Charak Samhita
बहिर्मार्गाश्रितं साध्यमसाध्यमुभयाश्रितम् । विसर्पं दारुणं विद्यात् सुकृच्छ्रं त्वन्तराश्रयम् ॥२४॥
Externally situated visarpa is curable, internally situated visarpa is very serious and difficult to cure whereas externally as well as internally situated type is incurable.
english translation
bahirmArgAzritaM sAdhyamasAdhyamubhayAzritam । visarpaM dAruNaM vidyAt sukRcchraM tvantarAzrayam ॥24॥
hk transliteration by Sanscript