Metastatic adenocarcinoma of unknown primary site

A 58-year-old woman was referred to the general surgery clinic with a 3-month history of abdominal masses. She had not undergoneabdominal surgery or trauma previously. On physical examination, she had nontender masses in the right lower abdomen. The results of labor atory studies were unremarkable. Computed tomography (CT) of the ab domen and pelvis was performed for further evaluation.

Abdominal CT revealed well-defined multiloculated cystic lesions within the right rectus muscle. The lesions measured 6 × 4 cm (Figure 1) and 3 × 3 cm (Figure 2). The rest of the imaging exam ination was unremarkable.

The patient underwent surgery during which the abdominal wall was partially removed and reconstructed using mesh. The histologic diagnosis was adenocarcinoma. The patient’s medical history, physical examination, imaging studies and pathologic evaluations did not indicate theprimary site of the disease.

Metastatic adenocarcinoma of unknown primary site

The patient received adjuvant chemo therapy. Twelve months later, the patient presented with similar clinical findings. At this time, CTshowed a 3 × 3-cm recurrent cystic mass on the mesh (Figure 3). The patient underwent repeat abdominal wall resection. A year later, thepatient’s condition worsened, and CT revealed metastases to the peritoneum, liver, subcutaneous abdominal wall, and inguinal lymph node.The patient died 32 months after diagnosis.

Primary malignant tumors of the ab dominal wall are extremely rare. The most frequent tumors include lymphoma, melanoma, andmalignant fibrous histiocytoma in adults, and sarcoma in children.¹Metastatic lesions involving the abdominal wall can be frequentlyencountered in clinical practice. Metastases can develop in this region in a hematogenous or lymphatic dissemination.

In female patients with metastatic tumor, the most common primary site is the ovary, followed by the colon and breast. In male patients,the most common primary tumor is malignant melanoma.²In most metastases to the anterior abdominal wall, the patient’s primary tumor isalready known and/or metastases to the anterior abdominal wall arise together with other metastases.³To our knowledge, there are few reported cases of cancer of unknown primary site that were found to have metastasized to the cutaneous-subcutaneous anterior abdominal wall andno cases presenting as an isolated intramuscular abdominal wall mass. An interesting characteristic of this case is that the lesions wererestricted to the abdominal wall for a long period and metastasis (such as to the liver, peritoneum, and lymph nodes) emerged months afterthe anterior abdominal wall metastasis.

The occurrence of abdominal wall metastases from an unknown primary adenocarcinoma is very rare. But, as shown in this case, it shouldbe considered in the differential diagnosis of abdominal wall masses.