A 61 year old woman attending a follow-up appointment two months after excision of tubular carcinoma of the breast complained of an abdominal wall mass. The lesion was subcutaneous, mildly tender, and had a nodular consistency. The patient was worried that the soft tissue mass might be a recurrence of follicular lymphoma, which had been diagnosed in April 2001, although her disease had been stable after five cycles of chemotherapy. The possibility of metastatic breast carcinoma was low considering the good prognostic features of tubular carcinoma.
The lesion was excised and the 4×2×2 cm mass of subcutaneous tissue seemed to consist solely of fibroadipose tissue. Microscopically, we identified a widespread infiltrate of plasma cells, lymphocytes, and eosinophils within the subcutaneous adipose tissue, in a septal and lobular distribution, indicating inflammation or panniculitis.
A large proportion of the inflammatory cells were eosinophils. The lymphocytes formed follicular aggregates, particularly adjacent to blood vessels (fig 1). The architecture of these aggregates was benign. The lymphocytes were normal and immunohistochemistry confirmed a normal distribution of T cells and B cells. We found no evidence of light chain restriction, and Bcl-2 immunoreactivity was negative within the follicle centres, confirming the morphological impression of a reactive lymphoid infiltrate with no evidence of follicular lymphoma.
Fig 1 Medium power view (×200) of follicular aggregates of lymphoid cells in a perivascular distribution with a heavy infiltrate of eosinophils in the background
In addition to the perivascular lymphoid aggregates and panniculitis, lymphocytes and eosinophils were seen within small blood vessel walls, indicating vasculitis (fig 2). In summary, we found no evidence of malignancy after the tissue was examined microscopically on multiple levels.
Fig 1 High power view (×400) showing vasculitis—small blood vessel destruction and inflammation with a prominent eosinophilic component. Note the red blood cells within the vessel lumens
Lobular panniculitis with paraseptal lymphoid follicles and vasculitis are found in lupus panniculitis, which is seen in systemic and discoid lupus erythematosus.1
Eosinophils have been reported in up to a quarter of patients with this disorder, making it a possible diagnosis in our patient.2
The microscopic features of the subcutaneous inflammation seen in dermatomyositis are indistinguishable from those seen in lupus, but a muscle biopsy would be needed to make such a diagnosis.3
Traumatic and factitial panniculitis are characterised by a mixed lobular and septal panniculitis, but they can be excluded in this case because of the absence of fat cyst formation, necrosis, and infiltrates of macrophages and multinucleate giant cells.4
Such features are also seen in post-steroid panniculitis, where multiple subcutaneous nodules develop up to a month after cessation of steroids.5
Our patient satisfied none of the 11 diagnostic criteria for systemic lupus erythematosus as set out by the American Rheumatism Association.6
After discussion with her surgeon, it transpired that the patient had been receiving subcutaneous injections of mistletoe extract as complementary therapy aimed at treating her lymphoma. She used an aqueous, whole plant extract of mistletoe grown on ash trees, called “Abnoba viscum fraxini.” This was a self administered subcutaneous injection (20 mg three times a week), which she started 12 months before presentation. She had heard about the use of mistletoe extract in palliative oncology from a friend, and she was referred to a complementary therapist through her general practitioner. She is still in remission two and a half years later with no further side effects. Her injection site corresponded with the site of excision so, in view of her negative investigations, signs, and symptoms of lupus erythematosus, we considered the microscopic features to be a direct inflammatory response to mistletoe extract and conducted a review of the literature to compare our findings.