Case 176. 
Leishmania tropica infection (cutaneous leishmaniasis) (64 y-o M)
    Biopsy from a 4 x 2 cm painless neck nodule with central ulceration in a Japanese man who traveled in India    
Key words : Leishmania tropica, cutaneous leishmaniasis, Leishmania major
Leishmaniasis is transmitted by 2-3 mm-sized sandfly Phlebotomus papatasii. The urban type, mainly affecting the head and neck skin, is caused by L. tropica and prevailing in India through the middle east. Dogs carry this protozoa.   The upper to mid-dermis is densely filled with vacuolated macrophages (HE, low power).
Oil immersion observation discloses nucleated round particles in the vacuolated cytoplasm of macrophages (HE). The morphology resembles yeast-form fungi such as Penicillium marneffei and Histoplasma capsulatum.   In the deep dermis, foreign body granulomatous reaction is observed, with only a few pathogens demonstrated (HE).
Stamp cytology preparation shows round-shaped amastigotes phagocytized by macrophages (Giemsa). The nucleus and kinetoplast (paranucleus) can be recognized.   Electron micrograph of Leishmania tropica in the cytoplasm of a macrophage. The 3 μm-sized amastigotes contain a round nucleus with characteristic chromatin condensation, mitochondria, a blepharoplast, a kinetoplast without forming flagella, and a row of microtubules just beneath the plasma membrane.
Leishmania tropica cultured from the biopsy specimen
Under the acellular culture condition, the protozoa transforms into the form of promastigote, a flagellated and elongated morphology seen in the mid-gut of the vector. Cutaneous leishmaniasis is a benign, self-limiting infection of leishmanian parasites. Regarding the visceral leishmaniasis (kala azar), refer to case 50.
  Reference case 176A
Cutaneous leishmaniasis of rural (African) type, caused by L. major, in a Japanese male who volunteered for plantation in Mali. Multiple hemorrhagic and ulcerated skin lesion are seen on both arms (gross findings).
Reference case 176A
Numerous amastigotes are phagocytized by macrophages in the dermis (HE). PAS and Grocott stains are negative. The number of protozoa in the lesion is dependent on the timing of biopsy. In the old regressing lesion, fewer pathogens are seen in granulomatous reactions.
  Reference case 176A
Immunostaining using a 1:1,000 diluted patient's own serum, identifying intracellular microbes in paraffin section (indirect immunoperoxidase). The patient's serum was not cross-ractive with L. tropica in the presented case. Generally speaking, the specificity of the patient serum is high enough in case of protozoan or helminthic infection.