How many letters does the top answer for “a doctor who specializes in diseases of the blood and blood-forming organs” have?

The most common answer is haematologist (13 letters).

Crossword clue: a doctor who specializes in diseases of the blood and blood-forming organs

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

haematologist 13 letters wn-def

a doctor who specializes in diseases of the blood and blood-forming organs

hematologist 12 letters wn-def

a doctor who specializes in diseases of the blood and blood-forming organs