SZ Tan, CY Ng, IM Nawroz, KA JamiesonRC Marks
Shi Zhuan TAN Medical Student University of Edinburgh
Chye Yew NG MRCSEd Specialist Registrar in Orthopaedics South East Scotland Rotation
Ibrahim M NAWROZ FRCPath Consultant Pathologist Fife Acute Hospitals NHS Trust
Katharine A JAMIESON FRCR Consultant Radiologist Fife Acute Hospitals NHS Trust
Robert C MARKS FRCS (Orth) Consultant Orthopaedic Surgeon Fife Acute Hospitals NHS Trust Institution: Victoria Hospital, Hayfield Road, Kirkcaldy, Fife KY2 5AH.
Corresponding author: CHYE YEW NG E-mail: chyeng@gmail.com
SMJ 2008 53(4): 10
Abstract
Soft tissue amyloidoma of the extremities is extremely rare and there are
only 12 reported cases in the English literature to date. We present a case of
soft tissue amyloidoma of the thigh in a 74-year-old lady.
Key words: amyloidoma, soft tissue amyloidoma, extremity swelling
Background
Amyloid refers to pertinacious, eosinophilic, amorphous material that when
stained with Congo red exhibits a characteristic green birefringence under
polarised light.1 Amyloidosis describes a group of disorders
characterised by the extracellular deposition of amyloid substance which results
in tissue damage. Historically, it has been classified as systemic (primary or
secondary), organ-limited, or localised depending on the extent of tissues
involved. In addition, amyloid deposits can be categorised according to the
peptide (AL type or AA type) in which amyloid is formed.2 AL type
amyloid protein consists of variable segment of immunoglobulin light chains
produced in abnormal quantities due to monoclonal proliferation of plasma cells
or B-lymphocytes.1 In most cases, it occurs on its own as a primary
amyloidosis with occult plasma cell proliferation. However, it can also be seen
in patients with myeloma, Waldenstroms's macroglobulinaemia, monoclonal
gammopathy of uncertain significance and lymphoma. The AA type, on the other
hand, consists of acute phase protein produced in excess in chronic inflammation
such as rheumatoid arthritis and inflammatory bowel disease or in chronic
infection such as tuberculosis, bronchiectasis and osteomyelitis.1
.
The localised form of amyloid deposit as a mass or nodule in the absence
of systemic involvement is known as amyloidoma. It is the least common
presentation of tissue amyloid deposition and can be found in multiple body
sites, including the respiratory, genitourinary, and gastrointestinal tracts,
central nervous system, skin, breast and internal viscera especially the lung.3
Amyloidoma of soft tissues is exceedingly rare and occur most frequently in the
mediastinum and retroperitoneum.4 Amyloidoma of soft tissues in the
extremities are even more unusual and there have only been 12 reported cases in
the English literature to date. We report a new case of soft tissue amyloidoma
of the thigh in an elderly woman during routine follow-up after a total hip
replacement.
Case report
A 74-year-old lady who recently had a right total hip replacement
complained of a painful mass in her left upper thigh during a routine outpatient
review. She denied any previous trauma to this area. She was obese and suffered
from multiple medical problems including insulin-dependent diabetes mellitus,
hypertension, hyperlipidaemia, coronary artery disease, peripheral vascular
disease, hypothyroidism and chronic anaemia.
Clinically, the mass was localised at the anterior aspect of the upper
thigh. It was subcutaneous, firm and measured 4x3cm. MRI scan suggested an area
of fat necrosis within the subcutaneous fat overlying the vastus lateralis (fig.1a
& b). However the lesion showed enhancement with gadolinium (fig.2).
She then underwent excisional biopsy of the mass. Histopathology report showed
hyalinised fibrofatty soft tissue with extensive deposition of amorphous
eosinophlic amyloid material associated with focal foreign body giant cell
reaction (fig.3a) and focal
chronic inflammation which includes mature plasma cells. The amorphous debris
showed the characteristic apple-green birefringence under polarised light
examination with Congo red indicating amyloid deposits (fig.3b).
The plasma cell infiltrate is polyclonal on immunohistochemical staining for
kappa and lambda light chain (fig.3c&d) and immunohistochemical study for AL
protein is negative.
Further investigations, including urine Bence-Jones protein, serum
electrophoresis, a rectal biopsy and a transthoracic echocardiogram, had been
normal.
Discussion:
Among the previous 12 reported cases of soft tissue amyloidoma of the
extremities, 10 of the 12 lesions were found on the lower limb in which four
were on the leg,5-8 three in the popliteal fossa,9-11 one
in the ankle,12 one in the hip13 and one in the thigh14.
The remaining two cases occurred on the shoulder15 and the upper arm16
respectively. Soft tissue amyloidoma of the extremities usually present as a
subcutaneous mass5-16 which progressively enlarges12, 13
and may be associated with mild to moderate aching pain12, 16. The
mean age at diagnosis for amyloidoma of soft tissues is 66 years old4
and 56 years old for amyloidoma of soft tissues of the extremities based on the
12 previously reported cases.
The main differential diagnoses include fat necrosis and soft tissue
sarcoma. Diagnosis with MRI is unreliable and tissue biopsy for
immunohistochemistry is essential for definitive diagnosis. In our case, the MRI
signal characteristics were not typical of any particular malignant or benign
lesion, though are compatible with the findings in previous cases of soft tissue
amyloidoma.16 In view of the areas of low signal on the T2 images and
the strand like appearances fat necrosis was considered but in view of the
gadolinium enhancement a malignant lesion could not be excluded.
The aetiology of amyloidoma of soft tissue of the extremities remains
unclear. Two of the twelve cases reported a history of trauma to the area and
both of them had amyloidoma of the AL type. 8, 12 Eight patients had
some comorbidities including breast cancer, non-hodgkin lymphoma receiving
chemotherapy, renal failure, primary biliary cirrhosis, hypertension,
hyperlipidaemia, peripheral vascular disease, diabetes mellitus and
hypothyroidism. Of these eight
patients, five had the AA type amyloid; 5, 6, 7, 11, 16 one who was
undergoing chronic haemodialysis had the ß-2 microglobulin type amyloid;9
one who reported trauma to the site of amyloidoma and who also suffered from
hypercholesterolemia, diverticulosis and hypothyroidism had the AL type amyloid;
8 and there was a patient with unknown type amyloid.14 Two of
the eight patients were diabetic and both of them had amyloidoma of AA type.
7, 16 Although amyloid deposition can be a pathological feature of type II
diabetes mellitus, amyloidoma is rarely associated with the condition. In the
series of 14 cases of soft tissue amyloidomas reported by Krishnan et al. only
one case was found to be associated with diabetes mellitus and it was
phenotypically AA amyloid. 4
It is imperative to make a distinction between AL and AA amyloidoma as
patients with AL amyloidoma have a poorer prognosis. Krishnan et al. found that
10 of his 14 patients had AL amyloid and 80% of them subsequently developed
lymphoplasmacytic malignant neoplasm.4 Progression to disseminated
disease is also common and additional tumours develop after an interval of three
to nine months.17 In contrast, AA amyloidomas tend not to recur or
develop immunocyte dyscrasias and are usually cured by excision. 4, 5
Amyloidoma is an unusual cause of soft tissue mass in the limb however a
systematic approach incorporating clinical, radiological and pathological
assessments will lead one to reaching the diagnosis.
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