Sister Mary Joseph nodule: A rare case of umbilical metastasis

Sister Mary Joseph (SMJ) nodules are metastatic deposits situated within the umbilicus that arise from an intra-abdominal malignancy.1 Sister Mary Joseph Dempsey (1856–1939) was the superintendent nurse and surgical assistant to William James Mayo at St Mary's Hospital (Minnesota, USA) during the early days of the Mayo Clinic.2 She was the first to make an association between the umbilical nodule and intra-abdominal malignancy in 1928.2 The clinical presentation of SMJ nodules is variable and misleading. It most commonly presents as a firm, painless, umbilical lump.3 Alternatively, it may be painful, ulcerating or discharging.3 The skin overlying the nodule may be normal or show erythema.3 Often the nodule remains unnoticed by patients or passed off by physicians as umbilical hernias or infection.1, 2 It is common for patients with these nodules to be otherwise asymptomatic. In 80% of cases these lesions are the first sign of a malignancy.1 Prognosis is poor as its presence suggests an advanced metastatic process. The most common histological presentation for SMJ nodules is adenocarcinoma (53.8%) or mucinous adenocarcinoma (19.6%),4 but other types of cancer have also been reported.5 The most common primary site is the ovaries in women (38.8%), and the colon in men (46.2%).4 The primary site is unable to be located in one fifth of cases.4, 5 Ultrasound is often the first imaging modality utilised for patients presenting with umbilical lumps.1, 6 It is useful due to its ability to image small structures with detail.7 It lacks ionising radiation, is inexpensive and non-invasive.7 This case report aims to highlight the importance of recognising SMJ nodules as well as providing an improved understanding of the clinical presentations, sonographic features, and differential diagnoses of palpable umbilical masses. SMJ nodules represent the tip of the iceberg for more extensive intra-abdominal pathology and is therefore something that sonographers need to be aware of within the clinical setting. A 38-year-old female presented to a suburban radiology clinic with a 2-week-old umbilical lump. It was red and mildly uncomfortable. No change in size was demonstrated with straining or standing. There was no history of trauma or previous imaging. The patient was otherwise well. The patient's general practitioner requested an ultrasound examination of the umbilicus to determine the nature of the lump. An umbilical ultrasound was performed using a 12–5 linear transducer on a Phillips IU22 ultrasound machine (Philips Healthcare). The patient was positioned supine and plenty of warm gel was used to reduce air artefact (Figure 1). The ultrasound examination demonstrated a 21 × 23 × 22 mm well-defined, homogeneous mass, isoechoic to the surrounding subcutaneous fat (Figure 2). There were hyperechoic foci within the mass (Figure 3) and internal vascularity detected with colour Doppler imaging (Figure 4). The mass was located at the umbilicus and extended from the skin's dermal surface to the superficial aspect of the linea alba. The surrounding subcutaneous fat and rectus abdominus muscle appeared normal. No collection or extension of the mass was demonstrated on dynamic imaging. The palpable lump was reported as an unusual isoechoic mass at the umbilicus. Following consultation with her doctor, the patient re-presented to the radiology 2 weeks later for an ultrasound-guided core biopsy. Pre-biopsy ultrasound examination demonstrated marked increase in size (25 × 33 × 31 mm) of the umbilical lump (Figure 5) and marked vascularity (Figure 6). Upon these findings differential diagnosis favoured umbilical metastasis. Due to the high suspicion of an intra-abdominal primary cancer, the referring doctor was contacted, and an abdominopelvic computed tomographic (CT) scan was undertaken rather than performing the biopsy. The CT scan uncovered disseminated abdominal malignancy. Metastatic deposits were found in the upper abdomen, pelvis, and umbilicus. Magnetic resonance imaging (MRI) of the pelvis and positron emission tomography (PET)/CT imaging (Figure 7) of the whole body offered no definitive clues toward a primary source however mucinous adenocarcinoma was determined to be the histopathological diagnosis. Chemotherapy was used to treat and slow the progression of disease. It is a common misconception that all umbilical lumps are umbilical or para umbilical hernias.1 Umbilical lumps may also be inflammatory lesions, benign tumours, or malignant tumours.8, 9 Umbilical tumours are rare and may be benign or malignant. Malignant lesions may be primary or secondary. By far the most common umbilical tumours (83%) are malignant lesions in the form of secondary metastases (SMJ nodules).10 Their incidence has reduced over time and was estimated to be around 1.7 per 10,000 cancer cases in 2014.4 Medical imaging is utilised to help clinicians with differential diagnosis due to the clinical ambiguity of umbilical lumps. Although ultrasound is often the first imaging modality to be utilised for umbilical lumps,7 misdiagnosis can occur. One study looking at the diagnosis of the SMJ nodules using ultrasound found that the biggest limitation for accurate diagnosis was the sonographer's knowledge and experience.1 Sonographers and radiologists must be able to define and distinguish between key clinical and sonographic features to provide accurate findings and ensure appropriate treatment, management or further investigation. Table 1 describes common ultrasound and clinical features of umbilical lumps for different pathologies. In this case, a hernia could be ruled out as there was no mobility of the mass on dynamic imaging, no abdominal wall defect, and no communication of tissue deeper within the abdomen. An inflammatory process was also unlikely as the patient's clinical history lacked previous trauma, surgery or foreign body. The mass was firm, solid and painless with sonographically normal appearing adjacent subcutaneous fat and rectus muscle. There were no clinical signs consistent with cellulitis or abscess such as diffuse cutaneous erythema and oedema,13 or sonographic appearances such as diffusely echogenic, thickened, hyperaemic subcutaneous fat or fluid collection with mobile internal echoes.13 It was also unlikely that the lump was a benign tumour such as an omphalith, lipoma or keloid scar due to the demonstrated marked vascularity in the lump, which is not a feature of these lesions.14 Similarly, endometriosis was unlikely as the patient did not report the lesion to be painful or to change with her menstrual cycle.12 A primary or secondary cancer needed to be ruled out in this case. There are numerous types of primary malignant umbilical tumours, however, they are exceedingly rare, constituting 12% of cases versus 88% of cases being secondary in nature.5 One study found the most common type being primary cutaneous melanoma,5 the sonographic features of which have significant cross-over with SMJ nodules (Table 1).15 The mass had suspicious malignant sonographic features. It was well-defined, lobular, solid, heterogeneous and highly vascular, in a young adult female with little to no medical history which justified cross-sectional imaging and biopsy. Whole body PET/CT and pelvic MRI imaging revealed that the lump was likely to be a malignant secondary tumour, in addition to multiple other abdominopelvic deposits. The histological diagnosis of mucinous adenocarcinoma confirms this. There are multiple potential primary sites for mucinous adenocarcinoma such as the colon, breast, lung, rectum and pancreas.5 Despite whole body PET/CT and pelvic MRI imaging, no primary site was determined. The sonographic features of the SMJ nodule described in this case are similar to that described in the literature.3 Table 2 summarises these sonographic features. SMJ nodules have been reported as well-defined hypoechoic masses with irregular, lobular or spiculated margins, more commonly heterogenous than homogeneous and can contain small internal echogenic foci.3 They almost always demonstrate prominent internal vascularity.11 The mass may extend from the peritoneum to the dermal layer, but often leaving the rectus abdominus muscle and subcutaneous fat unaffected.3 Prognosis is poor for patients presenting with SMJ nodules. Mean survival time from diagnosis is approximately 8 months,4 but depends on the degree of disease and the types and aggressiveness of treatments.1, 16, 17 Treatment and management is controversial with some authors proposing palliative care due to such poor long-term prognosis.1 For treatment options, surgery with adjuvant therapy or chemotherapy alone have been used and have varying degrees of success and application. Better survival time (21 months) has been recorded in patients that have had surgery and adjuvant therapy.1 Chemotherapy alone has shown to have a mean survival time of 10 months.17 For this patient chemotherapy was used. Surgical intervention was not undertaken, likely due to the complexity of disease. When sonographically examining a patient with a potentially sinister pathology, sonographers should be aware that a timely diagnosis hastens treatment and improves prognostic outcomes. It is important to describe the sonographic features of a mass, and then align them to clinical features to fully inform further diagnostics and treatment. Ultrasound is a powerful tool to help determine the nature of umbilical lumps. This case report has discussed the clinical pathway and medical imaging of a patient presenting with an umbilical lump. Not all umbilical lumps are hernias, and this case illustrates the clinical and sonographic features of SMJ nodules. Although SMJ nodules are rare, sonographers and radiologists should be aware of the sonographic and clinical features of umbilical lumps to identify these phenomena and differentiate them from other more common differential diagnoses. This manuscript does not contain any identifying information of patients. While patient consent was not obtained for the use of their data or experiences in this manuscript, no identifiable details are presented herein.