A few observations:
--Lichen planus does not start as trench mouth; they are separate and unrelated conditions, although there is no reason they cannot occur simultaneously.
--Other muco-cutaneous disorders, such as lichenoid reactions and mucous membrane pemphigoid, can be mistaken for lichen planus, but...
--Usually, oral lichen planus manifests in the mouth in an easily recognizable way.
--When these conditions cannot be identified on sight, a biopsy followed by conventional histologic exam and direct immunofluorescence studies can more conclusively derive a diagnosis
--Most importantly, your description bears little resemblance to either lichen planus or other autoimmune mucocutaneous disorders. Had you stated that the lump seemed like a blister, or was intermittent, that might suggest a vesiculo-bullous condition like pemphigoid or pemphigus, or even a mucous retention cyst
. But a solid lump suggests a solid lesion.
Most of these solid lesions are what we call "reactive"-- they represent proliferative connective tissue, sometimes referred to as either a "fibroma", or a "pyogenic granuloma
", or a "giant cell granuloma". When less conspicuously bloody or filled with blood vessels, they're usually just "fibromas".
However, that is not to say that a diagnosis can be assumed. More serious conditions, including infection
, granulomatous disease, and even malignancy of either the surface tissue or the minor salivary glands can occur in this area. Especially because a photograph is unavailable, this would necessitate a formal diagnostic assessment.
The best type of clinician to do the job would be a clinical oral pathologist or an oral surgeon. Your general dentist can provide you with an appropriate referral, or you may consult the online directories of either the American Association of Oral and Maxillofacial Surgeons
or the American Academy of Oral & Maxillofacial Pathology.
Hope this helps...