The correct diagnosis is Venus Lake of the Lip
A mass disfigures the left upper lip near the corner of the mouth. This mass, which is not ulcerated and appears to lie below the lip mucosa/skin, looks as though it would feel soft, and on palpation it did. A dark blue, almost black hue is attenuated by the intervening epithelium. The color is confined to the center of the mass, most prominently just beneath the vermilion border. This lesion is a venous lake, an innocuous dilatation of surface vein(s) found on the lips and ears of aged persons.1-8 The remainder of the lip area appears healthy.
The cheek and uppermost philtrum look pinker than normal and a bit telangiectatic; these findings are consistent with solar injury. Tiny excoriations dot the anterior neck at the bottom of the photograph but are unrelated to the venous lake. The chin sports minute shaving cuts, one almost healed. Perioral skin appears normal.
A highly gratifying feature of physical diagnosis is the confidence that a lesion does not warrant referral or biopsy to rule out troublesome or ominous look-alikes: I did not call the dermatologist to corroborate that this was neither a nevus nor the beginning of a malignant melanoma. I did not call a dentist to exclude lip cancer or a hepatologist to confirm what I already knew—that this was not a spider angioma1 and that there was no evidence of occult cirrhosis. Nor did I call on a gastroenterologist to consider conditions whose cutaneous manifestations suggest a particular cause of GI bleeding.1
Because the patient had a basal cell carcinoma on the face, one could suspect that this new lesion was of the same type. But this is the "wrong" surface for solar injury, including cancer: the up-facing lower lip is much more prone to squamous cell carcinoma. If the face and back of the neck were cross-hatched with solar elastosis or the face were full of keratoses that suggested exceptional heliodermatosis (sun-damaged skin), one might worry more, but this man's skin looks good overall. Nor is the lesional epithelium thickened or crossed by telangiectases. The lack of ulceration provides less reassurance, since early basal cell carcinoma may have an apparently unbroken skin surface.
A third group of differential diagnoses includes pigmented lip lesions such as are found in patients with Addison disease and Peutz-Jeghers syndrome.3 The large and solitary nature of this mass renders such a prospect unlikely, even before one has noted that its slate-blue color differs markedly from the brown expected in those conditions. The color might lead us to consider lead poisoning (although the blue line associated with this condition runs on the gingiva9), argyria,10 or even mino-cycline pigmentation.11 However, the locale is wrong for all of those. Moreover, in these conditions, the color arises from something other than contained venous blood that is relatively static.
Perhaps the most realistic differential diagnosis is mucocele, but these lesions should not blanch with pressure, whereas venous lake does so.3 Furthermore, one can at times observe the mucoid character of the material within a mucocele and feel concomitant fluctuance on palpation.
If the diagnosis is in doubt, the application of pressure should reduce or empty a venous lake because the contained blood is only seldom thrombosed,2 and it is not confined by small tortuous channels. The lesion can be pressed with a finger or a transparent glass slide or plastic lens. The glass slide application constitutes an old but useful technique, diascopy.