Max Wilms, the German surgeon (1867–1918) who first described it.

Approximately 500 cases are diagnosed in the U.S. annually. The majority (75%) occur in otherwise normal children; a minority (25%) are associated with other developmental abnormalities. It is highly responsive to treatment, with about 90% of patients surviving at least five years.

Peritoneal mesothelioma is the name given to the cancer that attacks the lining of the abdomen. This type of cancer affects the lining that protects the contents of the abdomen and which also provides a lubricating fluid to enable the organs to move and work properly.

The peritoneum is made of two parts, the visceral and parietal peritoneum. The visceral peritoneum covers the internal organs and makes up most of the outer layer of the intestinal tract. Covering the abdominal cavity is the parietal peritoneum.

Signs and symptoms of pseudomyxoma peritonei may include abdominal or pelvic pain and/or bloating, distension, digestive disorders, weight changes, increased girth, and infertility.

A primary tumor is a tumor growing at the anatomical site where tumor progression began and proceeded to yield a cancerous mass. Most cancers develop at their primary site but then go on to metastasize or spread to other parts of the body. These further tumors are secondary tumors.

Most cancers continue to be called after their primary site, as in breast cancer or lung cancer for example, even after they have spread to other parts of the body. Cancer of unknown primary origin is where secondary tumors are found, but the original primary site cannot be decided.

The differential diagnosis of serous carcinoma not otherwise specified includes:

- Ovarian serous carcinoma, a type of ovarian cancer.

- Uterine serous carcinoma, also known as "uterine papillary serous carcinoma", a type of uterine cancer.

- Fallopian tube serous carcinoma, a type of uterine tube cancer.

- Cervical serous carcinoma, a rare type of cervical cancer.

- Primary peritoneal serous carcinoma, a very rare cancer that arise from the peritoneum.

There has been the suggestion that the above diagnoses really represent one entity.

Krukenberg tumors often come to the attention when they cause abdominal or pelvic pain, bloating, ascites, or pain during sexual intercourse. Krukenberg tumors can occasionally provoke a reaction of the ovarian stroma which leads to hormone production, that results in vaginal bleeding, a change in menstrual habits, or hirsutism, or occasionally virilization as a main symptom.

All these symptoms are non-specific and can also arise with a range of problems other than cancer, and a diagnosis can only be made following confirmatory investigations such as computed tomography (CT) scans, laparotomy and/or a biopsy of the ovary.

Primary peritoneal cancer or carcinoma is also known as serous surface papillary carcinoma, primary peritoneal carcinoma, extra-ovarian serous carcinoma, primary serous papillary carcinoma, psammomacarcinoma. It was historically classified under "carcinoma of unknown primary" (CUP). Primary peritoneal cancer (PPC, or PPCa) is a cancer of the cells lining the peritoneum, or abdominal cavity.

Some studies indicate that up to 15% of serous ovarian cancers are thought to be actually primary peritoneal carcinomas in origin.

Histomorphological and molecular biological characteristics suggest that serous carcinomas, which include ovarian serous carcinoma, uterine serous carcinoma, Fallopian tube serous carcinoma, cervical serous carcinoma, and primary peritoneal serous carcinoma really represent one entity.

Most cancers typically present as a single primary tumor. Over the course of time—particularly if the primary tumor is left untreated—smaller "satellite" tumors will appear at other places in the body, a phenomenon known as metastasis. Less commonly, a metastatic tumor is found first; but in most such cases, the primary tumor can then be located via examination and testing. Rarely (3-5% of the time), the primary tumor cannot be found because it is too small, or because it has regressed due to immune system activity or other factors. In such situations a diagnosis of cancer of unknown primary origin (CUP) is made.

CUP usually comes to attention because of masses or swellings found somewhere in the body, either by physical examination or on medical imaging performed for another indication. The disease typically develops rapidly, and metastases may occur in places in the body that are otherwise unusual. Comprehensive physical examination is part of the process to identify a possible primary source of cancer; this should include the breasts, lymph nodes, the skin, external genitals, as well as an internal examination of the rectum and of the pelvic organs.

The location of metastases may be a clue as to the underlying source, even if this cannot be found on investigations. For instance, a woman in whom there is axillary lymphadenopathy (swelling in the lymph nodes of the armpit) it is likely that the cancer originated in the breast, and men with lymph node deposits in the mediastinum of the chest and/or retroperitoneal space of the abdomen may have a germ cell tumor.

A Krukenberg tumor refers to a malignancy in the ovary that metastasized from a primary site, classically the gastrointestinal tract, although it can arise in other tissues such as the breast. Gastric adenocarcinoma, especially at the pylorus, is the most common source. Krukenberg tumors are often (over 80%) found in both ovaries, consistent with its metastatic nature.

Pseudomyxoma peritonei (PMP) is a clinical condition caused by cancerous cells (mucinous adenocarcinoma) that produce abundant mucin or gelatinous ascites. The tumors cause fibrosis of tissues and impede digestion or organ function, and if left untreated, the tumors and mucin they produce will fill the abdominal cavity. This will result in compression of organs and will destroy the function of colon, small intestine, stomach, or other organs. Prognosis with treatment in many cases is optimistic, but the disease is lethal if untreated, with death by cachexia, bowel obstruction, or other types of complications.

This disease is most commonly caused by an appendiceal primary cancer (cancer of the appendix); mucinous tumors of the ovary have also been implicated, although in most cases ovarian involvement is favored to be a metastasis from an appendiceal or other gastrointestinal source. Disease is typically classified as low- or high-grade (with signet ring cells). When disease presents with low-grade histologic features the cancer rarely spreads through the lymphatic system or through the bloodstream.

Appendix cancer or appendiceal cancers are rare malignancies of the vermiform appendix.

Gastrointestinal stromal tumors are rare tumors with malignant potential. Primary lymphomas can occur in the appendix. Breast cancer, colon cancer, and tumors of the female genital tract may metastasize to the appendix.

Cancer of unknown primary origin (CUP, "occult cancer") is a cancer that is determined to be at the metastatic stage at the time of diagnosis, but a primary tumor cannot be identified. A diagnosis of CUP requires a clinical picture consistent with metastatic disease and one or more biopsy results inconsistent with a primary tumor.

CUP is found in about 3 to 5% of all people diagnosed with invasive cancer, and carries a poor prognosis in most (80 to 85%) of those circumstances. The other 15 to 20% of patients, however, have a relatively long survival with appropriate treatment.

Patients usually present with pain and limited range of motion caused by tumor's proximity to the joint space. Swelling may occur, as well, if the tumor has been growing for a long time. Some patients may be asymptomatic until they develop a pathologic fracture at the site of the tumor. They usually originate from the epiphysis of long bones, but in rare cases, they may arise from anterior arc of the ribs.

The symptoms may include muscular aches and pains in arms or legs and abdominal pain. Patients may also experience nerve pain which feels like an electric shock due to weight bearing.

In medicine, the Sister Mary Joseph nodule or more commonly node, also called Sister Mary Joseph sign, refers to a palpable nodule bulging into the umbilicus as a result of metastasis of a malignant cancer in the pelvis or abdomen.

Gastrointestinal malignancies account for about half of underlying sources (most commonly gastric cancer, colonic cancer or pancreatic cancer, mostly of the tail and body of the pancreas), and men are even more likely to have an underlying cancer of the gastrointestinal tract. Gynecological cancers account for about 1 in 4 cases (primarily ovarian cancer and also uterine cancer). Nodules will also, rarely, originate from appendix cancer spillage Pseudomyxoma peritonei. Unknown primary tumors and rarely, urinary or respiratory tract malignancies cause umbilical metastases. How exactly the metastases reach the umbilicus remains largely unknown. Proposed mechanisms for the spread of cancer cells to the umbilicus include direct transperitoneal spread, via the lymphatics which run alongside the obliterated umbilical vein, hematogenous spread, or via remnant structures such as the falciform ligament, median umbilical ligament, or a remnant of the vitelline duct. Sister Mary Joseph nodule is associated with multiple peritoneal metastases and a poor prognosis.

ARMS usually occurs in the skeletal muscle tissue of the extremities, but it is still very common in the torso, head, and neck regions. The primary tumor often presents itself as a soft mass of tissue that is painless, but the tumor can be detected if it starts to put pressure on other structures in the primary site. A large fraction of patients who are diagnosed with ARMS, roughly 25-30 percent, will have metastases at the time of diagnosis. The standard sites for metastases to form are the bone marrow, the bones, and distal nodes. Typical treatment options for patients who have been diagnosed with ARMS include standard surgery, radiation therapy, and intensive chemotherapy.