A 37-year-old man with a history of receptive and penetrating anal sex with men presented with abdominal pain, bright red blood per rectum, and fevers. Recent evaluation by his primary care doctor was notable for negative urine for Neisseria gonorrhea and Chlamydia trachomatis. Rectal swab on admission was positive for C. trachomatis. The patient was ultimately diagnosed with lymphogranuloma venereum, a disease typically seen in tropical climates, although it is more common now in western countries, specifically in men who have sex with men. Treatment consisted of a course of doxycycline for 3 weeks, with resolution of symptoms.

A 53-year-old man with tuberous sclerosis complex presented with severe, acute, right lower quadrant pain. The patient was found to have ileocolonic intussusception and a cecal mass on imaging. Diagnostic colonoscopy revealed a 3-cm cecal lesion which was grossly equivocal for hamartoma, adenoma, or other neoplasm, biopsies of which revealed villous adenoma. Given the lesion was believed to represent the trigger point for intussusception, the patient was referred for surgical resection, the histopathology from which the lesion was identified to be invasive adenocarcinoma. The patient underwent hemicolectomy, with plans for routine postoperative colon cancer surveillance. This case is unique because previously published literature has not described adenocarcinoma in an adult with tuberous sclerosis complex and it calls attention to the need to maintain unsuspected cancer high on the differential in adults with intussusception.

BACKGROUND Distinguishing between primary and metastatic malignancy can be challenging despite advances in diagnostic imaging, tissue sampling techniques, and immunohistochemistry. CASE REPORT Herein, we describe 2 cases of obscure liver lesions which were ultimately determined to be malignant and from metastatic disease. In both cases, the liver metastases were uniquely "homomorphic," i.e., radiographically resembling the primary tumor source (in the first case a dilated tubular appearance akin to the hepatopancreatic ampulla and in the second case a haustrated bowel appearance akin to the colon). CONCLUSIONS These cases illustrate the recently reported concept of tumor homomorphism as a potential diagnostic pearl to facilitate timely diagnosis of malignant-appearing liver lesions of obscure etiology and source and thereby guide management accordingly.

Distinguishing between a primary malignancy and a metastasis can be challenging in some cases. Herein, we describe 2 cases of gastric lesions that were endoscopically sampled and ultimately found to be metastatic from a renal-cell carcinoma. In both cases, the gastric metastases were endoscopically homomorphic to the primary organ (the kidney); i.e., grossly resembling and thus providing an endoscopic clue as to the primary tumor source. We report on the evaluation of obscure metastatic gastric involvement of malignancy and present the concept of homomorphism as a potential diagnostic clue in determining the source of unknown and often unsuspected primary malignancy.

Background

While in children intussusception is often idiopathic, in adults it is commonly caused by a pathologic condition functioning as a lead point. It is important to note that a variety of pathologic conditions may trigger intussusception, with malignancy being a relatively frequent culprit in adults; this should be considered high on the differential diagnosis during evaluation.

Case summary

This is a case of a 40-year-old female presenting to the emergency department (ED) with three days of acute on chronic, peri-umbilical abdominal pain described as waxing and waning, and pressure-like in nature. Initial computed tomography (CT) of the abdomen and pelvis with contrast in the ED (after her pain had resolved) re-demonstrated a previously noted 13 mm lesion in the gastric antrum but no clear cause of the pain. Endoscopic ultrasound was pursued, and the mass lesion was sampled via fine needle biopsy. Post-procedure the patient experienced another episode of severe pain which prompted a repeat stat CT abdomen and pelvis with contrast; this re-demonstrated the 13 mm antral lesion and in addition was remarkable for a gastro-gastric intussusception. An upper gastrointestinal gastrograffin series was ordered (completed only after the pain had subsided) and showed resolution of the intussusception. Histopathology was consistent with a diagnosis of low-grade neuroendocrine tumor (NET). Surgery was initially deferred during the hospitilization given the low grade pathology of the lesion; however further multidisciplinary discussion between Surgery, Oncology, and Gastroenterology recommended resection given the patient's recurrent abdominal pain with the NET functioning as a lead point for further intussusception, and the patient thus underwent robotically-assisted wedge resection.

Conclusion

We present a unique case of severe, intermittent, peri-umbilical pain related to gastro-gastric intussusception caused by an antral NET lead point. The case highlights the importance of considering neoplasms as the cause of intussusception in adults and the greater diagnostic yield when imaging is obtained while symptoms (in this case severe, episodic abdominal pain) are most apparent.