Mystery Lipomas and the Deceptive Ultrasound
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The GP initially queried exostosis of the mastoid due to its position and atypical presentation and arranged for a CT scan. The CT report suggested the post-auricular lesion may represent lymphadenopathy but it could not be characterized by the scan and an ultrasound was recommended. The USS reported the lesion was ‘probably’ a lipoma and subsequently the patient was referred to our department on a routine basis for excision.
The clinical presentation did not correlate with the radiological finding of lipoma. The site was relatively uncommon for a lipoma and the lesion was firm and fixed. An MRI scan was subsequently arranged and ruled out the diagnosis of lipoma. It proposed the swelling could be a cavernous hemangioma or lymph node but that it was not suggestive of anything sinister. The two imaging modalities giving contrasting advice, with no real correlation with the clinical picture, triggered a multidisciplinary approach and discussions with the radiological team. It was agreed to proceed with a core biopsy to gain a histological diagnosis.
An USS-guided core biopsy was deemed the appropriate option due to the uncertain nature of the swelling, to establish a histological diagnosis. The pathology report vindicated this thorough and convoluted process as the core biopsy revealed a follicular lymphoma.
Given the histology result, surgical excision of the swelling was deemed unnecessary and the patient was referred to the Haematology team for further management.
Lipomas are the most common mesenchymal tumour seen by clinicians, with subcutaneous lipomas accounting for the majority of cases. Classically, they arise in the fifth to seventh decade and can develop anywhere where adipose tissue is present . Their clinical presentation is diverse, with various sites of origin and depth of lesion. They often appear on the trunk, upper arms, shoulders and neck. They are soft, non tender and usually mobile on examination . Lipomas can progressively grow in size and present to the general practitioner or plastic surgery clinic as a large soft tissue swelling. If a swelling is > 5 cm, it is important for the clinician to consider a more sinister pathology, such as sarcoma. Features suggestive of possible malignancy and therefore urgent investigation and possible sarcoma MDT referral include the following: painful lesions, growing in size, > 5 cm and being deep to the deep fascia .
Typically, ultrasound is the first-line investigation for soft tissue masses. It is a simple and readily available imaging modality. An experienced radiologist can identify the type of soft tissue mass and can guide the clinician towards further investigations such as MRI or tissue biopsy .
In a large proportion of cases, USS is able to diagnose the soft tissue swelling using a quick and non invasive method so treatment can swiftly follow. However, in some unique cases, ultrasound results can be misleading, as we have demonstrated here. Incorrect diagnosis in this case may have been attributed to difficulty in scanning the post-auricular region and possible inexperience of the radiologist. Ultrasound scanning is user dependent, dynamic in nature, and appearances of lipomas can vary greatly particularly if they are deep-seated. A recent systemic review calculated the overall sensitivity and specificity of ultrasound in the diagnosis of lipomas was 86.87% (95% CI = 82.14–90.73) and 95.95% (95% CI = 93.75–97.54), respectively . While these figures show outstanding sensitivity and specificity, it is not always watertight when diagnosing lipoma and relating back to the clinical presentation and examination is always crucial as demonstrated here.
Where there is still a degree of uncertainty, MRI is a valuable imaging modality to visualize soft tissue. Typically lipomas being composed mostly of adipose tissue have a similar appearance to that of subcutaneous tissue on MRI and have a distinct, recognizable appearance of a discrete, homogenous, encapsulated fatty mass .
MRI scans have been reported to be 100% specific in diagnosing simple lipomas. It is also a useful imaging modality to differentiate between simple lipomas and lipoma variants .
Interestingly in this case, both the ultrasound and the MRI reports failed to provide the correct diagnosis, with USS indicating a lipoma but the MRI ruling it out suggesting another possible culprit. Inconclusive imaging with contradictory diagnoses and the patient’s atypical clinical presentation solidified the clinician’s initial intuition that the jigsaw puzzle still did not fit. This triggered the need for a conclusive tissue diagnosis in the form of a soft tissue biopsy.
The location, differential diagnosis and possible future treatment options, including further surgical management, must be considered before any biopsy procedure is performed. Commonly, biopsies can be open/excision or percutaneous. Percutaneous methods typically involve using a fine needle to aspirate cells, or a wider hollow needle which removes a larger sample of tissue, termed a core biopsy. Where fine needle aspiration allows for the aspirated cells to be analysed at the bedside by the pathologist, a core biopsy provides a greater tissue sample through multiple passes. A core biopsy allows for histological analysis which is more accurate and informative . Both types of percutaneous biopsy have the advantage of minimizing seeding of potentially malignant tumours, however are not as specific as excision biopsies.
It should be remembered that a percutaneous biopsy represents a small sample of the lesion. Multiple core biopsies may be required for large lesions with site planning to sample suspicious areas that appear heterogenous on imaging. The biopsy tracts can then be excised at a later date with formal resection in the case of malignancy. It is therefore important for someone of appropriate expertise to perform these biopsies to get an accurate representation of the most suspicious tissue. If the lesion is small, < 2 cm, an excision biopsy may be considered, and in some cases an incisional biopsy may be preferred .
In this case, an USS-guided core biopsy was chosen as the nature of the lesion was still unknown and complete excision may not have been necessary, depending on the pathology result. It may have also impacted on further management at a later stage if the entire lesion was excised. The positioning of the lesion would have made excision more complex, with possible skin dissection or other means of reconstruction being required due to adherence to the overlying skin. An argument could be made that consideration for a biopsy should have been made at an earlier stage and this may have been the case if the patient was initially seen by the Plastic Surgery team. However, as the initial CT scan was ordered in primary care which recommended a follow up USS, the patient already had two different imaging modalities prior to being referred for a Plastics opinion. The discrepancies in existing radiological findings coupled with history and clinical examination led to a more cautious approach delaying biopsy to ascertain further imaging and radiology MDT input. This ultimately facilitated a safe multidisciplinary approach to achieving a tissue diagnosis through an appropriate biopsy. Given the histology result of follicular lymphoma, further excision of the swelling was not required.
Follicular lymphoma is a slow growing subtype of non-Hodgkin’s lymphoma originating from B Cells. It classically presents with painless lymphandenopathy and ‘B’ symptoms which include fever, night sweats and weight loss. This patient did not present with any systemic symptoms. The lymphadenopathy may be present in the neck, groin or axilla. The enlarged lymph nodes are usually painless and firm. The lymphadenopathy can be either generalized, affecting more than one region, or localized [9, 10].
Due to the slow progression of the disease, patients may not require treatment for some time. If they present in a more advanced stage of the disease, there are multiple treatment options including radiotherapy, chemotherapy and immunotherapy .
Ultrasound scanning is a valuable investigation in diagnosing soft tissue masses in a large number of cases; however, this report exposes its limitations.
An ideal investigation should be able to provide an accurate diagnosis, identify serious pathology, such as malignancy, and therefore guide the clinician towards the appropriate treatment.
With common things being common, for instance with the majority of soft tissue swellings being lipomas, it could have been easy to continue with an inappropriate surgical management plan on the basis of an USS report. This suggestion of a ‘probable’ lipoma on USS was correctly questioned, despite this modality usually being so sensitive and specific to lipomas. The clinician correctly went back to basics with history and examination deciding that this puzzle did not yet quite fit. Eventually challenging these investigative reports, with a multidisciplinary approach, lead to safe and correct management of the mystery lipoma.
This case report has raised an important learning point that investigations are only as valuable as the clinician who interprets them, correlating them with the clinical presentation. A collaborative approach with the multidisciplinary team, including discussion with the radiologist, helped to form an appropriate management plan. The clinician’s experience and intuition is the single most valuable tool when diagnosing not only soft tissue swellings but throughout all medical and surgical specialties.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
None needed as a case report.
Informed consent was obtained from all individual participants included in the study. A Hospital Trust consent form was signed by the relevant patient giving consent for use of images in publication, a copy of which is filed with the patients’ case notes.
- 1.Nadar MM, Bartoli CR, Kasdan ML. Lipomas of the hand: a review and 13 patient case series. Eplasty. 2010;10:e66.Google Scholar
- 9.Salles G. Clinical features, prognosis and treatment of follicular lymphoma. ASH Education Book. 2007;2007(1):216–25.Google Scholar
- 10.Freedman, A., Friedberg, J. Patient education: follicular lymphoma in adults (beyond the basics). UptoDate. Retrieved November 2018 from https://www.uptodate.com/contents/follicular-lymphoma-in-adults-beyond-the-basics.