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Alistair Robson


...a rose by any other name would smell as sweet?” Well, on this occasion I don’t agree, Mr Shakespeare. This is particularly the case when the name is “pseudo-lymphoma”, an oft used term in dermatopathology, guaranteed to make my hackles rise. Part of my ire stems from the pathologist “diagnosing” pseudo-lymphoma - an oxymoron in my view. To diagnose is to a) recognise a disease or B) to find the cause of (a problem). So, concluding with pseudolymphoma means that whatever else you might have done you have not made a diagnosis. The typical context is familiar; a dense lymphoid infiltrate, perhaps some cytological atypia, variable epidermal involvement, no tattoo, for example, or a history of vaccination site, or other potential cause; not being convinced the infiltrate is malignant a “diagnosis” of pseudolymphoma is made,with the wonderful illusion that one’s work is done, a label affixed. Move on. In some instances the cause is known, such as drug-induced pseudolymphoma in a patient on anti-epileptics. This latter use is less irksome, I’ll concede, but either one can make a diagnosis or one can’t. If there are no persuasive diagnostic features in such an infiltrate then maybe one is dealing with a pseudo-pseudolymphoma viz. a lymphoma. A lymphoid infiltrate of unknown significance is a more correct, certainly honest, admission to the clinician. Yesterday, I could have signed out pseudo-dermatomyositis (drug-reaction), pseudo-eczema (pityriasis rosea), pseudo-psoriasis (seborrheic dermatitis). So, let’s drop pseudolymphoma as a pseudo-diagnosis, or risk another gem from the Bard, Macduff’s lament, “Confusion now hath made his masterpiece“.

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This is an interesting topic. I do agree that we have a tendency to lump 'unknown entities into 'known entities (read my posts on [url="https://dermpathpro.com/blog/12/entry-109-follicular-psoriasis-is-this-a-true-entity/"]Follicular psoriasis[/url] and[url="https://dermpathpro.com/blog/12/entry-110-lichen-planus-follicularis-tumidus-is-this-really-a-variant-of-lp-misnomers/"] Lichen planus follicularis tumidus[/url]), just because that satisfies our ego, and makes us feel that we are making a positive diagnosis, rather than making a negative diagnosis (I do not know).

Also, the problem I think is that we too often confuse 'diagnosis' with 'disease'. Diagnosis is an 'opinion' in contrast to 'disease' which is something that has a set pattern of signs and symptoms etc.

[i][url="http://www.thefreedictionary.com/disease"][b]Disease[/b][/url] refers to 'A pathological condition of a part, organ, or system of an organism resulting from various causes, such as infection, genetic defect, or environmental stress, and characterized by an identifiable group of signs or symptoms'

[url="http://www.thefreedictionary.com/diagnosis"][b]Diagnosis[/b][/url] on the other hand refers to:
a. the identification of diseases by the examination of symptoms and signs and by other investigations
b. [u]an opinion or conclusion so reached[/u][/i]

So by this definition, even 'I do not know' is a 'diagnosis' (albeit a negative one) :). One may or may be able to identify the actual 'disease' by the process of 'diagnoses'.

The examples quoted (Pityriasis Rosea and Seborrhoeic Dermatitis etc) refer to 'diseases'. On the other hand 'Pseudo-lymphoma' is a 'diagnosis', (an 'opinion' based on analysis of symptoms, signs, and lab tests) rather than a 'disease' per se.For that matter there are a number of other 'diagnoses' in Dermatology (like 'dermatitis', 'folliculitis' etc) that are not actual 'diseases'.

I personally believe that most pseudo-lymphoma's are probably insect bite reactions (solitary ones, when no other cause is identifiable). So, I do not have a problem with the 'diagnosis' of 'Pseudo-Lymphoma', just as I have no problem with the 'diagnosis of an 'Insect bite reaction', as long as one understands the import (that this is 'something of unknown or known trigger, that simulates a lymphoma, but is not actually one!') of that 'diagnosis' (read opinion), and is not calling pseudo-lymphoma a 'disease' per se.

I have more of a problem with calling clinically benign entities 'Malignant'. Ex: 'Cutaneous Marginal zone Lymphoma', which in some cases is clearly linked to Borrelia and has an excellent prognosis. I believe that the clinical history, response to treatment and excellent prognosis, strongly support a simple reactive process. The extremely rare cases of blastic transformation reported, might be secondary to chronic bone marrow stimulation and hyperactivity (akin to a Marjolin's ulcer). Obviously, I cannot prove this!
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